Integrated approaches to natural resources management—Theory and practice Land Degrad. Dev. (IF 9.787) Pub Date : 2018-04-19 Anna Tengberg; Sandra Valencia
To meet multiple environmental objectives, integrated programming is becoming increasingly important for the Global Environmental Facility, the financial mechanism of the Multilateral Environmental Agreements, including the UN Convention to Combat Desertification. However, integration is often not well defined. We therefore focus on identifying key aspects of integration and assessing their implementation in natural resources management projects. To that end, we draw on systems thinking literature and carry out an analysis of a random sample of Global Environmental Facility integrated projects and in‐depth case studies demonstrating lessons learned and good practice. We highlight the need for projects to identify clearer system boundaries and main feedback mechanisms within those boundaries, in order to effectively address drivers of environmental change. We propose a theory of change for integrated natural resources management projects, where short‐term environmental and socioeconomic benefits will first accrue at the local level. Implementation of improved integrated natural resources management technologies and practices at the local level can then be extended through spatial planning and strengthening of innovation systems. Financing and incentive mechanisms at the watershed and/or landscape/seascape level coupled with supporting policies could sustain and enhance ecosystem services at even larger scales and longer time spans. The evolving scientific understanding of factors influencing social, technical, and institutional innovations and transitions towards sustainable management of natural resources should be harnessed and integrated into influencing models and theory of change for complex social‐environmental problems, such as land degradation, and be coupled with up‐to‐date approaches for learning, adaptive management, and scaling up.
Changes in soil organic carbon fractions in response to different tillage practices under a wheat‐maize double cropping system Land Degrad. Dev. (IF 9.787) Pub Date : 2018-04-19 Jian‐Fu Xue; Chao Pu; Xin Zhao; Yan‐Hua Wei; Yun‐Long Zhai; Xiang‐Qian Zhang; Rattan Lal; Hai‐Lin Zhang
To understand the turnover of soil organic carbon (SOC) and the improvement of soil quality in response to tillage practices, it is important to identify changes in labile SOC fractions, for example, permanganate oxidizable organic carbon (POxC) and particulate organic carbon (POC). Five tillage treatments were initially undertaken in a winter wheat (Triticum aestivum L., mid‐October to early‐June)–summer maize (Zea mays L., mid‐June to early‐October) system in the North China Plain in 2008 with changes being examined in 2012–2013. These treatments included plough tillage with residue removed, plough tillage with residue incorporation, no tillage with residue mulching, subsoiling with residue incorporation, and rotary tillage (tillage with a rotary tiller) with residue incorporation for the winter wheat season; summer maize was only managed with the NTM treatment. The greatest POxC and POC concentrations at the 0–5‐cm depth were observed under RTR and NTM treatments (p < .05), respectively. Both STR and RTR recorded larger POxC and POC concentrations at the 5–10‐cm depth (p < .05). Both POxC and POC concentrations for STR treatment were significantly higher than those under RTR, NTM, and PT0 treatments in the 20–50‐cm soil profile. The POC concentrations in each soil layer of 0–30‐cm showed a significant response to residue amount, temperature, and precipitation; and POxC concentrations did not record similar responses. Therefore, subsoiling with residue incorporation could be a potential tillage practice to manage labile SOC pool in top soil (0–50‐cm) in the North China Plain region.
Effects of rotational prescribed burning and sheep grazing on moorland plant communities: Results from a 60‐year intervention experiment Land Degrad. Dev. (IF 9.787) Pub Date : 2018-04-19 Gregg Milligan; Rob J. Rose; John O'Reilly; Rob H. Marrs
The effect of prescribed burning for conservation management of plant communities is controversial for moorlands growing on peat. These ecosystems provide many services that may be damaged by fire, hence it is important to fully assess its impact on all aspects of ecosystem structure and function experimentally over relatively long time‐scales. This paper describes change in community composition, major plant species, and plant functional types on moorland on peat in upland Britain over 60 years subject to 3 burning treatments after an initial burn in 1954/1955: no further burn and burning at 10‐ and 20‐year intervals (all ± sheep grazing). Data were analysed using multivariate and univariate methods. Vegetation composition and individual species abundance reflected the degree of disturbance. The least disturbed was dominated by Calluna vulgaris and pleurocarpous mosses, whereas the most disturbed treatment (burned every 10 years) had greater Eriophorum vaginatum, Sphagnum spp., acrocarpous mosses, liverworts, and lichens. The 20‐year treatment was intermediate in response disturbance. Repeated burning increased species abundance‐weighted Ellenberg values for moisture, reaction, light through time, and fertility; the exception was the 10‐year rotation for fertility. These confirm that prescribed burning is not deleterious to peat‐forming species (Eriophorum spp. and Sphagnum spp.), indeed these species were found in greater abundance in frequently burned treatments. It also confirms that a no‐burn policy will lead to increasing dominance of C. vulgaris, a flammable, fire‐adapted shrub, which increases summer wildfire risk. These results inform conservation management policy for moorland vegetation growing on peat; for this site, a 20‐year prescribed burning rotation is recommended.
Retention performances of green roofs worldwide at different time scales Land Degrad. Dev. (IF 9.787) Pub Date : 2018-04-19 Matteo Hellies; Roberto Deidda; Francesco Viola
Urbanization process is rapidly converting forested areas and grasslands to residential, commercial, or industrial spaces, triggering soil degradation and significantly increasing impervious surfaces. Consequently, man‐made environments experience significant decrease of infiltration and groundwater recharge, enhancing the problems related to the management and protection from increased stormwater runoff. Green roofs are structural measures able to mitigate these negative drawbacks due to anthropic transformation, retaining and detaining stormwater runoff, with the main advantage of reducing hydraulic loads on combined storm sewer systems. Hydrological performance of green roofs have been studied in different parts of the world under different climatic conditions, but a comprehensive study that provides global responses, even in an approximate way, is still missing. The aim of this work is to assess the convenience and the feasibility of installing green roofs in any target area of the world, providing a rough indication of geographic regions where green roof installation is possible with good hydrological performance, and feasible in rainfed conditions with low vegetation water stress. To do that, we explored in silico green roofs' hydrological performance worldwide, using climatological forcings from ERA‐Interim database as input for a simple conceptual hydrological model to estimate green roof outputs, in terms of evapotranspiration and runoff.
Contrasting suspended sediment export in two small agricultural catchments: Cross‐influence of hydrological behaviour and landscape degradation or stream bank management Land Degrad. Dev. (IF 9.787) Pub Date : 2018-04-19 Amphone Vongvixay; Catherine Grimaldi; Rémi Dupas; Ophélie Fovet; François Birgand; Nicolas Gilliet; Chantal Gascuel‐Odoux
The study aimed to identify hydrological and landscape factors that influence sediment transport in 2 agricultural catchments in north‐western France—Moulinet and Kervidy‐Naizin—with the same climate, size, and bedrock but with contrasting suspended sediment (SS) fluxes. Discharge and SS concentrations were continuously monitored at the catchment outlets for 9 hydrological years. Data were examined at annual, seasonal, and individual storm‐flow event scales. Storm events were classified into 3 types—single small, successive, and major events—whose effect on sediment transport was studied. At the annual scale, SS yields were higher in Moulinet (16–63 × 103 kg km−2) than in Kervidy‐Naizin (3–22 × 103 kg km−2) despite similar water fluxes. However, Kervidy‐Naizin had higher potential for hillslope erosion because of more frequent occurrence of saturation excess runoff, more frequent bare soil in cultivated area, and fewer hedgerows. Major storm events were also stronger in this catchment. Although high SS concentrations and fluxes occurred only during a few major events in Kervidy‐Naizin, SS export was always substantial throughout the year in Moulinet. We hypothesised that bank degradation due to cattle trampling generated the higher SS export in the Moulinet catchment. This hypothesis was confirmed by the large decrease in SS fluxes following construction of watering troughs in the middle of the study period. In the Kervidy‐Naizin catchment, natural woody vegetation or grass buffer strips along the stream effectively protect the stream from bank erosion or a possible influx of hillslope erosion particles, except during some major events in winter.
Short‐term and midterm evolution of topsoil organic matter and biological properties after prescribed burning for pasture recovery (Tella, Central Pyrenees, Spain) Land Degrad. Dev. (IF 9.787) Pub Date : 2018-04-19 Cecilia M. Armas‐Herrera; Clara Martí; David Badía; Oriol Ortiz‐Perpiñá; Antonio Girona‐García; Juan Luis Mora
We determined the short‐ and medium‐term effects of prescribed burns on soil organic matter content and biological activity in grazing areas invaded by the shrub Echinospartum horridum (Vahl) Rothm. in the Pyrenees of Huesca (Spain). Soil samples were collected at 0–1, 1–2, and 2–3 cm depths in triplicate just before the burn, immediately after the burn (T0), and 1 and 5 years later (T1 and T5). We analysed the contents of total soil organic C and N, soil respiration, microbial biomass C, and β‐d‐glucosidase and acid phosphatase activities. Fire provoked an immediate high decrease in the contents of soil organic C (−40.2%) and N (−26.3%) in the first 3 cm, which were even lower at T5 (−50.3% and −46.5%, respectively). This can be explained as follows: (a) low incorporation of burned organic matter due to removal by wind and run‐off; (b) changes in microclimate increasing soil temperature and enhancing mineralization; and (c) a stimulating effect on decomposition due to the release of nutrients. Soil biological activity was affected at T0 in the first 3 cm (−49.3% glucosidase, −48.2% phosphatase, and −54.5% respiration rate). Microbial biomass C content was also affected by fire at T0 (−32.3%) but was close to its initial value at T5. The results suggest that these soils are particularly sensitive to fire. Adjusting the frequency and intensity of the burns is necessary to minimize their impact on the soil and to ensure the suitability of this management practice.
Long‐term impact of land use changes on soil erosion in an agricultural catchment (in the Western Polish Carpathians) Land Degrad. Dev. (IF 9.787) Pub Date : 2018-04-19 Małgorzata Kijowska‐Strugała; Anna Bucała‐Hrabia; Piotr Demczuk
The change in land use and land cover (LULC) from natural vegetation to agricultural in mountain areas usually dramatically accelerates soil erosion rates if the land is used for crop production. The aim of research was to calculate soil erosion magnitude basing on the Revised Universal Soil Loss Equation (RUSLE) in response to long‐term changes in LULC in an agricultural Homerka catchment (19.3 km2) of the Polish Carpathians. The changes in LULC were derived from cadastral maps for 1846 and orthophotomaps for 2009. Three variants with different factors, rainfall–run‐off erosivity (R), practice support (P), and LULC, were analysed to investigate which has had the greatest impact on soil erosion changes over the last 160 years. An increase in forest area (by 67.81%) and decrease in cultivated land (by 91.94%) were observed, primarily due to the collapse of the communist system. The estimated soil erosion using the RUSLE model in the analysed catchment decreased by 77% (from 18.13 t ha−1 yr−1 in 1846 to 4.11 t ha−1 yr−1 in 2009). The long‐term changes in soil erosion rates and their spatial distribution are mainly associated with transformation from cultivated land to forest or grassland. The P factor was responsible for reduction of soil erosion rates by 8%, a minor impact. Over the last 160 years, the average and maximum annual precipitation changes were also statistically insignificant. Results reveal a dominant role of human impact, particularly with respect to LULC on soil erosion changes in mid‐mountain areas.
