Root penetration in deep soil layers stimulates mineralization of millennia-old organic carbon

Shahzad, Tanvir; Rashid, Muhammad Imtiaz; Maire, Vincent; Barot, Sébastien; Perveen, Nazia; Alvarez, Gaël; Mougin, Christian; Fontaine, Sébastien

doi:10.1016/j.soilbio.2018.06.010

Cited by 88 publications

(61 citation statements)

References 62 publications

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“…Inclusion of the priming effects on microbial biomass can improve predictions of global soil organic C stocks and predictions of their change due to climate forcing over the 21st century (Guenet et al, ). The vulnerability of soil organic matter to increased decomposition with increased plant inputs that alleviate microbial C limitation indicates that deep soil C may be vulnerable to decomposition if elevated CO 2 and N enrichment change root exudation by plants (Phillips, Bernhardt, & Schlesinger, ; Shahzad et al, ).…”

Section: How Carbon Limitation Of Soil Decomposers Drives Ecosystem Pmentioning

confidence: 99%

Microbial carbon limitation: The need for integrating microorganisms into our understanding of ecosystem carbon cycling

Soong

Fuchslueger

Marañón-Jiménez

et al. 2020

Global Change Biology

338

152

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Numerous studies have demonstrated that fertilization with nutrients such as nitrogen, phosphorus, and potassium increases plant productivity in both natural and managed ecosystems, demonstrating that primary productivity is nutrient limited in most terrestrial ecosystems. In contrast, it has been demonstrated that heterotrophic microbial communities in soil are primarily limited by organic carbon or energy. While this concept of contrasting limitations, that is, microbial carbon and plant nutrient limitation, is based on strong evidence that we review in this paper, it is often ignored in discussions of ecosystem response to global environment changes. The plant‐centric perspective has equated plant nutrient limitations with those of whole ecosystems, thereby ignoring the important role of the heterotrophs responsible for soil decomposition in driving ecosystem carbon storage. To truly integrate carbon and nutrient cycles in ecosystem science, we must account for the fact that while plant productivity may be nutrient limited, the secondary productivity by heterotrophic communities is inherently carbon limited. Ecosystem carbon cycling integrates the independent physiological responses of its individual components, as well as tightly coupled exchanges between autotrophs and heterotrophs. To the extent that the interacting autotrophic and heterotrophic processes are controlled by organisms that are limited by nutrient versus carbon accessibility, respectively, we propose that ecosystems by definition cannot be ‘limited’ by nutrients or carbon alone. Here, we outline how models aimed at predicting non‐steady state ecosystem responses over time can benefit from dissecting ecosystems into the organismal components and their inherent limitations to better represent plant–microbe interactions in coupled carbon and nutrient models.

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Section: How Carbon Limitation Of Soil Decomposers Drives Ecosystem Pmentioning

confidence: 99%

Microbial carbon limitation: The need for integrating microorganisms into our understanding of ecosystem carbon cycling

Soong

Fuchslueger

Marañón-Jiménez

et al. 2020

Global Change Biology

338

152

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“…Deeper soils have been shown to be at least as, if not more susceptible to priming-induced losses of SOC than shallower soils [20,145] because low inputs of fresh substrates have often limited decomposition in deep soils [146,147]. Thus, changes in land use that increase fresh C inputs through the soil profile, for instance through the introduction of deeprooted grasses, could stimulate the destabilization of older buried C with root exudates and rhizodeposition [146,148].…”

Section: Primingmentioning

confidence: 99%

What do we know about soil carbon destabilization?

Bailey

Pries

Lajtha

2019

Environ. Res. Lett.

159

106

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Most empirical and modeling research on soil carbon (C) dynamics has focused on those processes that control and promote C stabilization. However, we lack a strong, generalizable understanding of the mechanisms through which soil organic carbon (SOC) is destabilized in soils. Yet a clear understanding of C destabilization processes in soil is needed to quantify the feedbacks of the soil C cycle to the Earth system. Destabilization includes processes that occur along a spectrum through which SOC shifts from a ‘protected’ state to an ‘available’ state to microbial cells where it can be mineralized to gaseous forms or to soluble forms that are then lost from the soil system. These processes fall into three general categories: (1) release from physical occlusion through processes such as tillage, bioturbation, or freeze-thaw and wetting-drying cycles; (2) C desorption from soil solids and colloids; and (3) increased C metabolism. Many processes that stabilize soil C can also destabilize C, and C gain or loss depends on the balance between competing reactions. For example, earthworms may both destabilize C through aggregate destruction, but may also create new aggregates and redistribute C into mineral horizon. Similarly, mycorrhizae and roots form new soil C but may also destabilize old soil C through priming and promoting microbial mining; labile C inputs cause C stabilization through increased carbon use efficiency or may fuel priming. Changes to the soil environment that affect the solubility of minerals or change the relative surfaces charges of minerals can destabilize SOC, including increased pH or in the reductive dissolution of Fe-bearing minerals. By considering these different physical, chemical, and biological controls as processes that contribute to soil C destabilization, we can develop thoughtful new hypotheses about the persistence and vulnerability of C in soils and make more accurate and robust predictions of soil C cycling in a changing environment.

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“…While this could lead to enhanced potential for mineral associations at depth, and thus longer-term SOC storage, rapid fluxes of DOC can also result in increased DOC export [67,131]. Moreover, increased and continuing fresh C inputs to deeper soil layers can enhance bulk SOC decomposition for years to decades [115,117,132,133] by providing deep microbial communities with the energy to synthesize extracellular enzymes for SOC decomposition [4,[133][134][135]. That is, the introduction of fresh organic C compounds to deeper soil layers can stimulate, or prime, microbial activities, alleviating potential energetic barriers to SOC decomposition that may have existed.…”

Section: Climate Changementioning

confidence: 99%

The Case for Digging Deeper: Soil Organic Carbon Storage, Dynamics, and Controls in Our Changing World

2019

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Most of our terrestrial carbon (C) storage occurs in soils as organic C derived from living organisms. Therefore, the fate of soil organic C (SOC) in response to changes in climate, land use, and management is of great concern. Here we provide a unified conceptual model for SOC cycling by gathering the available information on SOC sources, dissolved organic C (DOC) dynamics, and soil biogeochemical processes. The evidence suggests that belowground C inputs (from roots and microorganisms) are the dominant source of both SOC and DOC in most ecosystems. Considering our emerging understanding of SOC protection mechanisms and long-term storage, we highlight the present need to sample (often ignored) deeper soil layers. Contrary to long-held biases, deep SOC—which contains most of the global amount and is often hundreds to thousands of years old—is susceptible to decomposition on decadal timescales when the environmental conditions under which it accumulated change. Finally, we discuss the vulnerability of SOC in different soil types and ecosystems globally, as well as identify the need for methodological standardization of SOC quality and quantity analyses. Further study of SOC protection mechanisms and the deep soil biogeochemical environment will provide valuable information about controls on SOC cycling, which in turn may help prioritize C sequestration initiatives and provide key insights into climate-carbon feedbacks.

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Root penetration in deep soil layers stimulates mineralization of millennia-old organic carbon

Cited by 88 publications

References 62 publications

Microbial carbon limitation: The need for integrating microorganisms into our understanding of ecosystem carbon cycling

Microbial carbon limitation: The need for integrating microorganisms into our understanding of ecosystem carbon cycling

What do we know about soil carbon destabilization?

The Case for Digging Deeper: Soil Organic Carbon Storage, Dynamics, and Controls in Our Changing World

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