Plant functional diversity promotes ecosystem multifunctionality in abandoned karst farmland under changing rainfall...

Global climate change is altering the frequency and intensity of rainfall, with consequent effects on ecosystem multifunctionality (EMF). However, under more frequent extreme rainfall conditions, it remains unclear whether abiotic and biotic factors exert identical effects on EMF, and what the primary drivers of EMF are.

In this study, we quantified EMF using both averaging and multiple-threshold approaches. Within the framework of Hill-Chao numbers, plant biodiversity and soil microbial diversity were measured. We explored the effects of abiotic factors, plant diversity, and soil microbial diversity on EMF in abandoned karst farmland by simulating changes in the frequency of rainfall events of varying intensities. By manipulating rainfall frequency across different intensities while maintaining natural annual rainfall totals, we assessed its influence on multifunctionality and identified the primary drivers of variation.

Increased frequency of heavy rainfall reduced plant biodiversity but had positive effects on the maintenance of EMF, although these effect were not significant (P > 0.05). Among abiotic factors, soil moisture content exhibited a positive relationship with EMF. Notably, plant functional diversity emerged as a primary driver, with its positive effect on EMF strengthening at higher functional thresholds (e.g., EMF_T50 and EMF_T90). Furthermore, abiotic factors affected EMF through both direct and indirect pathways, with the indirect effects primarily mediated by functional diversity, particularly under high-threshold multifunctionality.

These findings suggest that, under projected future increases in extreme rainfall events, enhancing plant functional diversity should be a priority during the early succession of abandoned karst farmland. Strategies aimed at increasing plant functional diversity may benefit the restoration of ecosystem functions in degraded landscapes.