Understanding the controls on the amount and persistence of soil organic carbon (C) is essential for predicting its sensitivity to global change. The response may depend on whether C is unprotected, ...isolated within aggregates, or protected from decomposition by mineral associations. Here, we present a global synthesis of the relative influence of environmental factors on soil organic C partitioning among pools, abundance in each pool (mg C g−1 soil), and persistence (as approximated by radiocarbon abundance) in relatively unprotected particulate and protected mineral‐bound pools. We show that C within particulate and mineral‐associated pools consistently differed from one another in degree of persistence and relationship to environmental factors. Soil depth was the best predictor of C abundance and persistence, though it accounted for more variance in persistence. Persistence of all C pools decreased with increasing mean annual temperature (MAT) throughout the soil profile, whereas persistence increased with increasing wetness index (MAP/PET) in subsurface soils (30–176 cm). The relationship of C abundance (mg C g−1 soil) to climate varied among pools and with depth. Mineral‐associated C in surface soils (<30 cm) increased more strongly with increasing wetness index than the free particulate C, but both pools showed attenuated responses to the wetness index at depth. Overall, these relationships suggest a strong influence of climate on soil C properties, and a potential loss of soil C from protected pools in areas with decreasing wetness. Relative persistence and abundance of C pools varied significantly among land cover types and soil parent material lithologies. This variability in each pool's relationship to environmental factors suggests that not all soil organic C is equally vulnerable to global change. Therefore, projections of future soil organic C based on patterns and responses of bulk soil organic C may be misleading.
In the first global meta‐analysis to examine both radiocarbon and C concentrations among different soil C pools, we found that three critical carbon pools (free particulate, occluded particulate, and mineral associated) respond differently to climate. Moisture had an almost equal influence as temperature on C persistence and abundance, highlighting the need for climate change studies focused on moisture manipulations. The strong variation in pool characteristics and their relationship to environmental factors indicates that we need to go beyond bulk soil carbon measurements to understand and model the responses of soil organic carbon to global change; it is critical to evaluate distinct pools as response variables.
One of the largest uncertainties in the terrestrial carbon cycle is the timing and magnitude of soil organic carbon (SOC) response to climate and vegetation change. This uncertainty prevents models ...from adequately capturing SOC dynamics and challenges the assessment of management and climate change effects on soils. Reducing these uncertainties requires simultaneous investigation of factors controlling the amount (SOC abundance) and duration (SOC persistence) of stored C. We present a global synthesis of SOC and radiocarbon profiles (nProfile = 597) to assess the timescales of SOC storage. We use a combination of statistical and depth‐resolved compartment models to explore key factors controlling the relationships between SOC abundance and persistence across pedo‐climatic regions and with soil depth. This allows us to better understand (i) how SOC abundance and persistence covary across pedo‐climatic regions and (ii) how the depth dependence of SOC dynamics relates to climatic and mineralogical controls on SOC abundance and persistence. We show that SOC abundance and persistence are differently related; the controls on these relationships differ substantially between major pedo‐climatic regions and soil depth. For example, large amounts of persistent SOC can reflect climatic constraints on soils (e.g., in tundra/polar regions) or mineral absorption, reflected in slower decomposition and vertical transport rates. In contrast, lower SOC abundance can be found with lower SOC persistence (e.g., in highly weathered tropical soils) or higher SOC persistence (e.g., in drier and less productive regions). We relate variable patterns of SOC abundance and persistence to differences in the processes constraining plant C input, microbial decomposition, vertical C transport and mineral SOC stabilization potential. This process‐oriented grouping of SOC abundance and persistence provides a valuable benchmark for global C models, highlighting that pedo‐climatic boundary conditions are crucial for predicting the effects of climate change and soil management on future C abundance and persistence.
One of the largest uncertainties in the terrestrial carbon cycle is the timing and magnitude of soil organic carbon (SOC) response to climate and vegetation change. We present a global synthesis of SOC and radiocarbon profiles to assess the timescales of SOC storage and the relationship between SOC abundance and persistence across pedo‐climatic regions. This process‐oriented grouping of SOC abundance and persistence provides a valuable benchmark for global C models, highlighting that pedo‐climatic boundary conditions are crucial for predicting the effects of climate change and soil management on future C abundance and persistence.
