Does pH matter for ecosystem multifunctionality? An empirical test in a semi‐arid grassland on the Loess Plateau

Abstract Globally, higher inputs of acid deposition and anthropogenic reactive nitrogen cause lower pH in soils, that is, soil acidification, which may broadly influence both above‐ and below‐ground biota and their habitats. However, we know little about the consequences of soil acidification for a wide range of ecosystem functions and services (i.e. ecosystem multifunctionality). Here, we examined the impacts of short‐term soil acidification on 19 ecosystem functions relevant to ecosystem primary productivity and the cycling and/or storage of soil carbon (C), nitrogen (N) and phosphorus (P) using a 2‐year acid addition field experiment in a semi‐arid grassland on the Loess Plateau, China. We further assessed the potential pathways through which plant diversity and soil processes drive ecosystem multifunctionality (hereafter, EMF, EMF‐productivity, EMF‐C, EMF‐N, EMF‐P). We found that soil acidification suppressed 15 of the 19 individual ecosystem functions. By accounting for other biotic and abiotic confounding variables, we found that soil pH remains to be the dominant one explaining the variation in EMF, EMF‐C and EMF‐N. The underlying mechanisms of soil pH driving multifunctionality varied substantially among the groups of multifunctionality. Specifically, plant‐related variables (i.e. species richness and abundance) exhibited stronger mediating effects on EMF‐productivity and EMF‐C than did soil properties (i.e. soil K + , Ca 2+ , Mg 2+ and Na + ions) and microbial‐related variables (i.e. microbial biomass C and N). Our findings provide empirical evidence that short‐term soil acidification could have greater negative effects on ecosystem multifunctionality than expected in the arid and semi‐arid areas where alkaline soils are commonly seen. This study also indicates that more attention should be paid to the biological mechanisms mediating multifunctional ecosystems under a global change scenario in the future. Read the free Plain Language Summary for this article on the Journal blog.