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opencc-zeroJan 2023View details →

Channelling of basal resources and use of allochthonous marine carbon by soil arthropods of the Wadden Sea salt marsh

Salt marshes are located between the marine and terrestrial systems. Because they form as sediment accumulates, they comprise a gradient of shore height with differing inundation frequencies and associated abiotic soil conditions. Along this gradient, both autochthonous vascular plant resources and allochthonous marine algal or detrital resources are available, with the availability of both varying with season and salt marsh zone. However, little is known about the importance of either resource for the soil animal food web. We investigated both spatial and temporal resource use of the soil macro- and mesofauna of the salt marsh using neutral lipid fatty acids (NLFAs). Generally, irrespective of season and zone the soil animal food web relied on carbon originating from autochthonous vascular plants and associated bacteria and fungi, with the role of bacteria generally exceeding that of fungi. However, the channelling of fungal resources consistently peaked in October, whereas seasonal changes in the channelling of plant and bacterial resources varied among salt marsh zones. Further, variations in the channelling of resources with season and zone varied among salt marsh animal species. Although being only minor, allochthonous resources of marine origin contributed to soil food web nutrition across salt marsh zones and seasons. The contribution of algae to soil food web nutrition depended on inundation frequency and season, i.e. algal productivity. Overall, the results demonstrate that the salt marsh soil fauna predominantly relies on autochthonous vascular plant resources, with the contribution of allochthonous marine resources being minor and restricted to few taxa.

opencc-by-4.0Feb 2023View details →

Data set for the article "One-time freeze-thawing or carbon input events have long-term legacies in soil microbial communities"

The following are data and code used for statistical analysis and figure plotting in the manuscript Gorka et al. (2023) "One-time freeze-thawing or carbon input events have long-term legacies in soil microbial communities", Geoderma, <a href="https://doi.org/10.1016/j.geoderma.2023.116399">https://doi.org/10.1016/j.geoderma.2023.116399</a> It contains the following files: <ol> <li>Microbial PLFA and NLFA analysis files (contained in Fatty_acid_analysis.zip) <ul> <li>PLFA and NLFA abundance data, in nmol C g-1 dw (in fatty_acid_data.csv)</li> <li>Taxonomic specificities of fatty acids, needed for R-script to run (in phylum.csv)</li> <li>An R Script reproducing the statistical analysis, figure plotting and output for tables, as used in the manuscript (Fatty_acid_analysis.R)</li> </ul> </li> <li>Soil C and N stoichiometry analysis files (contained in TOC_TN_analysis.zip) <ul> <li>Dissolved organic C (DOC), total dissolved N (TN), and C and N in microbial biomass (Cmic, Nmic) abundance data, in mg g-1 dw (in toc_tn_data.csv)</li> <li>An R Script reproducing the statistical analysis, figure plotting and output for tables, as used in the manuscript (TOC_TN_analysis.R)</li> </ul> </li> </ol>

opencc-by-4.0Feb 2023View details →

Soil, litter and vegetation carbon for the 6 simulations performed in CLM5 of "Chemistry-albedo feedbacks offset up to a third of forestation's CO2 removal benef"

Soil, litter and vegetation carbon for the 6 simulations performed in CLM5 (Table S1) of "Chemistry-albedo feedbacks from reforestation reduce climate benefits and crop yields" i.clm5.global_MF_SSP1.h1.2015-2100_zip.nc    - SSP126_MF_Land i.clm5.global_SSP1_nolulcc.clm2.h1.2015-2100_zip.nc - SSP126_2015_Land  i.clm5.global_SSP1.h1.2015-2100_zip.nc    - SSP126_Land i.clm5.global_MF_SSP3.02.h1.2015-2100_zip.nc  - SSP370_MF_Land i.clm5.global_SSP3.02.h1.2015-2100_zip.nc - SSP370_Land i.clm5.global_SSP3_nolulcc.clm2.h1.2015-2100_zip.nc - SSP370_2015_Land   These simulations were performed by Dr James King, University of Sheffield.

