当前期刊: Ecological Applications Go to current issue    加入关注   
显示样式:        排序: 导出
我的关注
我的收藏
您暂时未登录!
登录
  • Vegetation management for urban park visitors: a mixed methods approach in Portland, Oregon
    Ecol. Appl. (IF 4.378) Pub Date : 2020-01-23
    Michelle L. Talal; Mary V. Santelmann

    Urban park managers are tasked with maintaining ecological function and quality of parks while also meeting visitor preferences. The purpose of this study was to better understand how managers currently manage vegetation in parks in Portland, Oregon. Twenty‐one urban park manager interviews were completed regarding 15 parks, which included natural‐passive use, recreational‐active use, and multi‐use park types. Responses were coded for themes and patterns of meaning. Mixed methods were used to evaluate the urban park manager interview data in the context of visitor interview and plant community composition data collected at the same parks. Non‐metric multidimensional scaling ordinations were used to identify urban park manager and visitor perspectives correlated with different park types and their vegetation. Across park types, managers discussed maintenance as a favorite aspect of plant management, while ecosystem management was often described by managers of natural‐passive use parks. Some managers indicated that they would make no changes to plant management, but the majority provided detailed recommendations such as enhancing maintenance, increasing staffing, adding plants, updating infrastructure, and improving plant species selection. There are opportunities to better meet the preferences of both managers and visitors by continuing to maintain large trees and trail/path vegetation for accessibility, removing invasive/harmful plants, and improving plant selection to include those which are heartier, more colorful, produce flowers, and are disease‐resistant, climate‐adapted, and provide habitat for a variety of species. While urban park managers discussed how they incorporated visitor preferences and accessibility in plant management, they also described limitations such as funding, staff resources, and undesirable visitor behaviors. Increased communication and collaboration among governmental agencies, non‐profit organizations, and community members, as well as continued investment in park management and interdisciplinary mixed methods research have the potential to enhance the many ecological and social benefits of urban parks.

    更新日期:2020-01-24
  • Forest management influences the effects of streamside wet areas on stream ecosystems
    Ecol. Appl. (IF 4.378) Pub Date : 2020-01-23
    Maitane Erdozain; Caroline Emilson; David Kreutzweiser; Karen Kidd; Nadia Mykytczuk; Paul Sibley

    Riparian zones contain areas of strong hydrological connectivity between land and stream, referred to as variable source areas (VSAs), and are considered biogeochemical control points. However, little is known about whether VSAs influence stream communities and whether this connectivity is affected by forest management. To address this, we used multiple biotic and abiotic indicators to: 1) examine the influence of VSAs on riparian vegetation and stream ecosystems by comparing VSA and non‐VSA reaches; and 2) explore how forest management may affect the influence of VSAs on stream ecosystems. We detected some significant differences between VSA and non‐VSA reaches in the riparian vegetation (greater understory and lower tree density) and stream ecosystem indicators (greater dissolved organic matter aromaticity, microbial biomass, peroxidase activity and collector‐gatherer density, and lower dissolved organic carbon concentrations, algal biomass and predatory macroinvertebrate density), which suggests that VSAs may create a more heterotrophic ecosystem locally. However, we show some evidence that forest management activities (specifically, road density) can alter the influence of VSAs and eliminate the differences observed at lower forest management intensities, and that the most hydrologically‐connected areas seem more sensitive to disturbance. Therefore, we suggest that the heterogeneity in hydrological connectivity along riparian zones should be considered when planning forest harvesting operations and road building (e.g., wider riparian buffers around VSAs).

    更新日期:2020-01-23
  • Weighting and aggregating expert ecological judgments
    Ecol. Appl. (IF 4.378) Pub Date : 2020-01-23
    Victoria Hemming; Anca M. Hanea; Terry Walshe; Mark A. Burgman

    Performance weighted aggregation of expert judgments, using calibration questions, has been advocated to improve pooled quantitative judgments for ecological questions. However, there is little discussion or practical advice in the ecological literature regarding the application, advantages or challenges of performance weighting. In this paper we 1) illustrate how the IDEA protocol with four‐step question format can be extended to include performance weighted aggregation from the Classical Model, and 2) explore the extent to which this extension improves pooled judgments for a range of performance measures. Our case study demonstrates that performance weights can improve judgments derived from the IDEA protocol with four‐step question format. However, there is no a‐priori guarantee of improvement. We conclude that the merits of the method lie in demonstrating that the final aggregation of judgments provides the best representation of uncertainty (i.e. validation), whether that be via equally weighted or performance weighted aggregation. Whether the time and effort entailed in performance weights can be justified is a matter for decision‐makers. Our case study outlines the rationale, challenges, and benefits of performance weighted aggregations. It will help to inform decisions about the deployment of performance weighting and avoid common pitfalls in its application.

    更新日期:2020-01-23
  • Regional mapping of species‐level continuous foliar cover: beyond categorical vegetation mapping
    Ecol. Appl. (IF 4.378) Pub Date : 2020-01-23
    Timm W. Nawrocki; Matthew L. Carlson; Jeanne L.D. Osnas; E. Jamie Trammell; Frank D.W. Witmer

    The ability to quantify spatial patterns and detect change in terrestrial vegetation across large landscapes depends on linking ground‐based measurements of vegetation to remotely sensed data. Unlike non‐overlapping categorical vegetation types (i.e., typical vegetation and land cover maps), species‐level gradients of foliar cover are consistent with the ecological theories of individualistic response of species and niche space. We collected foliar cover data for vascular plant, bryophyte, and lichen species and 17 environmental variables in the Arctic Coastal Plain and Brooks Foothills of Alaska from 2012 to 2017. We integrated these data into a standardized database with 13 additional vegetation survey and monitoring datasets in northern Alaska collected from 1998 to 2017. To map the patterns of foliar cover for six dominant and widespread vascular plant species in arctic Alaska, we statistically associated ground‐based measurements of species distribution and abundance to environmental and multi‐season spectral covariates using a Bayesian statistical learning approach. For five of the six modeled species, our models predicted 36% to 65% of the observed species‐level variation in foliar cover. Overall, our continuous foliar cover maps predicted more of the observed spatial heterogeneity in species distribution and abundance than an existing categorical vegetation map. Mapping continuous foliar cover at the species level also revealed ecological patterns obscured by aggregation in existing plant functional type approaches. Species‐level analysis of vegetation patterns enables quantifying and monitoring landscape‐level changes in species, vegetation communities, and wildlife habitat independently of subjective categorical vegetation types and facilitates integrating spatial patterns across multiple ecological scales. The novel species‐level foliar cover mapping approach described here provides spatial information about the functional role of plant species in vegetation communities and wildlife habitat that are not available in categorical vegetation maps or quantitative maps of broadly defined vegetation aggregates.

    更新日期:2020-01-23
  • Effects of fixatives on stable isotopes of fish muscle tissue: implications for trophic studies on preserved specimens
    Ecol. Appl. (IF 4.378) Pub Date : 2020-01-23
    LM Durante; AJM Sabadel; RD Frew; T Ingram; SR Wing

    Isotopic ecology has been widely used to understand spatial connectivity and trophic interactions in marine systems. However, its potential for monitoring an ecosystems’ health and function has been hampered by the lack of consistent sample storage and long‐term studies. Preserved specimens from museum collections are a valuable source of tissue for analyses from ancient and pre‐modern times, but isotopic signatures are known to be affected by commonly used fixatives. The aim of the present study was to understand the effects of fixatives on isotopic signatures of bulk tissue (δ13Cm and δ15Nm) and amino acids (δ13CAA and δ15NAA) of fish muscle and to provide correction equations for the isotopic shifts. Two specimens of each: blue cod (Parapercis colias), blue warehou (Seriolella brama) and king salmon (Oncorhynchus tschawytscha) were sampled at five locations along their dorsal musculature, at four time periods: (1) fresh, (2) after one month preserved in formalin, (3) three and (4) twelve months fixed in either ethanol or isopropanol. Lipid content was positively correlated with C:N ratio (r2=0.83) and had a significant effect on δ13C after treatments, but not on δ15N. C:N ratio (for δ13Cm) and %N (for δ15Nm) from preserved specimens contributed to the most parsimonious mixed models, which explained 79 % of the variation due to fixation and preservation for δ13C and 81% for δ15N. δ13CAA were generally not affected by fixatives and preservatives, while most δ15NAA showed different signatures between treatments. δ15NAA variations did not affect the magnitude of differences between amino acids, allowing scientists to retrieve ecological information (e.g. trophic level) independently of time under preservation. Corrections were applied to the raw data of the experiment, highlighting the importance of δ13Cm and δ15Nm correction when fish muscle tissues from wet collections are compared to fresh samples. Our results make it possible to retrieve δ13Cm, δ15Nm, δ13CAA and δ15NAA from museum specimens and can be applied to some of the fundamental questions in ecology, such as trophic baseline shifts and changes in community’s food web structure through time.

    更新日期:2020-01-23
  • Horticultural availability and homeowner preferences drive plant diversity and composition in urban yards
    Ecol. Appl. (IF 4.378) Pub Date : 2020-01-23
    Jeannine Cavender‐Bares; Josep Padullés Cubino; William D. Pearse; Sarah E. Hobbie; A.J. Lange; Sonja Knapp; Kristen C. Nelson

    Understanding the factors that influence biodiversity in urban areas is important for informing management efforts aimed at enhancing the ecosystem services in urban settings and curbing the spread of invasive introduced species. We determined the ecological and socioeconomic factors that influence patterns of plant richness, phylogenetic diversity and composition in 133 private household yards in the Minneapolis‐Saint Paul Metropolitan area, Minnesota, USA. We compared the composition of spontaneously occurring plant species and those planted by homeowners with composition in natural areas (at the Cedar Creek Ecosystem Science Reserve) and in the horticulture pool of species available from commercial growers. Yard area and fertilizer frequency influenced species richness of the spontaneous species but expressed homeowner values did not. In contrast, the criteria that homeowners articulated as important in their management decisions—including aesthetics, wildlife, neatness and food provision—significantly predicted cultivated species richness. Strikingly, the composition of plant species that people cultivated in their yards resembled the taxonomic and phylogenetic composition of species available commercially. In contrast, the taxonomic and phylogenetic composition of spontaneous species showed high similarity to natural areas. The large fraction of introduced species that homeowners planted was a likely consequence of what was available for them to purchase. The study links the composition and diversity of yard flora to their natural and anthropogenic sources and sheds light on the human factors and values that influence the plant diversity in residential areas of a major urban system. Enhanced understanding of the influences of the sources of plants—both native and introduced—that enter urban systems and the human factors and values that influence their diversity is critical to identifying the levers to manage urban biodiversity and ecosystem services.

    更新日期:2020-01-23
  • Bee communities and pollination services in adjacent crop fields following flower removal in an invasive forest shrub
    Ecol. Appl. (IF 4.378) Pub Date : 2020-01-23
    Michael J Cunningham‐Minnick; Valerie E Peters; Thomas O Crist

    The habitat boundaries between crops and semi‐natural areas influence bee movements and pollination services to crops. Edges also provide favorable conditions for invasive plants, which may usurp pollinators and reduce visitation to native or crop plants. Alternatively, floral displays of alien plants may facilitate, or increase, the pollination success of adjacent plants by attracting more pollinators to the area. Therefore, pollination services of bees from semi‐natural habitats to crop areas should vary with the presence of invasive floral resources and distance from habitat edges. To test the hypothesis that floral resources of invasive forest shrubs affect the bee community and pollination services in adjacent crop fields, we conducted a two‐year field experiment along forest‐crop edges at five isolated forest remnants. We removed flower buds from a dominant invasive shrub, Lonicera maackii (Amur honeysuckle), along forest‐crop edges and paired removals with controls of intact flowers. The bee community, their pollination services, and flower visitation rates were quantified along a 200 m gradient into an adjacent crop field using pan traps and sentinel cucumber plants. Impacts to the bee community were dependent of bee functional traits. Larger bees visited fewer sentinel cucumber flowers in flower removal plots, which corresponded with decreased cucumber pollination compared to plots with honeysuckle flowers at distances >100 m from forest edges. Small‐bodied and weaker flying bees visited sentinel plants more frequently closer to the forest edge and increased pollination services to cucumber at distances <100 m from L. maackii shrubs in flower removal plots. After two years, bee abundance and species richness increased within flower removal plots across all distances. High functional diversity of the bee community increased pollination services to sentinel plants and increased cucumber production within 200 m from forest remnants. Our findings suggest that dense floral resources of invasive shrubs suppressed forest‐edge bee communities and their pollination services, but also attracted large‐bodied generalist bees which were effective pollinators. This study helps explain how life histories and functional attributes of bees can predict either facilitation or suppression of pollination services to crop or native plants in response to invasive floral resources.

    更新日期:2020-01-23
  • Hydropeaking affects germination and establishment of riverbank vegetation
    Ecol. Appl. (IF 4.378) Pub Date : 2020-01-23
    María D. Bejarano; Álvaro Sordo‐Ward; Carlos Alonso; Roland Jansson; Christer Nilsson

    Hydropeaking, defined as frequent and rapid variation in flow in regulated rivers with hydropower plants over a short period of time, usually sub‐daily to weekly, alters hydraulic parameters such as water levels or flow velocity and exerts strong impacts on fluvial ecosystems. We evaluated the effects of hydropeaking on riverbank vegetation, specifically assessing the germination and establishment of seedlings and cuttings of plant species representing a variation in traits. We used seeds and seedlings and cuttings varying in size as phytometers, and transplanted them to riverbanks both above and below dams used for hydropower production in northern Sweden, selected to represent a gradient in hydropeaking intensity, and along a free‐flowing reach. We also analyzed sub‐daily water level variables modified by hydropeaking to identify variables key in explaining the observed vegetation patterns. We found that plant responses to hydropeaking varied with species, with flood‐intolerant species being the most strongly affected, as early as the germination stage. In contrast, seeds of flood‐tolerant species managed to germinate and survive the early establishment phase, although strong erosive processes triggered by hydropeaking eventually caused most of them to fail. The fate of flood‐intolerant species identifies germination as the most critical life‐history stage. The depth and frequency of the inundation were the leading variables explaining plant responses, while the duration of shallow inundation explained little of the variation. The rise and fall rates of water levels were key explaining variation in germination success. Based on the results, we propose restoration measures to enhance establishment of riparian plant communities while minimizing the impact on hydropower electricity production. Given the strong decrease in the germination of species intolerant to prolonged flooding with hydropeaking, planting of seedlings, preferably of large sizes, together with restrictions in the operation of the power plant during the establishment phase to enhance survival would be the best restoration option. Given the high probability of plant uprooting with hydropeaking, bank protection measures have the potential to increase riparian‐plant survival of all species, including flooding tolerant ones.