Given the importance of soil for the global carbon cycle, it is essential to understand not only how much carbon soil stores but also how long this carbon persists. Previous studies have shown that ...the amount and age of soil carbon are strongly affected by the interaction of climate, vegetation, and mineralogy. However, these findings are primarily based on studies from temperate regions and from fine‐scale studies, leaving large knowledge gaps for soils from understudied regions such as sub‐Saharan Africa. In addition, there is a lack of data to validate modeled soil C dynamics at broad scales. Here, we present insights into organic carbon cycling, based on a new broad‐scale radiocarbon and mineral dataset for sub‐Saharan Africa. We found that in moderately weathered soils in seasonal climate zones with poorly crystalline and reactive clay minerals, organic carbon persists longer on average (topsoil: 201 ± 130 years; subsoil: 645 ± 385 years) than in highly weathered soils in humid regions (topsoil: 140 ± 46 years; subsoil: 454 ± 247 years) with less reactive minerals. Soils in arid climate zones (topsoil: 396 ± 339 years; subsoil: 963 ± 669 years) store organic carbon for periods more similar to those in seasonal climate zones, likely reflecting climatic constraints on weathering, carbon inputs and microbial decomposition. These insights into the timescales of organic carbon persistence in soils of sub‐Saharan Africa suggest that a process‐oriented grouping of soils based on pedo‐climatic conditions may be useful to improve predictions of soil responses to climate change at broader scales.
We present insights into soil organic carbon (SOC) cycling, based on a new broad‐scale radiocarbon and mineral dataset for sub‐Saharan Africa. We found that in moderately weathered soils in seasonal climate zones with poorly crystalline and reactive clay minerals, SOC persists longer on average than in highly weathered soils in humid regions with less reactive minerals. Soils in arid climate zones store SOC for periods more similar to those in seasonal climate zones, likely reflecting climatic constraints on weathering, C inputs and microbial decomposition. These insights into the timescales of SOC persistence in soils of sub‐Saharan Africa suggest that a process‐oriented grouping of soils based on pedo‐climatic conditions may be useful to improve predictions of soil responses to climate change at broader scales.
In the age of big data, soil data are more available and richer than ever, but – outside of a few large soil survey resources – they remain largely unusable for informing soil management and ...understanding Earth system processes beyond the original study. Data science has promised a fully reusable research pipeline where data from past studies are used to contextualize new findings and reanalyzed for new insight. Yet synthesis projects encounter challenges at all steps of the data reuse pipeline, including unavailable data, labor-intensive transcription of datasets, incomplete metadata, and a lack of communication between collaborators. Here, using insights from a diversity of soil, data, and climate scientists, we summarize current practices in soil data synthesis across all stages of database creation: availability, input, harmonization, curation, and publication. We then suggest new soil-focused semantic tools to improve existing data pipelines, such as ontologies, vocabulary lists, and community practices. Our goal is to provide the soil data community with an overview of current practices in soil data and where we need to go to fully leverage big data to solve soil problems in the next century.
Increasing land transformation in the Amazon basin, from forest to post-forest usage such as pastureland, agriculture and agroforestry, triggers significant changes in hydrology, soil fertility and ...regional climatology. However, relatively little is known about Amazon basin soil chemistry in general and about its possible alteration with recent land-use change.
We present robust pedogeochemical data for 65 elements and oxides, and evidence for modification due to recent deforestation and post-forest land use on upland soils in Amazonas state, Brazil. Differences emerge in median element concentrations between these two land-cover types, and between central and southern parts of the basin. These new data, a product of the bi-national EcoRespira-Amazon (ERA) project, are based on triplicate sampling under different seasonal conditions at 29 sites, representing ca. 740,000km2 and average annual meteorological conditions. Mineral soil samples (TOP: 0–20cm; BOT: 30–50cm) characterize the active upper rhizosphere. Data were obtained with very tight quality control from sampling to analysis (following GEMAS protocols), using various overlapping analytical methods. Some major, minor and trace element concentrations deviate strongly from established world soil averages, including the recent PEGS2.
Geological (lithological) and weathering boundary conditions define the primary soil chemical signal. This is overprinted by biogeochemical forces (ecosystem feedbacks), and recently by human intervention (change of land cover, deforestation). The general assumption of depleted tropical soils is not justified as such – a more differentiated view is needed, since carbon and macronutrients such as nitrogen and phosphorous, albeit not always plant-available, do often occur in relatively high concentrations (median values TOP: 1.9, 0.15 and 0.02wt%). Calcium, magnesium and potassium are truly depleted (median values TOP: 0.025, 0.095 and 0.065wt%), albeit with noticeable variance. Trace elements, from silver to zirconium and including REE, show highly differentiated responses. Most are relatively enriched in post-forest soils; a subtle signal that is interpreted as reduced plant-soil interaction. BOT concentrations are generally higher than those in TOP soil, reflecting weathering conditions and biogeochemical cycling – with interesting exceptions (Br, Cd, Rb).