opencc-zeroDec 2022View details →

Data from: Climatic water availability mainly drives context-dependency of tree functional diversity effects on soil organic carbon storage in European forests

The interplay of forest stand and environmental factors shape soil organic C (SOC) storage in forest ecosystems but little is known about their relative impacts in different soil layers. Moreover, how environmental factors modulate the impact of stand factors, particularly species mixing, on SOC storage, is largely unexplored. In this study conducted in 21 forest triplets (two-species mixed stand and respective monocultures nearby) distributed in Europe, we tested the hypothesis that stand factors (functional identity and diversity) have stronger effects on topsoil (FF+0-10 cm) C storage than environmental factors (climatic water availability, clay+silt content, oxalate-extractable Al - Alox) but that the opposite occurs in the subsoil (10-40 cm). We also tested the hypothesis that functional diversity improves SOC storage under high climatic water availability, clay+silt contents, Alox. We characterized functional identity as the proportion of broadleaved species (beech and/or oak), and functional diversity as the product of broadleaved and conifer (pine) proportions. The results show that functional identity was the main driver of topsoil C storage while climatic water availability had the largest control on subsoil C storage. Contrary to expectations, functional diversity decreased topsoil C storage under increasing climatic water availability but the opposite was observed in the subsoil. Functional diversity effects on topsoil C increased with increasing clay+silt content, while its effects on subsoil C was negative at increasing Alox content. This suggests that functional diversity effect on SOC storage along environmental gradients depends on the specific environmental factor and the soil depth under consideration.

opencc-zeroMay 2023View details →

The contribution of Fe(III) reduction to soil carbon mineralization in montane meadows depends on soil chemistry, not parent material or microbial community

The long-term stability of soil carbon (C) is strongly influenced by organo-mineral interactions. Iron (Fe)-oxides can both inhibit microbial decomposition by providing physicochemical protection for organic molecules and enhance rates of C mineralization by serving as a terminal electron acceptor, depending on redox conditions. Restoration of floodplain hydrology in montane meadows has been proposed as a method of sequestering C for climate change mitigation. However, dissimilatory microbial reduction of Fe(III) could lead to C losses under increased reducing conditions. In this study, we explored variations in Fe-C interactions over a range of redox conditions and in soils derived from two distinct parent materials to elucidate biochemical and microbial controls on soil C cycling in Sierra Nevada montane meadows. Differences in parent material were associated with different rates of Fe(III) reduction at increasing soil moisture levels, but not with differences in soil C mineralization. Known Fe(III)-reducing taxa were present in all samples but neither the relative abundance nor richness of Fe(III) reducers corresponded with measured rates of Fe(III) reduction. Under reducing conditions, our results suggest that Fe(III) reduction contributes to C mineralization only when Fe-bound C is present. However, Fe-bound C was not present in all of our soils and was below theoretical limits for C sorption onto Fe-oxides where it was found. Overall, our results suggest that meadow-specific soil chemistry drives Fe-C interactions and that the impact of Fe on C cycling in montane meadows may be smaller than in other ecosystems.

opencc-zeroDec 2022View details →

Grazing in a megagrazer-dominated savanna does not reduce soil carbon stocks, even at high intensities

