Topography is tightly coupled with soil organic carbon (SOC) cycling in sloping landscapes. However, we know little about the spatial variation of SOC accumulation and persistence along a topographic gradient and the controlling processes. Here, we assessed the spatial variation of SOC and its composition along a topographic gradient in a humid mountain forest. The variables associated with environmental

Symbiotic nitrogen- (N) fixing trees can influence multiple biogeochemical cycles by fixing atmospheric N, which drives net primary productivity and soil carbon (C) and N accumulation, as well as by mobilizing soil phosphorus (P) and other nutrients to support growth and metabolism. The soil micronutrient molybdenum (Mo) is essential to N-fixation, yet surprisingly little is known of whether N-fixing

Early forest re-establishment in landforms constructed from materials such as overburden or mine waste is partly determined by nitrogen (N) availability in reclamation covers. Here we examined whether the ecosystem model ecosys which simulates key processes governing N availability such as mineralization, plant N uptake and N return to soil through litterfall could be used to forecast potential N limitations

Nitrogen (N) trace gas emission pulses produced after wetting dry soils may be important pathways of ecosystem N loss. However, the rates and mechanisms controlling these emissions remain unclear. We tested whether changes in microbial community structure and increased rates of atmospheric N deposition could explain N emissions at two desert sites differing in atmospheric N deposition by ~ six fold

Terrestrial carbon (C)-climate feedbacks depend strongly on how soil organic matter (SOM) decomposition responds to temperature. This dependency is often represented in land models by the parameter Q10, which quantifies the relative increase of microbial soil respiration per 10 °C temperature increase. Many studies have conducted paired laboratory soil incubations and inferred “active” and “slow” pool

Floodplains play a crucial role in water quality regulation via denitrification. This biogeochemical process reduces nitrate (NO3−), with aquifer saturation, organic carbon (OC) and N availability as the main drivers. To accurately describe the denitrification in the floodplain, it is necessary to better understand nitrate fluxes that reach these natural bioreactors and the transformation that occurs

Due to the geographical expanse of grasslands with depleted organic matter stocks, there has been growing interest in the management of these ecosystems for C sequestration to help mitigate climate change. It is generally accepted that management practices intending to increase forage production (e.g. decreasing grazing density) result in increased soil C stocks by increasing the return of biomass

The sediment–water interfaces (SWI) of streams serve as important biogeochemical hotspots in watersheds and contribute to whole-catchment reactive nitrogen budgets and water-quality conditions. Recently, the SWI has been identified as an important source of nitrous oxide (N2O) produced in streams, with SWI residence time among the principal controls on its production. Here, we conducted a series of

Atmospheric deposition is an important component of the nutrient cycles of terrestrial ecosystems, but field measurements are especially scarce in tropical regions. In this study we analysed 15 months of precipitation chemistry collected in an old growth tropical forest located in French Guiana. We measured nutrient inputs via bulk precipitation and throughfall and used the canopy budget model to estimate

The seasonally stratified continental shelf seas are highly productive, economically important environments which are under considerable pressure from human activity. Global dissolved oxygen concentrations have shown rapid reductions in response to anthropogenic forcing since at least the middle of the twentieth century. Oxygen consumption is at the same time linked to the cycling of atmospheric carbon

Conversion of landscapes to large-scale agriculture has substantially increased the loading of bioavailable nitrogen (N) to stream networks through extensive artificial drainage and fertilizer application. Floodplain restoration may enhance N cycling in agricultural stream systems by increasing residence time of floodwaters in contact with bioreactive surfaces that retain or remove excess N. Microbially-mediated

We tested the hypothesis that benthic fluxes will increase spatially in a coastal deltaic floodplain as sediment organic matter increases in response to developing hydrogeomorphic zones along a chronosequence of the active Mississippi River Delta. A continuous flow-through core system was used to incubate intact sediment cores from three hydrogeomorphic zones along a chronosequence in the emerging