    更新日期:2020-01-23
  • Plant diversity effect on water quality in wetlands: a meta‐analysis based on experimental systems
    Ecol. Appl. (IF 4.378) Pub Date : 2020-01-22
    Jacques Brisson; Mariana Rodriguez; Charles A. Martin; Raphaël Proulx

    The ecological literature reports little empirical evidence from biodiversity – ecosystem functioning (BEF) experiments in wetland systems, even though wetlands are widely known for their water filtering capacity. Experiments comparing the effect of plant monocultures and mixtures on water quality to improve pollutant removal efficiency in treatment wetlands share the characteristics of classical BEF experiments, and so could provide insights for wetland management. To add to our understanding of BEF relationships in wetlands, we evaluated plant diversity effects on water purification through a meta‐analysis of freshwater experimental wetlands comparing monocultures to mixtures. We found 28 studies that matched our criteria for BEF analysis, for a total of 561 diversity effects on pollutant removal. Overall, the meta‐analysis shows no significant effect of plant richness on removal of total suspended solids, but a positive effect on chemical oxygen demand and total nitrogen removal, and a marginal effect on phosphorus removal. Thus, the results of this meta‐analysis are consistent with reports of an overall positive biodiversity effect on ecosystem properties. An analysis of moderator variables shows that the experimental context (size of the experimental units, nutrient load, duration of the experiment) does not explain much of the residual variance. For pollutants that benefit from a positive plant richness effects on removal, mixtures do not perform better than the best monoculture. We found no evidence that plant richness effects are due to functional complementarity among species rather than to the presence of particularly efficient species. Complementarity effects may be less prevalent in highly productive, nutrient‐rich wetlands, compared to nutrient‐limited environments such as natural grasslands. Although findings must be confirmed by long‐term field experiments under natural conditions, result from experimental wetland systems may contribute to a better understanding of biodiversity effect on ecosystem functions in wetlands, in addition to guide practices in natural wetland restoration and the use of constructed wetlands for water treatment.

    更新日期:2020-01-23
  • Direct evidence using a controlled greenhouse study for threshold effects of soil organic matter on crop growth
    Ecol. Appl. (IF 4.378) Pub Date : 2020-01-21
    Emily E. Oldfield; Stephen A. Wood; Mark A. Bradford

    Soil organic matter (SOM) is a key indicator of soil fertility, and building SOM is assumed to decrease reliance on external inputs and ensure stable crop production. Recent syntheses of field data support this assumption with positive SOM‐productivity relationships that asymptote at ~ 4% SOM. Teasing out the directionality of this relationship – the extent to which SOM increases crop growth versus greater growth leading to higher SOM concentrations – requires controlled experimentation. To disentangle this causative pathway, we conducted a greenhouse experiment whereby we manipulated SOM concentrations from 1 to 9% and evaluated whether the SOM‐productivity relationship differed for spring wheat (Triticum aestivum, L.) under nitrogen fertilization crossed with irrigation due to the expectation that SOM buffers the effects of reduced fertilization and/or irrigation. We found that higher concentrations of SOM led to greater productivity (measured as aboveground biomass) up to a threshold of 5% SOM, after which productivity declined across all treatments. These declines occurred despite the fact that indicators of soil health (water holding capacity, microbial biomass, and bulk density) improved linearly with increasing SOM concentrations. That is, improvements in soil properties did not translate to gains in productivity at the highest SOM levels. Nitrogen fertilization led to greater productivity across all treatments, but to a greater relative extent at lower SOM levels, where we found that productivity on unfertilized soils with 4% SOM matched that of fertilized soils with 2% SOM. Differences in productivity on unfertilized soils due to irrigation emerged at higher SOM levels (>5%), highlighting SOM’s role in water retention. Our results demonstrate that building SOM leads to improved growth of a globally important crop; however, our results also indicated a pronounced SOM threshold, after which crop growth declined. This underscores the need to develop optimal SOM targets for desired agricultural and environmental outcomes.

    更新日期:2020-01-23
  • Not all urban landscapes are the same: interactions between urban land use and stress in a large herbivorous mammal
    Ecol. Appl. (IF 4.378) Pub Date : 2020-01-21
    Elizabeth A. Brunton; Christofer J. Clemente; Scott E. Burnett

    Urbanization significantly impacts the health and viability of wildlife populations yet it is not well understood how urban landscapes differ from non‐urban landscapes with regard to their effects on wildlife. This study investigated the physiological response of eastern grey kangaroos (Macropus giganteus) to land use at a landscape scale. Using fecal glucocorticoid metabolites (FGM) we compared stress levels of kangaroo populations in urban and non‐urban environments. We modeled FGM concentrations from 24 kangaroo populations against land use (urban or non‐urban) and other anthropogenic and environmental factors, using a linear modeling approach. We found that land use was a significant predictor of FGM concentrations in eastern grey kangaroos with significant differences in concentrations between urban and non‐urban populations. However, the direction of the relationship differed between northern and southern regions of Australia. In the northern study sites, kangaroos in urban areas had significantly higher FGM levels than their non‐urban counterparts. In contrast, in southern sites, where kangaroos occur in high densities in many urban areas, urban kangaroos had lower FGM concentrations than non‐urban kangaroos. Rainfall and temperature were also significant predictors of FGM and the direction of the relationship was consistent across both regions. These results are consistent with the contrasting abundance and persistence of kangaroo populations within the urban matrix between the two study regions. In the northern region many populations have declined over the last two decades and are fragmented, also occurring at lower densities than in southern sites. Our study indicates that it is the characteristics of urban environments, rather than the urban environment per se, which determines the extent of impacts of urbanization on kangaroos. This research provides insights into how the design of urban landscapes can influence large mammal populations.

    更新日期:2020-01-22
  • Oceanographic drivers of winter habitat use in Cassin’s Auklets
    Ecol. Appl. (IF 4.378) Pub Date : 2020-01-21
    Michael E. Johns; Pete Warzybok; Jaime Jahncke; Mark Lindberg; Greg A. Breed

    Reduced prey abundance and severe weather can lead to a greater risk of mortality for seabirds during the non‐breeding winter months. Resource patterns in some regions are shifting and becoming more variable in relation to past conditions, potentially further impacting survival and carryover to the breeding season. As animal tracking technologies and methods to analyze movement data have advanced, it has become increasingly feasible to draw fine‐scale inference about how environmental variation affects foraging behavior and habitat use of seabirds during this critical period. Here, we used archival light‐sensing tags to evaluate how interannual variation in oceanography affected the winter distribution of Cassin's Auklets from Southeast Farallon Island, California. Thirty‐five out of 93 geolocators deployed from 2015 to 2017 were recovered and successfully recorded light‐level data, from which geographic positions were estimated. Step‐selection functions were applied to identify environmental covariates that best explained winter movement decisions and habitat use, revealing Cassin's Auklets dispersed farther from the colony during a winter with warm SST anomalies, but remained more centralized near the breeding colony during two average winters. Movement patterns were driven by avoidance of areas with higher sea surface temperatures and possible limits of dispersal from the breeding colony, and selection for areas with well‐defined mesoscale fronts and cooler surface waters. Through multiple years of tagging and the application of step‐selection functions, a robust and widely applied approach for analyzing animal movement in terrestrial species, we show how interannual differences in the movement patterns of a small seabird are driven by oceanographic variability across years. Understanding the winter habitat use of seabirds can help inform changes in population structure and measures of reproductive success, aiding managers in determining potential causes of breeding failures.

    更新日期:2020-01-22
  • Managing salmon for wildlife: Do fisheries limit salmon consumption by bears in small Alaskan streams?
    Ecol. Appl. (IF 4.378) Pub Date : 2020-01-21
    Alexandra E. Lincoln; Ray Hilborn; Aaron J. Wirsing; Thomas P. Quinn

    Ecosystem‐based management requires consideration of overlapping resource use between humans and other consumers. Pacific salmon are an important resource for both fisheries and populations of wildlife around the Pacific rim, including coastal brown bears (Ursus arctos); salmon consumption has been positively linked to bear density, body size, and reproductive rate. As a case study within the broader context of human–wildlife competition for food, we used 16–22 yr of empirical data in four different salmon‐bearing systems in southwestern Alaska to explore the relationship between sockeye salmon (Oncorhynchus nerka) availability and consumption by bears. We found a negative relationship between the annual biomass of salmon available to bears and the fraction of biomass consumed per fish, and a saturating relationship between salmon availability and the total annual biomass of salmon consumed by bears. Under modeled scenarios, bear consumption of salmon was predicted to increase only with dramatic (on the order of 50–100%) increases in prey availability. Even such large increases in salmon abundance were estimated to produce relatively modest increases in per capita salmon consumption by bears (2.4–4.8 kg·bear−1·d−1, 15–59% of the estimated daily maximum per capita intake), in part because bears did not consume salmon entirely, especially when salmon were most available. Thus, while bears catching salmon in small streams may be limited by salmon harvest in some years, current management of the systems we studied is sufficient for bear populations to reach maximum salmon consumption every 2–4 yr. Consequently, allocating more salmon for brown bear conservation would unlikely result in an ecologically significant response for bears in these systems, though other ecosystem components might benefit. Our results highlight the need for documenting empirical relationships between prey abundance and consumption, particularly in systems with partial consumption, when evaluating the ecological response of managing prey resources for wildlife populations.

    更新日期:2020-01-22
  • Snagfall the first decade after severe bark beetle infestation of high‐elevation forests in Colorado, USA
    Ecol. Appl. (IF 4.378) Pub Date : 2020-01-21
    Charles C. Rhoades; Robert M. Hubbard; Paul R. Hood; Banning J. Starr; Daniel B. Tinker; Kelly Elder

    The persistence and fall rate of snags (standing dead trees) generated during bark beetle outbreaks have consequences for the behavior, effects, and suppression of potential wildfires, hazard tree and timber salvage operations, wildlife habitat, and numerous ecosystem processes. However, post‐beetle snagfall dynamics are poorly understood in most forest types. We tagged standing live and dead lodgepole pine (Pinus contorta), subalpine fir (Abies lasiocarpa), and Engelmann spruce (Picea engelmannii), including beetle‐killed pine snags following the peak of a recent mountain pine bark beetle outbreak in watersheds at the Fraser Experimental Forest in northcentral Colorado and sampled snagfall 10 and 12 years later. Bark beetle attacks began in 2003, peaked by 2006, and killed 78% of overstory lodgepole pine in 133 plots distributed across a range of stand and site conditions. Of those snags, only 17% fell between 2007 and 2018. Most snags broke at ground level, due to butt rot, and were oriented downhill. In contrast, snags that tipped up or snapped off above the ground were oriented with the prevailing winds. Equal numbers of snags fell singly and in multiple‐tree groups, and equal numbers remained elevated rather than in contact with the ground. Lodgepole pine snagfall was 1.6‐times higher on steep slopes (>40%) where dead pine density was higher, compared to flatter sites. Based on our findings and previous research, we estimate that one‐half the beetle‐killed lodgepole pine in high‐elevation forests such as those at Fraser may fall within 15–20 yr of beetle infestation, but that some pine snags are likely to persist for decades longer. Post‐outbreak snagfall dynamics create a multiple‐decade legacy of bark beetle outbreaks that will persist longer in high‐elevation compared to lower‐elevation forests.

    更新日期:2020-01-22
  • Comparing abundance distributions and range maps in spatial conservation planning for migratory species
    Ecol. Appl. (IF 4.378) Pub Date : 2020-01-14
    A. Johnston; T. Auer; D. Fink; M. Strimas‐Mackey; M. Iliff; K. V. Rosenberg; S. Brown; R. Lanctot; A. D. Rodewald; S. Kelling

    Most spatial conservation planning for wide‐ranging or migratory species is constrained by poor knowledge of species’ spatiotemporal dynamics and is only based on static species’ ranges. However, species have substantial variation in abundance across their range and migratory species have important spatiotemporal population dynamics. With growing ecological data and advancing analytics, both of these can be estimated and incorporated into spatial conservation planning. However, there is limited information on the degree to which including this information affects conservation planning. We compared the performance of systematic conservation prioritizations for different scenarios based on varying the input species’ distributions by ecological metric (abundance distributions versus range maps) and temporal sampling resolution (weekly, monthly, or quarterly). We used the example of a community of 41 species of migratory shorebirds that breed in North America, and we used eBird data to produce weekly estimates of species’ abundances and ranges. Abundance distributions at a monthly or weekly resolution led to prioritizations that most efficiently protected species throughout the full annual cycle. Conversely, spatial prioritizations based on species’ ranges required more sites and left most species insufficiently protected for at least part of their annual cycle. Prioritizations with only quarterly species ranges were very inefficient as they needed to target 40% of species’ ranges to include 10% of populations. We highlight the high value of abundance information for spatial conservation planning, which leads to more efficient and effective spatial prioritization for conservation. Overall, we provide evidence that spatial conservation planning for wide‐ranging migratory species is most robust and efficient when informed by species’ abundance information from the full annual cycle.