Recent studies suggest that wild animals can promote ecosystem carbon sinks through their impacts on vegetation and soils. However, livestock studies show that intense levels of grazing reduce soil organic carbon (SOC), leading to concerns that rewilding with large grazers may compromise ecosystem carbon storage. Furthermore, wild grazers can both limit and promote woody plant recruitment and survival on savanna grasslands, with both positive and negative impacts on SOC, depending on the rainfall and soil texture contexts. We used grazing lawns in one of the few African protected savannas that are still dominated by megagrazers (>1000 kg), namely white rhinoceros (Ceratotherium simum), as a model to study the impact of prolonged and intense wild grazing on SOC stocks. We contrasted SOC stocks between patches of varying grazing intensity and woody plant encroachment in sites across different rhino habitat types. We found no differences in SOC stocks between the most- and least-grazed plots in any of the habitats. Intermediately grazed plots, however, had higher SOC stocks in the top 5 cm compared to most and least grazed plots, but only in the closed-canopy woodland habitat and not in the open habitats. Importantly, we found no evidence to support the hypothesis that wild grazing reduces SOC, even at high grazing intensities by the world's largest megagrazer. Compared to the non-encroached reference plots, woody encroached plots had higher SOC stocks in soils with low clay content and lower SOC stocks in soils with high clay content, although only in the top 5 cm. Accordingly, our study highlights that wild grazers may influence SOC indirectly through their impact on tree-grass ratios in grassy ecosystems. Our study thus provides important insights for future nature-based climate solutions that focus on wild grazer conservation and restoration.

opencc-by-4.0May 2023View details →

Dataset of manuscript "No detectable upper limit of mineral associated carbon in temperate agricultural soils"

Dataset of carbon fractions (mineral associated organic carbon and particulate organic carbon) detected in a subset of topsoil samples of the first German Agricultural Soil Inventory.

opencc-zeroMay 2023View details →

Drivers of soil organic carbon stock during tropical forest succession

Soil organic matter contributes to productivity in terrestrial ecosystems and contains more carbon than is found in the atmosphere. Yet, there is little understanding of soil organic carbon (SOC) sequestration processes during tropical forest succession, particularly after land abandonment from agriculture practices. Here we used vegetation and environmental data from two large-scale surveys covering a total landscape area of 20,000 ha in Southeast Asia to investigate the effects of plant species diversity, functional trait diversity, phylogenetic diversity, aboveground biomass, and environmental factors on SOC sequestration during forest succession. We found that functional trait diversity plays an important role in determining SOC sequestration across successional trajectories. Increases in SOC carbon storage were associated with indirect positive effects of species diversity and succession age via functional trait diversity, but phylogenetic diversity and aboveground biomass showed no significant relationship with SOC stock. Furthermore, the effects of soil properties and functional trait diversity on SOC carbon storage shift across elevation. Synthesis: Our results suggest that reforestation and restoration management practices that implement a trait-based approach by combining long-lived and short-lived species (conservative and acquisitive traits) to increase plant functional diversity could enhance SOC sequestration for climate change mitigation and adaptation efforts, as well as accelerate recovery of healthy soils.

Effects of plant traits and ecosystem properties on wave attenuation and soil carbon content

Understanding the relationships among the environment, species traits and ecosystem properties is important for developing management measures that optimize the delivery of ecosystem services (ESs). Here, we identify the most important relationships responsible for the delivery of two key ESs provided by tidal marshes: (1) nature-based shoreline protection through wave attenuation and (2) mitigation of climate change through soil carbon storage. In two tidal zones below and above the mean high water (MHW, Elbe Estuary, Germany) level, we measured environmental parameters, such as soil salinity and inundation, as well as plant traits representing adaptations to hydrodynamic stress and strongly influencing decomposition rates. Multiple linear regression results showed that wave attenuation rates were positively related to aboveground community biomass and stem bending resistance, and soil organic carbon was positively related to stem-specific density (below the MHW level). In the tidal zone above the MHW level, soil carbon density was governed by inundation duration and decomposition rates. Our study highlights that (1) ES delivery is not equally spread across tidal marshes and (2) ecosystem management should stimulate the development and persistence of habitat diversity (here, low and high marsh zones) to maximize ES delivery potential. Securing the delivery of the two studied ESs under climate change will depend on providing suitable (landward) space to sustain the functioning of the two marsh zones. In the studied marshes, these services are highly dependent on a few species (i.e., wave attenuation on Schoenoplectus tabernaemontani and Bolboschoenus maritimus and carbon storage on Phragmites australis), and as such, current and future ESs strongly depend on specific species' responses to changing environmental conditions.

opencc-by-4.0Feb 2023View details →

Biotic and abiotic factors controlling spatial variation of mean carbon turnover time in forest soil