Molybdenum (Mo) is an essential trace metal that plays a central role in biological nitrogen fixation (BNF) as the cofactor in the conventional form of the nitrogenase enzyme. The low availability of Mo in soils often constrains BNF in many terrestrial ecosystems. Atmospheric sources may supply a critical source of exogenous Mo to regions with highly weathered soils likely low in Mo, particularly in

Dissolved organic carbon (DOC) derived from plant litter plays an important role in the ecosystem carbon balance and soil biogeochemistry. However, in boreal coniferous forests no integrated understanding exists of how understory vegetation contributes to litter leaching of DOC, nitrogen (N) and phosphorus (P) with different bioavailability at the forest stand level. We characterized water extractable

Sulphur (S) is a key macronutrient for all organisms, with similar cellular requirements to that of phosphorus (P). Studies of S cycling have often focused on the inorganic fraction, however, there is strong evidence to suggest that freshwater microorganisms may also access dissolved organic S (DOS) compounds (e.g. S-containing amino acids). The aim of this study was to compare the relative concentration

Biological nitrogen fixation (BNF), a key reaction of the nitrogen cycle, is catalyzed by the enzyme nitrogenase. The best studied isoform of this metalloenzyme requires molybdenum (Mo) at its active center to reduce atmospheric dinitrogen (N2) into bioavailable ammonium. The Mo-dependent nitrogenase is found in all diazotrophs and is the only nitrogenase reported in diazotrophs that form N2-fixing

Dissolved organic carbon (DOC) flux is an important mechanism to convey soil carbon (C) from aboveground organic debris (litter) to deeper soil horizons and can influence the formation of stable soil organic C compounds. The magnitude of this flux depends on both infiltration and DOC production rates which are functions of the climatic, soil, topographic and ecological characteristics of a region.

We present the application of dual stable isotope analyses of NO3 (δ15N-NO3 and δ18O-NO3) to provide a comprehensive assessment of the provenance, partitioning, and conversion of nitrate across the Day River Basin (DRB), Vietnam, which is heavily impacted by agriculture and urbanization. Stable isotope compositions of river water δ18O-H2O, in addition to their δ15N-NO3 and δ18O-NO3 signatures, were

Fluorescence spectroscopy is a common tool to assess optical dissolved organic matter (DOM) and a number of characteristics, including DOM biodegradability, have been inferred from these analyses. However, recent findings on soil and DOM dynamics emphasize the importance of ecosystem-scale factors, such as physical separation of substrate from soil microbial communities and soil physiochemical cycles

Salt marsh biogeochemical processes are regulated by ecosystem structure (e.g. plant community composition). However, plant-specific responses to stressors such as elevated nutrient inputs can have differing impacts on nitrogen (N) removal and carbon (C) sequestration. We conducted a field manipulation to investigate the impact of elevated nutrient loading on ecosystem C dynamics and nitrate reduction

Over the last century, anthropogenic activities have increased nitrogen (N) deposition considerably, which significantly affects ecosystem processes and has the potential to induce N saturation in the future. The continuous increase in N deposition may cause a non-linear response in soil respiration (Rs), an important component of carbon (C) cycling. However, little is known about N saturation threshold

Methane is produced microbially in vast quantities in sediments throughout the world’s oceans. However, anaerobic oxidation of methane (AOM) provides a near-quantitative sink for the produced methane and is primarily responsible for preventing methane emissions from the oceans to the atmosphere. AOM is a complex microbial process that involves several different microbial groups and metabolic pathways

Streambank legacy sediments may be important sources of sediment and nutrients from Mid-Atlantic watersheds. However, little is known about the nutrient processing roles of microorganisms that inhabit legacy sediments, let alone their composition, diversity, and distributions. In this study, we sampled 15 streambanks at multiple depths throughout four watersheds in the Mid-Atlantic Region of the USA

Chronic elevated nitrogen deposition has increased nitrogen availability in many forest ecosystems globally, and this phenomenon has been suggested to increase soil nitrification. Although it is believed that increased nitrogen availability would also increase nitrous oxide (N2O) emissions from forest ecosystems, its impact on N2O flux is poorly known. In this study, 3-years monitoring of N2O emissions