Modeling biophysical and anthropogenic effects on soil erosion over the last 2,000 years in central Mexico Land Degrad. Dev. (IF 9.787) Pub Date : 2018-04-19 Maria Lourdes González‐Arqueros; Armando Navarrete‐Segueda; Manuel E. Mendoza
Erosion prediction models recreate past scenarios, assess future ones, and determine the best explanatory variables of the soil erosion process. They are widely used and contribute valuable data for landscape management. This paper presents an estimation of soil erosion in the Teotihuacan Valley Basin in central Mexico, assessing its response to biophysical and anthropogenic components during 4 periods within the past 2,000 years. The valley has undergone past and recent anthropogenic erosion and, during the past 2 millennia, has experienced a marked variation in precipitation, variations in land use, soil management, and to a lesser extent, variations in soil type. With the use of the Water Erosion Prediction Project model, we estimated how the above‐mentioned parameters affect soil losses under 4 scenarios: (a) humid conditions (900 mm yr−1) during the Teotihuacan Period (1–650 CE), (b) dry conditions (370 mm yr−1) during the Aztec Period (1325–1521 CE), (c) humid conditions (900 mm yr−1) during the Aztec Period, and (d) present conditions (after 1970 CE; 560 mm yr−1). Comparison of scenarios and a principal component analysis of soil loss according biophysical components showed topography to be the most closely related parameter to soil erosion. Land use and soil type also showed a relationship with soil erosion, particularly during the Aztec Period; climate change did not appear to be the most significant factor in soil loss. Estimation of soil erosion by means of models is an inexpensive way to find answers to future challenges concerning soil erosion in a changing environment.
THE APPLICATION OF CIVIC TECHNOLOGIES IN A FIELD SURVEY OF LANDSLIDES Land Degrad. Dev. (IF 9.787) Pub Date : 2018-04-06 František Chudý; Martina Slámová; Julián Tomaštík; Daniel Tunák; Miroslav Kardoš; Šimon Saloň
Nature‐based solutions: The need to increase the knowledge on their potentialities and limits Land Degrad. Dev. (IF 9.787) Pub Date : 2018-04-16 João Paulo Fernandes; Nuno Guiomar
This paper analyzes the concept of nature‐based solutions as instruments to turn anthromes more nature compatible, efficient, causing less degradation, and developing new biodiversity hotspots. It is mainly focused on solutions using living organisms (in particular plants and microorganisms) to perform functions such as those of soil‐ and water‐bioengineering interventions in order to ensure the safety of human infrastructures and constructions in contexts of conflict between natural processes and human needs. Further, it handles the problematic of reintroducing natural processes and functions in the built environment (urban, industrial, infrastructures, etc.) in order to recover, recreate, or reinvent nature in humanized landscapes and developing a more creative relation between humans and natural elements, processes, and functions. It presents, furthermore, the contribution of natural solutions to a wide variety of decontamination processes and prevention and recovery of degraded land and natural resources. Finally, we discuss the way these solutions can be implemented and the cultural, organizational, administrative and governance, paradigmatic, and practice changes it implies. Examples are given on the different issues presented as well on the possible implementation solutions.
Estimating sustainable biomass harvesting level for charcoal production to promote degraded woodlands recovery: A case study from Mutomo District, Kenya Land Degrad. Dev. (IF 9.787) Pub Date : 2018-04-17 Geoffrey M. Ndegwa; Udo Nehren; Dieter Anhuf; Miyuki Iiyama
Charcoal is an important urban fuel; however, when production is unregulated, it is a major cause of land and forest degradation. Production through selective harvesting of the preferred large, hardwood tree species leads to a degraded residual forest or woodland composed of juvenile hardwood trees and unused softwood tree species. This situation can be addressed by ensuring that the rate of preferred tree species extraction does not exceed the mean annual increment. This study estimated the sustainable rate of tree harvesting for charcoal in Mutomo District, based on field data collected between December 2012 and January 2013, through a forest inventory. The woodlands are subjected to selective logging for charcoal production, an activity undertaken by about half of the residents for their livelihood. The study findings show that charcoal production through selective logging has led to a reduction of the hardwood trees biomass density to 3.8 t ha−1 compared with an estimated desirable level of 12.5 t ha−1. The results also show that it would take between 25 and 31 years for the woodlands to recover to the desirable stocking level if harvesting was completely stopped. This duration would increase to between 54 and 64 years if 80% of the mean annual increment was harvested for charcoal production and 20% was retained for woodlands recovery. As the residents of Mutomo District are poor and highly dependent on charcoal production for their livelihood, a harvesting plan based on the latter option would set the woodlands on the path to recovery and ensuring a sustainable livelihood source.
An improved method for determination of aggregate stability using laser diffraction Land Degrad. Dev. (IF 9.787) Pub Date : 2018-04-17 Andrzej Bieganowski; Tomasz Zaleski; Bartłomiej Kajdas; Agata Sochan; Agnieszka Józefowska; Michał Beczek; Jerzy Lipiec; Marcin Turski; Magdalena Ryżak
Soil aggregate water stability is very important from both scientific and practical points of view. This stability is a critical factor in a soil's susceptibility to water erosion and, in turn, land degradation. The most popular measure of soil aggregate stability is the water resistance index (WRI), which is commonly measured using the wet‐sieving method. Using the laser diffraction method in order to observe changes in the median of the particle size distribution and determine soil aggregate stability was first proposed in 2010. However, the method was not suitable for weak aggregates. The aim of this study was to present a measure of aggregate stability using laser diffractometry, aggregate stability index (ASILD). Determination of the ASILD is based on the calculation of the directional coefficient of the straight line interpolated from 2 points: (a) the value calculated as the mean of the lower and upper nominal sieve sizes used for soil aggregate separation and (b) the median of the first measurement after the adding of the dry aggregates into the measuring system of the laser diffractometer.
Offsetting land degradation through nitrogen and water management during maize cultivation under arid conditions Land Degrad. Dev. (IF 9.787) Pub Date : 2018-04-16 Hafiz Mohkum Hammad; Farhat Abbas; Shafqat Saeed; Shah Fahad; Artemi Cerdà; Wajid Farhad; Chaves Cordoba Bernardo; Wajid Nasim; Muhammad Mubeen; Hafiz Faiq Bakhat
The best management of soil, irrigation, and crop nutrients is among major components of sustainable agriculture that reduces groundwater contamination, prevents soil degradation, and guarantees the best resource use efficiency. Trials were conducted to optimize maize (Zea mays L.) yield by experimenting various irrigation water regimes, nitrogen (N) application rates, and methods in 96 pots under arid environmental conditions during autumn 2012. Crop hydrological and agronomic characteristics were assessed under a completely randomized design with factorial arrangements. Water and N stress to the plants under observation significantly reduced the water potential, osmotic potential, and turgor pressure of the leaves. Crop growth rate and total dry matter production were significantly improved by an increase in N fertilizer application up to 300 kg ha−1 (equivalent to 4.8 g N pot−1) for all water regimes. Grain per cob, 1,000‐grain weight, and final grain yield were higher at 100% field capacity with the application of 300 kg N ha−1 under the soil N application method than those under foliar N application treatments. The best N rate for optimum grain production was attained by 300 kg ha−1 with 575‐mm supplemental irrigation water ha−1. The quadratic equation fitting revealed that the effect of N on crop growth parameters was higher than that of the supplemental irrigation; therefore, a water deficit may partly be managed by adding N to the soil. These water and N managements may be used in formulating agricultural practices to avoid degradation of lands for soil and environmental conditions similar to those of the current study warranting a field research.
An estimation of the extent of cropland abandonment in mountainous regions of China Land Degrad. Dev. (IF 9.787) Pub Date : 2018-04-16 Shengfa Li; Xiubin Li; Laixiang Sun; Guiying Cao; Guenther Fischer; Sylvia Tramberend
With the wages for migrant workers increasing dramatically in China since 2003, the size of the agricultural labour forces has been shrinking rapidly. Intensively substituting agricultural machinery for the shrinking farm labour force is hardly possible for croplands in the mountainous regions of China where mechanization is difficult to achieve due to small field size and rough terrain. This has eventually led to cropland abandonment in these regions. Considering the high pressure for food security in China, cropland abandonment in the mountainous regions should not be ignored. By employing a novel method, this study estimates the extent of recently abandoned croplands (period 2000–2010) and the changes that can be expected in the future in China's mountainous areas. The results show that the total extent of abandoned croplands in Chinese mountainous counties during the period 2000 to 2010 is estimated at 147 million mu (1 mu = 666.67 m2); in total, about 28% of croplands in mountainous counties was abandoned, including croplands converted in the Grain for Green Programme. With 3 scenario assumptions, a sizeable extent, 114 to 203 million mu, of croplands may be abandoned from 2010 to 2030 with the rapid decrease and ageing of projected farm labour forces. This could exacerbate the future challenges of maintaining China's food security. A substantial increase in agricultural project investments, including land consolidation and agricultural productive fixed assets, especially microtillage machines, could help mitigate the risk of cropland abandonment. Additionally, land‐use and environmental policymaking should take into account the expanding cropland abandonment in mountainous regions.
Dry‐stone wall terrace monitoring and modelling Land Degrad. Dev. (IF 9.787) Pub Date : 2018-04-17 Federico Preti; Alessandro Errico; Marco Caruso; Andrea Dani; Enrico Guastini
Dry‐stone wall agricultural terraces are widespread all over the world and represent an effective retaining structure for farming purposes. However, dry‐stone walls can be subjected to degradation and damages, with complex and expensive maintenance. Such high costs are the most relevant drivers of land abandonment in many agricultural areas of Europe and of other continents, resulting in a progressive loss of cultivable surface, cultural heritages, and landscape traditional elements. Therefore, a more effective and efficient management of these systems is needed. As a contribution, in the present paper, an innovative modelling approach system is proposed. The presented model is able to describe hydrological processes on a terraced slope and to analyze the destabilizing pressures acting on the retaining dry‐stone walls in the most critical portion of each terrace. The model structure is based on the results of multidisciplinary field monitoring campaigns on water circulation in terraced landscapes carried out on a terraced vineyard (Lamole, Tuscany, Italy). A monitoring station was set up on a recently reconstructed dry‐stone wall, to measure the parameters influencing the pressures acting on the retaining structure. The results show a good capability of the model to predict the distribution and intensity of stresses on the instrumented dry‐stone wall over time and space. Such stresses were related to the earth pressure and to hydrostatic pressures (water accumulation), without the occurrence of soil saturation. Detecting the most failure‐prone portions of a terraced system, this approach can support landowners and land planners in managing these complex and fragile environments.
Excessive pruning and limited regeneration cause population decline of Faidherbia albida in the Rift Valley of Ethiopia Land Degrad. Dev. (IF 9.787) Pub Date : 2018-04-10 Tesfaye Shiferaw Sida; Frédéric Baudron; Dejene Adugna Deme; Motuma Tolera; Ken E. Giller
Scattered Faidherbia albida trees provide multiple ecological and production benefits across the Sahel. The intensive management and use of this important tree may impede its regeneration. Regeneration bottlenecks were explored and population dynamics modelled. On experimental plots in which seed of F. albida was sown, exposure to the first two months of dry season resulted in a quarter of seedling mortality. Exposure to season‐long free grazing and browsing caused significantly greater seedling mortality. Results from monitoring 100 permanent plots scattered over the landscape showed that adult population density was 4.2±0.3 (mean ± se) trees ha‐1 and dominated by old age classes. 60% of the total population were older than 30 years. The density for juveniles was 1.4±0.2 (mean ± se) individuals ha‐1. The annual rates of decline were 1.2%, 51.3%, and 63.2% for adults, seedlings, and saplings, respectively. Our model predicted that the F. albida population will start to decline within 1‐2 decades to eventually fall below one tree per hectare within 60 years under current management. The model highlighted that the limited seed source, caused by excessive pruning, was the main constraint for recruitment. Appropriate land management policy to ensure adequate seed production would avert current trends in decline of F.albida populations.