Data description This dataset is associated with the paper "Biotic and abiotic factors controlling spatial variation of mean carbon turnover time in forest soil". This dataset includes the soil organic carbon turnover time (τsoc) based on radiocarbon signals at the global and regional scales. Global synthesis The analysis of global soil radiocarbon data was done using the International Soil Radiocarbon Database (ISRaD v.1.0; Lawrence et al., 2020). ISRaD is an open source data with the records of 8 biomes (i.e., forest, grassland, cropland, shrubland, savanna, tundra, permafrost, and others). Since we focus on the turnover time of SOC (τsoc) based on radiocarbon occurring in the natural forest ecosystem, so we limited our study to data from soil depth within 200 cm in the forest ecosystem. We built a database of radiocarbon-based soil turnover time (τsoc) of 1897 soil samples from 245 forest locations worldwide. It covers a wide geographical range (35.65 oS ‒ 68.8 oN; 159.64 °W – 173.57 °E) and a broad nature climate zone (-5.2 oC to 40.0 oC; 58.66 mm to 6900 mm) over the half a century (1958 – 2017). Where forest age is missing, we derived it from The global forest age dataset (GFAD v 1.0; Poulter et al., 2018). The GFAD database represents the distribution of forest stand age during 2000 – 2010 years. Regional analysis  Soil sampling in forests across the Eastern Asian Monsoon region We sampled soils from twelve permanent forest plots in five mountains in the Eastern Asian Monsoon region (Table 1, Figure 1, and S1). Five of the twelve forest plots are members of the Smithsonian Forest Global Earth Observatory network (ForestGEO, https://forestgeo.si.edu/; Anderson-Teixeira et al., 2018; Chu et al., 2019). The other seven forest plots are members of China's National Ecosystem Research Network (CNERN, http://www.cern.ac.cn). In the Eastern Asian Monsoon region, more than half of the total annual rainfall occurs in the summer season (i.e., June, July, and August) (Tardif et al., 2020; Tian et al., 2003). We estimated the τsoc by the radiocarbon dating analysis of up to 100 cm of soil depth in each forest plot. For each plot, we separated the whole soil increment into the surface (0 – 30 cm) and deep (30 – 100 cm) layers to test the radiocarbon signal due to the high financial cost. Details of the location, climate, and vegetation for each sampling site are provided in Table 1 and Supplementary Text 1. Nine soil cores (2.5 cm in diameter) were collected in each forest plot, and a depth of 10 cm separated each soil column from 0 to 100 cm. In total, 108 soil profiles were sampled across the 12 forest plots. The accumulated aboveground litter was collected and measured in an area of 50 cm × 50 cm in each forest plot, with three replicates adjacent to each soil profile. Fine roots (< 2 mm in diameter) were manually picked from soil samples. The litter and root samples were dried at 65 °C for 48 hours using an oven and then weighed for dry mass. The elevation and other geographic information of each forest plot were measured during the soil sampling.

opencc-by-4.0Jun 2023View details →

Data from Comparing organic carbon bound to different minerals in wetland and upland soils

Here is the data and drawing code  for "comparing organic carbon bound to different minerals in wetland and upland soils". Mineral binding of organic carbon (OC) is vital for soil organic carbon (SOC) persistence. However, the relative importance of two main types of soil minerals - metal oxides and silicate clay - in SOC protection remains unclear, hampering our ability to predict and protect this important pool of persistent SOC. Here, using sequential dissolution by dithionite and hydrofluoric acid, we quantified OC bound to metal oxides versus silicate clay in soils from contrasting environments (i.e., wetlands and uplands).  We find that metal oxides override silicate clay in SOC protection in both wetlands and uplands, and OC bound to soil minerals (especially metal oxides) constitutes a higher fraction of SOC in wetlands than uplands, suggesting an underappreciated role of mineral protection in wetland SOC preservation. Furthermore, using lignin phenol analysis in tandem, we find that silicate clay dissolution may release an addition of ~23% lignin phenols from soils, potentially providing a means to assess ‘hidden’ lignin in mineral matrices. These findings highlight the important role of different soil minerals in the protection of SOC and its components in contrasting terrestrial environments, and advance our understanding of predicting and protecting this important pool of persistent SOC.

