Pre-existing global change legacies regulate the responses of multifunctionality to warming

Abstract

Soil biodiversity and function are critical for supporting life and providing essential services for human beings on Earth. We know that soils are highly vulnerable to warming in terrestrial ecosystems. However, it remains unclear whether the legacies of pre-existing global changes can exacerbate the responses of soil biodiversity and function to warming. To address this knowledge gap, we conducted a four-month growth chamber experiment to investigate the responses of soil biodiversity - focusing on three fungal functional groups (soil pathogen, saprotroph and ectomycorrhizal richness) and soil multifunctionality (measured by seven enzyme activities associated with C, N, P, and S cycling) to simulated warming. The soils were collected from four groups of global change located within the same experimental station in Australia, which were subjected to multiple global change factors, including CO₂ enrichment, altered precipitation patterns, irrigation and fertilization, and nutrient addition. In general, soil biodiversity and multifunctionality in soils previously subjected to global changes were more susceptible to warming than those in control soils (i.e., without pre-existing global changes). Different biotic and abiotic factors drove multifunctionality under ambient and warming conditions. Specifically, soil ectomycorrhizal diversity, primarily driven by soil pH, had a more significant positive influence on soil multifunctionality than soil properties under ambient conditions. These findings suggest that environmental filtering may also regulate the biodiversity of fungal functional groups and functions in soils subjected to pre-existing global changes. While under warming conditions, soil dissolved organic C was more important than soil biodiversity (i.e., saprotroph richness) in affecting soil multifunctionality. Our results demonstrate that the legacies of global changes may weaken the positive effects of soil biodiversity and its interactions with soil physicochemical properties in regulating soil functions in response to warming. Taken together, our work indicates that pre-existing global change legacies regulate the responses of multifunctionality to warming, with implication for understanding how climate change and soil legacies influence soil conservation in a warmer world.