Effect of stand origin and slope position on infiltration pattern and preferential flow on a Loess hillslope Land Degrad. Dev. (IF 9.787) Pub Date : 2018-04-02 Xuemei Mei; Qingke Zhu; Lan Ma; Dong Zhang; Yu Wang; Wenjing Hao
Preferential flow is expected to provide an important pathway to replenish soil water at deep soil layers in arid or semiarid areas; however, few studies have addressed this topic, especially in semiarid Loess hillslopes. This study aimed to quantify the effect of stand origin and slope position on the contribution of preferential flow to total infiltration and spatial variations in water flow. A blue dye tracer experiment was conducted to visualize water flow in Robinia pseudoacacia plantation (PL), natural forestland (NF), and natural grassland (NG) at the upslope, midslope, and downslope, and semivariance analysis was used to determine spatial variability at the centimeter scale. The results showed that role of macropore flow was dominant in upslope and midslope, and larger in NF than that in PL and NG, due to presence of abundant root systems in the upper soil of NF. Moreover, contribution of preferential flow at the upper slope in NF was larger than that in PL. At the downslope, the role of rock fragments coverage at the downslope was emphasized, leading lateral flow dominant at the downslope in PL and NG. In addition, contribution of preferential flow and vertical variability of infiltration at the downslope in PL was higher than that in NF. The findings demonstrate that compared with PL, NF has a more positive impact on increasing infiltration and preferential flow that can replenish deep soil water, and reducing surface runoff and soil erosion. The presence of rock fragments coverage can make lateral flow dominant at the downslope on the Loess hillslope, related to water movement along the slope toward streams and catchment outlets.
Structural heterogeneity of vegetation fire ash Land Degrad. Dev. (IF 9.787) Pub Date : 2018-04-02 Anna Brook; Lea Wittenberg; Daniella Kopel; Maria Polinova; Dar Roberts; Charles Ichoku; Nurit Shtober‐Zisu
Any wildfire generates ash, the solid residue derived from burning biomass. Vegetation fire ash consists of charred organic material, charcoal, and inorganic mineral substances. Recent studies identified ash deposits as a dual system: soil and ash strata. The addition of ash to the soil profile alters soil properties and dynamics. A thorough analysis of ash–soil profile reveals a structural appearance of thin laminas. The laminas differ in a variety of physical properties and mineral composition. This research aims at assessing the unique properties of ash–soil profiles by performing an infrared spectroscopic study and statistical analysis. For that purpose, several laboratory experiments were conducted. The paper presents semiquantitative results of spectral analysis calculated by 4 statistical methods. The results indicate a well‐established laminar structure of the ash and evaluate the characteristics of each lamina. The proposed methodology was examined under real‐world conditions; a field experiment of 2‐m2 parcel with in situ O horizon was flamed and burned out. The field samples illustrated the formation of microlaminas, which proved to be similar to the laboratory samples. This detailed approach may promote a better understanding of the complex nature to the ash, the ash–soil interactions and its effect on the edaphic ecosystem.
Influence of different sewage sludges and composts on growth, yield, and trace elements accumulation in rice and wheat Land Degrad. Dev. (IF 9.787) Pub Date : 2018-03-30 Umair Riaz; Ghulam Murtaza; Saifullah; Muhammad Farooq
The use of sewage sludge (SS) and solid waste composts in agriculture is considered as one of the best disposal options. In this study, impact of different composts and SS was evaluated on the soil quality, growth, and yield performance of rice and wheat crops. Four types of composts and SS were collected from different sources and applied in soil at 0.5% (5 g kg−1 soil) and 1.0% (10 g kg−1 soil) in comparison with chemical fertilizer (no SS/compost). The application of all types of composts at all the tested rates increased the straw and grain yields of both the crops compared with control. Nevertheless, application of Lahore compost and all SS (1.0%) resulted in a significant increase in the concentration of cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn) in plant parts. The Cd concentration in rice grains with Lahore compost and Kasur SS applied at the rate of 1.0% was above the safe limit. The trace elements in wheat grains with all composts and SS at all the tested rates remained within safe limits. The release of amendment bound trace elements in soil solution was highly dependent upon dissolved organic carbon and concentration of these trace elements especially for Cu and Zn. Application of SS at low level (0.5%) and compost (except Lahore compost) at both levels could be a better strategy to exploit their benefits in terms of crop performance and soil quality. However, application of SS and compost at high rates may lead to accumulation of trace elements in rice grains limiting its suitability for human consumption.
The role of rapid glacier retreat and landscape transformation in controlling the post‐Little Ice Age evolution of paraglacial coasts in central Spitsbergen (Billefjorden, Svalbard) Land Degrad. Dev. (IF 9.787) Pub Date : 2018-03-30 Mateusz C. Strzelecki; Antony J. Long; Jeremy M. Lloyd; Jakub Małecki; Piotr Zagórski; Łukasz Pawłowski; Marek W. Jaskólski
In Svalbard, the rapid glacier retreat observed since the end of the Little Ice Age (LIA) has transformed the geomorphology and sediment budgets of glacial forelands, river valleys, and slope systems. To date, relatively little information exists regarding the impact of such a profound glacial landscape degradation on the evolution of coastal environment. This paper addresses this deficiency by detailing the post‐LIA sediment fluxes to the coastal zone in Billefjorden, central Spitsbergen (Svalbard). We analysed the response of the gravel‐dominated barrier coast to the decay of Ferdinandbreen, one of the fastest retreating glaciers in the region. Glacier retreat resulted in the development of paraglacial sediment cascade where eroded and reworked glacigenic sediments progressed through alluvial fans to the coast, thus feeding gravel‐dominated spit systems in Petuniabukta. We demonstrated that the coastal systems in central Spitsbergen responded abruptly to post‐LIA climatic changes. The acceleration of coastal erosion and associated spit development was coincident with rapid climate warming that dates from the 1980s and has been associated with longer ice‐free periods and activation of multiple sediment supply sources from the deglaciated landscape. In colder phases of post‐LIA period, coastal zone development was subdued and strongly dependent on the efficiency of sediment transport via in a longshore drift. Finally, we discuss the differences in the post‐LIA coastal responses between central Spitsbergen and western Spitsbergen highlighting the efficiency of paraglacial sediment delivery from land to the coast controlled by the state of glacial systems, bedrock topography, and development of river channels.
The influence of trees, shrubs, and grasses on microclimate, soil carbon, nitrogen, and CO2 efflux: Potential implications of shrub encroachment for Kalahari rangelands Land Degrad. Dev. (IF 9.787) Pub Date : 2018-03-30 Andrew David Thomas; David R Elliott; Andrew John Dougill; Lindsay Carman Stringer; Stephen Robert Hoon; Robin Sen
Shrub encroachment is a well‐documented phenomenon affecting many of the world's drylands. The alteration of vegetation structure and species composition can lead to changes in local microclimate and soil properties which in turn affect carbon cycling. The objectives of this paper were to quantify differences in air temperatures, soil carbon, nitrogen, and CO2 efflux under trees (Vachellia erioloba), shrubs (Grewia flava), and annual and perennial grasses (Schmidtia kalahariensis and Eragrostis lehmanniana) collected over three seasons at a site in Kgalagadi District, Botswana, in order to determine the vegetation‐soil feedback mechanism affecting the carbon cycle. Air temperatures were logged continuously, and soil CO2 efflux was determined throughout the day and evening using closed respiration chambers and an infrared gas analyser. There were significant differences in soil carbon, total nitrogen, CO2 efflux, light, and temperatures beneath the canopies of trees, shrubs, and grasses. Daytime air temperatures beneath shrubs and trees were cooler compared with grass sites, particularly in summer months. Night‐time air temperatures under shrubs and trees were, however, warmer than at the grass sites. There was also significantly more soil carbon, nitrogen, and CO2 efflux under shrubs and trees compared with grasses. Although the differences observed in soils and microclimate may reinforce the competitive dominance of shrubs and present challenges to strategies designed to manage encroachment, they should not be viewed as entirely negative. Our findings highlight some of the dichotomies and challenges to be addressed before interventions aiming to bring about more sustainable land management can be implemented.
To dam, or not to dam? Abolishment of further flooding impedes the natural revegetation processes after long‐term fluvial deposition of copper tailings Land Degrad. Dev. (IF 9.787) Pub Date : 2018-03-24 Nina Nikolic; Ljiljana Kostic; Miroslav Nikolic
Long‐term potentials and constraints of nature to spontaneously recover after severe degradation by toxic mine waste, and general principles of mutual modifications of spontaneous vegetation and soils during this process, have remained widely unknown. This study investigates the effect of flooding on natural restoration of a model locality in Eastern Serbia, complexly degraded by 70‐years fluvial deposition of sulfidic copper (Cu) mine tailings in a floodplain along 80 km of the polluted river flow. We analyzed multivariate response of forest vegetation (floristic and structural parameters) together with physical and chemical properties of concomitant soils and sediments. Floods strongly modify the interactions between soil and vegetation. Three very different types of forest vegetation constitute the response of the nature to key soil adverse factors (excessive Cu availability, low nutrients, and low pH); combined with drought, these constraints completely inhibit revegetation. Continual flooding after mine closure, despite the pollution it still brings in, fosters a faster development of highly specialized vegetation and most importantly faster buildup of soil organic matter necessary for phytostabilization of substantial amounts of Cu tailings present in the floodplain. We show that enhanced nutrient fluxes facilitated by natural flooding regime might overrun the constraining effect of deposited Cu also for natural vegetation.
Glyphosate and AMPA concentrations in wind‐blown material under field conditions Land Degrad. Dev. (IF 9.787) Pub Date : 2018-03-23 Virginia C. Aparicio; Silvia Aimar; Eduardo De Gerónimo; Mariano J. Mendez; José L. Costa
Agricultural intensification in fragile arid and semiarid environments has led to an increase in soil degradation, mainly through wind erosion. Argentina is an agricultural and cattle‐farming country, which has increased its productivity in the last few decades, widening the boundaries of farm land and the use of herbicides to control weeds. Glyphosate, which accounts for 65% of the Argentinian pesticides market, is strongly retained in soil. The World Health Organization concluded that there was evidence to classify glyphosate as ‘probably carcinogenic to humans.’ In this context, the objective of this study was to determine the presence and concentration of glyphosate and aminomethylphosphonic acid (AMPA) in wind‐blown material in 3 areas in Argentine semiarid regions (Chaco, La Pampa, and San Luis). In 1‐ha2 plots, left uncovered and levelled, the wind‐blown material was collected at heights of 13.5, 50, and 150 cm during 18 erosion events. The wind‐blown material carried by the wind at a height of 150 cm had concentrations of 247 and 218 μg kg−1 of glyphosate and AMPA, respectively. This material was enriched 60 times in glyphosate and 3 times in AMPA as compared with the original soil. This shows that the eroded material can, potentially, have a negative impact on the ecosystem and also on human health, depending on the proportion of this material released into the atmosphere in suspension as particulate matter. This study is, to our knowledge, the first to report concentrations of glyphosate and AMPA in wind‐blown material under field conditions.
