Soil pH plays an important role driving ecosystem multifunctionality in a semiarid grassland on the Loess Plateau

Background/Question/Methods - The acid deposition and anthropogenic reactive nitrogen inputs often decrease soil pH and result in multiple ecological effects, including changes in plant and microbial communities and other soil properties. Those changes may further influence the ability of ecosystem to maintain multiple functions and services simultaneously (i.e. multifunctionality). However, how soil acidification may affect ecosystem multifunctionality remains still unclear. Taking advantage of a 2-yr acid addition experiment in a semi-arid grassland on the Loess Plateau, we examined the effects of soil acidification on functional scenarios including primary productivity, the cycling and storage of carbon, nitrogen and phosphorus. Random forest and structural equation models were used to assess the relative importance of soil properties, plants and microbial communities in driving the ecosystem multifunctionality as well as those functional scenarios.

Results/Conclusions - We found that acid addition altered soil properties, plant communities, microbial properties, and reduced ecosystem multifunctionality significantly. However, the strengths of direct and indirect effects of soil pH on multifunctionality varied when different functional scenarios were examined. Soil properties (i.e. pH and extractable Al³⁺) consistently exhibited stronger effects on multifunctionality than did the plant-related and microbial-related variables, especially the functions relating to primary productivity and carbon cycling. Plant-related variables (i.e. species richness and abundance) showed significant effects on ecosystem multifunctionality only when the functions relating to primary productivity were examined. These results indicated that soil pH plays an important role driving ecosystem multifunctionality in a semi-arid grassland on the Loess Plateau. Our study can help advance the understanding to the effects of global change factors (e.g. nutrient enrichment and acid deposition) on ecosystem multifunctionality via alteration in soil pH, and provides new insights to better develop sustainable strategies for ecosystem management.