Data for: How do harvesting methods applied in continuous-cover forestry and rotation forest management impact soil carbon storage and degradability in boreal Scots pine forests?

Forest management affects soil carbon (C) storage through forest composition, microclimate and litter inputs. How two major forest management systems, continuous-cover forestry (CCF) and clear-cut-based rotation forest management (RFM), differ in their impact on soil C in boreal forests is still poorly understood, however. We compared their effects on soil organic carbon (SOC) storage and quality in boreal Scots pine (Pinus sylvestris L.) dominated forests in eastern Finland. We tested the hypotheses that (1) colder microclimates and continuous litter inputs will lead to higher SOC stocks in CCF plots than in clear-cuts and (2) the more labile litter in clear-cuts with varying ground vegetation will enhance SOC decomposition rates. We sampled uncut mature forests, clear-cuts, retention-cuts and gap-cuts, in which we analysed SOC concentrations and calculated the stocks. We measured stand characteristics such as diameter-at-breast height, basal area, dominant tree height, and understorey species coverage of the various treatments and modelled the above- and belowground litter inputs based on these parameters. We used laboratory incubation and sequential fractionation of SOC to assess its degradability under standardized conditions. To estimate the decomposition rate in the various environments we incubated cellulose bags in situ. We assessed the impact of microclimate on SOC decomposition, using data from soil-temperature and soil-moisture field measurements. We quantified the microbial biomass C pool, using chloroform fumigation extraction to gain insight on the impact of forest management practice on soil microbes. The SOC concentrations and SOC stocks did not differ significantly between the treatments, despite the presence of a warmer microclimate and lower litter inputs in the clear-cut plots. However, we found differences in the quality of the SOC. Soils in clear-cut sites showed lower proportions of labile SOC compounds than did the other treatments. As hypothesized, the decomposition rates were elevated in clear-cuts, but were equally as high within the canopy gaps on gap-cut stands. Our work highlights that forest management affects the quality, degradability, long-term accumulation and storage of SOC. We conclude that the accumulation of labile compounds in uncut forests and retention-cuts, combined with the decreased decomposition rates, indicate a higher potential for future C accumulation in the soil than in clear-cuts.

opencc-by-4.0Jun 2023View details →

Soil labile nitrogen pools for the Carbon action ACA experiment for year 2022 (4th year of experiment)

This dataset describes labile nitrogen pools following four years of carbon farming experiments in the Carbon Action ACA dataset of 20 farms. The soils were sampled in July and analyzed for Total N, ISNT-N, Autoclave citrate protein -N, Water soluble organic N, inorganic N and potentially mineralizable N.  The analysis is published open access in Soil Use And Management. https://doi.org/10.1111/sum.12930

Data for: Soil organic carbon contents of collected soil samples from China's black soil region

The long-term use of cropland and cropland reclamation from natural ecosystems led to soil degradation. This study investigated the effect of the long-term use of cropland and cropland reclamation from natural ecosystems on soil organic carbon (SOC) content and density over the past 35 years. Altogether, 2140 topsoil samples (0–20 cm) were collected across Northeast China. Landsat images were acquired from 1985 to 2020 through Google Earth Engine, and the reflectance of each soil sample was extracted from the Landsat image that its time was consistent with sampling. The hybrid model that included two individual SOC prediction models for two clustering regions was built for accurate estimation after k-means clustering. The probability hybrid model, a combination between the hybrid model and classification probabilities of pixels, was introduced to enhance the accuracy of SOC mapping. Cropland reclamation results were extracted from the land cover time series dataset at a 5-year interval. Our study indicated that: (1) Long-term use of cropland led to a 3.07 g kg-1 and 6.71 Mg C ha-1 decrease in SOC content and density, respectively, and the decrease of SOC stock was 0.32 Pg over the past 35 years; (2) Nearly 64% of cropland had a negative change in terms of SOC content from 1985 to 2020; (3) Cropland reclamation track changed from high to low SOC content, and almost no cropland was reclaimed on the 'Black soils' after 2005; (4) Cropland reclamation from wetlands resulted in the highest decrease, and reclamation period of years 31–35 decreased when SOC density and SOC stock were 16.05 Mg C ha-1 and 0.005 Pg, respectively, while reclamation period of years 26–30 from forest witnessed SOC density and stock decreases of 8.33 Mg C ha-1 and 0.01 Pg, respectively. Our research results provide a reference for SOC change in the black soil region of Northeast China and can attract more attention to the area of the protection of 'Black soils' and natural ecosystems.