Carbon balance as affected by biosolid application in reforestations Land Degrad. Dev. (IF 9.787) Pub Date : 2018-03-24 Alejandro Valdecantos; David Fuentes
Soils of Mediterranean drylands are characterized by a low fertility and organic matter content because of past land use and disturbances regime. The restoration of these degraded lands faces at the same time problems related to water scarcity and the unpredictability of precipitations with problems with soil physical, chemical, and microbiological properties. Organic amendments may help to improve soil properties and, consequently, enhance planted seedling establishment and performance. In this study, we assessed the C balance of 3 Mediterranean areas planted with Pinus halepensis Mill. seedlings with different treatments of biosolid application. The assessment was conducted at different times after the establishment of treatments and the C dynamics are discussed. We considered 3 biosolid types (air‐dried, fresh sludge, and composted sludge) in application doses ranging from 10 to 320 Mg (d.w.) ha−1. We quantified basal area, pine biomass, biomass of spontaneous vegetation, litter, root density, and soil organic matter. All 3 experimental restoration studies improved restoration success in terms of basal area (ranging from 15% to 300%), especially in composted biosolid at 30 Mg (d.w.) ha−1, whereas litter and, especially, root biomass increased with all biosolid treatments and times since application. Soil organic C was higher in application doses above 30 Mg (dry weight) ha−1 due to the organic matter applied with the sludges. The increment in C sequestration rates associated to these restoration treatments ranged between 0.046 and 0.293 kg C m2 yr−1. These results confirm the suitability of organic amendments as restoration technique in Mediterranean degraded drylands.
Comparing topsoil charcoal, ash, and stone cover effects on the postfire hydrologic and erosive response under laboratory conditions Land Degrad. Dev. (IF 9.787) Pub Date : 2018-02-02 Sergio Alegre Prats; João Rafael Cardoso de Brito Abrantes; Celeste de Oliveira Alves Coelho; Jan Jacob Keizer; João Luis Mendes Pedroso de Lima
Wildfires typically transform vegetation and litter into a heterogeneous layer of ash and charred material covering the soil surface that can substantially modify the postfire hydrological and erosive response. To further elucidate the influence of postfire covering layers on sheet and concentrated flow erosion, we carried out laboratory rainfall and inflow simulations on 5 distinct soil surface conditions: bare soil, with a protective cover of char, ash, stones, and a combination thereof simulating field conditions. Each of 3 replicate simulations per treatment involved 4 runs, the first 2 simulating just rain (at 56 mm hr−1) under dry and wet soil conditions and the next 2 simulating rain together with inflow at high and extreme rates (0.76 and 1.4 L min−1). Overall runoff over the 4 runs together was lower for all 4 types of protective cover than for bare soil, but ash and char were clearly less effective than stones and, in particular, field conditions with runoff reductions of 25%, 23%, 40%, and 70%, respectively. Stones and field conditions were similarly effective in reducing overall erosion rates (with 47% and 77%, respectively), whereas ash and char even slightly increased overall erosion rates compared to bare soil. Ash and char were effective in reduction erosion but only during the first 2 runs under simulated rainfall. The greater effectiveness of the field conditions suggested synergistic effects between its 3 components, probably due to the stones enhancing infiltration and increasing flow resistance, thereby hampering detachment of ash and char and/or enhancing their deposition.
Postagrogenic development of Retisols in the middle taiga subzone of European Russia (Komi Republic) Land Degrad. Dev. (IF 9.787) Pub Date : 2018-02-05 Alexey A. Dymov; Yuriy A. Dubrovskiy; Viktor V. Startsev
Reforestation on abandoned agricultural lands is widespread in the belt of boreal forests. We analyzed the morphological and physicochemical properties of a Plaggic Glossic Retisol (Siltic, Cutanic) site that had been abandoned either 7, 19, or 85 years ago, as well as a Glossic Stagnic Retisol (Siltic, Cutanic) as a control. Involvement of forest soils in agricultural use results in the degradation of organic horizons, which are not restored until many decades after the termination of active agricultural use. Arable soil horizons were preserved and were clearly identified 85 years after the land had been abandoned. The morphological features of the eluvial and subeluvial horizons were determined at all sites. Soils at sites that had been abandoned for 7 and 19 years showed lower acidity and higher base saturation compared to the background soil. Total carbon stocks were lower at the abandoned sites. The slow increase of carbon stocks after the soil had been abandoned is caused by C increase as in the organic as in the topsoil mineral horizons. Soils that had been abandoned for 7 and 19 years contained less water‐extractable forms of C and N than the control and 85‐year forest soils. Agricultural use leads to a reduction in C stocks of forest soils. The postagrogenic soil C sequestration rate was estimated to be 30–40 g·m−2·yr−1.
Effects of environmental factors on soil organic carbon under natural or managed vegetation restoration Land Degrad. Dev. (IF 9.787) Pub Date : 2018-02-06 Pei‐Lei Hu; Shu‐Juan Liu; Ying‐Ying Ye; Wei Zhang; Ke‐Lin Wang; Yi‐Rong Su
To expand the scientific understanding of soil organic carbon (SOC) accumulation in restored ecosystems, we used 246 soil samples from a rocky catchment (10.24 km2) in an ecologically fragile karst area of southwest China and measured the effects of environmental factors under different vegetation restoration types (managed, including forage grassland and plantation forest, or natural, including grassland, shrubland, and secondary forest) on soil organic carbon content (SOCC) and soil organic carbon density (SOCD). Significantly higher SOCC and SOCD were found in natural vegetation than in managed vegetation and tillage land but no differences in SOCC or SOCD were detected between managed vegetation and tillage land. The environmental factors include rock outcrop ratio (ROR), bulk density, altitude, soil depth, slope gradient, and pH, all showing significant effect on SOC. The proportion of variations in SOCC and SOCD explained by environmental factors was higher in natural vegetation restoration than in managed vegetation restoration, and this proportion increased along the successional gradient. However, the environmental factors driving variations in SOCC and SOCD differed according to vegetation type. Soil bulk density had the strongest effect on SOCC variation in all vegetation types, except for forage grassland, in which the variation was instead controlled by ROR. The variation of SOCD was mainly driven by ROR in most vegetation types, except for tillage land and forage grassland, in which the driving factor was altitude. This results indicated that natural vegetation restoration is more beneficial to SOC sequestration than managed vegetation restoration and thus for mitigating global climate change. Accordingly, future studies should take these different environmental drivers under different vegetation restoration types into consideration when modeling SOC and guiding restoration management.
Drift sand fields as a result of past and current deforestation in the Silesian‐Cracow Upland, Poland Land Degrad. Dev. (IF 9.787) Pub Date : 2018-02-08 Renata Dulias
The Silesian‐Cracow Upland, due to the exceptionally large reserves of various natural resources, was under the influence of intense human activity throughout the last millennium. Economic development of the Upland began in the Middle Ages by mining and smelting of iron ore, silver, and lead; from the 18th to the 20th century, the area experienced intense exploitation of coal, zinc and lead ores, stowing sands, as well as dolomites and limestone. Mining and metallurgy have almost always been associated with deforestation. The sandy substrate devoid of vegetation was subjected to aeolian processes, resulting in numerous fields of drift sands. In this paper, based on the analysis of archival and contemporary cartographic materials, as well as historical and archaeological studies and field research, spatial distribution of drift sands was determined, its origin, the time of creation, and durability in the landscape. Research showed that drift sands appeared in the Middle Ages and its ‘desert’ character persisted for 200–300 years, often even for 400–500 years. In the second half of the 20th century, most of the former areas with drift sands were afforested. Currently, bare sands are found only on 2 areas in the Silesian‐Cracow Upland. As unique landscapes, they require special protection because of the biodiversity and geodiversity. Research confirmed that historical interpretations are a valuable source of information about the old landscapes. This knowledge can and should be used by local authorities, institutions, and societies to manage the space, respecting the traces of the settlement and the economic past.
Increased soil methane emissions and methanogenesis in oil contaminated areas Land Degrad. Dev. (IF 9.787) Pub Date : 2018-02-08 Juejie Yang; Guanghe Li; Yi Qian; Fang Zhang
Crude oil exploration and related activities cause severe soil contamination and land degradation. However, how soil CH4 and CO2 fluxes respond to oil contamination is poorly understood. To address this question, we conducted in situ investigation of CH4 and CO2 emissions in the Shengli Oilfield, China. CH4 emissions from contaminated soils were 60–1,800 μg·m−2·hr−1, much higher than those from uncontaminated soils (29–33 μg·m−2·hr−1). CO2 fluxes of 2–78 mg·m−2·hr−1 were lower from contaminated soils compared with uncontaminated controls (78–104 mg·m−2·hr−1). The variance of CH4 and CO2 fluxes could be explained to 78.0% by soil properties and oil well age (p < .001) as suggested by the redundancy analysis and the variance partitioning analysis. On the basis of the Illumina MiSeq sequencing of the archaeal 16S rRNA gene, the relative abundance of methanogens over archaea increased by 8 times in contaminated soils compared with that in the uncontaminated soils, suggesting enhanced methanogenesis processes. The proportion of hydrogenotrophic methanogens over the total methanogens increased from 35% in the uncontaminated soil to 43% in the contaminated soils, consistent with the higher apparent fractionation factor (αC) in the stable isotope analysis. Both microbial and isotopic results suggested that the hydrogenotrophic methanogenesis relatively enhanced with the oil contamination, with less dominance of the acetoclastic methanogenesis. The dramatically increased CH4 emissions under oil contamination call for great attention as a potentially important anthropogenic source of CH4 in the atmosphere.
Identifying sediment source areas in a Mediterranean watershed using the SWAT model Land Degrad. Dev. (IF 9.787) Pub Date : 2018-02-12 Giovanni Francesco Ricci; Anna Maria De Girolamo; Ossama M.M. Abdelwahab; Francesco Gentile
This study aims to evaluate the suitability of the Soil and Water Assessment Tool model in simulating runoff and sediment loss in the Carapelle (SE Italy), a typical Mediterranean watershed, where continuous measurements of streamflow and sediment concentration were collected over a 5‐year period, on a half‐hour timescale, processed on a daily timescale. After sensitivity analysis, the model was calibrated and validated for runoff and sediment. Statistics show generally satisfactory efficiency. To further improve sediment simulation performance, we used a seasonal calibration scheme, in which data recorded in the dry and wet seasons were used to calibrate sediments separately, on a seasonal basis. We also tested the model's capability in identifying the major sediment source zones and river segments where there is sediment deposition. On the basin scale, the average water yield (186 mm) corresponds to 27% of the total rainfall (686 mm), and average annual sediment load was estimated to be 6.8 t ha−1 year−1. On the subbasin scale, a gradient of sediment yield was found that is characterised by a large difference among the upper (7 to 13 t ha−1 year−1), central, and lower parts (<1 t ha−1 year−1) of the study area. Conversely, deposition in channel flow has its highest values in the central part of the watershed, where there is an alluvial plain. Winter wheat and olive land use are the major source areas, in terms of sediment. This study confirms that the Mediterranean watershed is a fragile ecosystem, and measures are needed to mitigate soil depletion.
