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

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

Life history strategies of soil microbiomes may determine their environmental adaptability and influence soil carbon-climate feedbacks. Here, we investigate trade-offs among microbial high yield (Y), resource acquisition (A), and stress tolerance (S) strategies and their consequences for soil carbon mineralization potential along an aridity gradient spanning 9.6 million square kilometers. Y-A-S strategies show nonlinear threshold responses to aridity, where a surge in S- and A-strategies and a sharp decline in Y-strategy occur once aridity exceeds critical levels. The aridity threshold for the Y-strategy occurs after those of S- and A-strategies, as increasing carbon allocation into stress tolerance and resource acquisition comes at the expense of growth. The Y-strategy negatively impacts, while A- and S-strategies positively impact soil carbon mineralization potential. Importantly, aridification intensifies these impacts. Overall, our findings suggest that variations in microbial Y-A-S strategies significantly influence soil carbon cycling and should be considered in microbial models. This study shows that soil microbes adapt to aridity by shifting their yield, resource acquisition and stress tolerance strategies, and that aridification amplifies the effects of these strategies on soil carbon mineralization.

Heterogeneous climatic controls on tropical-forest biomass

Widespread Increase in Global Plant Water Stress Obscured by Greening

Understanding the vulnerability of plants to more severe and frequent drought events and developing adaptive management strategies requires robust methods for quantifying long‐term changes in plant water stress (PWS). Most data‐driven explorations of long‐term trends in PWS have focused on alterations in canopy structure (e.g., leaf area index) or canopy structure‐dependent variables (e.g., gross primary productivity and evapotranspiration). This is largely because long‐term trends in canopy structure are relatively easy to detect from satellite observations. However, a focus on structural responses limits our ability to detect physiological stress due to challenges in isolating it from the effects of structural greening. Consequently, this difficulty hampers a comprehensive examination of long‐term PWS in the context of global greening trends. To address this gap, we developed a new process‐based metric for PWS to isolate physiological responses from structural greening, which we then used to detect global PWS trends over the past four decades. Combining site‐level and satellite observations at the half‐degree resolution across the globe, we found that accounting for greening‐related changes substantially alters the sign of long‐term PWS trends inferred from traditional approaches. Specifically, our study reveals a significant increase in PWS that is only detectable when accounting for structural greening trends. When greening trends are not accounted for, global PWS appears to have decreased over time. Overall, our results highlight the need to integrate structural dynamics and greening into PWS detection. Such an integration of observations and land models will improve our understanding of plant‐water‐energy interactions.

Soil Moisture Thresholds for the Temperature Sensitivity of Ecosystem Respiration

Ecosystem respiration (ER) is the largest source of biogenic CO2 to the atmosphere, and its temperature sensitivity (Q10) before reaching maximum values is crucial for understanding land–climate feedback. However, despite decades of studies showing that Q10 varies considerably across space, time, and biomes, the mechanisms underlying this variability remain unresolved. Here we demonstrate that global variation in Q10 can be reconciled within a unified hydrothermal framework. Using data from 142 eddy covariance sites around the world, we show that Q10 exhibits unimodal responses to soil moisture. At each site, Q10 first increases with soil moisture, peaks at a threshold (SMth), and then declines. This SMth is ecosystem‐specific, which consistent with mechanisms involving plant–soil–microbial interactions, shaped by long‐term hydroclimatic regimes and soil physical constraints. Global mapping of SMth shows that about 25% of the planet's vegetated land currently operates above SMth, including many carbon‐rich peatlands and tropical forests, where moderate drying may amplify temperature sensitivity and accelerate carbon loss. By identifying soil moisture thresholds as a first‐order control on Q10, our study provides a unifying mechanism that links hydrological state to the thermal sensitivity of carbon fluxes. This framework offers a predictive basis for anticipating respiration responses to climate change by explicitly resolving whether shifts in soil moisture move ecosystems toward or away from these critical thresholds.

Divergent responses of ecosystem water use efficiency to environmental drivers in arid versus humid regions.

Ecosystem water use efficiency (EWUE), defined as carbon gain per unit water consumed, is increasingly used as an integrative indicator to support land and water management under climate change. However, whether long-term EWUE trends and their dominant drivers provide consistent guidance for ecosystem restoration and management across contrasting hydroclimatic regions remains unclear. Using global datasets from 2000 to 2023, we found that global EWUE increased by 13.3%, but with strong spatial heterogeneity. Hyper-arid regions exhibited a pronounced increase (15.9%), whereas humid regions showed negligible change (0.59%). Attribution analysis reveals that the global EWUE increase was mainly associated with improvements in soil water use efficiency (SWUE), defined here as the ratio of gross primary productivity to soil evaporation, which contributed 64.6% to the observed trend. Notably, arid ecosystems exhibited a temporal shift in EWUE sensitivity around 2015, characterized by weakened soil-moisture sensitivity and a marked increase in atmospheric CO2 sensitivity. This transition suggests that recent efficiency gains in water-limited regions increasingly rely on CO2 fertilization rather than hydrological regulation, potentially increasing the exposure of restoration investments to extreme drought risk. In contrast, humid ecosystems showed a "double suppression" pattern, in which limited GPP enhancement and persistent water losses from both soil evaporation and plant transpiration jointly constrained further EWUE increases. These findings demonstrate that EWUE trends cannot be directly translated into uniform management strategies. We suggest that effective management in arid regions should consider physical evaporation suppression (e.g., via ground cover), whereas humid forest strategies may benefit from stand structure optimization to mitigate saturation effects. Such differentiation provides a reliable basis for designing region-specific restoration policies and avoiding maladaptive decisions under increasing climate variability.

Site‐specific climate responses of soil decomposer biodiversity in forests

Climate change strongly impacts forest ecosystems, exacerbating drought stress, tree mortality, and shifts in species composition. While aboveground changes are well documented, belowground biodiversity and its response to climate‐driven alterations remain less studied. Soil‐dwelling decomposer organisms such as oribatid mites (Oribatida), earthworms (Lumbricidae), and terrestrial isopods (Oniscidae) play a crucial role in maintaining ecosystem functions through the decomposition of organic matter and nutrient cycling. Abiotic soil conditions drive soil animal communities and the effect of climate change on a forest also depends on soil properties such as water‐holding capacity. This study examines the relationship between environmental conditions and decomposer communities in the municipal forest of Darmstadt, Germany, characterized by distinct edaphic and climatic gradients (dry in the West and moist in the East). In the study region, climate change strongly increased tree mortality albeit with high variation across sites. Oribatid mites and earthworms were significantly more abundant in the moister eastern region, while isopods showed no clear abundance differences but higher diversity in the drier west. Decomposer communities were primarily related to soil moisture and tree community composition, with canopy openness playing a crucial role in microclimatic variation. Microclimatic changes in response to tree damage and altered species composition significantly influenced decomposer communities. Drought‐prone sites were favored by drought‐tolerant taxa, suggesting ongoing shifts in belowground biodiversity. The study underscores the importance of integrating belowground organisms and processes in climate impact assessments in forests to better understand ecosystem resilience and functionality in changing forest environments.