    更新日期:2020-01-14
  • Spatial variation in exploited metapopulations obscures risk of collapse
    Ecol. Appl. (IF 4.378) Pub Date : 2020-01-13
    Daniel K. Okamoto; Margot Hessing‐Lewis; Jameal F. Samhouri; Andrew O. Shelton; Adrian Stier; Philip S. Levin; Anne K. Salomon

    Unanticipated declines among exploited species have commonly occurred despite harvests that appeared sustainable prior to collapse. This is particularly true in the oceans where spatial scales of management are often mismatched with spatially complex metapopulations. We explore causes, consequences, and potential solutions for spatial mismatches in harvested metapopulations in three ways. First, we generate novel theory illustrating when and how harvesting metapopulations increases spatial variability and in turn masks local‐scale volatility. Second, we illustrate why spatial variability in harvested metapopulations leads to negative consequences using an empirical example of a Pacific herring metapopulation. Finally, we construct a numerical management strategy evaluation model to identify and highlight potential solutions for mismatches in spatial scale and spatial variability. Our results highlight that spatial complexity can promote stability at large scales, however, ignoring spatial complexity produces cryptic and negative consequences for people and animals that interact with resources at small scales. Harvesting metapopulations magnifies spatial variability, which creates discrepancies between regional and local trends while increasing risk of local population collapses. Such effects asymmetrically impact locally constrained fishers and predators, which are more exposed to risks of localized collapses. Importantly, we show that dynamically optimizing harvest can minimize local risk without sacrificing yield. Thus, multiple nested scales of management may be necessary to avoid cryptic collapses in metapopulations and the ensuing ecological, social, and economic consequences.

    更新日期:2020-01-14
  • Drought exacerbates negative consequences of high-intensity cattle grazing in a semiarid grassland.
    Ecol. Appl. (IF 4.378) Pub Date : 2019-11-24
    Sara Souther,Matthew Loeser,Timothy E Crews,Thomas Sisk

    Grasslands managed for grazing are the largest land-use category globally, with a significant proportion of these grasslands occurring in semiarid and arid regions. In such dryland systems, the effect of grazing on native plant diversity has been equivocal, some studies suggesting that grazing reduces native plant diversity, others that grazing increases or has little impact on diversity. One impediment towards generalizing grazing effects on diversity in this region is that high levels of inter-annual variation in precipitation may obfuscate vegetative response patterns. By analyzing a long-term dataset collected over a 20-year period in a semiarid grassland, we explicitly evaluated the role of climate in regulating the effect of cattle grazing on plant communities, finding that climate interacted with grazing intensity to shape grassland communities. Community composition of plots that were intensively grazed varied considerably in response to climatic variation and native species richness was low relative to ungrazed and moderately grazed plots. Following a severe drought in 2002, exotic species richness rapidly increased in the high-intensity grazing plots. While this pattern was mirrored in the other treatments, exotic species richness increased to a greater extent and was slower to return to pre-drought levels in the high intensity grazing plots. Overall, moderate grazing, even compared to grazing cessation, stabilized grassland communities through time, increased resilience to drought, and maintained the highest levels of native plant diversity and lowest levels of exotic diversity. These findings suggest that grazing, at moderate levels, may support grassland resilience to climate change in semiarid regions. However, grazing that exceeds tolerances, particularly in combination with extreme climatic events, like drought, can alter plant composition over relatively long timescales and possibly increase invasibility by non-native species.

    更新日期:2020-01-14
  • Bioturbation by a reintroduced digging mammal reduces fuel loads in an urban reserve.
    Ecol. Appl. (IF 4.378) Pub Date : 2019-10-10
    C M Ryan,R J Hobbs,L E Valentine

    Digging animals may alter many characteristics of their environment as they disrupt and modify the ground's surface by creating foraging pits or burrows. Extensive disturbance to the soil and litter layer changes litter distribution and availability, potentially altering fuel loads. In many landscapes, including peri-urban areas, fire management to reduce fuel loads is complex and challenging. The reintroduction of previously common digging animals, many of which are now threatened, may have the added benefit of reducing fuel loads. We experimentally examined how the reintroduction of a marsupial bandicoot, quenda (Isoodon fusciventer), altered surface fuel loads in an urban bush reserve in Perth, Western Australia. Foraging activities of quenda (where they dig for subterranean food) were substantial throughout the reserve, creating a visibly patchy distribution in surface litter. Further, in open plots where quenda had access, compared to fenced plots where quenda were excluded, quenda foraging significantly reduced litter cover and litter depth. Similarly, estimated surface fuel loads were nearly halved in open plots where quenda foraged compared to fenced plots where quenda were absent (3.6 c.f. 6.4 tonnes ha-1 ). Fire behaviour modelling, using the estimated surface fuel loads, indicated the predicted rate of spread of fire were significantly lower for open plots where quenda foraged compared to fenced plots under both low (29.2 c.f. 51.4 m hr-1 ; total fuels) and high (74.3 c.f. 130.4 m hr-1 ; total fuels) fire conditions. Although many environments require fire, including the bushland where this study occurred, fire management can be a considerable challenge in many landscapes, including urban bushland reserves which are usually small and close to human infrastructure. The reintroduction of previously common digging species may have potential value as a complimentary tool for reducing fuel loads, and potentially, fire risk.

    更新日期:2020-01-14
  • Artificial light at night, in interaction with spring temperature, modulates timing of reproduction in a passerine bird
    Ecol. Appl. (IF 4.378) Pub Date : 2020-01-13
    Davide M. Dominoni; Johan Kjellberg Jensen; Maaike de Jong; Marcel E. Visser; Kamiel Spoelstra

    The ecological impact of artificial light at night (ALAN) on phenological events such as reproductive timing is increasingly recognized. In birds, previous experiments under controlled conditions showed that ALAN strongly advances gonadal growth, but effects on egg‐laying date are less clear. In particular, effects of ALAN on timing of egg laying are found to be year‐dependent, suggesting an interaction with climatic conditions such as spring temperature, which is known have strong effects on the phenology of avian breeding. Thus, we hypothesized that ALAN and temperature interact to regulate timing of reproduction in wild birds. Field studies have suggested that sources of ALAN rich in short wavelengths can lead to stronger advances in egg‐laying date. We therefore tested this hypothesis in the Great Tit (Parus major), using a replicated experimental set‐up where eight previously unlit forest transects were illuminated with either white, green, or red LED light, or left dark as controls. We measured timing of egg laying for 619 breeding events spread over six consecutive years and obtained temperature data for all sites and years. We detected overall significantly earlier egg‐laying dates in the white and green light vs. the dark treatment, and similar trends for red light. However, there was a strong interannual variability in mean egg‐laying dates in all treatments, which was explained by spring temperature. We did not detect any fitness consequence of the changed timing of egg laying due to ALAN, which suggests that advancing reproduction in response to ALAN might be adaptive.

    更新日期:2020-01-14
  • Unfolding the effects of different forestry treatments on microclimate in oak forests: results of a 4-year experiment.
    Ecol. Appl. (IF 4.378) Pub Date : null
    Bence Kovács,Flóra Tinya,Csaba Németh,Péter Ódor

    Stable below-canopy microclimate of forests is essential for their biodiversity and ecosystem functionality. Forest management necessarily modifies the buffering capacity of woodlands. However, the specific effects of different forestry treatments on site conditions, the temporal recovery after the harvests and the reason of the contrasts between treatments are still poorly understood. The effects of four different forestry treatments (clear-cutting, retention tree group, preparation cutting and gap-cutting) on microclimatic variables were studied within a field experiment in a managed oak dominated stand in Hungary, before (2014) and after (2015-2017) the interventions by complete block design with six replicates. From the first post-treatment year, clear-cuts differed the most from the uncut control due to the increased irradiance and heat load. Means and variability of air and soil temperature increased, air became dryer along with higher soil moisture levels. Retention tree groups could effectively ameliorate the extreme temperatures but not the mean values. Preparation cutting induced slight changes from the original buffered and humid forest microclimate. Despite the substantially more incoming light, gap-cutting could keep the cool and humid air conditions and showed the highest increase in soil moisture after the interventions. For most microclimate variables, we could not observe any obvious trend within three years. Though soil temperature variability decreased with time in clear-cuts, while soil moisture difference continuously increased in gap- and clear-cuts. Based on multivariate analyses, the treatments separated significantly based mainly on the temperature maxima and variability. We found that (i) the effect sizes among treatment levels were consistent throughout the years; (ii) the climatic recovery time for variables appears to be far more than three years and (iii) the applied silvicultural methods diverged mainly among the temperature maxima. Based on our study, the spatially heterogeneous and fine-scaled treatments of continuous cover forestry (gap-cutting, selection systems) are recommended. By applying these practices, the essential structural elements creating buffered microclimate could be more successfully maintained. Thus, forestry interventions could induce less pronounced alterations in environmental conditions for forest-dwelling organism groups.

    更新日期:2020-01-14
  • Interrelated ecological impacts of climate change on an apex predator
    Ecol. Appl. (IF 4.378) Pub Date : 2020-01-10
    Kristin L. Laidre; Stephen Atkinson; Eric V. Regehr; Harry L. Stern; Erik W. Born; Øystein Wiig; Nicholas J. Lunn; Markus Dyck

    Climate change has broad ecological implications for species that rely on sensitive habitats. For some top predators, loss of habitat is expected to lead to cascading behavioral, nutritional, and reproductive changes that ultimately accelerate population declines. In the case of the polar bear (Ursus maritimus), declining Arctic sea ice reduces access to prey and lengthens seasonal fasting periods. We used a novel combination of physical‐capture, biopsy darting, and visual aerial observation data to project reproductive performance for polar bears by linking sea‐ice loss to changes in habitat use, body condition (i.e., fatness), and cub production. Satellite telemetry data from 43 (1991‐1997) and 38 (2009‐2015) adult female polar bears in the Baffin Bay subpopulation showed that bears now spend an additional 30 days on land (90 days total in the 2000s compared to the 1990s), a change closely correlated with changes in spring sea‐ice breakup and fall sea‐ice formation. Body condition declined for all sex, age, and reproductive classes and was positively correlated with sea‐ice availability in the current and previous year. Furthermore, cub litter size was positively correlated with maternal condition and spring breakup date (i.e., later breakup leading to larger litters), and negatively correlated with the duration of the ice‐free period (i.e., longer ice‐free periods leading to smaller litters). Based on these relationships we projected reproductive performance three polar bear generations into the future (approximately 35 years). Results indicate that two‐cub litters, previously the norm, could largely disappear from Baffin Bay as sea‐ice loss continues. Our findings demonstrate how concurrent analysis of multiple data types collected over long periods from polar bears can provide a mechanistic understanding of the ecological implications of climate change. This information is needed for long‐term conservation planning, which includes quantitative harvest risk assessments that incorporate estimated or assumed trends in future environmental carrying capacity.

    更新日期:2020-01-13
  • High‐severity wildfire leads to multi‐decadal impacts on soil biogeochemistry in mixed‐conifer forests
    Ecol. Appl. (IF 4.378) Pub Date : 2020-01-10
    Nicholas C. Dove; Hugh D. Safford; Gabrielle N. Bohlman; Becky L. Estes; Stephen C. Hart

    During the past century, systematic wildfire suppression has decreased fire frequency and increased fire severity in the western United States of America. While this has resulted in large ecological changes aboveground such as altered tree species composition and increased forest density, little is known about the long‐term, belowground implications of altered, ecologically novel fire regimes, especially on soil biological processes. To better understand the long‐term implications of ecologically novel, high‐severity fire, we used a 44‐y high‐severity fire chronosequence in the Sierra Nevada where forests were historically adapted to frequent, low‐severity fire, but were fire suppressed for at least 70 years. High‐severity fire in the Sierra Nevada resulted in a long‐term (44 + y) decrease (>50%, p < 0.05) in soil extracellular enzyme activities, basal microbial respiration (56‐72%, p < 0.05), and organic carbon (>50%, p < 0.05) in the upper 5 cm compared to sites that had not been burned for at least 115 y. However, nitrogen (N) processes were only affected in the most‐recent fire site (4 y post‐fire). Net nitrification increased by over 600% in the most recent fire site (p < 0.001), but returned to similar levels as the unburned control in the 13‐y site. Contrary to previous studies, we did not find a consistent effect of plant cover type on soil biogeochemical processes in mid‐successional (10‐50 y) forest soils. Rather, the 44‐y reduction in soil organic carbon (C) quantity correlated positively with dampened C cycling processes. Our results show the drastic and long‐term implication of ecologically novel, high‐severity fire on soil biogeochemistry and underscore the need for long‐term fire ecological experiments.

    更新日期:2020-01-13
  • Aligning biodiversity conservation and agricultural production in heterogeneous landscapes
    Ecol. Appl. (IF 4.378) Pub Date : 2020-01-10
    Van Butsic; Tobias Kuemmerle; Leo Pallud; Kate J. Helmstedt; Leandro Macchi; Matthew D. Potts

    Understanding the trade‐offs between biodiversity conservation and agricultural production has become a fundamental question in sustainability science. Substantial research has focused on how species’ populations respond to agricultural intensification, with the goal to understand whether conservation policies that spatially separate agriculture and conservation or, alternatively, integrate the two are more beneficial. Spatial heterogeneity in both species abundance and agricultural productivity have been largely left out of this discussion, although these patterns are ubiquitous from local to global scales due to varying land capacity. Here, we address the question of how to align agricultural production and biodiversity conservation in heterogeneous landscapes. Using model simulations of species abundance and agricultural yields, we show that trade‐offs between agricultural production and species’ abundance can be reduced by minimizing the cost (in terms of species abundance) of agricultural production. We find that when species’ abundance and agricultural yields vary across landscapes, the optimal strategy to minimize trade‐offs is rarely pure land sparing or land sharing. Instead, landscapes that combine elements of both strategies are optimal. Additionally, we show how the reference population of a species is defined has important influences on optimization results. Our findings suggest that in the real world, understanding the impact of heterogeneous land capacity on biodiversity and agricultural production is crucial to designing multi‐use landscapes that jointly maximize conservation and agricultural benefits.