Addition of graphene sheets enhances reductive dissolution of arsenic and iron from arsenic contaminated soil Land Degrad. Dev. (IF 9.787) Pub Date : 2018-02-13 Zheng Chen; Heng Li; Wende Ma; Dun Fu; Kezeng Han; Haitao Wang; Ning He; Qingbiao Li; Yuanpeng Wang
The deposition of slag from a realgar tailing mine has caused serious land degradation to those farming and mining coexisting areas. However, nanomaterial‐mediated biogeochemical arsenic cycle from arsenic‐enriched soil was severely limited. In this study, the environmental impact of graphene oxide (GO) and reduced GO (rGO) on the speciation and mobilization of Fe/As from the flooding of arsenic‐enriched soil was investigated. Regarding overall performance, rGO exhibited a more significant facilitation than GO on mediating microbial reduction of Fe(III)/As(V). The maximal levels of soluble Fe(II) and As(III) in the soil supplemented with acetate alone were 53.58 g.m−3 and 9592 mg·m−3 during the 50‐day culture period. Nearly 1.37‐fold and 1.15‐fold of As(III) levels were released when amending with rGO acetate and GO acetate. Meanwhile, approximately 1.40‐fold and 1.24‐fold of Fe(II) levels were released under the same conditions. The underlying mechanism was correlated with the interactions between graphene and microbial activities. The properties of GO have been evolved through microbial reduction and eventually exhibited characteristics similar to rGO. Additionally, the application of graphene potentially altered the compositions of the microbial community and increased the abundance of some metal‐reducing bacteria (e.g., Bacillus, Geobacter, and Desulfitobacterium), thereby favouring the dissolved organic matter bioavailability for bioreduction of Fe(III)/As(V). In addition, promotion of the electron transfer process of As(V)/Fe(III) reduction was predominantly responsible for the crucial role that rGO exhibited as a special redox‐active mediator and electrical conductor. These findings might provoke more consideration of the integrated ecological effects of graphene and evaluate their environmental impact on land degradation.
Modeling variations in soil salinity in the oasis of Junggar Basin, China Land Degrad. Dev. (IF 9.787) Pub Date : 2018-02-15 Ligang Ma; Shengtian Yang; Zibibula Simayi; Qing Gu; Jiadan Li; Xiaodong Yang; Jianli Ding
Soil salinization leads to a significant degradation for oasis land. Variations in soil salinity are controlled by geologic, geomorphic, climatic, and hydrologic factors that are scale dependent. Many factors characterize soil salinity and its variations. Empirical mode decomposition (EMD) and correlation analysis are usually applied to examine the variations of soil salinity at different scales. However, few researches have been conducted on the modeling of these variations among different scales that requires further development and refinement. This paper investigates the potential of assessing scale‐specific variations in soil salinity via EMD using 2 modeling approaches (random forest and linear models). The remotely sensed environmental factors including land surface temperature, evapotranspiration, Tropical Rainfall Measuring Mission precipitation, and digital elevation model products were used as inputs for the models. The Junggar Basin in Xinjiang Province of China was selected as study area because the oasis was quite typical in the whole country and even in mid‐Asia. Soil salinity data and environmental factors were first decomposed using the EMD algorithm. Then, the decomposed components of the remotely sensed environmental factors were evaluated, and the most important components of each factor were selected to model the salinity variations that were represented by the decomposed components of soil salinity. The salinity variations estimated from the environmental factors were favorably consistent with the decomposed components of the soil salinity data, with coefficients of determination (R2) ranging from 0.24–0.52 and 0.73–0.98 for the linear and random forest models, respectively. In addition, land surface temperature and salinity were coupled well at the 326‐ and 334‐km scale. Our results showed that reasonably accurate results can be obtained using the proposed approach.
History of fires and vegetation since the Neolithic in the Cantabrian Mountains (Spain) Land Degrad. Dev. (IF 9.787) Pub Date : 2018-02-19 Virginia Carracedo; Raquel Cunill; Juan Carlos García‐Codron; Albert Pèlachs; Ramon Pérez‐Obiol; Joan Manuel Soriano
Fire has been one of the main causes of disturbance of vegetation over time, and since the Neolithic has become an irreplaceable tool for the opening of forest spaces and maintenance of pastures. Previous studies showed that the intensity and effects of wildfires are related to the biomass and controlled by climate factors. However, in regions such as Cantabria, where agriculture and livestock have spread throughout the territory since prehistory, fires should also be closely related to human land uses. The aim of this paper was to investigate the history of fires and vegetation since the Neolithic in the Cantabrian Mountains, using sedimentary charcoal and pollen data to study the role of human activities in the processes that have shaped ecosystems throughout the Holocene. The asynchrony and quantitative differences in the results obtained at different sites indicate significant variations in fire patterns at regional scale since the Neolithic, although the type and size of each basin also had a strong influence on charcoal accumulation. Maximum values for charcoal accumulation rate at La Molina were observed between the Neolithic and the Bronze Age but occurred after about 3500 cal years BP at El Cueto de la Avellanosa. At El Sertal, low charcoal accumulation rate values were observed, probably because the sequence begins in a space that already had been cleared; the maximum values occurred during the most recent millennium. These data provide evidence that fire has been a key factor in forest retreat and in maintaining open landscapes since the Neolithic.
Impact of stone bunds on temporal and spatial variability of soil physical properties: A field study from northern Ethiopia Land Degrad. Dev. (IF 9.787) Pub Date : 2018-02-20 Andreas Klik; Christoph Schürz; Stefan Strohmeier; Nigus Demelash Melaku; Feras Ziadat; Andreas Schwen; Claudio Zucca
In the Ethiopian Highlands, stone bunds (SBs) are a common practice for soil and water conservation, influencing runoff and erosion processes from sloped agricultural areas. The objective of this study was to investigate how SBs affect spatiotemporal relationships of these processes to better understand their impacts on soil water development at the smallholder farmer's field level. Study area was the Gumara‐Maksegnit Watershed in northern Ethiopia, where two representative transects were investigated: One transect crossed a 71 m‐long field intersected by 2 SBs traced along the contour. The second transect crossed a similar hillslope without conservation structures at a length of 55 m representing baseline (untreated) conditions (no stone bund). During the rainy season of 2012, bulk density and volumetric water content were monitored, and tension disc infiltrometer experiments were performed to determine the saturated hydraulic conductivity and to derive soil water retention characteristics. Our observations show that SB decreased significantly soil bulk density in center and lower zones of SB transect compared with no stone bund. No temporal change was observed. Results targeting the surface soil moisture indicate that infiltration was higher with SB and happened earlier in the rainy season in the zones around the SBs. Saturated hydraulic conductivity was positively affected by SB and increased significantly. Improved soil hydrology by SB fields may increase crop yields by higher soil water contents but also by extending the growing season after the rainy season. Therefore, SBs are a successful measure to establish climate‐resilient agriculture in the Ethiopian Highlands.
The cost‐efficiency and reliability of two methods for soil organic C accounting Land Degrad. Dev. (IF 9.787) Pub Date : 2018-02-20 Raphael A. Viscarra Rossel; Dick J. Brus
Sequestering organic carbon (C) in soil can help to combat land degradation, improve food security, and mitigate greenhouse gas emissions and climate change. But we need reliable, cost‐efficient methods to assess, monitor, and verify the change. Here, we compared two methods for the direct measurement of soil organic C stocks and for monitoring the change. Our aims were to quantify the soil organic C stock in two carbon estimation areas, under cropping and grazing, using composite sampling with two designs and proximal sensing. We compared the two schemes in terms of the (a) accuracy of the estimated C stocks, the total cost, and the cost‐efficiency, calculated as the ratio of the accuracy of the estimate and the total cost, and (b) uncertainty of the estimated standard error of the estimated C stocks. We found that compositing was cheaper but more inaccurate than sensing. Sensing was 1.2 to 2.1 times more cost‐efficient than compositing. We also found that the uncertainty of the estimated standard errors from compositing was large and unreliable, which can hinder the quantification of a minimum detectable difference in organic C stocks. We show that the sensor‐derived spatially explicit data can also be used to map the C stocks, which can help to optimise the sampling design in subsequent monitoring rounds. Our findings have important implications for the development of C measurement and monitoring methodologies. Visible–near infrared and gamma attenuation sensing can accurately, cost‐efficiently, and reliably monitor and verify changes in soil C stocks.
Grass and maize vegetation systems restore saline‐sodic soils in the Songnen Plain of northeast China Land Degrad. Dev. (IF 9.787) Pub Date : 2018-02-22 Shasha Luo; Lei Tian; Chunling Chang; Shaojie Wang; Jianfeng Zhang; Xue Zhou; Xiujun Li; Lam‐Son Phan Tran; Chunjie Tian
Establishment of an appropriate vegetation system for reclamation of saline‐sodic soils requires studies for specific salt‐affected region(s). The phytoremediation of saline‐sodic soils has not been well documented in the Songnen Plain of northeast China. Thus, in this study, we aimed to investigate the effects of grass (G) and maize (Zea mays L.; M) vegetation systems, which were established for 5 years, on soil properties of 10 typical saline‐sodic sampling sites across the Songnen Plain, in comparison with respective nonvegetated areas that were used as controls (CK) for the evaluation of variability among the sampling sites. Physicochemical properties, such as soil moisture, bulk density, porosity, saturated hydraulic conductivity, aggregate stability, pH, electric conductivity, total salt, organic C, total N, and C/N ratio, were analyzed. G and M vegetation significantly produced a 108% and 153% improvement in soil quality, respectively. Additionally, metagenomic analysis of the soil bacterial community revealed that vegetation enhanced the ability of the bacteria to survive in saline‐sodic soils, relative to the control. The composition of the bacterial community was highly correlated with all of the soil physicochemical properties. G vegetation had better effects than M vegetation in enhancing soil organic C, total N and aggregate stability, whereas M vegetation more favorably adjusted soil pH, physical structure, and bacterial community than G vegetation did. Collectively, these findings demonstrate that M vegetation has a greater impact than G vegetation on repairing saline‐sodic soils in the Songnen Plain of northeast China.
Biochar influences soil carbon pools and facilitates interactions with soil: A field investigation Land Degrad. Dev. (IF 9.787) Pub Date : 2018-02-22 Ali El‐Naggar; Yasser M. Awad; Xiang‐Yu Tang; Chen Liu; Nabeel Khan Niazi; Shih‐Hao Jien; Daniel C.W. Tsang; Hocheol Song; Yong Sik Ok; Sang Soo Lee
Biochar promotes the storage of organic carbon (OC) in soils. OC is unevenly distributed in soils among different particle‐size fractions showing different structures, functions, and stability. The objective of this study was to investigate the biochar–soil interactions and the redistribution of soil C in different soil fractions based on a 2‐year field experiment. Fractionation was done by particle sizes including coarse sand (250–2,000 μm), fine sand (53–250 μm), and silt/clay (<53 μm). Integrated spectroscopic techniques were employed to examine physical characteristics of biochar–soil interactions in different soil fractions. Application of biochar increased OC by 37%, 42%, and 76% in soil particle‐size fractions of 53–250, <53, and 250–2,000 μm, respectively. This was supported by X‐ray fluorescence spectroscopy analysis, which showed an increase of C contents by 5–56% with biochar addition. The highest increment in OC was found in coarse sand fraction, and redistribution of OC was detected depending on various soil particle sizes. Results of scanning electron microscopy combined with electron dispersive X‐ray spectroscopy analysis showed the interactions between soil and biochar, which could be attributed to oxidized functional groups (OCO, CO, and CO) captured by the X‐ray photoelectron spectroscopy. The long‐term aged biochar could be beneficial to enhance soil quality by promoting OC storage and facilitating positive biochar–soil interactions.
