Microbial drought resistance is achieved at the expense of soil carbon loss

Soil pH regulates organic carbon pool by changing microbial life-history strategy.

INTRODUCTION The stability of the vast soil carbon pool, crucial for climate regulation, depends on microbial processes that govern carbon loss as CO2 or its stabilization in soil. Microbial life-history strategies, representing tradeoffs between resource acquisition (A-strategy) and growth yield (Y-strategy), are central to soil organic carbon (SOC) dynamics. However, how abiotic factors modulate these strategies and, in turn SOC fate remains unclear. OBJECTIVES Using the black soil region of Northeast China, which harbors substantial yet vulnerable SOC reserves, this study aimed to identify the dominant abiotic driver shaping microbial life-history strategies and to elucidate how this driver influences SOC stabilization pathways. METHODS We conducted a field survey combining metagenomic profiling of microbial attributes (diversity, functional potential, and inferred life-history strategy) with measurements of soil properties including extracellular enzyme activities and SOC fractions. This integrative approach traced the pathway from abiotic drivers to microbial traits and ultimately to carbon allocation. RESULTS Soil pH emerged as the key environmental gradient, with a threshold at pH 6.43 marking a systemic shift in microbial ecology and carbon processing. Acidic soils (pH 4.60-6.43) favored A-strategists, characterized by large genomes, enriched carbohydrate-active enzymes, and high extracellular enzyme activity, enabling polymer degradation and humification but limiting mineral-associated organic carbon (MAOC) formation. In contrast, neutral soils (pH 6.43-8.87) supported Y-strategists with streamlined genomes and biosynthetic metabolism, promoting microbial necromass accumulation and MAOC stabilization. Distinct functional guilds underpinned the A- and Y-strategies and frequent horizontal gene transfer in acidic soils further reinforced the A-strategy dominance under low pH. CONCLUSION Our findings reveal a mechanistic link between microbial life-history strategies and SOC stabilization, demonstrating that pH may shape the balance between A- and Y-strategists and their contrasting carbon pathways. This insight enhances predictive models of SOC dynamics and highlights pH management as a key lever for agroecosystems carbon retention.

Facing a harsh climate: terrestrial plant functional strategies in a changing world

A machine learning approach and utilizing multi-source satellite remote-sensing and field-collected sPlotOpen measurements data, the first global community-level map of CSR functional strategy variations is generated, providing critical insights into global plant community dynamics under challenging abiotic conditions.

Resource acquisition is more sensitive than carbon storage in soil microorganisms under climate extremes

Drought and warming can disrupt soil microbial processes and ecosystem functioning. Although soil microorganisms can exhibit physiological adjustments to drought, it remains unclear how they allocate resources between extracellular resource acquisition, potential oxidative metabolism, and carbon storage during drought and recovery, particularly under constant warming and/or heat waves. Here, we tested the effects of drought on microbial resource allocation strategies across warming regimes during the resistance and recovery phases. We performed a full-factorial outdoor mesocosm experiment combining drought with constant warming and periodic heat waves, applied individually and in combination. We measured the potential activities of extracellular enzymes as proxy for the acquisition of microbial resources, the activity of dehydrogenase as a proxy for the potential active oxidative metabolism, and microbial glycogen pools as a proxy for carbon storage. We also quantified drought legacy effects by measuring microbial functioning before the new drought treatments, capturing the influence of the drought imposed in the previous year. During the resistance phase, dehydrogenase activity and glycogen pools remained stable, despite reduced extracellular enzyme production, while enzyme allocation shifted towards oxidative enzymes associated with acquisition of recalcitrant C in warming regimes. One month after rewetting, all microbial proxies no longer differed from the control soil moisture conditions. Drought legacy effects were observed in extracellular enzymes, dehydrogenase activity, and glycogen pools, with glycogen exhibiting the strongest legacy effect. We conclude that the asymmetrical responses of extracellular resource acquisition and internal C storage to drought and warming may function as strategies for microbial survival in increasingly variable climates.

Deep carbon in agricultural soils: considerations for its treatment in soil carbon studies

Carbon reaches deep soil via roots, dissolved and colloidal transport, preferential flow, bioturbation, and soil mixing. Droughts may promote deep rooting but also suppress microbial activity. At depth, carbon persistence and vulnerability are regulated by interacting constraints that differ fundamentally from those operating near the surface. Hence, its study must acknowledge the unique carbon inputs and environmental constraints. This review offers a perspective on the utility and potential shortcomings of current approaches to studying deep soil organic carbon (dSOC) in the context of sources, transport pathways, stabilization and vulnerability across depth and their interactions with pedogenic horizonation, climate and environmental change. Evidence suggests that dSOC functions as a distinct component of the soil carbon cycle rather than a slow-cycling reflection of surface SOC. Persistence of dSOC cannot be solely explained by the chemical recalcitrance of SOC. Instead, dSOC stability is a composite of the hydrological, gaseous, mineralogical and biological constraints controlling microbial functions and access to SOC. Importantly, these are more accurately described as horizon-dependent rather than strictly depth-dependent. Although the particulate/mineral-associated organic matter framework remains useful, its interpretation may become ambiguous in deep soils. Hence, a mechanistic understanding of dSOC persistence requires coupling changes to C inputs, transfer pathways, mineral interactions, hydrological connectivity and biological constraints across pedogenic horizons. As soil horizon-dependent heterogeneity governs the persistence of chemically labile C compounds, horizon-aware sampling and testing would avoid misrepresenting mechanisms controlling dSOC. Incubation and warming studies imposing ecologically implausible conditions may measure short-term microbial physiological stress responses rather than climate-relevant SOC vulnerability.

Microbial regulation of soil nitrogen dynamics along a stand density gradient of Mongolian pine plantations

Temperature sensitivity (Q10) and soil type influence carbon and nitrogen mineralization in temperate ecosystems

The temperature sensitivity of soil carbon (C) and nitrogen (N) mineralization commonly expressed as the Q 10 coefficient, plays a pivotal role in regulating soil–atmosphere greenhouse gas exchanges in temperate ecosystems. This review synthesizes findings from 181 peer-reviewed studies (1960–2025) to evaluate how soil properties, substrate quality, microbial traits, and land-use history interact to shape Q 10 dynamics under climatic warming. Using a structured, thematically coded literature review, we identify mechanistic pathways that govern mineralization responses across major temperate soil orders. Clay-rich soils with high short-range ordered (SRO) minerals consistently exhibit low Q 10 values (1.3–2.0) due to mineral protection of soil organic matter (SOM). In contrast, coarse-textured and disturbed soils exhibit elevated thermal sensitivity (> 3.0). Microbial C use efficiency (CUE), enzyme activity, and functional group composition further modulate mineralization responses, especially under seasonal freeze–thaw or rewetting events. Land-use transitions, including tillage, afforestation, and organic amendments, significantly alter Q 10 by altering aggregation, SOM accessibility, and microbial community structure. Despite advances, Earth system models often overlook the spatiotemporal heterogeneity of Q 10 , limiting prediction accuracy. We highlight the need for integrating depth-resolved mineralogical traits, microbial acclimation, and management history into climate–soil feedback frameworks. This synthesis advances a mechanistic foundation for improving biogeochemical models and informing soil-based climate mitigation strategies.