    更新日期:2020-01-11
  • Inorganic N addition replaces N supplied to switchgrass (Panicum virgatum) by arbuscular mycorrhizal fungi.
    Ecol. Appl. (IF 4.378) Pub Date : null
    Laura C Jach-Smith,Randall D Jackson

    Arbuscular mycorrhizal fungi (AMF) provide many benefits in agroecosystems including improved soil tilth, carbon sequestration, and water and nutrient transfer to plants. AMF are known to affect plant nitrogen (N) dynamics and transfer N to plants, but there have been few studies addressing whether the amount of N transferred to plants by AMF is agronomically relevant. We used δ15 N natural abundance methods and δ15 N mass balance equations to estimate the amount of plant N derived from AMF transfer in perennial grasses managed for bioenergy production under different N addition treatments (0, 56 and 196 kg N ha-1 ). Differentiation of δ15 N among plant, soil N, and AMF pools was higher than anticipated leading to calculations of 34 to 55% of plant N transferred by AMF in the treatments receiving no N addition to 6 to 22% of plant N transferred to plants in high-N addition treatments. AMF extra-radical hyphae biomass was significantly reduced in the high-N (196 kg N ha-1 ) addition treatments, which was negatively correlated to enriched plant δ15 N. Our results suggest that N addition decreases AMF N transfer to plants. When N was limiting to plant growth, AMF supplied agronomically significant amounts of plant N, and a higher proportion of overall plant N. Because differentiation between N pools was greater than expected, stable isotope measurements can be used to estimate N transfer to AMF plant hosts.

    更新日期:2020-01-11
  • Large‐scale and local climatic controls on large herbivore productivity: implications for adaptive rangeland management
    Ecol. Appl. (IF 4.378) Pub Date : 2020-01-10
    Edward J. Raynor; Justin D. Derner; David L. Hoover; William J. Parton; David J. Augustine

    Rangeland ecosystems worldwide are characterized by a high degree of uncertainty in precipitation, both within and across years. Such uncertainty creates challenges for livestock managers seeking to match herbivore numbers with forage availability to prevent vegetation degradation and optimize livestock production. Here, we assess variation in annual large herbivore production (LHP, kg/ha) across multiple herbivore densities over a 78‐yr period (1940–2018) in a semiarid rangeland ecosystem (shortgrass steppe of eastern Colorado, USA) that has experienced several phase changes in global‐level sea surface temperature (SST) anomalies, as measured by the Pacific Decadal Oscillation (PDO) and the El Niño–Southern Oscillation (ENSO). We examined the influence of prevailing PDO phase, magnitude of late winter (February–April) ENSO, prior growing‐season precipitation (prior April to prior September) and precipitation during the six months (prior October to current April) preceding the growing season on LHP. All of these are known prior to the start of the growing season in the shortgrass steppe and could potentially be used by livestock managers to adjust herbivore densities. Annual LHP was greater during warm PDO irrespective of herbivore density, while variance in LHP increased by 69% (moderate density) and 91% (high density) under cold‐phase compared to warm‐phase PDO. No differences in LHP attributed to PDO phase were observed with low herbivore density. ENSO effects on LHP, specifically La Niña, were more pronounced during cold‐phase PDO years. High herbivore density increased LHP at a greater rate than at moderate and low densities with increasing fall and winter precipitation. Differential gain, a weighted measure of LHP under higher relative to lower herbivore densities, was sensitive to prevailing PDO phase, ENSO magnitude, and precipitation amounts from the prior growing season and current fall–winter season. Temporal hierarchical approaches using PDO, ENSO, and local‐scale precipitation can enhance decision‐making for flexible herbivore densities. Herbivore densities could be increased above recommended levels with lowered risk of negative returns for managers during warm‐phase PDO to result in greater LHP and less variability. Conversely, during cold‐phase PDO, managers should be cognizant of the additional influences of ENSO and prior fall–winter precipitation, which can help predict when to reduce herbivore densities and minimize risk of forage shortages.

    更新日期:2020-01-11
  • Modeling avian full annual cycle distribution and population trends with citizen science data
    Ecol. Appl. (IF 4.378) Pub Date : 2020-01-08
    Daniel Fink; Tom Auer; Alison Johnston; Viviana Ruiz‐Gutierrez; Wesley M. Hochachka; Steve Kelling

    Information on species’ distributions, abundances, and how they change over time is central to the study of the ecology and conservation of animal populations. This information is challenging to obtain at landscape scales across range‐wide extents for two main reasons. First, landscape‐scale processes that affect populations vary throughout the year and across species’ ranges, requiring high‐resolution, year‐round data across broad, sometimes hemispheric, spatial extents. Second, while citizen science projects can collect data at these resolutions and extents, using these data requires appropriate analysis to address known sources of bias. Here, we present an analytical framework to address these challenges and generate year‐round, range‐wide distributional information using citizen science data. To illustrate this approach, we apply the framework to Wood Thrush (Hylocichla mustelina), a long‐distance Neotropical migrant and species of conservation concern, using data from the citizen science project eBird. We estimate occurrence and abundance across a range of spatial scales throughout the annual cycle. Additionally, we generate intra‐annual estimates of the range, intra‐annual estimates of the associations between species and characteristics of the landscape, and interannual trends in abundance for breeding and non‐breeding seasons. The range‐wide population trajectories for Wood Thrush show a close correspondence between breeding and non‐breeding seasons with steep declines between 2010 and 2013 followed by shallower rates of decline from 2013 to 2016. The breeding season range‐wide population trajectory based on the independently collected and analyzed North American Breeding Bird Survey data also shows this pattern. The information provided here fills important knowledge gaps for Wood Thrush, especially during the less studied migration and non‐breeding periods. More generally, the modeling framework presented here can be used to accurately capture landscape scale intra‐ and interannual distributional dynamics for broadly distributed, highly mobile species.

    更新日期:2020-01-08
  • Land-sharing vs. land-sparing urban development modulate predator-prey interactions in Europe.
    Ecol. Appl. (IF 4.378) Pub Date : null
    Jukka Jokimäki,Jukka Suhonen,Yanina Benedetti,Mario Diaz,Marja-Liisa Kaisanlahti-Jokimäki,Federico Morelli,Tomás Pérez-Contreras,Enrique Rubio,Philipp Sprau,Piotr Tryjanowski,Juan Diego Ibánez-Álamo

    Urban areas are expanding globally as a consequence of human population increases, with overall negative effects on biodiversity. To prevent the further loss of biodiversity, it is urgent to understand the mechanisms behind this loss to develop evidence-based sustainable solutions to preserve biodiversity in urban landscapes. The two extreme urban development types along a continuum, land-sparing (large, continuous green areas and high-density housing) and land-sharing (small, fragmented green areas and low-density housing) have been the recent focus of debates regarding the pattern of urban development. However, in this context, there is no information on the mechanisms behind the observed biodiversity changes. One of the main mechanisms proposed to explain urban biodiversity loss is the alteration of predator-prey interactions. Using ground nesting birds as a model system and data from nine European cities, we experimentally tested the effects of these two extreme urban development types on artificial ground nest survival and whether nest survival correlates with the local abundance of ground-nesting birds and their nest predators. Nest survival (n = 554) was lower in land-sharing than in land-sparing urban areas. Nest survival decreased with increasing numbers of local predators (cats and corvids) and with nest visibility. Correspondingly, relative abundance of ground nesting birds was greater in land-sparing than in land-sharing urban areas, though overall bird diversity was unaffected by the pattern of urban development. We provide the first evidence that predator-prey interactions differ between the two extreme urban development types. Changing interactions may explain the higher proportion of ground-nesting birds in land-sparing areas, and suggest a limitation of the land-sharing model. Nest predator control and the provision of more green-covered urban habitats may also improve conservation of sensitive birds in cities. Our findings provide information on how to further expand our cities without severe loss of urban-sensitive species and give support for land-sparing over land-sharing urban development.

    更新日期:2020-01-08
  • Bee pollinator functional responses and functional effects in restored tropical forests
    Ecol. Appl. (IF 4.378) Pub Date : 2020-01-08
    Paula María Montoya‐Pfeiffer; Ricardo R. Rodrigues; Isabel Alves dos Santos

    Wild pollinators are necessary for ensuring plant reproduction, not only among crop fields but also remnant and restored ecosystems. Restoration activities should, therefore, lead to wild pollinator recovery, and thus be monitored to evaluate effects on pollinator diversity and functionality. We assessed bee pollinator functional responses in restoration plantings by creating functional groups (traits: body size, nesting location, sociality, and foraging strategy), comparing their abundance and diversity to that of other habitats (i.e., conserved and degraded primary forest fragments, anthropogenic wetlands, and sugarcane fields), and testing for an effect of source habitat (i.e., primary forest fragments) isolation. We analyzed functional effects on pollen transportation by identifying the pollen grains attached on the bodies of bees; creating plant functional groups with the identified species (traits: habit, successional class, geographic origin, and pollination mode); comparing their frequency, diversity, and interaction network structure among habitats; and searching for key interactions in network modules. In general, the abundance and diversity of bee communities and the frequency and diversity of the interacting plant species in restoration plantings were lower than those in primary forest fragments but higher than those in anthropogenic wetlands and sugarcane fields, suggesting that restoration plantings better enhance bee community recovery and functionality than other disturbed habitats. The interacting bees and plants were also negatively affected by habitat isolation, demonstrating the importance of primary forest fragments to supply bee populations to restored sites. The structure of interaction networks was little affected by habitat change and isolation, but the composition and diversity of functional groups varied significantly. There were more effects on larger bee species with more restricted nesting and floral requirements, and the woody species with which they interact most frequently. We identified key functional groups of bee pollinators that deserve priority for conservation because they play an important role in the pollen transportation of some the most relevant species in remnant forests and restoration plantings and also respond more negatively to habitat disturbances. Restoration efforts should include provisioning of nesting resources and management and conservation of primary forest remnant fragments that represent source habitats for them.

    更新日期:2020-01-08
  • Shipping alters the movement and behavior of Arctic cod (Boreogadus saida), a keystone fish in Arctic marine ecosystems
    Ecol. Appl. (IF 4.378) Pub Date : 2020-01-06
    Silviya V. Ivanova; Steven T. Kessel; Mario Espinoza; Montana F. McLean; Caitlin O'Neill; Justin Landry; Nigel E. Hussey; Rob Williams; Svein Vagle; Aaron T. Fisk

    Anthropogenic noise associated with shipping has emerged as a major disruptor of aquatic animal behavior worldwide. The Arctic marine realm has historically experienced little noise‐generating human activity; however, the continual loss of sea ice has facilitated a dramatic increase in shipping activity. Here, we use a combination of acoustic telemetry and modeling of ship noise to examine the temporospatial habitat use of key Arctic forage fish, Arctic cod (Boreogadus saida) in the presence and absence of vessels in Resolute Bay, Nunavut, Canada. The presence and movement of vessels induced a horizontal shift in the home ranges of Arctic cod with low core overlap when compared to periods without vessel activity. Home range displacement occurred near the vessel. Individuals also altered their swimming behaviors in response to vessel presence with searching decreasing and travelling increasing in proportion. Results indicate that Arctic cod perceive vessel noise and presence as a threat and react by moving away and decreasing exploratory activities. These changes in fish behavior also coincide with the critical open water feeding period suggesting an interruption in exploitation of important and seasonally abundant food resources, and carry broader implications for dependent seabirds and marine mammals, and indirectly for all Arctic indigenous peoples’ subsistence and long‐term cultural traditions. Our study implies that strategic management is required for aquatic acoustic disturbance as an environmental stressor in the Arctic marine ecosystem, and highlights ecologically and socially important impacts that require timely conservation action.

    更新日期:2020-01-06
  • Influence of protogynous sex change on recovery of fish populations within marine protected areas
    Ecol. Appl. (IF 4.378) Pub Date : 2020-01-06
    E.E. Easter; M.S. Adreani; S.L. Hamilton; M.A. Steele; S. Pang; J.W. White

    Marine protected areas (MPAs) are increasingly implemented as a conservation tool worldwide. In many cases, they are managed adaptively: the abundance of target species is monitored, and observations are compared to some model‐based expectation for the trajectory of population recovery to ensure that the MPA is achieving its goals. Most previous analyses of the transient (short‐term) response of populations to the cessation of fishing inside MPAs have dealt only with gonochore (fixed‐sex) species. However, many important fishery species are protogynous hermaphrodites (female‐to‐male sex‐changing). Because size‐selective harvest will predominantly target males in these species, harvesting not only reduces abundance but also skews the sex ratio towards females. Thus the response to MPA implementation will involve changes in both survival and sex ratio, and ultimately reproductive output. We used an age‐structured model of a generic sex‐changing fish population to compare transient population dynamics after MPA implementation to those of an otherwise similar gonochore population, and examine how different features of sex‐changing life history affect those dynamics. We examined both demographically open (most larval recruitment comes from outside the MPA) and demographically closed (most larval recruitment is locally produced) dynamics. Under both scenarios, population recovery of protogynous species takes longer when fishing was more intense pre‐MPA (as in gonochores), but also depends heavily on the mating function – the degree to which the sex ratio affects reproduction. If few males are needed and reproduction is not affected by a highly‐female biased sex ratio, then population recovery is much faster; if males are a limiting resource, then increases in abundance after MPA implementation are much slower than for gonochores. Unfortunately the mating function is largely unknown for fishes. In general, we expect that most protogynous species with haremic mating systems will be in the first category (few males needed), though there is at least one example of a fish species (though not a sex‐changing species) for which males are limiting. Thus a better understanding of the importance of male fish to population dynamics is needed for the adaptive management of MPAs.