Major and minor element concentration change with deforestation. Display omitted
•High-quality dataset for Brazilian Amazon basin upland (terra firme, oxisol) soil chemistry (65 elements)•Fully quantified major, minor and most (ultra)trace elements (no PGE's)•Emerging pedogeochemical deforestation effects•Significant deviation from average world soil values (major, minor and trace elements)
The Amazon rainforest, formerly pristine and highly biodiverse, is increasingly under threat from deforestation for cattle grazing, other forms of agriculture, mining and development. To better ...understand which land management type best serves sustainability aims, we compare soil gas exchange (CO2, CH4, N2O) and soil chemistry for forested land with post-forest land at 13 locations and 29 sites within the state of Amazonas, Brazil. We find that forest soils show distinctively different signals and signatures compared to soils in post-forest land use cases. Crucial answers emerge regarding the limits of system resilience as well as sustainable alternatives to deforestation and current land-use practices. We carry out a socioeconomic evaluation and discuss the likely reasons for inaction and how to overcome them.
Radiocarbon is a critical constraint on our estimates of
the timescales of soil carbon cycling that can aid in identifying mechanisms
of carbon stabilization and destabilization and improve the ...forecast of soil
carbon response to management or environmental change. Despite the wealth of
soil radiocarbon data that have been reported over the past 75 years, the
ability to apply these data to global-scale questions is limited by our
capacity to synthesize and compare measurements generated using a variety of
methods. Here, we present the International Soil Radiocarbon Database
(ISRaD; http://soilradiocarbon.org, last access: 16 December 2019), an open-source archive of soil data that
include reported measurements from bulk soils, distinct soil carbon pools
isolated in the laboratory by a variety of soil fractionation methods,
samples of soil gas or water collected interstitially from within an intact
soil profile, CO2 gas isolated from laboratory soil incubations, and
fluxes collected in situ from a soil profile. The core of ISRaD is a relational
database structured around individual datasets (entries) and organized
hierarchically to report soil radiocarbon data, measured at different
physical and temporal scales as well as other soil or environmental
properties that may also be measured and may assist with interpretation and
context. Anyone may contribute their own data to the database by entering it
into the ISRaD template and subjecting it to quality assurance protocols.
ISRaD can be accessed through (1) a web-based interface, (2) an R package
(ISRaD), or (3) direct access to code and data through the GitHub
repository, which hosts both code and data. The design of ISRaD allows for
participants to become directly involved in the management, design, and
application of ISRaD data. The synthesized dataset is available in two
forms: the original data as reported by the authors of the datasets and an
enhanced dataset that includes ancillary geospatial data calculated within
the ISRaD framework. ISRaD also provides data management tools in the
ISRaD-R package that provide a starting point for data analysis; as an
open-source project, the broader soil community is invited and encouraged
to add data, tools, and ideas for improvement. As a whole, ISRaD provides
resources to aid our evaluation of soil dynamics across a range of spatial
and temporal scales. The ISRaD v1.0 dataset is
archived and freely available at https://doi.org/10.5281/zenodo.2613911 (Lawrence et al., 2019).
This study aimed to determine the influence of gene candidates on mycophenolic acid (MPA) response during the first year of renal transplantation.
A total of 218 renal transplant recipients who ...received MPA from the first day of transplantation at a fixed dose of 2 g/day were genotyped for ABCB1, ABCC2, UGT2B7, UGT1A9, SLCO1B1, SLCO1B3 and IMPDH1 polymorphisms. Clinical end points were MPA-related adverse drug reactions (ADRs) and acute rejection episodes during the first year post-transplantation.
After correction for multiple statistical testing, SLCO1B1 (encoding the hepatic uptake transporter OATP1B1) was the only gene associated with MPA-related ADRs, showing a 75% risk reduction in favor of a protective effect of the SLCO1B1*5 allele (p = 0.002). In vitro experiments showed that MPA metabolites MPA-phenyl-glucuronide and MPA-acyl-glucuronide are substrates of OATP1B1. Their transport was decreased in the presence of the variant transporter (OATP1B1*5).
These results suggest for the first time that carriers of the SLCO1B1*5 allele seem to be protected from MPA-related ADRs.
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