Diverging impacts of precipitation change on aboveground and belowground ecosystem functioning in a desert steppe

Precipitation is a limiting factor for various system functions in desert steppe ecosystems, and its impacts on aboveground and belowground processes may diverge. To evaluate these differences, for five years, we conducted field experiments to examine the effects of four different precipitation treatments [natural precipitation (W_CK), as well as a 50% decrease (W_- 50%), 50% increase (W_+ 50%), and 100% increase (W_+ 100%) in natural precipitation] on the functioning of a desert steppe.

The results showed that W_- 50% significantly reduced aboveground ecosystem multifunctionality (AEMF), while W_+ 50% and W_+ 100% significantly increased AEMF and ecosystem multifunctionality (EMF). There was no significant difference in belowground ecosystem multifunctionality (BEMF) between these treatments. Furthermore, precipitation alterations significantly modified soil water content and pH, while also influencing vegetation coverage and species richness. Partial Least Squares Path Modeling (PLS-PM) revealed that precipitation primarily drove changes in AEMF through a direct cascading pathway by significantly regulating the soil microenvironment, rather than directly through shifts in vegetation characteristics. Additionally, the model demonstrated a lack of explanatory power for BEMF.

The asymmetric precipitation response of desert steppes highlights the critical need to determine belowground stability thresholds for sustainable ecosystem management under climate extremes.