    更新日期:2020-01-06
  • Suitable climatic habitat changes for Mexican conifers along altitudinal gradients under climatic change scenarios.
    Ecol. Appl. (IF 4.378) Pub Date : null
    Erika Gómez-Pineda,Cuauhtémoc Sáenz-Romero,Juan Manuel Ortega-Rodríguez,Arnulfo Blanco-García,Xavier Madrigal-Sánchez,Roberto Lindig-Cisneros,Leonel Lopez-Toledo,Martha Elena Pedraza-Santos,Gerald E Rehfeldt

    The high biodiversity of the Mexican montane forests is concentrated on the Trans-Mexican Volcanic Belt, where several Protected Natural Areas exist. Our study examines the projected changes in suitable climatic habitat for five conifer species that dominate these forests. The species are distributed sequentially in overlapping altitudinal bands: Pinus hartwegii at the upper timberline, followed by Abies religiosa, the overwintering host of the Monarch butterfly at the Monarch Butterfly Biosphere Reserve, P. pseudostrobus, the most important in economic terms, and P. devoniana and P. oocarpa, which are important for resin production and occupy low altitudes where montane conifers merge with tropical dry forests. We fit a bioclimatic model to presence-absence observations for each species using the Random Forests classification tree with ground plot data. The models are driven by normal climatic variables from 1961-1990, which represents the reference period for climate-induced vegetation changes. Climate data from an ensemble of 17 general circulation models were run through the classification tree to project current distributions under climates described by the RCP 6.0 watts/m2 scenario for the decades centered on years 2030, 2060 and 2090. The results suggest that, by 2060, the climate niche of each species will occur at elevations that are between 300 to 500 m higher than at present. By 2060, habitat loss could amount to 46 to 77%, mostly affecting the lower limits of distribution. The two species at the highest elevation, P. hartwegii and A. religiosa, would suffer the greatest losses while, at the lower elevations, P. oocarpa would gain the most niche space. Our results suggest that conifers will require human assistance to migrate altitudinally upwards in order to recouple populations with the climates to which they are adapted. Traditional in situ conservation measures are likely to be equivalent to inaction and will therefore be incapable of maintaining current forest compositions.

    更新日期:2020-01-06
  • Fragmentation and thresholds in hydrological flow-based ecosystem services.
    Ecol. Appl. (IF 4.378) Pub Date : null
    Amy Thomas,Dario Masante,Bethanna Jackson,Bernard Cosby,Bridget Emmett,Laurence Jones

    Loss and fragmentation of natural land cover due to expansion of agricultural areas is a global issue. These changes alter the configuration and composition of the landscape, particularly affecting those ecosystem services (benefits people receive from ecosystems) which depend on interactions between landscape components. Hydrological mitigation describes the bundle of Ecosystem services provided by landscape features such as woodland which interrupt the flow of runoff to rivers. These services include sediment retention, nutrient retention and mitigation of overland water flow. The position of woodland in the landscape and the landscape topography are both important for hydrological mitigation. Therefore, it is crucial to consider landscape configuration and flow pathways in a spatially explicit manner when examining the impacts of fragmentation. Here we test the effects of landscape configuration using a large number (> 7,000) of virtual landscape configurations. We created virtual landscapes of woodland patches within grassland, superimposed onto real topography and stream networks. Woodland patches were generated with user-defined combinations of patch number and total woodland area, placed randomly in the landscape. The Ecosystem Service model used hydrological routing to map the 'mitigated area' upslope of each woodland patch. We found that more fragmented woodland mitigated a greater proportion of the catchment. Larger woodland area also increased mitigation, however, this increase was non-linear, with a threshold at 50% coverage, above which there was a decline in service provision. This nonlinearity suggests that the benefit of any additional woodland depends on two factors: the level of fragmentation and the existing area of woodland. Edge density (total edge of patches divided by area of catchment) was the best single metric in predicting mitigated area. Distance from woodland to stream was not a significant predictor of mitigation, suggesting that agri-environment schemes planting riparian woodland should consider additional controls such as the amount of fragmentation in the landscape. These findings highlight the potential benefits of fragmentation to hydrological mitigation services. However, benefits for hydrological services must be balanced against any negative effects of fragmentation or habitat loss on biodiversity and other services.

    更新日期:2020-01-04
  • What is known and unknown about the effects of plastic pollution: A meta-analysis and systematic review.
    Ecol. Appl. (IF 4.378) Pub Date : null
    K Bucci,M Tulio,C M Rochman

    As a consequence of the global ubiquity of plastic pollution, scientists, decision-makers, and the public often ask whether macroplastics (>5mm) and microplastics (<5mm) have a realized ecological threat. In 2016, we conducted a systematic review of the literature and made a call for further research testing hypotheses about ecological effects. In the subsequent years, the amount of relevant research has risen tremendously. Here, we re-assess the literature to determine the current weight of evidence about the effects of plastic pollution across all levels of biological organization. Our data spans marine, freshwater, and terrestrial environments. We extracted data from 139 lab and field studies testing 577 independent effects across a variety of taxa and with various types, sizes, and shapes of plastic. Overall, 59% of the tested effects were detected. Of these, 58% were due to microplastics and 42% were due to macroplastics. Of the effects that were not detected, 94% were from microplastics and 6% were from macroplastics. We found evidence that whether or not an effect is detected, as well as the severity and direction of the effect, is driven by dose, particle shape, polymer type, and particle size. Based on our analyses, there is no doubt that macroplastics are causing ecological effects, however the effects of microplastics are much more complex. We also assessed the environmental relevancy of experimental studies by comparing the doses used in each exposure to the concentrations and sizes of microplastics found in the environment. We determined that only 17% of the concentrations used in experimental studies have been found in nature, and that 80% of particle sizes used in experiments fall below the size range of the majority of environmental sampling. Based on our systematic review and meta-analysis, we make a call for future work that recognizes the complexity of microplastics and designs tests to better understand how different types, sizes, shapes, doses, and exposure durations affect wildlife. We also call for more ecologically and environmentally relevant studies, particularly in freshwater and terrestrial environments.

    更新日期:2020-01-04
  • Land use alters relationships of grassland productivity with plant and arthropod diversity in Inner Mongolian grassland
    Ecol. Appl. (IF 4.378) Pub Date : 2019-12-28
    Xinyu Wang; Frank Yonghong Li; Kuanyan Tang; Yanan Wang; Guga Suri; Zheng Bai; Taogetao Baoyin

    The threats of land‐use intensification to biodiversity have motivated considerable research directed toward understanding the relationship between biodiversity and ecosystem functioning (BEF). Functional diversity is deemed a better indicator than species diversity to clarify the BEF relationships. However, most tests of the BEF relationship have been conducted in highly controlled plant communities, with terrestrial animal communities largely unexplored. Additionally, most BEF studies examined the effects of biodiversity on ecosystem functions, with the effects of ecosystem functioning strength on biodiversity hardly considered. Based on a 6‐yr grassland experiment in the typical steppe region of Inner Mongolia, we examined the variation of taxonomic diversity (TD) and functional diversity (FD) of both plant and arthropod communities, and their relations with grassland productivity, across three land management types (moderate grazing, mowing, and enclosure). We aimed to clarify the interrelations among plant FD, arthropod FD, grassland productivity, and soil factors. We found the following: (1) Grassland under mowing performed best in terms of sustaining a high TD and FD of plants and arthropods compared to that under grazing and enclosure. (2) The relationships between plant and arthropod diversity and productivity varied with management types. Plant TD and FD were negatively related, whereas arthropod FD was positively related with productivity under enclosure; plant FD, but not arthropod FD, was positively related with productivity under grazing; arthropod FD, but not plant FD, was negatively related with productivity under mowing. (3) Grassland productivity was positively interrelated with plant FD, but not plant TD; and was negatively interrelated with arthropod TD, but not arthropod FD across different management types. The respective positive vs. negative bidirectional relationships of productivity with plant diversity vs. arthropod diversity, were majorly a consequence of divergent grazing/mowing effects on plant vs. arthropod diversity. The results indicate that grazing increases plant diversity, but decreases arthropod diversity, whereas fall mowing provides a management strategy for conservation of both trophic levels. These results also provide new insights into the effects of land‐use changes on biodiversity and ecosystem processes, and indicate the importance of incorporating the functional interrelations among different trophic groups in sustainable grassland management.

    更新日期:2020-01-04
  • Assessing the ecological impacts of biomass harvesting along a disturbance severity gradient.
    Ecol. Appl. (IF 4.378) Pub Date : null
    Valerie J Kurth,Anthony W D'Amato,John B Bradford,Brian J Palik,Christopher E Looney

    Disturbance is a central driver of forest development and ecosystem processes with variable effects within and across ecosystems. Despite the high levels of variation in disturbance severity often observed in forests following natural and anthropogenic disturbance, studies quantifying disturbance impacts often rely on categorical classifications, thus limiting opportunities to examine potential gradients in ecosystem response to a given disturbance or management regime. Given the potential increases in disturbance severity associated with global change, as well as shifts in management regimes related to procurement of biofuel feedstocks, there is an increasing need to quantitatively describe disturbance severity and associated responses of forest development, soil processes, and structural conditions. This study took advantage of two replicated large-scale studies of forest biomass harvesting in Populus tremuloides and Pinus bansksiana forests, respectively, to develop and test the utility of a continuous, quantitative disturbance severity index (DSI) for describing post-harvest response of plant communities and nutrient pools to different levels of biomass removal and legacy retention (i.e., live trees and coarse woody material). There was a high-degree of variability in DSI within categorical treatments associated with different levels of legacy retention and regression models using DSI as a predictor explained a portion of the variation (>50%) for many of the ecosystem- and community-level responses to biomass harvesting examined. Nutrient losses associated with biomass harvesting were positively related to disturbance severity, particularly in P. tremuloides forests, with post-harvest nutrient availability generally declining along the gradient of impacts. Consistent with expectations from ecological theory, species richness and diversity of woody plant communities were greatest at intermediate disturbance severities and regeneration densities of dominant trees species were most abundant at highest levels of disturbance. Although categorical benchmarks will continue to be the primary way through which management guidelines are conveyed to practitioners, evaluation of their effectiveness at sustaining ecosystem functioning should be through continuous analyses, such as the DSI approach used in this study, to allow for the more precise identification of thresholds that ensure a range of desirable outcomes exist across managed landscapes.

    更新日期:2020-01-04
  • Avian influenza virus prevalence in marine birds is dependent on ocean temperatures.
    Ecol. Appl. (IF 4.378) Pub Date : null
    Jeffrey S Hall,Robert J Dusek,Sean W Nashold,Joshua L TeSlaa,R Bradford Allen,Daniel A Grear

    Waterfowl and shorebirds are the primary hosts of influenza A virus (IAV), however, in most surveillance efforts large populations of birds are not routinely examined, specifically marine ducks and other birds that reside predominately on or near the ocean. We conducted a long-term study sampling sea ducks and gulls in coastal Maine for IAV and found a virus prevalence (1.7%) much lower than is typically found in freshwater duck populations. We found wide year-to-year variation in virus detection in sea ducks and that the ocean water temperature was an important factor affecting IAV prevalence. In particular, the ocean temperature that occurred 11 days prior to collecting virus positive samples were important while water temperature measured concurrently with host sampling had no explanatory power for viral detection. We also experimentally showed that IAV is relatively unstable in sea water at temperatures typically found during our sampling. This represents the first report of virus prevalence and actual environmental data that helps explain the variation in marine IAV transmission dynamics.

    更新日期:2020-01-04
  • Human eutrophication drives biogeographic saltmarsh productivity patterns in China.
    Ecol. Appl. (IF 4.378) Pub Date : null
    Xiao Xu,Hao Liu,Yuanzhan Liu,Chenhao Zhou,Lianghao Pan,Changming Fang,Ming Nie,Bo Li

    Saltmarshes are important natural carbon sinks with a large capacity to absorb exogenous nutrient inputs. The effects of nutrients on biogeographic productivity patterns, however, have been poorly explored in saltmarshes. We conducted field surveys to examine how complex environments affect productivity of two common saltmarsh plants, invasive Spartina alterniflora and native Phragmites australis, along an 18,000-km latitudinal gradient on the Chinese coastline. We harvested peak aboveground biomass as a proxy for productivity, and measured leaf functional traits (e.g., leaf area, specific leaf area [SLA], leaf nitrogen [N] and phosphorus [P]), soil nutrients (dissolved inorganic N (DIN) and available P (AP)), and salinity. We compiled data on mean annual temperature (MAT) and exogenous nutrients (both N and P). Then, we examined how these abiotic factors affect saltmarsh productivity using both linear mixed effect models and structural equation modelling. Using a trait-based approach, we also examined how saltmarsh productivity responds to changing environments across latitude. Exogenous nutrients (both N and P) compared with temperature and other variables (e.g., DIN, AP, salinity) were the dominant factors in explaining the biogeographic productivity patterns of both S. alterniflora and P. australis. Leaf size-related traits (e.g., leaf area), rather than leaf economic traits (e.g., SLA, leaf N and P), can be used to indicate the positive effects of exogenous nutrients on the productivity of these two species. Our results demonstrated that human eutrophication surpassed temperature as the major driver of biogeographic saltmarsh productivity pattern, challenging current models in which biogeographic productivity pattern is primarily controlled by temperature. Our findings have potential broad implications for the management of S. alterniflora, which is a global invader, as it has benefited from coastal eutrophication. Furthermore, exogenous nutrient availability and leaf size need to be integrated into earth system models that are used to predict global plant productivity in saltmarshes.

    更新日期:2020-01-04
  • Carbon sequestration and biodiversity co‐benefits of preserving forests in the western United States
    Ecol. Appl. (IF 4.378) Pub Date : 2019-12-27
    Polly C. Buotte; Beverly E. Law; William J. Ripple; Logan T. Berner

    Forest carbon sequestration via forest preservation can be a viable climate change mitigation strategy. Here, we identify forests in the western conterminous United States with high potential carbon sequestration and low vulnerability to future drought and fire, as simulated using the Community Land Model and two high carbon emission scenario (RCP 8.5) climate models. High‐productivity, low‐vulnerability forests have the potential to sequester up to 5,450 Tg CO2 equivalent (1,485 Tg C) by 2099, which is up to 20% of the global mitigation potential previously identified for all temperate and boreal forests, or up to ~6 yr of current regional fossil fuel emissions. Additionally, these forests currently have high above‐ and belowground carbon density, high tree species richness, and a high proportion of critical habitat for endangered vertebrate species, indicating a strong potential to support biodiversity into the future and promote ecosystem resilience to climate change. We stress that some forest lands have low carbon sequestration potential but high biodiversity, underscoring the need to consider multiple criteria when designing a land preservation portfolio. Our work demonstrates how process models and ecological criteria can be used to prioritize landscape preservation for mitigating greenhouse gas emissions and preserving biodiversity in a rapidly changing climate.