Ants respond more strongly to grazing than changes in shrub cover Land Degrad. Dev. (IF 9.787) Pub Date : 2018-03-02 Gabriella N. Radnan; David J. Eldridge
Increases in the cover or density of woody plants (encroachment) and overgrazing by European livestock are 2 major drivers of ecosystem structure and function in drylands and are often associated with land degradation. Although the effects of encroachment and overgrazing on vascular plants are relatively well known, little is known about their effects on arthropods such as ants. We examined ant community composition at sites ranging in shrub cover in a wooded dryland in eastern Australia, testing the notion that increasing shrub cover and grazing intensity would alter ant assemblages and functional group composition. We used ants because they are abundant, diverse, and respond to small‐scale environmental changes. Increasing shrub cover had no effect on ant richness, diversity, or evenness but increased the abundance of Subordinate Camponotini. Larger shrubs tended to have greater ant richness, and abundance of Cold Climate Specialists, but fewer Generalized Myrmicinae and Hot Climate Specialists. More intense grazing was associated with greater ant richness, diversity, and evenness; a greater abundance of Hot Climate Specialists and Dominant Dolichoridae; and lower abundance of Subordinate Camponotini. Our study indicates that changes in grazing intensity had stronger effects on ant richness than any increase in shrub cover. The effects of grazing likely resulted from changes in soil surface complexity such as barer ground associated with grazing‐induced degradation.
Recent greening (1981–2013) in the Mu Us dune field, north‐central China, and its potential causes Land Degrad. Dev. (IF 9.787) Pub Date : 2018-03-02 Zhiwei Xu; Rui Hu; Kexin Wang; Joseph A. Mason; Shuang‐Ye Wu; Huayu Lu
Desertification of arid and semiarid land is a severe environmental problem. Better understanding of the desertification process, in the context of changing climate and growing human activities, is essential for policy‐making on desertification control strategies and land‐use management in these environmentally sensitive areas. In this study, we analyze vegetation change and dune activity over the years 1981–2013 in Mu Us, a semiarid dune field in north‐central China, using remote sensing techniques and geomorphic analysis. During this period, we have observed an increasing trend in vegetation greenness, indicated by the Normalized Difference Vegetation Index, which is consistent with the decreasing trend of the dune mobility index. Changes in dune morphologies in the study area indicate that dunes are being stabilized under vegetation growth, and this morphological change could potentially be used to detect the long‐term trend in desertification. Based on a detailed analysis of both climatic and socioeconomic data, we found that the decadal changes in wind strength have significant impact on the long‐term vegetation rehabilitation in the study area and that the short‐term variations in vegetation growth are associated with interannual fluctuations in precipitation. Policy‐driven, large ecological restoration projects implemented in recent decades can exert a positive impact on vegetation restoration, especially under favourable climatic conditions. This study implies that such climatic conditions may offer a window of opportunity for land regeneration in semiarid northern China.
Root growth improvement of mesquite seedlings and bacterial rhizosphere and soil community changes are induced by inoculation with plant growth‐promoting bacteria and promote restoration of eroded desert soil Land Degrad. Dev. (IF 9.787) Pub Date : 2018-03-02 Cristina Galaviz; Blanca R. Lopez; Luz E. de‐Bashan; Ann M. Hirsch; Maskit Maymon; Yoav Bashan
Soil degradation is an ecological disturbance, usually human‐caused, that negatively affects the vegetation and climate of an ecosystem, particularly arid and semiarid environments. These degraded soils can be restored by using native perennial plants inoculated with specific microorganisms. We studied the changes in root growth and the rhizosphere bacterial community of mesquite seedlings (Prosopis articulata) after inoculation with the endophytic bacteria Bacillus pumilus ES4, over 3 cycles of growth in the same soil under desert climatic conditions, and found that inoculation significantly enhanced root biomass during the growth cycles but not shoot biomass or root and shoot lengths. Fluorescent in situ hybridization analysis demonstrated that B. pumilus colonized the root cap, apical meristem, and elongation zone, forming small colonies, on roots from soil‐grown mesquite. Inoculation also significantly changed the bacterial community structure of rhizophere and nonrhizosphere (without plants) soils based on denaturing gradient gel electrophoresis profiles. The changes were highly stable, and the bacterial community structure was maintained throughout the experimental period and not affected by plant replacement. The 16S rRNA pyrosequencing confirmed the changes on structure of bacterial community and revealed an impact on the top taxonomic levels analyzed. The rhizospheres of inoculated plants showed a significant increase in the abundance of Proteobacteria and Acidobacteria coupled with a concomitant decrease in Actinobacteria, whereas an opposite response was observed in nonrhizospheric degraded soils. Overall, inoculation with B. pumilus reduced bacterial diversity but increased the Rhizobium population in the soil. The class Bacilli, despite B. pumilus inoculum, showed minimal variation.
Rebuilding soil carbon in degraded steppe soils of Eastern Europe: The importance of windbreaks and improved cropland management Land Degrad. Dev. (IF 9.787) Pub Date : 2018-03-02 Martin Wiesmeier; Marina Lungu; Valerian Cerbari; Boris Boincean; Rico Hübner; Ingrid Kögel‐Knabner
Long‐term cultivation of steppe soils in a nonsustainable way caused severe soil degradation and reduced agricultural productivity in Eastern Europe, one of the world's most important areas for cereal production. In order to combat soil erosion and maintain yields, a widespread system of tree windbreaks was introduced in the 1950s, accompanied by improved agricultural practices in recent years. However, information on the effectiveness of such measures to rebuild soil organic carbon (SOC) is scarce. The objective of this study was to estimate the OC storage potential of the fine mineral fraction of degraded arable steppe soils in Moldova and to quantify SOC sequestration rates under (a) windbreaks, (b) cropland with improved crop rotation/manure application, and (c) cropland with cover cropping. Natural grassland relicts served as a reference to estimate the SOC saturation potential. Our results revealed a low SOC saturation of 50% under conventional agricultural use due to high SOC losses, indicating a high potential for SOC sequestration. Relatively high SOC sequestration rates were determined for topsoils (0–30 cm) under windbreaks (0.9 t ha−1 yr−1), improved crop rotation/manure application (1.3 t ha−1 yr−1), and cover cropping (1.9 t ha−1 yr−1). In this regard, sequestration rates derived from OC changes of the fine fraction may be more reliable than total SOC‐based rates, particularly for windbreaks with high proportions of labile SOC. We conclude that implementation of improved agricultural management together with the maintenance of windbreaks is a promising strategy to rebuild SOC, reduce widespread soil erosion and compaction, and secure Moldova's agricultural productivity.
Evaluating the new soil erosion map of Hungary—A semiquantitative approach Land Degrad. Dev. (IF 9.787) Pub Date : 2018-03-08 István Waltner; László Pásztor; Csaba Centeri; Katalin Takács; Béla Pirkó; Sándor Koós; Péter László
Soil erosion by water is one of the most significant forms of soil degradation globally, especially in Europe. A new soil erosion risk map of Hungary has been compiled and published recently, using the combined outputs of the Universal Soil Loss Equation and Pan‐European Soil Erosion Risk Assessment models. Our study aimed at providing evaluation of the map by using semiquantitative validation data obtained from the Hungarian Soil Degradation Subsystem of the National Environmental Information System. The Soil Degradation Subsystem database contained information at farm level as well as indicators based on laboratory data for 5‐ha representative plots. On the basis of the semiquantitative analysis, the map results align well with the farm‐based degradation data and provide viable information not only at the regional scale but also at the farm scale. However, indicators from representative plots did not support model results, indicating possible conflict between farm‐ and plot‐level data. Cross‐comparison of these indicators showed only limited correlation between farm‐ and plot‐level indicators.
Stabilized biomass ash as a sustainable substitute for commercial P‐fertilizers Land Degrad. Dev. (IF 9.787) Pub Date : 2018-03-08 Michela Pasquali; Alessandra Zanoletti; Laura Benassi; Stefania Federici; Laura E. Depero; Elza Bontempi
The reuse of biomass ash as a fertilizer is generally recognized as good practice with several environmental benefits. However, the possible presence of leachable heavy metals in this ash limits the potential extent of its application and the implementation of an appropriate legal framework. For the first time, a method to stabilize wood ash based on the use of other by‐products (coal fly ash and rice husk ash) is presented. No commercial chemicals are employed in the procedure. The results show that despite the initial presence of leachable heavy metals in the ash, the final obtained material is stable. In addition, the lowering of pH (from 13.5 to approximately 7.5) due to carbonation reactions and the addition of Ca‐rich ash increases the phosphorous availability compared with the starting wood ash and makes the obtained material suitable for use in soil fertilization. The sustainability of the new proposed technology is quantitatively discussed with regard to the differences in embodied energy and CO2 footprint of phosphorous between raw materials and stabilized wood ash. This work shows that the prospects for energy saving and CO2 footprint reduction using stabilized wood ash as a substitute for inorganic commercial P‐fertilizers are significant and offer a new way to reach these objectives. The simplicity of the method and the general availability of the by‐products employed in the stabilization also render the procedure suitable for applications in developing countries.
Functional metabolic diversity of the bacterial community in undisturbed resource island soils in the southern Sonoran Desert Land Degrad. Dev. (IF 9.787) Pub Date : 2018-03-08 D. Edisa Garcia; Blanca R. Lopez; Luz E. de‐Bashan; Ann M. Hirsch; Maskit Maymon; Yoav Bashan
Resource islands (RIs), a natural revegetation phenomenon in arid lands, consist of a single nurse tree or few large shrubs and numerous understory nurslings. We analyzed 18 individual mesquite RIs for plant diversity and richness, area, trunk diameter (reflecting age), soil characteristics, physiological functionality of microbial populations, and interactions among these variables. Nursing Capacity reflected the availability of habitat and was positively correlated to plant richness, but not to plant diversity. No relationship between plant diversity and bacterial diversity was found. The structure of the bacterial communities of RIs differed from the bacterial communities of bare areas, which showed greater richness and diversity compared with those of RIs. The Nursing Capacity of the RIs was related to plant richness and accompanied by variations in soil properties. A high correlation was found by substrate utilization analysis between metabolic parameters of bacteria and diversity and richness of plants in the RIs. RI bacterial communities were more metabolically active and could degrade different carbon sources than bare area communities. RI bacterial communities contained species with greater capability to metabolize diverse carbon substrates in soil with more organic matter. Bacteria from low, medium, and high plant diversity areas were cultured and found to belong to four bacterial families. This study demonstrates that numerous parameters interact, but not every parameter significantly affected bacterial activity in the RI.
