Root Traits Predict the Soil Functional Responses of Subtropical Plant Species to Experimental Drought

Substantial interspecific variation in both drought responses and soil functioning among woody species poses significant challenges for predicting drought impacts on soil functioning in species-rich tropical and subtropical forests. However, critical knowledge gaps remain regarding how soil functions respond to drought across different plant species. We conducted a three-phase (10 months of well-watered conditions, 1 month of drought treatment, and 2 months of rewetting) seedling experiment to assess how drought impacts on eight rhizosphere soil functions related to carbon, nitrogen, and phosphorus cycling vary across 10 woody species. We tested whether plant species' preferences to arid versus moist habitats and functional traits could predict variation in the resistance and recovery of soil functions to drought. We found that soil functions of species adapted to the arid habitat or those possessing stronger drought-tolerant traits (e.g., lower leaf water potential at turgor loss point) showed comparable resistance to their counterparts. Species with lower root N:P ratios and root non-structural carbon concentrations consistently recovered faster in all four measured soil enzyme activities. Our results demonstrate that root chemical traits, particularly root N:P ratios and root non-structural carbon concentrations, strongly predict soil enzyme activity recovery from drought. These findings significantly improve our understanding and prediction of drought impacts on soil functioning in species-rich forests.