Soil stores over 2500 Pg carbon (C), with the majority of C stored in deep soil layers (> 30 cm). Soil C can be lost to the atmosphere when organic compounds are mineralized to carbon dioxide (CO2, via oxidative decay or respiration) and moved upward through the soil profile (via diffusion). Soil moisture status can influence the balance between respiration and diffusion, thereby altering the soil

The Walker and Syers model predict that phosphorus (P) availability decreases with time leading to a final stage known as retrogression. We tested the validity of the Walker and Syers model in the Canary Islands, a soil chronosequence ranging from 300 years to 11 million years under recurrent episodes of atmospheric dust-containing P inputs. In particular, we compared our results with those from the

Northern lakes are a source of greenhouse gases to the atmosphere and contribute substantially to the global carbon budget. However, the sources of methane (CH4) to northern lakes are poorly constrained limiting our ability to the assess impacts of future Arctic change. Here we present measurements of the natural groundwater tracer, radon, and CH4 in a shallow lake on the Yukon-Kuskokwim Delta, AK

The frequently observed discrepancy between estimations of N2O emissions at regional or global scale based either on field data or inventories (bottom-up) or on direct atmospheric observations (top-down) suggests that riparian areas and river surfaces play a significant role as hot spots of emission. We developed a modeling procedure to assess N2O emissions occurring during the transfer of water masses

Peatlands have accumulated vast quantities of organic carbon over thousands of years but it is unclear how these sensitive ecosystems will respond to future climate change. If emissions of methane from peatlands increase, then they may contribute increasingly towards climatic warming due to the higher greenhouse warming potential of this gas. We investigated the radiocarbon concentration of methane

Precise assessment of soil organic carbon (OC) storage requires understanding of soil type and depth specific differences in organic matter (OM) stabilization. Therefore, we aimed to analyze OC dynamics down the soil profile and to clarify the effect of depth on the importance of aggregate formation and mineral adsorption for OC storage in mature beech forest soils developed from different parent materials

Large uncertainties in estimates of methane (CH4) emissions from tropical inland waters reflect the paucity of information at appropriate temporal and spatial scales. CH4 concentrations, diffusive and ebullitive fluxes, and environmental parameters in contrasting aquatic habitats of Lake Janauacá, an Amazon floodplain lake, measured for two years revealed patterns in temporal and spatial variability

We studied in 2013 and 2014 the spring carbon dynamics in a Boreal landscape consisting of a lake and 15 inflowing streams and an outlet. The first year had weather and a hydrological regime typical of past years with a distinct spring freshet connected with the thaw of the average snowpack. The latter year had higher air temperatures which did not permit snow accumulation, despite similar winter precipitation

Ge/Si ratios of plant phytoliths have been widely used to trace biogeochemical cycling of Si. However, until recently, information on how much of the Ge and Si transferred from soil to plants is actually stored in phytoliths was lacking. The aim of the present study is to (i) compare the uptake of Si and Ge in three grass species, (ii) localize Ge and Si stored in above-ground plant parts and (iii)

Soil aggregates govern soil organic carbon (SOC) sequestration. But, sparse understanding about the process leads to inaccuracy in predicting potential of soil to stabilize C in warming world. We appraised effects of 43 years of fertilization on relative temperature sensitivity of SOC decomposition (Q10) in soil aggregates to know whether SOC quality or quantity governs Q10. Treatments were: fallow

During litter decomposition, three major fates of litter carbon (C) are possible: emission as carbon dioxide (CO2) into the atmosphere, leaching of dissolved organic carbon (DOC), and translocation and transformation into soil organic carbon (SOC). Soil moisture, one of the key drivers of litter decomposition, is predicted to change in the future due to shifts in precipitation patterns. We explored

Agricultural streams receive large inputs of nutrients, such as nitrate (NO3−) and ammonium (NH4+), which impact water quality and stream health. Streambed sediments are hotspots of biogeochemical reactivity, characterised by high rates of nutrient attenuation and denitrification. High concentrations of nitrous oxide (N2O) previously observed in stream sediments point to incomplete denitrification