Early response of Quercus robur seedlings to soil compaction following germination Land Degrad. Dev. (IF 9.787) Pub Date : 2018-03-08 Martina Cambi; Barbara Mariotti; Fabio Fabiano; Alberto Maltoni; Andrea Tani; Cristiano Foderi; Andrea Laschi; Enrico Marchi
Logging operations using heavy machinery effect changes in soil characteristics due to compaction; such conditions can negatively influence seedling development. In stands managed on the basis of close‐to‐nature silviculture or continuous cover forestry, successful establishment of natural regeneration after logging is important to ensure the proper functioning of a forest ecosystem, to promote soil recovery, and to prevent and mitigate land degradation processes (such as soil erosion, mudflow, waterlogging, and landslides) related to soil compaction and rutting. This work aimed to assess the early response of Quercus robur seedlings to soil compaction during the first 1.5 months after germination. The study was carried out in a controlled environment using 8 L containers filled with natural alluvial soil. Three levels of soil compaction were applied in a laboratory using a compression‐testing machine placed on the top surface of the soil in the containers. The morphological traits of the seedling shoot and root systems were analysed to compare 3 compaction levels. There were significant differences in seedling traits among the treatments, and they indicated that increasing levels of compaction reduced early seedling growth after emergence. Compaction had a larger impact on the root system, particularly the development at depth (root system depth, and main root length), compared with the shoot system. Our results suggest that compaction affects seedling root system growth following the first growth stages after germination; thus, compaction represents an additional critical factor for seedling establishment, particularly in environments where early growth is crucial for overcoming the dry season.
The application of natural landform analogy and geology‐based spoil classification to improve surface stability of elevated spoil landforms in the Bowen Basin, Australia—A review Land Degrad. Dev. (IF 9.787) Pub Date : 2018-03-08 Bevan Emmerton; Jon Burgess; Joan Esterle; Peter Erskine; Thomas Baumgartl
Large‐scale open cut mining has occurred within the Bowen Basin for over 4 decades, transitioning from shallow mining depths and limited spoil elevation to increased mining depths, prestripping and increasingly elevated mesa‐like landforms.
Dynamic effects of biochar concentration and particle size on hydraulic properties of sand Land Degrad. Dev. (IF 9.787) Pub Date : 2018-03-08 Branimir Trifunovic; Howell B. Gonzales; Sujith Ravi; Brenton S. Sharratt; Sanjay K. Mohanty
Large‐scale application of biochar has been promoted as a strategy for improving soil quality in agricultural and contaminated lands, as biochar has the potential to alter soil physical and biogeochemical properties. Biochar at different concentrations has been shown to have inconsistent effects on soil hydrological properties, yet the cause of the inconsistency is not well understood. To investigate the relative roles of biochar size and concentration, we mixed pure sand with a commercially available biochar varying its concentrations and particle sizes and measured saturated (Ksat) and unsaturated hydraulic conductivity and water‐retention characteristics. An increase in the concentration of fine biochar (<2 mm) consistently decreased Ksat and increased saturated moisture content. In contrast, an increase in the concentration of unsieved (mixture of coarse and fine) biochar up to 5% (by volume) increased Ksat, whereas any further increases in unsieved biochar concentration decreased Ksat. Increase in biochar concentration, irrespective of particle size, consistently decreased the unsaturated hydraulic conductivity. Measuring the changes in the characteristics of water‐retention curves of biochar–sand mixtures with biochar particle size, we showed that added biochar can either decrease (clog) or increase pore spaces in the mixture on the basis of the quantity of fine biochar fraction, which in turn could decrease or increase the hydraulic conductivity of the mixture. Thus, biochar concentration and particle size must be taken into consideration to maximize the intended hydrological benefits of biochar amendment.
Object‐oriented soil erosion modelling: A possible paradigm shift from potential to actual risk assessments in agricultural environments Land Degrad. Dev. (IF 9.787) Pub Date : 2018-03-08 Pasquale Borrelli; Katrin Meusburger; Cristiano Ballabio; Panos Panagos; Christine Alewell
Over the last 2 decades, geospatial technologies such as Geographic Information System and spatial interpolation methods have facilitated the development of increasingly accurate spatially explicit assessments of soil erosion. Despite these advances, current modelling approaches rest on (a) an insufficient definition of the proportion of arable land that is exploited for crop production and (b) a neglect of the intra‐annual variability of soil cover conditions in arable land. To overcome these inaccuracies, this study introduces a novel spatio‐temporal approach to compute an enhanced cover‐management factor (C) for revised universal soil loss equation‐based models. It combines highly accurate agricultural parcel information contained in the Land Parcel Identification System with an object‐oriented Landsat imagery classification technique to assess spatial conditions and interannual variability of soil cover conditions at field scale. With its strong link to Land Parcel Identification System and Earth observation satellite data, the approach documents an unprecedented representation of farming operations. This opens the door for the transition from the currently used potential soil erosion risk assessments towards the assessment of the actual soil erosion risk. Testing this method in a medium‐size catchment located in the Swiss Plateau (Upper Enziwigger River Catchment), this study lays an important foundation for the application of the very same methods for large‐scale or even pan‐European applications. Soil loss rates modelled in this study were compared with the insights gained from emerging techniques to differentiate sediment source contribution through compound‐specific isotope analysis on river sediments. The presented technique is adaptable beyond revised universal soil loss equation‐type soil erosion models.
Peat bog and alluvial deposits reveal land degradation during 16th‐ and 17th‐century colonisation of the Western Carpathians (Czech Republic) Land Degrad. Dev. (IF 9.787) Pub Date : 2018-03-09 Veronika Kapustová; Tomáš Pánek; Jan Hradecký; Valentina Zernitskaya; Simon M. Hutchinson; Monika Mulková; Jan Sedláček; Vojtěch Bajer
Wallachian (shepherd) colonisation of the upper parts of the Carpathians, the second largest mountain range in Europe, provides a unique opportunity to study human‐induced ecological changes and subsequent sediment mobilisation within slope and fluvial systems. The Wallachians came to the nearly pristine landscape in the Czech part of the Western Carpathians during the 16th to 17th century bringing large‐scale deforestation and grazing to the upper parts of its ridges. Despite the importance of this event, there is a lack of high‐resolution multiproxy reconstructions to help decipher the relative influence of anthropogenic and climate factors on this landscape. Here, we provide an approximately 2.1‐kyr record obtained from a peat bog where, using chronological, sedimentological, and pollen analyses, we were able to differentiate between environmental conditions before, during, and after colonisation. Prior to colonisation, climate deterioration following the onset of Little Ice Age caused changes in forest composition and erosion events (causing a ~ad 0–1500 gap in the record). Abrupt human‐induced deforestation detected in the pollen record, together with the abundant fine‐grained minerogenic content of peat deposits between ad ~1640 and ad 1870, corresponds to increased run‐off and sheet erosion on slopes, enhanced by Little Ice Age climate deterioration. The sedimentary record in alluvial deposits downstream indicates that the colonisation of the mountain slopes in this region not only had a local effect on soil degradation, but it also increased the net aggradation of overbank deposits within valley floors. After reforestation, net aggradation was replaced by river incision into alluvia.
Distribution of cadmium, copper, lead, and zinc in mudflat salt‐soils amended with sewage sludge Land Degrad. Dev. (IF 9.787) Pub Date : 2018-03-12 Yanchao Bai; Yiyun Yan; Wengang Zuo; Chuanhui Gu; Yongxiang Guan; Xukui Wang; Haitao Zhao; Yuhua Shan; Hongbo Shao; Ke Feng
Applying sewage sludge to mudflat salt‐soils can rapidly improve soil physicochemical properties and enhance pollution potential. Nevertheless, the heavy metal distribution in leachate and mudflat salt‐soils with sludge amendment remains unclear. The present work was aimed primarily at investigating the fates of Cd, Cu, Pb, and Zn in mudflat salt‐soils amended by sludge. A leaching column experiment in a greenhouse was conducted to analyze the leaching losses of the metals in the sludge‐amended soils and to evaluate the uptake of these metals by maize (Zea mays L.) seedlings, using a mudflat salt‐soil amended with 0, 30, 75, 150, and 300 g sludge per kg soil. The results indicated that metal concentrations were significantly correlated negatively with pH and positively with dissolved organic carbon concentration in leachate of sludge‐amended soils. The sewage sludge application enhanced metal uptake without inhibiting the growth of maize. The sludge treatments enhanced metal concentrations in top layer (0–20 cm) of soil in the leaching column but did not change metal concentrations in soil layer of 20–40 cm (p > .05). Immobile fraction of Pb and mobile fraction of Cd, Cu, and Zn increased with increasing rates of sludge addition. Long‐term field studies are required for further evaluation of the impacts of recycling sludge on heavy metal behaviors including leaching, accumulation, and dynamic change of metal fractions in mudflat salt‐soils.
Establishing and validating a root water uptake model under the effects of superabsorbent polymers Land Degrad. Dev. (IF 9.787) Pub Date : 2018-03-12 Renkuan Liao; Peiling Yang; Haoliang Yu; Wenyong Wu; Shumei Ren
In‐depth understanding of the patterns of root water uptake (RWU) is the key to improving the water‐use efficiency of plants. Superabsorbent polymers (SAPs) can repeatedly absorb and then release water to plants when needed, which substantially increases the water‐use efficiency of plants in arid and semiarid farming. However, it also creates a challenge in modeling RWU due to unstable soil hydraulic parameters and the unclear response of root growth to SAP application. A controlled soil column experiment was conducted to investigate the response of two important root indexes, that is, root length density (RLD) and root nitrogen mass density (RND), to SAP application, as well as their relationships with RWU. The results showed that the use of the SAP caused a steady increase in RND, and it also substantially increased the RLD in the early stage, but the rate of increase gradually slowed over time. The effect of unstable soil hydraulic parameters on RWU was analyzed in a numerical experiment, which indicated that the time‐dependent effect of SAP on soil hydraulic parameters should be considered to avoid errors in calculating RWU. A specific method for calculating the RWU source/sink term in the Richards equation was proposed and ultimately used as the theoretical value of RWU to verify the RWU models based on RLD and RND to ensure the best one was selected. The results showed that RND was better able to be used for development of the RWU model to simulate the patterns of RWU under SAP application.
Fingerprinting sediment sources in a large agricultural catchment under no‐tillage in Southern Brazil (Conceição River) Land Degrad. Dev. (IF 9.787) Pub Date : 2018-03-13 Tales Tiecher; Jean Paolo Gomes Minella; Olivier Evrard; Laurent Caner; Gustavo Henrique Merten; Viviane Capoane; Elizeu Jonas Didoné; Danilo Rheinheimer dos Santos
Brazil is a leader in the adoption of conservation agriculture practices and technologies. However, the impact of these practices on sediment sources at the catchment scale has not been quantified yet, particularly in grain growing regions, where a conservationist no‐tillage system is implemented to protect soils. To address this knowledge gap, a sediment fingerprinting study based on elemental geochemistry was carried out in a large agricultural catchment (804 km2) of Southern Brazil where no‐tillage practices dominate. A total of 156 soil samples were taken to characterize the three main potential sediment sources: cropland (n = 79), unpaved roads (n = 41), and channel banks (n = 36). Sediment sampling was performed using a time‐integrated sampler (n = 33) and by collecting fine‐bed material (n = 34) at five locations across the catchment. Sediment was also sampled during flood events at the catchment outlet (n = 20). Sediment source contributions were calculated using an optimal suite of geochemical properties and a mixing model. Results showed that although the catchment is not particularly sensitive to soil erosion (i.e., deep clayey soils with gentle slopes), the amount of sediment supplied by cropland to the river network remains very high (up to 1.63 Mg·ha−1·year−1). Sediment fingerprinting results showed that even when no‐tillage is implemented, cropland remains an important source of sediment, supplying up to 70% of the material transiting the Conceição River. Accordingly, the current conservation farming system in this catchment needs to be improved to further reduce soil erosion and sediment yield.