    更新日期:2020-01-04
  • From metabarcoding to metaphylogeography: separating the wheat from the chaff.
    Ecol. Appl. (IF 4.378) Pub Date : null
    Xavier Turon,Adrià Antich,Creu Palacín,Kim Praebel,Owen Simon Wangensteen

    Metabarcoding is by now a well-established method for biodiversity assessment in terrestrial, freshwater and marine environments. Metabarcoding data sets are usually used for α- and β-diversity estimates, that is, interspecies (or inter-MOTU) patterns. However, the use of hypervariable metabarcoding markers may provide an enormous amount of intraspecies (intra-MOTU) information - mostly untapped so far. The use of cytochrome oxidase (COI) amplicons is gaining momentum in metabarcoding studies targeting eukaryote richness. COI has been for a long time the marker of choice in population genetics and phylogeographic studies. Therefore, COI metabarcoding data sets may be used to study intraspecies patterns and phylogeographic features for hundreds of species simultaneously, opening a new field which we suggest to name metaphylogeography. The main challenge for the implementation of this approach is the separation of erroneous sequences from true intra-MOTU variation. Here, we develop a cleaning protocol based on changes in entropy of the different codon positions of the COI sequence, together with co-occurrence patterns of sequences. Using a data set of community DNA from several benthic littoral communities in the Mediterranean and Atlantic seas, we first tested by simulation on a subset of sequences a two-step cleaning approach consisting of a denoising step followed by a minimal abundance filtering. The procedure was then applied to the whole data set. We obtained a total of 563 MOTUs that were usable for phylogeographic inference. We used semiquantitative rank data instead of read abundances to perform AMOVAs and haplotype networks. Genetic variability was mainly concentrated within samples, but with an important between-seas component as well. There were inter-group differences in the amount of variability between and within communities in each sea. For two species the results could be compared with traditional Sanger sequence data available for the same zones, giving similar patterns. Our study shows that metabarcoding data can be used to infer intra- and interpopulation genetic variability of many species at a time, providing a new method with great potential for basic biogeography, connectivity and dispersal studies, and for the more applied fields of conservation genetics, invasion genetics, and design of protected areas.

    更新日期:2020-01-04
  • A statistical forecasting approach to metapopulation viability analysis.
    Ecol. Appl. (IF 4.378) Pub Date : null
    Paige E Howell,Blake R Hossack,Erin Muths,Brent H Sigafus,Ann Chenevert-Steffler,Richard B Chandler

    Conservation of at-risk species is aided by reliable forecasts of the consequences of environmental change and management actions on population viability. Forecasts from conventional population viability analysis (PVA) are made using a two-step procedure in which parameters are estimated, or elicited from expert opinion, and then plugged into a stochastic population model without accounting for parameter uncertainty. Recently-developed statistical PVAs differ because forecasts are made conditional on models fitted to empirical data. The statistical forecasting approach allows for uncertainty about parameters, but it has rarely been applied in metapopulation contexts where spatially-explicit inference is needed about colonization and extinction dynamics and other forms of stochasticity that influence metapopulation viability. We conducted a statistical metapopulation viability analysis (MPVA) using 11 years of data on the federally-threatened Chiricahua leopard frog (Lithobates chiricahuensis) to forecast responses to landscape heterogeneity, drought, environmental stochasticity, and management. We evaluated several future environmental scenarios and pond restoration options designed to reduce extinction risk. Forecasts over a 50-yr time horizon indicated that metapopulation extinction risk was < 4% for all scenarios, but uncertainty was high. Without pond restoration, extinction risk is forecasted to be 3.9% (95% CI: 0-37%) by year 2066. Restoring six ponds by increasing their hydroperiod reduced extinction risk to < 1% and greatly reduced uncertainty (95% CI: 0 - 2%). Our results suggest that managers can mitigate the impacts of drought and environmental stochasticity on metapopulation viability by maintaining ponds that hold water throughout the year and keeping them free of invasive predators. Our study illustrates the utility of the spatially explicit statistical forecasting approach to MPVA in conservation planning efforts.

    更新日期:2020-01-04
  • Responses of diversity, productivity, and stability to the nitrogen input in a tropical grassland.
    Ecol. Appl. (IF 4.378) Pub Date : null
    Preeti Verma,R Sagar

    Atmospheric nitrogen (N) deposition is a matter of serious concern for the structure and functioning of global ecosystems, but the effect of N application of species diversity (D), primary productivity (P) and stability (S) of tropical grassland ecosystems is not known. The present study reports the effects of different levels of N application on species composition, and the D, P, S and their relationships in a tropical grassland. Within the experimental grassland, 72 1 × 1m plots with 6 N-input levels and with 12 replicates, were established in 2013. For three years, different doses of urea as a source of N were applied to the plots. Data on individuals and biomass of each species were recorded and statistically analysed. The study revealed that the N applied caused variations in species composition, D, P and S. Below 90 kg N-dose; D was positively related to P and S, while above this level, the relations were negative due to N induced responses of species and functional group composition as well as biomass distribution among them. The optimum applied N levels for maximum D (50-60 Kg N), P (120 Kg N) and a positive relation of S with D up to 90-Kg N-treatment suggested that the 90 Kg N-dose could be a maximum dose of N which the grassland can tolerate. Hence, N application should not exceed 90 Kg level for sustainability of the structure and functioning of tropical grassland ecosystem.

    更新日期:2020-01-04
  • Highly diversified crop-livestock farming systems reshape wild bird communities.
    Ecol. Appl. (IF 4.378) Pub Date : 2019-11-02
    Olivia M Smith,Christina M Kennedy,Jeb P Owen,Tobin D Northfield,Christopher E Latimer,William E Snyder

    Agricultural intensification is a leading threat to bird conservation. Highly diversified farming systems that integrate livestock and crop production might promote a diversity of habitats useful to native birds foraging across otherwise-simplified landscapes. At the same time, these features might be attractive to nonnative birds linked to a broad range of disservices to both crop and livestock production. We evaluated the influence of crop-livestock integration on wild bird richness and density along a north-south transect spanning the U.S. West Coast. We surveyed birds on 52 farms that grew primarily mixed vegetables and fruits alone or integrated livestock into production. Crop-livestock systems harbored higher native bird density and richness relative to crop-only farms, a benefit more pronounced on farms embedded in nonnatural landscapes. Crop-livestock systems bolstered native insectivores linked to the suppression of agricultural pest insects but did not bolster native granivores that may be more likely to damage crops. Crop-livestock systems also significantly increased the density of nonnative birds, primarily European Starlings (Sturnus vulgaris) and House Sparrows (Passer domesticus) that may compete with native birds for resources. Models supported a small, positive correlation between nonnative density and overall native bird density as well as between nonnative density and native granivore density. Relative to crop-only farms, on average, crop-livestock systems exhibited 1.5 times higher patch richness, 2.4 times higher density of farm structures, 7.3 times smaller field sizes, 2.4 times greater integration of woody crops, and 5.3 times greater integration of pasture/hay habitat on farm. Wild birds may have responded to this habitat diversity and/or associated food resources. Individual farm factors had significantly lower predictive power than farming system alone (change in C statistic information criterion (ΔCIC) = 80.2), suggesting crop-livestock systems may impact wild birds through a suite of factors that change with system conversion. Collectively, our findings suggest that farms that integrate livestock and crop production can attract robust native bird communities, especially within landscapes devoted to intensified food production. However, additional work is needed to demonstrate persistent farm bird communities through time, ecophysiological benefits to birds foraging on these farms, and net effects of both native and nonnative wild birds in agroecosystems.

    更新日期:2020-01-04
  • Small mammal responses to long-term large-scale woodland creation: the influence of local and landscape-level attributes.
    Ecol. Appl. (IF 4.378) Pub Date : 2019-11-02
    Elisa Fuentes-Montemayor,Mark Ferryman,Kevin Watts,Nicholas A Macgregor,Natasha Hambly,Stephen Brennan,Ruth Coxon,Holly Langridge,Kirsty J Park

    Habitat loss and fragmentation greatly affect biological diversity. Actions to counteract their negative effects include increasing the quality, amount and connectivity of seminatural habitats at the landscape scale. However, much of the scientific evidence underpinning landscape restoration comes from studies of habitat loss and fragmentation, and it is unclear whether the ecological principles derived from habitat removal investigations are applicable to habitat creation. In addition, the relative importance of local- (e.g., improving habitat quality) vs. landscape-level (e.g., increasing habitat connectivity) actions to restore species is largely unknown, partly because studying species responses over sufficiently large spatial and temporal scales is challenging. We studied small mammal responses to large-scale woodland creation spanning 150 yr, and assessed the influence of local- and landscape-level characteristics on three small mammal species of varying woodland affinity. Woodland specialists, generalists, and grassland specialists were present in woodlands across a range of ages from 10 to 160 yr, demonstrating that these species can quickly colonize newly created woodlands. However, we found evidence that woodlands become gradually better over time for some species. The responses of individual species corresponded to their habitat specificity. A grassland specialist (Microtus agrestis) was influenced only by landscape attributes; a woodland generalist (Apodemus sylvaticus) and specialist (Myodes glareolus) were primarily influenced by local habitat attributes, and partially by landscape characteristics. At the local scale, high structural heterogeneity, large amounts of deadwood, and a relatively open understory positively influenced woodland species (both generalists and specialists); livestock grazing had strong negative effects on woodland species abundance. Actions to enhance habitat quality at the patch scale focusing on these attributes would benefit these species. Woodland creation in agricultural landscapes is also likely to benefit larger mammals and birds of prey feeding on small mammals and increase ecosystem processes such as seed dispersal.

    更新日期:2020-01-04
  • Combining environmental DNA and species distribution modeling to evaluate reintroduction success of a freshwater fish.
    Ecol. Appl. (IF 4.378) Pub Date : 2019-11-05
    Maria Riaz,Mathias Kuemmerlen,Claudia Wittwer,Berardino Cocchiararo,Imran Khaliq,Markus Pfenninger,Carsten Nowak

    Active species reintroduction is an important conservation tool when aiming for the restoration of biological communities and ecosystems. The effective monitoring of reintroduction success is a crucial factor in this process. Here, we used a combination of environmental DNA (eDNA) techniques and species distribution models (SDMs) to evaluate the success of recent reintroductions of the freshwater fish Alburnoides bipunctatus in central Germany. We built SDMs without and with eDNA presence data to locate further suitable reintroduction sites and potentially overlooked populations of the species. We successfully detected eDNA of A. bipunctatus at all reintroduction sites, as well as several adjacent sites mostly in downstream direction, which supports the success of reintroduction efforts. eDNA-based species detection considerably improved SDMs for A. bipunctatus, which allowed to identify species presence in previously unknown localities. Our results confirm the usefulness of eDNA techniques as standard tool to monitor reintroduced fish populations. We propose that combining eDNA with SDMs is a highly effective approach for long-term monitoring of reintroduction success in aquatic species.

    更新日期:2020-01-04
  • Bayesian mechanistic modeling characterizes Gulf of Mexico hypoxia: 1968-2016 and future scenarios.
    Ecol. Appl. (IF 4.378) Pub Date : 2019-11-05
    Dario Del Giudice,V R R Matli,Daniel R Obenour

    The hypoxic zone in the northern Gulf of Mexico is among the most dramatic examples of impairments to aquatic ecosystems. Despite having attracted substantial attention, management of this environmental crisis remains challenging, partially due to limited monitoring to support model development and long-term assessments. Here, we leverage new geostatistical estimates of hypoxia derived from nearly 150 monitoring cruises and a process-based model to improve characterization of controlling mechanisms, historic trends, and future responses of hypoxia while rigorously quantifying uncertainty in a Bayesian framework. We find that November-March nitrogen loads are important controls of sediment oxygen demand, which appears to be the major oxygen sink. In comparison, only ~23% of oxygen in the near-bottom region appears to be consumed by net water column respiration, which is driven by spring and summer loads. Hypoxia typically exceeds 15,600 km2 in June, peaks in July, and declines below 10,000 km2 in September. In contrast to some previous Gulf hindcasting studies, our simulations demonstrate that hypoxia was both severe and worsening prior to 1985, and has remained relatively stable since that time. Scenario analysis shows that halving nutrient loadings will reduce hypoxia by 37% with respect to 13,900 km2 (1985-2016 median), while a +2°C change in water temperature will cause a 26% hypoxic area increase due to enhanced sediment respiration and reduced oxygen solubility. These new results highlight the challenges of achieving hypoxia reduction targets, particularly under warming conditions, and should be considered in ecosystem management.

    更新日期:2020-01-04
  • Can wildland fire management alter 21st-century subalpine fire and forests in Grand Teton National Park, Wyoming, USA?
    Ecol. Appl. (IF 4.378) Pub Date : 2019-11-02
    Winslow D Hansen,Diane Abendroth,Werner Rammer,Rupert Seidl,Monica G Turner

    In subalpine forests of the western United States that historically experienced infrequent, high-severity fire, whether fire management can shape 21st-century fire regimes and forest dynamics to meet natural resource objectives is not known. Managed wildfire use (i.e., allowing lightning-ignited fires to burn when risk is low instead of suppressing them) is one approach for maintaining natural fire regimes and fostering mosaics of forest structure, stand age, and tree-species composition, while protecting people and property. However, little guidance exists for where and when this strategy may be effective with climate change. We simulated most of the contiguous forest in Grand Teton National Park, Wyoming, USA to ask: (1) how would subalpine fires and forest structure be different if fires had not been suppressed during the last three decades? And (2) what is the relative influence of climate change vs. fire management strategy on future fire and forests? We contrasted fire and forests from 1989 to 2098 under two fire management scenarios (managed wildfire use and fire suppression), two general circulation models (CNRM-CM5 and GFDL-ESM2M), and two representative concentration pathways (8.5 and 4.5). We found little difference between management scenarios in the number, size, or severity of fires during the last three decades. With 21st-century warming, fire activity increased rapidly, particularly after 2050, and followed nearly identical trajectories in both management scenarios. Area burned per year between 2018 and 2099 was 1,700% greater than in the last three decades (1989-2017). Large areas of forest were abruptly lost; only 65% of the original 40,178 ha of forest remained by 2098. However, forests stayed connected and fuels were abundant enough to support profound increases in burning through this century. Our results indicate that strategies emphasizing managed wildfire use, rather than suppression, will not alter climate-induced changes to fire and forests in subalpine landscapes of western North America. This suggests that managers may continue to have flexibility to strategically suppress subalpine fires without concern for long-term consequences, in distinct contrast with dry conifer forests of the Rocky Mountains and mixed conifer forest of California where maintaining low fuel loads is essential for sustaining frequent, low-severity surface fire regimes.

