Plant canopies sustain soil C‐N‐P enzyme activities under climatic disequilibrium

Climate change is altering the conditions under which plant communities persist, potentially decoupling them from their climatic niches. Such climatic disequilibrium may have effects on plant–soil interactions, particularly through its influence on microbial functioning. However, the extent to which the mismatches between climatic optima of plant communities and local climate affect soil microbial processes remains poorly understood. We investigate how climatic disequilibrium in plant communities affects soil enzymatic activity involved in carbon and nutrient cycling. We analysed the activity of eight microbial extracellular enzymes related to carbon, nitrogen and phosphorus cycling in 300 soil samples collected beneath canopy plants and adjacent interspaces across 10 Mediterranean shrubland sites in the Iberian Peninsula. These sites span a gradient of plant community climatic disequilibrium, defined as the distance between local climate and the estimated climatic optimum of the plant species composing the community. Soil enzymatic activity did not differ between canopy and open soils in communities close to their climatic optimum. However, as climatic disequilibrium increased, enzymatic activity beneath plant canopies was generally higher than in adjacent interspaces. Soil organic matter accumulated beneath plant canopies helped sustain soil enzymatic activity despite increasing climatic disequilibrium. This indicates that plant canopies play an indirect buffering role in supporting soil microbial enzymatic functioning by supplying organic matter under increasing climatic stress. Synthesis : Our findings reveal that plant–soil interactions are sensitive to mismatches between plant communities and climate. By enhancing enzymatic functioning under conditions of climatic disequilibrium, canopy plants contribute to maintaining nutrient cycling processes and potentially ecosystem resilience. This highlights the importance of considering climatic niches of plants when assessing ecosystem responses to ongoing climate change.