Communicating risks to infrastructure due to soil erosion: A bottom‐up approach Land Degrad. Dev. (IF 9.787) Pub Date : 2018-03-13 Caspar J. M. Hewett; Carolyn Simpson; John Wainwright; Steve Hudson
Soil erosion is a major problem worldwide, affecting natural, agricultural, and urban environments through its impact on flood risk, water quality, loss of topsoil, eutrophication of water bodies, sedimentation of waterways, and damage to infrastructure such as roads, buildings, and utility supply networks. Thus, there is a need to identify risks to infrastructure associated with erosion and interventions needed to reduce those risks. Further, inclusive ways of communicating about mitigation strategies with stakeholders such as farmers, land managers, and policymakers are essential if interventions are to be implemented. Applying the Decision‐Support Matrix approach, which combines hydrologic and geomorphic principles with participatory action research, a tool for Communicating and Visualising Erosion‐associated Risks to Infrastructure (CAVERTI) was developed in collaboration with a variety of stakeholders including farmers, private landowners, asset owners, and environmental organisations, focusing on a case‐study area in northern England. The CAVERTI tool synthesises process understanding gained from modelling with knowledge and experience of stakeholders to address the sediment transport problem. Tool development was collaborative, ensuring that the problems and solutions presented are easily recognised by practitioners and decision‐makers. The tool helps to assess, manage, and improve understanding of risk from a multistakeholder perspective and presents mitigation options. We argue that visualisation and communication tools codeveloped by researchers and stakeholders are the best means of influencing decision‐makers to invest in mitigation. The CAVERTI tool is designed to encourage farmers, land, and asset owners to act to reduce erosion, providing multiple benefits from protecting local infrastructure to reducing pollution of waterways.
The effects of organic and mineral fertilizers on carbon sequestration, soil properties, and crop yields from a long‐term field experiment under a Swiss conventional farming system Land Degrad. Dev. (IF 9.787) Pub Date : 2018-03-14 Alexandra Maltas; Hedi Kebli; Hans Rudolf Oberholzer; Peter Weisskopf; Sokrat Sinaj
The effects of mineral fertilizers and organic amendments on soil properties, carbon (C) sequestration, and crop yields are studied in a 37‐year field experiment, Phosphorus–Potassium‐balanced design, in Switzerland.
Arable weed species associated with soil tillage systems under Mediterranean conditions Land Degrad. Dev. (IF 9.787) Pub Date : 2018-03-14 M.I. Santín‐Montanyá; C. Casanova Pena; E. Zambrana Quesada; F.J. Sánchez Jiménez; J.L. Tenorio Pasamón
Tillage soil erosion is seen as a great problem in the Mediterranean region and is worsened by the climatic conditions. Previous studies have shown a decrease in biodiversity in arable lands across Europe. Weeds are a major component of biodiversity within agro‐ecosystems, but few studies have aimed to associate weed species with soil tillage intensity. We performed an analysis to test the potential short‐term effects of different tillage systems on weed species under our study conditions. The emerged weed data were measured, comparing a conventional tillage system with conservational tillage systems (minimum tillage and no tillage) in 2 cropping systems (monoculture wheat and a rotation scheme of barley–legume–wheat–fallow). Compared with the tilled soil, higher weed density and weed species richness were observed in the conservation tillage plots. The weed density and weed species richness in the monoculture system were higher compared with those in the crop rotation system. We used classification and regression trees to analyze the relationship between the soil tillage systems and the weed community, taking into account the climatic conditions. The results indicate that different soil tillage systems produced tree models: Silene vulgaris (L.) was associated with the MT system and high and irregularly distributed rainfall; Hypecoum imberbe Sm. and Hypecoum procumbens (L.) were linked to MT plots with low and well‐distributed precipitation rates; and Cardaria draba (L.) was present all years independently of climatic conditions but was never found in the NT system, so its presence could be regarded as an indicator of tillage intensity.
The science of connected ecosystems: what is the role of catchment‐scale connectivity for healthy river ecology? Land Degrad. Dev. (IF 9.787) Pub Date : 2018-02-12 Ian C. Fuller; Russell G. Death
Riverine biological communities are highly resilient to extreme flood and/or drying disturbance regimes that would otherwise be destructive because these organisms can recolonise from upstream, floodplain or hyporheic refugia when suitable conditions return. Healthy rivers require a high degree of connectivity to support complex life cycles of many lotic organisms and associated ecosystem functioning. Similarly, connectivity is required for appropriate geophysical functioning; permitting flux of water and sediment that drives channel‐forming and ecological processes. Ecological and geophysical processes have operated in this temporal and spatial patchwork of disturbance and recovery pre‐Anthropocene. Human impacts are increasing constraints on river and floodplain connectivity, severing many natural pathways, and degrading river ecosystem functioning. River restoration seeks to re‐establish some of those biological and physical connections to enhance some level of system health. However, increasing sediment connectivity may be detrimental to river health in some instances. Strongly connected catchments can transmit excessive quantities of sediment from inappropriate land management, detrimental invasive species can spread more widely, and many ecosystem processes can exceed positive feedback control. Simply restoring connectivity will not necessarily lead to healthy river ecosystems. River management requires a greater understanding of how and when connectivity can and should be restored. While current thinking is often that greater connectivity is better, we illustrate with examples from New Zealand rivers that this is not always the case. The benefits and costs of maintaining or restoring river connectivity need to be given as much attention as the restoration and maintenance of river systems per se.
SOIL SEALING AND UNSEALING: STATE OF THE ART AND EXAMPLES Land Degrad. Dev. (IF 9.787) Pub Date : 2018-02-22 Silvia Tobias; Franz Conen; Adrian Duss; Leonore M. Wenzel; Christine Buser; Christine Alewell
Soil sealing for urban and infrastructure development constitutes the most intense form of land degradation and affects all ecosystem services. Researchers and policy makers have become aware of this fact and call for limiting development and compensating for new soil sealing with unsealing measures. In a literature review, we found that the state of research about the impacts of soil sealing is far more advanced than about the potential and prerequisites of unsealing. In practice, soil restoration after mining and construction activities as well as redevelopment or renaturation of abandoned industrial sites are increasingly important issues, but systematic research on the success of soil unsealing and restoration is rare. In particular, the development of soils and vegetation after unsealing and restoration measures as well as their potential to provide ecosystem services need more detailed investigation.
THE IMPACT OF CULTIVATED LAND SPATIAL SHIFT ON FOOD CROP PRODUCTION IN CHINA, 1990‐2010 Land Degrad. Dev. (IF 9.787) Pub Date : 2018-03-05 Yuanyuan Li; Xiubin Li; Minghong Tan; Xue Wang; Liangjie Xin
Cultivated land has been undergoing significant spatial shift during the last two decades in China, according to land‐use data derived from the Landsat Thematic Mapper. Based on soil organic matter data and yield data at county level, we developed a constant crop yield dataset at pixel level with a resolution of 1 km. Using this dataset, this paper quantitatively evaluates average crop yield change due to cultivated land spatial shift at national and regional levels. The results show: 1) at national level, the average crop yield per unit area decreased by 1.99% during the period 1990–2010. The main reason for this is that built‐up areas occupied a significant amount of high‐yield cultivated land while low‐yield land was converted in ecologically vulnerable areas. 2) In spite of 7.72 million ha cultivated land was converted to built‐up areas, especially in areas with high economic value, such as Huang–Huai–Hai Plain, 32.94 million ha land was converted to cultivated land, especially in Northeastern and Northwestern China. 3) The quality gap between cultivated land converted to built‐up areas (CLCBA) nationally and new cultivated land regionally suggests that the loss of 1 ha of CLCBA would, to achieve equivalency, need to be compensated by 1.54 ha of new land in Xinjiang, or more in Northeastern China. However, cultivated land expansion in these areas may cause land degradation and a series of ecological environment problems.
WIND EROSION REDUCTION BY WATER DIVERSION IN THE LOWER HEIHE RIVER BASIN, NORTHWEST CHINA Land Degrad. Dev. (IF 9.787) Pub Date : 2018-03-05 Haiming Yan; Jinyan Zhan; Huicai Yang; Wei Liu; Wei Li
The Lower Heihe River Basin (LHRB), a key ecological function zone in northwest China, has suffered from serious land degradation by wind erosion for decades, posing a great threat to the national ecological safety. This study explores dynamics of wind erosion and the soil conservation service (SCS) in this region following water diversion during 2001‐2010 with the Statistic Model of Wind Erosion on Small Watershed Basis based on remote sensing, climate and soil data, and impacts of driving factors on the SCS are revealed with scenario analysis. Results suggest the SCS represented by the soil retention amount was less than 500 tons km‐2 y‐1 in most parts of the study area and higher than 15,000 tons km‐2 y‐1 in a few wind erosion hotspots, including the East Juyanhai region, Dingxin Oasis, Ejina Oasis and its surrounding desert‐oasis transitional areas. The cumulative potential soil loss of the study area increased much faster than the cumulative soil retention amount, and fractional vegetation cover influenced by the Ecological Water Diversion Project played a dominant role in improving the SCS, accounting for 82·25% of the change in the SCS of the study area. Climate change played a subordinate role, but there were essential separate and interactive effects of climate factors on the SCS. This study provides a preliminary overview of hotspots of wind erosion and the SCS in the LHRB from a geographical perspective, laying a solid basis for combating land degradation by wind erosion in arid regions of northwest China.
PLANT GROWTH AND OIL CONTAMINATION ALTER THE DIVERSITY AND COMPOSITION OF BACTERIAL COMMUNITIES IN AGRICULTURAL SOILS ACROSS CHINA Land Degrad. Dev. (IF 9.787) Pub Date : 2018-03-09 Shuo Jiao; Weimin Chen; Junman Wang; Lu Zhang; Fan Yang; Yanbing Lin; Gehong Wei
The dynamics of microbial diversity in response to biotic and abiotic disturbances provide a sensitive indicator for evaluating the potential stability and degradation of soils in agro‐ecosystems. To determine the effect on soil bacterial communities of disturbances by plant growth (Robinia pseudoacacia) and oil contamination, we sequenced 16S rRNA genes using MiSeq technology. A greenhouse experiment was conducted using 21 agro‐soils from 19 provinces in China. Abiotic and biotic disturbances, including treating the soils with sterile water, crude oil, and/or an invasive plant, altered the bacterial community structure in the soils, increased bacterial richness, and reduced bacterial dispersion. Oil contamination exerted stronger effects on the bacterial α‐ and β‐diversity than plant growth. The different responses of bacterial communities and the core microbiome indicated that the disturbances shifted the prevalent soil microbial groups in agro‐ecosystems. Among different sampling sites, community dissimilarity increased with spatial distance. Edaphic factors (deterministic processes) exerted the primary influence on the assembly of soil microbiomes in agricultural fields, while geographic factors (stochastic processes) were less influential. The bacterial communities in agro‐soils from warmer regions were more sensitive to the disturbances. This study provides new insight into the alteration of soil microbiota by plant growth and oil contamination in agro‐ecosystems across a large spatial scale.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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