Dissolved organic carbon (DOC) from Oa horizons has been proposed to be an important contributor for subsoil organic carbon stocks. We investigated the fate of DOC by directly injecting a DOC solution from 13C labelled litter into three soil depths at beech forest sites. Fate of injected DOC was quantified with deep drilling soil cores down to 2 m depth, 3 and 17 months after the injection. 27 ± 26%

Mercury (Hg) release and migration from municipal solid waste landfills has been an important issue to nearby ecosystems and human health. To completely understand the Hg biogeochemical cycle in landfills, this review presents the Hg emission processes via different pathways, related controlling mechanisms, and critical Hg transport and transformation processes involving the diffusion and advection

Stable carbon (C) and nitrogen (N) isotope ratios of sedimentary organic matter (OM) can reflect the biogeochemical history of aquatic ecosystems. However, diagenetic processes in sediments may alter isotope records of OM via microbial activity and preferential degradation of isotopically distinct organic components. This study investigated the isotope alteration caused by preferential degradation

Wetting of dry soil triggers a pulse of microbial respiration that has been attributed to two broad mechanisms: (1) recycling of microbial cellular carbon (C), and (2) consumption of extracellular organic C made available to microbes by wetting. We evaluated these two mechanisms by measuring cumulative CO2 release, changes in the size and chemical composition of microbial biomass, and water-extractable

Abstract Biotically-mediated weathering helps to shape Earth’s surface. For example, plants expend carbon (C) to mobilize nutrients in forms whose relative abundances vary with depth. It thus is likely that trees’ nutrient acquisition strategies—their investment in rooting systems and exudates—may function differently following disturbance-induced changes in depth of rooting zones and soil nutrient

Abstract Molecular and compound specific isotope compositions of apolar lipids were characterized in soil mesocosms incubated for 1 year with or without 13C-labelled plant residues and earthworms, in order to investigate, at the molecular scale, the effect of earthworms on the fate of organic matter (OM) in soils. Molecular and isotope composition of long chain alkanes in casts confirmed that earthworms

Abstract Despite the importance of phosphorus (P) as a macronutrient, the factors controlling the pool sizes of organic and inorganic P (OP and IP) in soils are not yet well understood. Therefore, the aim of this study was to gain insights into the pools sizes of OP, IP and organic carbon (OC) in soils and soil particle size fractions. For this purpose, I analyzed the distribution of OP, IP, and OC

Abstract Quantifying ecosystem respiration remains challenging in aquatic ecosystems. Most investigators assume that nighttime and daytime respiration are equal. Recent studies suggest measuring dissolved oxygen isotopes during periods with and without photosynthesis can account for variations in daytime and nighttime respiration. These models are extremely sensitive to the oxygen isotopic fractionation

Abstract Nitrification and denitrification are traditionally assumed to occur under aerobic and anoxic conditions, respectively. However, new and interesting alternatives challenge the traditional assumption. Along this line, we provide dual-nitrate isotopic and chemical evidence for the occurrence of denitrification linked with heterotrophic nitrification in an upper oxic region and nitrification

Abstract Transitional areas between ecosystem types are often active biogeochemically due to resource limitation changes. Lotic-to-lentic transitions in freshwaters appear active biogeochemically, but few studies have directly measured nutrient processing rates to assess whether processing within the rivermouth is important for load estimates or the local communities. We measured oxic fluxes of inorganic

Abstract There has been considerable debate on how atmospheric deposition (AD) in the watershed alters the supply of dissolved organic carbon (DOC) to river and coastal ecosystems. Here we show how AD-N and –P in the Ganga River Basin (GRB) drives the delivery of DOC. We conducted three sets of studies, a 3 year (2016–2018) in situ trial, a 5 year (2014–2018) soil-spray experiment and a decadal-scale

Nitrate retention is an important ecosystem service provided by streams which reduces nitrogen loads to downstream ecosystems. However, most inferences about nitrate retention and uptake in streams are based on measurements at sub-annual scales. Our objective was to evaluate variation in nitration retention and solute concentrations at weekly to decadal time scales. We measured nitrate and chloride