Data from: Positive plant diversity effects on soil microbial drought resistance are linked to variation in labile carbon and microbial community structure

Biodiversity loss and drought are substantially altering both above-and belowground terrestrial ecosystem functioning, but mechanistic understanding of plant diversity effects on the drought resistance of soil microbial biomass remains limited. We designed a mesocosm experiment to examine drought resistance of soil microbial biomass along a plant species richness gradient (five plant species richness levels based on old-field communities). We calculated resistance of microbial biomass to drought and recorded key belowground properties which may influence microbial resistance to drought (i.e., microbial diversity, microbial community structure, soil carbon stocks and root biomass). Plant species richness had a positive effect on microbial resistance to drought. Variation in microbial resistance to drought was linked to properties of the fungal community in ambient soil (Shannon diversity, arbuscular mycorrhizal fungal richness and abundance) but not soil bacterial diversity. Moreover, microbial resistance to drought increased with increasing root biomass and dissolved organic carbon recorded under ambient conditions. These results highlight the importance of plant diversity for microbial biomass stability in our old-field study system with implications for biogeochemical cycling, and suggest that indirect effects of plant species richness on labile soil carbon and soil fungi may drive resistance of soil microbial biomass to drought.

opencc-by-4.0Jul 2023View details →

The positive effect of plant diversity on soil carbon depends on climate

The three files contain all data (Data S1) and all R code to produce all tables and figures of the manuscript entitled "The positive effect of plant diversity on soil carbon depends on climate".

Data from: Litter quality controls tradeoffs in soil carbon decomposition and replenishment in a subtropical forest

Species-rich forests can produce litter of varying carbon (C) and nitrogen (N) composition (i.e., quality), which can affect decomposition and play a central role in long-term soil organic carbon (SOC) accumulation. However, how differences in litter quality affect SOC decomposition and formation remains unclear over the full litter decomposition trajectory. We followed the in-situ complete decomposition of added 13C-labelled high- (low C:N) and low-quality (high C:N) leaf-litter and its effect on particulate (POM) and mineral-associated (MAOM) organic matter fractions over two years in a natural subtropical forest. We found that during early stages of decomposition, low-quality litter inputs decreased SOC via a positive priming effect (i.e., new C inputs favored decomposition of native SOC), but these SOC losses were offset by SOC gains observed via a negative priming effect during decomposition of high-quality litter. In contrast, this pattern reversed during late stages of decomposition—SOC losses via a positive priming effect induced by high-quality litter were offset by SOC gains via a negative priming effect induced by low-quality litter. Over the full decomposition of litter, both high- and low-quality litter stimulated microbial breakdown of SOC tied to POM, but also replenished more persistent SOC that associated with soil minerals (MAOM). Altogether, we observed that low-quality litter formed twice as much new SOC as high-quality litter (24% vs. 12% of added litter-C). We extend the notion of the priming effect from primarily a negative role promoting losses of native SOC, to a functional role that can replenish persistent SOC. Synthesis. Our measurements raise the possibility that, in species-rich forests, high- and low-quality litter decomposition play opposite but dynamically complementary roles in renewing POM—both by inducing its decomposition and formation—while exclusively favoring MAOM formation, which can help explain how differences in litter quality favor SOC accumulation and persistence. Global change factors that shift plant community composition may ultimately affect the fate of soil C, as changes in litter quality may force soil transitions from sinks to sources or sources to sinks of atmospheric CO2.

