Recently fixed carbon fuels microbial activity several  meters below the soil surface

Scheibe, Andrea; Sierra, Carlos A.; Spohn, Marie

doi:10.5194/bg-20-827-2023

Cited by 7 publications

(8 citation statements)

References 58 publications

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“…Under increased C inputs, the key challenge will be to ensure that newly added C is decomposed slowly, for example, due to mineral C adsorption. However, many studies have shown that most of the newly entered C, also at deeper depth, is decomposed relatively quickly and is typically not contributing to long‐term C storage (Balesdent et al., 2018; Scheibe et al., 2023; Stoner et al., 2021; Xiao et al., 2022).…”

Section: Discussionmentioning

confidence: 99%

Controls and relationships of soil organic carbon abundance and persistence vary across pedo‐climatic regions

von Fromm,

Hoyt,

Sierra

et al. 2024

Global Change Biology

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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.

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Section: Discussionmentioning

confidence: 99%

Controls and relationships of soil organic carbon abundance and persistence vary across pedo‐climatic regions

von Fromm,

Hoyt,

Sierra

et al. 2024

Global Change Biology

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“…Because transit times are directly related to CS (Equations 21 and 22), we expect only tundra and boreal forest soils to store C in the subsoil at timescales relevant for climate change mitigation, that is, in the order of decades to centuries. In fact, previous studies have found that a large proportion of carbon used by microorganisms in the subsoil is recent and does not contribute to C stabilization in the subsoil (Balesdent et al., 2018; Scheibe et al., 2023). Therefore, we would expect lower values of CS for tropical forests, grasslands, and cropland soils in comparison with boreal forests and tundra soils.…”

Section: Empirical Evidence From Soil Profilesmentioning

confidence: 98%

“…A distinct property of most soils is the decrease of radiocarbon ( 14 C) activity with depth, indicating a higher average age of carbon since plant uptake from the atmosphere and a decrease in decomposition rates with depth (He et al., 2016; Heckman et al., 2022; Hicks Pries et al., 2023; Lawrence et al., 2020; Mathieu et al., 2015; Rumpel & Kögel‐Knabner, 2011; Scheibe et al., 2023). Potential factors responsible for this age gradient include (c.f.…”

Section: Processes Contributing To the Formation Of Soil Carbon Profilesmentioning

confidence: 99%

Carbon sequestration in the subsoil and the time required to stabilize carbon for climate change mitigation

Sierra,

Ahrens,

Bolinder

et al. 2024

Global Change Biology

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Soils store large quantities of carbon in the subsoil (below 0.2 m depth) that is generally old and believed to be stabilized over centuries to millennia, which suggests that subsoil carbon sequestration (CS) can be used as a strategy for climate change mitigation. In this article, we review the main biophysical processes that contribute to carbon storage in subsoil and the main mathematical models used to represent these processes. Our guiding objective is to review whether a process understanding of soil carbon movement in the vertical profile can help us to assess carbon storage and persistence at timescales relevant for climate change mitigation. Bioturbation, liquid phase transport, belowground carbon inputs, mineral association, and microbial activity are the main processes contributing to the formation of soil carbon profiles, and these processes are represented in models using the diffusion–advection–reaction paradigm. Based on simulation examples and measurements from carbon and radiocarbon profiles across biomes, we found that advective and diffusive transport may only play a secondary role in the formation of soil carbon profiles. The difference between vertical root inputs and decomposition seems to play a primary role in determining the shape of carbon change with depth. Using the transit time of carbon to assess the timescales of carbon storage of new inputs, we show that only small quantities of new carbon inputs travel through the profile and can be stabilized for time horizons longer than 50 years, implying that activities that promote CS in the subsoil must take into consideration the very small quantities that can be stabilized in the long term.

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“…2). The likely reason for this is that both aridity and low temperatures lead to low decomposition rates 19,42 . Thus, at arid and cooler sites, SOC content is probably more strongly shaped by the decomposition rate than by the rate of organic carbon input to soil 43 , and consequently plant biomass and SOC are not correlated at these sites.…”

Section: Plant Biomass Soil Carbon and Climatementioning

confidence: 99%

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

Spohn,

Bagchi,

Biederman

et al. 2023

Nat Commun

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Little is currently known about how climate modulates the relationship between plant diversity and soil organic carbon and the mechanisms involved. Yet, this knowledge is of crucial importance in times of climate change and biodiversity loss. Here, we show that plant diversity is positively correlated with soil carbon content and soil carbon-to-nitrogen ratio across 84 grasslands on six continents that span wide climate gradients. The relationships between plant diversity and soil carbon as well as plant diversity and soil organic matter quality (carbon-to-nitrogen ratio) are particularly strong in warm and arid climates. While plant biomass is positively correlated with soil carbon, plant biomass is not significantly correlated with plant diversity. Our results indicate that plant diversity influences soil carbon storage not via the quantity of organic matter (plant biomass) inputs to soil, but through the quality of organic matter. The study implies that ecosystem management that restores plant diversity likely enhances soil carbon sequestration, particularly in warm and arid climates.

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Recently fixed carbon fuels microbial activity several meters below the soil surface

Cited by 7 publications

References 58 publications

Controls and relationships of soil organic carbon abundance and persistence vary across pedo‐climatic regions

Controls and relationships of soil organic carbon abundance and persistence vary across pedo‐climatic regions

Carbon sequestration in the subsoil and the time required to stabilize carbon for climate change mitigation

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

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