    更新日期:2020-01-04
  • Regional context and dispersal mode drive the impact of landscape structure on seed dispersal.
    Ecol. Appl. (IF 4.378) Pub Date : 2019-11-05
    Miriam San-José,Víctor Arroyo-Rodríguez,Jorge A Meave

    Land-use change modifies the spatial structure of tropical landscapes, shaping global biodiversity patterns. Yet, it remains unknown how key ecological processes, such as seed dispersal, can be affected by changes in landscape patterns, and whether such effects differ among regions with different climate and disturbance intensity. We assessed the effect of five landscape metrics (forest cover, matrix openness, forest edge density, forest fragmentation, and interpatch distance) on the seed rain recorded in two Mexican fragmented regions (20 forest sites per region): the more deforested, defaunated, and windy Los Tuxtlas rainforest (LTX), and the better-preserved Lacandona rainforest (LAC). We quantified the proportions of dispersed tree species and their seeds, separately evaluating wind- and animal-dispersed species. Our findings support the hypothesis that forest loss is more important than fragmentation per se, negatively impacting the seed rain in both regions. As expected, landscape patterns were comparatively more important for wind-dispersed seeds in LTX, probably because of stronger wind events in this region. Specifically, proportions of wind-dispersed seeds and species decreased with increasing edge density, suggesting that forest edges prevent dispersal of wind-dispersed species, which may occur if edges create physical barriers that limit wind flow. This pattern can also be caused by source limitation in landscapes with more forest edges, as tree mortality rates usually increase at forest edges. The wind-dispersed seed rain was also positively related to matrix openness, especially in LTX, where wind flow can be favored by the dominance of treeless anthropogenic matrices. Surprisingly, the proportion of animal-dispersed seeds in LTX was positively related to matrix openness and patch isolation, suggesting that seed dispersers in more deforested regions may be forced to concentrate in isolated patches and use the available habitat more intensively. Yet, as expected, patch isolation limited wind-dispersed seeds in LAC. Therefore, dispersal (and potentially regeneration) of wind-dispersed trees is favored in regions exposed to stronger wind events, especially in landscapes dominated by regularly shaped patches surrounded by open areas. Conversely, animal-dispersed seeds are primarily favored by increasing forest cover. Preventing forest loss is therefore critical to promote animal seed dispersal and forest recovery in human-modified rainforests.

    更新日期:2020-01-04
  • Dependent double-observer method reduces false-positive errors in auditory avian survey data.
    Ecol. Appl. (IF 4.378) Pub Date : 2019-10-21
    Kaitlyn M Strickfaden,Danielle A Fagre,Jessie D Golding,Alan H Harrington,Kaitlyn M Reintsma,Jason D Tack,Victoria J Dreitz

    Bias introduced by detection errors is a well-documented issue for abundance and occupancy estimates of wildlife. Detection errors bias estimates of detection and abundance or occupancy in positive and negative directions, which can produce misleading results. There have been considerable design- and model-based methods to address false-negative errors, or missed detections. However, false-positive errors, or detections of individuals that are absent but counted as present because of misidentifications or double counts, are often assumed to not occur in ecological studies. The dependent double-observer survey method is a design-based approach speculated to reduce false positives because observations have the ability to be confirmed by two observers. However, whether this method reduces false positives compared to single-observer methods has not been empirically tested. We used prairie songbirds as a model system to test if a dependent double-observer method reduced false positives compared to a single-observer method. We used vocalizations of ten species to create auditory simulations and used naive and expert observers to survey these simulations using single-observer and dependent double-observer methods. False-positive rates were significantly lower using the dependent double-observer survey method in both observer groups. Expert observers reported a 3.2% false-positive rate in dependent double-observer surveys and a 9.5% false-positive rate in single-observer surveys, while naive observers reported a 39.1% false-positive rate in dependent double-observer surveys and a 49.1% false-positive rate in single-observer surveys. Misidentification errors arose in all survey scenarios and almost all species combinations. However, expert observers using the dependent double-observer method performed significantly better than other survey scenarios. Given the use of double-observer methods and the accumulating evidence that false positives occur in many survey methods across different taxa, this study is an important step forward in acknowledging and addressing false positives.

    更新日期:2020-01-04
  • Warming and pollutants interact to modulate octocoral immunity and shape disease outcomes.
    Ecol. Appl. (IF 4.378) Pub Date : 2019-10-20
    Allison M Tracy,Ernesto Weil,C Drew Harvell

    Warming environments can alter the outcome of host-parasite relationships with important consequences for biodiversity. Warming often increases disease risk, and interactions with other environmental factors can intensify impacts by modifying the underlying mechanisms, such as host immunity. In coastal ecosystems, metal pollution is a pervasive stressor that influences disease and immunity in many organisms. Despite the crisis facing coral reefs, which stems in part from warming-associated disease outbreaks, the impacts of metal pollutants on scleractinian and octocoral disease are largely unknown. We investigated how warming oceans and copper pollution affect host immunity and disease risk for two diseases of the abundant Caribbean octocoral, the sea fan Gorgonia ventalina. Field surveys across a sediment copper concentration gradient in Puerto Rico, USA revealed that cellular immunity of sea fans increased by 12.6% at higher sediment copper concentrations, while recovery from multifocal purple spots disease (MFPS) tended to decrease. MFPS severity in the field increased at warmer sites. In a controlled laboratory experiment, sea fans were inoculated with live cultures of a labyrinthulid parasite to test the interactive effects of temperature and copper on immune activation. As in the field, higher copper induced greater immunity, but the factorial design of the experiment revealed that copper and temperature interacted to modulate the immune response to the parasite: immune cell densities increased with elevated temperature at lower copper concentrations, but not with high copper concentrations. Tissue damage was also greater in treatments with higher copper and warmer temperatures. Field and lab evidence confirm that elevated copper hinders sea fan immune defenses against damaging parasites. Temperature and copper influenced host-pathogen interactions in octocorals by modulating immunity, disease severity, and disease recovery. This is the first evidence that metal pollution affects processes influencing disease in octocorals and highlights the importance of immune mechanisms in environmentally mediated disease outbreaks. Although coral conservation efforts must include a focus on global factors, such as rapid warming, reducing copper and other pollutants that compromise coral health on a local scale may help corals fight disease in a warming ocean.

    更新日期:2020-01-04
  • Vegetation dynamics following compound disturbance in a dry pine forest: fuel treatment then bark beetle outbreak.
    Ecol. Appl. (IF 4.378) Pub Date : 2019-10-20
    Justin S Crotteau,Christopher R Keyes,Sharon M Hood,Andrew J Larson

    In the western United States, restoration of forests with historically frequent, low-severity fire regimes often includes fuel reduction that reestablish open, early-seral conditions while reducing fuel continuity and loading. Between 2001 and 2016, fuel reduction (e.g., thinning, prescribed burning, etc.) was implemented on over 26 million hectares of federal lands alone in the United States, reflecting the urgency to mitigate risk from high-severity wildfire. However, between 2001 and 2012, nearly 20 million hectares in the United States were impacted by mountain pine beetle (MPB; Dendroctonus ponderosae), compounding restoration effects in wildfire-hazard-treated stands. Knowledge of the effects of treatments followed by natural disturbance on long-term forest structure and communities is needed, especially considering that fuel treatments are increasingly being implemented and warming climate is predicted to exacerbate disturbance frequency and severity. We tested the interacting effects of treatments designed to reduce high-severity wildfire hazard in stands subsequently challenged by MPB outbreak on vegetation dynamics using a factorial experimental design (control, thin only, burn only, thin + burn) in a ponderosa pine (Pinus ponderosa)-dominated forest. Stands were treated by 2002, then impacted by MPB outbreak from 2005 to 2012. We assessed change in overstory and understory forest community structure, composition, and diversity over time. There were distinct thinning, burning, and year effects. Thinning immediately reduced overstory density; pine density then declined 4.5 times more in unthinned than thinned treatments due to MPB. Burning immediately reduced graminoid, shrub, and total understory cover by as much as 52%, resulting in greater species evenness than unburned treatments, but differences disappeared by 2016 due to growth and MPB outbreak. Similarly, multivariate analyses indicated forest communities were starkly different after treatment but became more similar over time, though key understory and overstory attributes still distinguish control and thin + burn. This study shows the value of long-term silvicultural experiments to evaluate treatment longevity and the compounded effects of treatment and natural disturbance. We demonstrate the homogenizing effects of treatment-induced growth coupled with MPB-caused tree mortality on management strategies that just treat the overstory (thinning) or understory (burning), showing that only combined treatments can provide the unique structural and compositional outcomes expected of restoration.

    更新日期:2020-01-04
  • Distribution and connectivity of protected areas in the Americas facilitates transboundary conservation.
    Ecol. Appl. (IF 4.378) Pub Date : 2019-10-24
    Daniel Thornton,Lyn Branch,Dennis Murray

    Large-scale anthropogenic changes to landscapes will cause species to move and shift their ranges against a backdrop of international political boundaries. Transboundary conservation efforts are therefore key to preserving intact and connected landscapes, particularly if such efforts can be implemented within the framework of protected area networks that provide for resiliency and persistence in the face of threats such as climate change. We studied the distribution, connectivity, and integrity of protected areas in regions near international borders within the Americas. We found that there is a greater proportion of land protected near vs. far from borders, with this effect extending approximately 125 km from the border. This trend was most pronounced when considering multiuse categories of protected areas in the analysis. We also found that there is greater connectivity of protected areas in border regions than more internally within countries, and relatively low rates of habitat loss within border-situated and internal protected areas. Our results indicate that protected area networks are larger and more connected if considered in a transboundary context and that efforts to conserve species and mitigate effects of long-term stressors like climate change will be most successful when planning includes neighboring countries. Despite a relative lack of attention to transboundary conservation in the Americas, our results suggest substantial opportunities for linking landscapes via a focus on international border regions and coordination across borders in protected areas management.

    更新日期:2020-01-04
  • Periphyton as an indicator of saltwater intrusion into freshwater wetlands: insights from experimental manipulations
    Ecol. Appl. (IF 4.378) Pub Date : 2019-12-24
    Viviana Mazzei; Benjamin J. Wilson; Shelby Servais; Sean P. Charles; John S. Kominoski; Evelyn E. Gaiser

    Saltwater intrusion has particularly large impacts on karstic wetlands of the Caribbean Basin due to their porous, carbonate bedrock and low elevation. Increases in salinity and phosphorus (P) accompanying saltwater intrusion into these freshwater, P‐limited wetlands are expected to alter biogeochemical cycles along with the structure and function of plant and algal communities. Calcareous periphyton is a characteristic feature of karstic wetlands and plays a central role in trophic dynamics, carbon storage, and nutrient cycling. Periphyton is extremely sensitive to water quality and quantity, but the effects of saltwater intrusion on these microbial mats remains to be understood. We conducted an ex situ mesocosm experiment to test the independent and combined effects of elevated salinity and P on the productivity, nutrient content, and diatom composition of calcareous periphyton from the Florida Everglades. We measured periphyton total carbon, nitrogen, and P concentrations and used settlement plates to measure periphyton accumulation rates and diatom species composition. The light and dark bottle method was used to measure periphyton productivity and respiration. We found that exposure to ~ 1 g P m‐2 yr‐1 significantly increased periphyton mat total P concentrations, but had no effect on any other response variable. Mats exposed to elevated salinity (~22 kg salt m‐2 yr‐1) had significantly lower total carbon and tended to have lower biomass and reduced productivity and respiration rates; however, mats exposed to salinity and P simultaneously had greater gross and net productivity. We found strong diatom species dissimilarity between fresh‐ and saltwater treated periphyton, while P additions only elicited compositional changes in periphyton also treated with saltwater. This study contributes to our understanding of how the ecologically important calcareous, periphyton mats unique to karstic, freshwater wetlands respond to increased salinity and P caused saltwater intrusion, and provides a guide to diatom indicator taxa for these two important environmental drivers.

    更新日期:2020-01-04
  • Rangeland sharing by cattle and bees: moderate grazing does not impair bee communities and resource availability
    Ecol. Appl. (IF 4.378) Pub Date : 2019-12-24
    Tal Shapira; Zalmen Henkin; Arnon Dag; Yael Mandelik

    Rangelands are a dominant anthropogenic land use and a main driver of natural habitat loss worldwide. Land sharing, the integration of agricultural production and biodiversity conservation, may provide a platform for managing rangelands to fulfill multiple ecosystem services. However, livestock grazing can greatly affect biodiversity and little is known about its effects on providers of focal ecosystem services, such as pollinators. We investigated the effect of cattle grazing on bee communities and their foraging and nesting resources in Mediterranean rangelands. Specifically, we explored the effect of moderate cattle grazing on flowering plant abundance, species richness and composition, the diversity of nesting substrates, and consequently, the possible effects on wild bee and honeybee foraging activity, species diversity and community composition. We conducted field research in the Mediterranean rangelands of Israel during the main bee activity season, in the spring of 2012 and 2013, comparing paired cattle‐grazed and ungrazed areas. The availability of floral and nesting resources for bees was unaffected or positively affected by grazing. Similarly, wild bee abundance, species richness and composition were not affected by grazing, but were instead shaped by spatiotemporal factors. Nor was honeybee activity level impaired by grazing. The foraging preferences of bees, as well as flower species composition and peak bloom differed between grazed and ungrazed areas. Therefore, in our studied rangelands, grazing had its main effect on the foraging choices of honeybees and wild bees, rather than on their abundance and diversity. Moreover, our results indicate the potentially important role of ungrazed patches in increasing nectar and pollen diversity and availability in rangelands for both honeybees and wild bees in the spring. Hence, maintaining a mosaic of moderately grazed and ungrazed patches is expected to provide the greatest benefits for wild bee conservation and honeybee activity in Mediterranean rangelands. Our findings support the notion of rangeland sharing by cattle and bees in Mediterranean ecosystems under moderate grazing intensities, mimicking the coexistence of honeybees, wild bees and cattle in Mediterranean ecosystems on an evolutionary timescale.