Tree biomass does not correlate with soil carbon stocks in forest-tundra ecotones along a 1100 km latitudinal gradient in Norway

Due to climate warming, forests are expanding to higher elevations and latitudes at the expense of tundra vegetation. While the subsequent increase in aboveground biomass is well-documented, there is much speculation regarding the effects on soil organic carbon (SOC) stocks. To provide insight into the consequences of tree encroachment into treeless tundra, we sampled SOC stocks across 36 forest-tundra ecotones along a 1100 km latitudinal gradient in Norway. Our results show that SOC stocks vary greatly within, as well as among treeline ecotones, and that SOC stocks do not correlate with tree biomass and tree species. SOC stocks do increase with temperature, and vary with slope steepness, slope aspect, and soil parent material. Applying a 'space-for-time substitution' perspective, our findings suggest that tree encroachment into tundra is unlikely to have immediate consequences for SOC stocks.

Depth-dependent effects of Ericoid Mycorrhizal shrubs on soil carbon and nitrogen pools are accentuated under Arbuscular Mycorrhizal Trees

Plant mycorrhizal associations influence the accumulation and persistence of soil organic matter and could therefore shape ecosystem biogeochemical responses to global changes that are altering forest composition. For instance, arbuscular mycorrhizal (AM) tree dominance is increasing in temperate forests, and ericoid mycorrhizal (ErM) shrubs can respond positively to canopy disturbances. Yet how shifts in the co-occurrence of trees and shrubs with different mycorrhizal associations will affect soil organic matter pools remains largely unknown. We examine the effects of ErM shrubs on soil carbon and nitrogen stocks and indicators of microbial activity at different depths across gradients of AM versus ectomycorrhizal (EcM) tree dominance in three temperate forest sites. We find that ErM shrubs strongly modulate tree mycorrhizal dominance effects. In surface soils, ErM shrubs increase particulate organic matter accumulation and weaken the positive relationship between soil organic matter stocks and indicators of microbial activity. These effects are strongest under AM trees that lack fungal symbionts that can degrade organic matter. In subsurface soil organic matter pools, by contrast, tree mycorrhizal dominance effects are stronger than those of ErM shrubs. Ectomycorrhizal tree dominance has a negative influence on particulate and mineral-associated soil organic matter pools, and these effects are stronger for nitrogen than for carbon stocks. Our findings suggest that increasing co-occurrence of ErM shrubs and AM trees will enhance particulate organic matter accumulation in surface soils by suppressing microbial activity while having little influence on mineral-associated organic matter in subsurface soils. Our study highlights the importance of considering interactions between co-occurring plant mycorrhizal types, as well as their depth-dependent effects, for projecting changes in soil carbon and nitrogen stocks in response to compositional shifts in temperate forests driven by disturbances and global change.

Cropland management impacts on soil organic carbon stock changes in US croplands from 1990 to 2015

This geospatial dataset represents soil organic carbon stock changes estimated from a counterfactual analysis of climate-smart soil management practices that were adopted in U.S. croplands between 1990 and 2015. The counterfactual scenarios are relative to historical cropland management implemented in the U.S. for the temporal domain of this study. These data provide a large-scale overview of the carbon stock changes in US cropland agricultural soils associated with conservation tillage, manure amendments, cover crops terminated with cultivation, cover crop terminated with herbicide, hay and pasture in rotation with annual crops, set-aside/Conservation Reserve Program lands. Data were generated using the DayCent ecosystem model driven by cropping histories in the USDA National Resources Inventory (NRI) and associated agricultural management data. The average annual stock change was calculated for each management practice to determine the impact. Average rates of annual stock changes on a per-hectare basis (averaged from 1990 to 2015) are presented as a gridded dataset. Data are in a GeoTIFF format on a 5 km grid.