Tropical peatlands are a significant carbon store and contribute to global carbon dioxide (CO2) and methane (CH4) emissions. Tropical peatlands are threatened by both land use and climate change, including the alteration of regional precipitation patterns, and the 3–4 °C predicted warming by 2100. Plant communities in tropical peatlands can regulate greenhouse gas (GHG) fluxes through labile carbon

The land-to-ocean export and subsequent preservation of terrestrial particulate organic carbon (POC) in oceans represents a major carbon sink in the global carbon cycle. Small mountainous rivers (SMRs) are hotspots of this process; however, how the sources and fluxes of POC change during rain events in low-gradient SMRs and how they compare with those in steep SMRs are unknown. Here, we combined the

Increases in atmospheric carbon dioxide (CO2) and global air temperature affect all terrestrial ecosystems and often lead to enhanced ecosystem productivity, which in turn dampens the rise in atmospheric CO2 by removing CO2 from the atmosphere. As most terrestrial ecosystems are limited in their productivity by the availability of nitrogen (N), there is concern about the persistence of this terrestrial

Acid organic soils drained for agriculture are hotspots for nitrous oxide (N2O) emissions. Previous studies have indicated that water table (WT) depth and nitrogen (N) availability are important environmental controls, however, little is known about pathways leading to N2O emission. We investigated a raised bog drained for agriculture (pH 4.6 to 5.5) with, respectively, rotational grass and a potato

Dimethylsulfoniopropionate (DMSP) is a ubiquitous organic sulfur compound that underpins sulfur cycling in the marine environment and is the precursor to the climatically active gas dimethylsulfide (DMS). Modelling studies have identified the Southern Ocean as a DMS hot spot during summer, yet except for the bloom forming haptophyte Phaeocystis, little is known about sulfur production by other important

Root mucilage (RM), a soil-born biohydrogel, affects the physical stability of the rhizosphere. One reason for this is attributed to the present polysaccharides which contribute to the formation of aggregates by acting as interparticulate glue. The aim of this study was to explore how physico-chemical properties of polymers of interparticulate gels influence this gluing and thus soil microstructural

Non-point source pollution of phosphorus (P) is a primary cause of eutrophication of aquatic ecosystems, and poses a persistent management challenge due to the dynamic and poorly understood processes controlling the transport and transformation of P at the watershed scale. We examined phosphorus inputs, retention, and riverine losses in 62 diverse watersheds that included a wide range of land cover

Variation in foliar and soil nitrogen (N) isotope composition (δ15N) across environmental gradients has been widely studied at various scales. However, much less is known about the patterns of N2-fixing species that are presumed to be independent of climatic factors due to their capacity to fix atmospheric N2. In this study, the foliar and soil δ15N in Caragana microphylla, a leguminous shrub important

A key challenge to understanding the effects of climate change and nutrient deposition on ecosystem functioning is our lack of knowledge about nutrient limitations of heterotrophic and phototrophic microbial communities. This is especially true in high elevation ecosystems where it has been shown that earlier melt-out of snow beds and glacial retreat is allowing photosynthetic microbes and plants to

Wild and prescribed fires are important sources of a broad suite of organic compounds collectively termed pyrogenic carbon (PyC). Most PyC compounds have additional sources beyond fire, adding uncertainty to their use as tracers. However, members of the anhydrosugar family of isomeric compounds—levoglucosan, galactosan and mannosan—are generated exclusively by the pyrolysis and combustion of cellulose

In the initial online version of the article, the final term in the second equation in the "Materials and methods" section was incorrectly shown as 100 instead of 1000. The original article has been corrected.

The transport of dissolved organic matter (DOM) across the land-ocean-aquatic-continuum (LOAC), from freshwater to the ocean, is an important yet poorly understood component of the global carbon budget. Exploring and quantifying this flux is a significant challenge given the complexities of DOM cycling across these contrasting environments. We developed a new model, UniDOM, that unifies concepts, state