    更新日期:2020-01-04
  • Harvest models of small populations of a large carnivore using Bayesian forecasting
    Ecol. Appl. (IF 4.378) Pub Date : 2019-12-23
    Henrik Andrén; N. Thompson Hobbs; Malin Aronsson; Henrik Brøseth; Guillaume Chapron; John D.C. Linnell; John Odden; Jens Persson; Erlend B. Nilsen

    Harvesting large carnivores can be a management tool for meeting politically set goals for their desired abundance. However, harvesting carnivores creates its own set of conflicts in both society and among conservation professionals, where one consequence is a need to demonstrate that management is sustainable, evidence‐based and guided by science. Furthermore, because large carnivores often also have high degrees of legal protection, harvest quotas have to be carefully justified and constantly adjusted to avoid damaging their conservation status. We developed a Bayesian state‐space model to support adaptive management of Eurasian lynx harvesting in Scandinavia. The model uses data from the annual monitoring of lynx abundance and results from long‐term field research on lynx biology, which has provided detailed estimates of key demographic parameters. We used the model to predict the probability that the forecasted population size will be below or above the management objectives when subjected to different harvest quotas. The model presented here informs decision makers about the policy risks of alternative harvest levels. Earlier versions of the model have been available for wildlife managers in both Sweden and Norway to guide lynx harvest quotas and the model predictions showed good agreement with observations. We combined monitoring data with data on vital rates and were able to estimate unobserved additional mortality rates, which are most probably due to poaching. In both countries, the past quota setting strategy suggests that there has been a de facto threshold strategy with increasing proportion, which means that there is no harvest below a certain population size, but above this threshold there is an increasing proportion of the population harvested as the population size increases. The annual assessment of the monitoring results, the use of forecasting models, and a threshold harvest approach to quota setting will all reduce the risk of lynx population sizes moving outside the desired goals. The approach we illustrate could be adapted to other populations of mammals worldwide.

    更新日期:2020-01-04
  • Does the leaf economic spectrum hold within plant functional types? A Bayesian multivariate trait meta‐analysis
    Ecol. Appl. (IF 4.378) Pub Date : 2019-12-23
    Alexey N. Shiklomanov; Elizabeth M. Cowdery; Michael Bahn; Chaeho Byun; Steven Jansen; Koen Kramer; Vanessa Minden; Ülo Niinemets; Yusuke Onoda; Nadejda A. Soudzilovskaia; Michael C. Dietze

    The leaf economic spectrum is a widely‐studied axis of plant trait variability that defines a trade‐off between leaf longevity and productivity. While this has been investigated at the global scale, where it is robust, and at local scales, where deviations from it are common, it has received less attention at the intermediate scale of PFTs. We investigated whether global leaf economic relationships are also present within the scale of plant functional types (PFTs) commonly used by Earth System models, and the extent to which this global‐PFT hierarchy can be used to constrain trait estimates. We developed a hierarchical multivariate Bayesian model that assumes separate means and covariance structures within and across PFTs and fit this model to seven leaf traits from the TRY database related to leaf longevity, morphology, biochemistry, and photosynthetic metabolism. Although patterns of trait covariation were generally consistent with the leaf economic spectrum, we found three approximate tiers to this consistency. Relationships among morphological and biochemical traits (SLA, N, P) were the most robust within and across PFTs, suggesting that covariation in these traits is driven by universal leaf construction trade‐offs and stoichiometry. Relationships among metabolic traits (Rd, Vc,max, Jmax) were slightly less consistent, reflecting in part their much sparser sampling (especially for high‐latitude PFTs), but also pointing to more flexible plasticity in plant metabolistm. Finally, relationships involving leaf lifespan were the least consistent, indicating that leaf economic relationships related to leaf lifespan are dominated by across‐PFT differences and that within‐PFT variation in leaf lifespan is more complex and idiosyncratic. Across all traits, these covariance were an important source of information, as evidenced by the improved imputation accuracy and reduced predictive uncertainty in multivariate models compared to univariate models. Ultimately, our study reaffirms the value of studying not just individual traits but the multivariate trait space and the utility of hierarchical modeling for studying the scale dependence of trait relationships.

    更新日期:2020-01-04
  • Integrated assessment of the spatial distribution and structural dynamics of deep benthic marine communities
    Ecol. Appl. (IF 4.378) Pub Date : 2019-12-23
    Jan Jansen; Piers K. Dunstan; Nicole A. Hill; Philippe Koubbi; Jessica Melbourne‐Thomas; Romain Causse; Craig R. Johnson

    Characterising the spatial distribution and variation of species communities and validating these characteristics with data from the field are key elements for an ecosystem‐based approach to management. However, models of species distributions that yield community structure are usually not linked to models of community dynamics, constraining understanding and management of the ecosystem, particularly in data‐poor regions. Here we use a qualitative network model to predict changes in Antarctic benthic community structure between major marine habitats characterised largely by seafloor depth and slope, and use multivariate mixture models of species distributions to validate the community dynamics. Further, we then assess how future increases in primary production associated with anticipated loss of sea‐ice may affect the ecosystem. Our study shows how both spatial and structural features of ecosystems in data‐poor regions can be analysed and possible futures assessed, with direct relevance for ecosystem‐based management.

    更新日期:2020-01-04
  • Carryover effects of temperature and pCO2 across multiple Olympia oyster populations
    Ecol. Appl. (IF 4.378) Pub Date : 2019-12-21
    Laura H Spencer; Yaamini R Venkataraman; Ryan Crim; Stuart Ryan; Micah J Horwith; Steven B Roberts

    Predicting how populations will respond to ocean change across generations is critical to effective conservation of marine species. One emerging factor is the influence of parental exposures on offspring phenotype, known as intergenerational carryover effects. Parental exposure may deliver beneficial or detrimental characteristics to offspring that can influence larval recruitment patterns, thus shaping how populations and community structure respond to ocean change. Impacts of adult exposure to elevated winter temperature and pCO2 on reproduction and offspring viability were examined in the Olympia oyster (Ostrea lurida) using three populations of adult, hatchery‐reared O. lurida, plus an additional cohort spawned from one of the populations. Oysters were sequentially exposed to elevated temperature (+4°C, at 10°C), followed by elevated pCO2 (+2204 µatm, at 3045 µatm) during winter months. Male gametes were more developed after elevated temperature exposure and less developed after high pCO2 exposure, but there was no impact on female gametes or sex ratios. Oysters previously exposed to elevated winter temperature released larvae earlier, regardless of pCO2 exposure. Those exposed to elevated winter temperature as a sole treatment released more larvae on a daily basis, but when also exposed to high pCO2 there was no effect. These combined results indicate that elevated winter temperature accelerates O. lurida spermatogenesis, resulting in earlier larval release and increased production, with elevated pCO2 exposure negating effects of elevated temperature. Altered recruitment patterns may therefore follow warmer winters due to precocious spawning, but these effects may be masked by coincidental high pCO2. Offspring were reared in common conditions for one year, then deployed for three months in four estuarine bays with distinct environmental conditions. Offspring of parents exposed to elevated pCO2 had higher survival rates in two of the four bays. This carryover effect demonstrates that parental conditions can have substantial ecologically relevant impacts that should be considered when predicting impacts of environmental change. Furthermore, Olympia oysters may be more resilient in certain environments when progenitors are pre‐conditioned in stressful conditions. Combined with other recent studies, our work suggests that the Olympia may be more equipped than other oysters for the challenge of a changing ocean.

    更新日期:2020-01-04
  • Predicting functional responses in agro-ecosystems from animal movement data to improve management of invasive pests.
    Ecol. Appl. (IF 4.378) Pub Date : 2019-10-10
    Mark Q Wilber,Sarah M Chinn,James C Beasley,Raoul K Boughton,Ryan K Brook,Stephen S Ditchkoff,Justin W Fischer,Steve B Hartley,Lindsey K Holmstrom,John C Kilgo,Jesse S Lewis,Ryan S Miller,Nathan P Snow,Kurt C VerCauteren,Samantha M Wisely,Colleen T Webb,Kim M Pepin

    Functional responses describe how changing resource availability affects consumer resource use, thus providing a mechanistic approach to prediction of the invasibility and potential damage of invasive alien species (IAS). However, functional responses can be context dependent, varying with resource characteristics and availability, consumer attributes, and environmental variables. Identifying context dependencies can allow invasion and damage risk to be predicted across different ecoregions. Understanding how ecological factors shape the functional response in agro-ecosystems can improve predictions of hotspots of highest impact and inform strategies to mitigate damage across locations with varying crop types and availability. We linked heterogeneous movement data across different agro-ecosystems to predict ecologically driven variability in the functional responses. We applied our approach to wild pigs (Sus scrofa), one of the most successful and detrimental IAS worldwide where agricultural resource depredation is an important driver of spread and establishment. We used continental-scale movement data within agro-ecosystems to quantify the functional response of agricultural resources relative to availability of crops and natural forage. We hypothesized that wild pigs would selectively use crops more often when natural forage resources were low. We also examined how individual attributes such as sex, crop type, and resource stimulus such as distance to crops altered the magnitude of the functional response. There was a strong agricultural functional response where crop use was an accelerating function of crop availability at low density (Type III) and was highly context dependent. As hypothesized, there was a reduced response of crop use with increasing crop availability when non-agricultural resources were more available, emphasizing that crop damage levels are likely to be highly heterogeneous depending on surrounding natural resources and temporal availability of crops. We found significant effects of crop type and sex, with males spending 20% more time and visiting crops 58% more often than females, and both sexes showing different functional responses depending on crop type. Our application demonstrates how commonly collected animal movement data can be used to understand context dependencies in resource use to improve our understanding of pest foraging behavior, with implications for prioritizing spatiotemporal hotspots of potential economic loss in agro-ecosystems.

    更新日期:2020-01-04
  • Grazing disturbance promotes exotic annual grasses by degrading soil biocrust communities.
    Ecol. Appl. (IF 4.378) Pub Date : 2019-10-10
    Heather T Root,Jesse E D Miller,Roger Rosentreter

    Exotic invasive plants threaten ecosystem integrity, and their success depends on a combination of abiotic factors, disturbances, and interactions with existing communities. In dryland ecosystems, soil biocrusts (communities of lichens, bryophytes, and microorganisms) can limit favorable microsites needed for invasive species establishment, but the relative importance of biocrusts for landscape-scale invasion patterns remains poorly understood. We examine effects of livestock grazing in habitats at high risk for invasion to test the hypothesis that disturbance indirectly favors exotic annual grasses by reducing biocrust cover. We present some of the first evidence that biocrusts increase site resistance to invasion at a landscape scale and mediate the effects of disturbance. Biocrust species richness, which is reduced by livestock grazing, also appears to promote native perennial grasses. Short mosses, as a functional group, appear to be particularly valuable for preventing invasion by exotic annual grasses. Our study suggests that maintaining biocrust communities with high cover, species richness, and cover of short mosses can increase resistance to invasion. These results highlight the potential of soil surface communities to mediate invasion dynamics and suggest promising avenues for restoration in dryland ecosystems.

    更新日期:2020-01-04
  • Disturbance regulates the density-body-mass relationship of soil fauna.
    Ecol. Appl. (IF 4.378) Pub Date : 2019-10-11
    Frank van Langevelde,Vincent Comor,Steven de Bie,Herbert H T Prins,Madhav P Thakur

    Theory on the density-body-mass (DBM) relationship predicts that the density of animal species decreases by the power of -0.75 per unit increase in their body mass, or by the power of -1 when taxa across trophic levels are studied. This relationship is, however, largely debated, as the slope often deviates from the theoretical predictions. Here, we tested the ability of the DBM relationship to reflect changes in the structure of communities subjected to an anthropogenic disturbance. The slope would become less steep if smaller animals were more impacted by the disturbance than the larger ones, whereas the slope would become steeper if larger animals were more affected than the smaller ones. We tested the changes in the DBM relationship by sampling soil fauna, i.e., nematodes, Collembola, and larger arthropods, from a semiarid grassland before and after spraying diesel fuel as disturbance. We applied three different treatments: a control, a light disturbance, and an intense disturbance. We found that the slopes of the DBM relationships before the disturbance were around -1 as predicted by theory. The slope became more positive (i.e., less steep) just after the disturbance, especially after the intense disturbance as smaller fauna suffered the most and early colonizers had larger body mass. Interestingly, we observed that the slopes converged back to -1 by 2 months post-disturbance. Our findings show that the response of soil fauna communities to anthropogenic disturbances could explain the large variation in observed slopes of the DBM relationships. We experimentally demonstrate that an animal community, when disturbed, shows a temporal pattern of DBM relationships ranging from deviations from the predicted slope to convergence to the predicted slope with time. We recommend that deviations in the DBM relationships after disturbances can provide insights in the trajectory of community recovery, and hence could be used for biomonitoring.

    更新日期:2020-01-04
Contents have been reproduced by permission of the publishers.
导出
全部期刊列表>>
2020新春特辑
限时免费阅读临床医学内容
ACS材料视界
科学报告最新纳米科学与技术研究
清华大学化学系段昊泓
自然科研论文编辑服务
加州大学洛杉矶分校
上海纽约大学William Glover
南开大学化学院周其林
课题组网站
X-MOL
北京大学分子工程苏南研究院
华东师范大学分子机器及功能材料
中山大学化学工程与技术学院
试剂库存
天合科研
down
wechat
bug