Land-use intensity indirectly affects soil multifunctionality via a cascade effect of plant diversity on soil bacterial diversity

Abstract

Land-use intensification impairs multiple soil ecosystem functions and services (hereafter ‘soil multifunctionality’; SMF) crucial to human wellbeing by influencing plant diversity and soil microbial communities. However, available information is limited on the contrasting and interaction effects of plant diversity and soil microbial communities on SMF under a gradient of land-use intensity (LUI). We measured five soil ecosystem functions associated with effective soil nutrients and water retention along 15 LUI gradients on Hainan Island, where land-use change and biodiversity loss has been severe. We used phospholipid fatty acid (PLFA) method to determine the diversity and composition of soil microbial communities. The relationships among LUI, plant diversity (species and functional diversity), soil microbial diversity (bacterial and eukaryotic diversity), and soil microbial composition (fungi/bacteria and Gram-positive/Gram-negative bacteria ratios), and SMF were examined. The LUI affected SMF indirectly by reducing plant diversity and its interaction with soil bacterial diversity. Specifically, with increase in LUI, loss of plant species diversity indirectly reduced SMF via reduction of soil bacterial diversity. In contrast, loss of tree height diversity reduced SMF directly and indirectly through decrease in soil bacterial diversity. Importantly, the indirect effect of LUI mediated by tree height diversity was stronger than that mediated by plant species diversity and soil bacterial diversity. These results provide evidence that the cascade effect of plant diversity to soil bacterial diversity mediates the impacts of land-use intensity on soil multifunctionality, and further suggest that focusing on tree height diversity may be helpful for sustainable ecosystem management and predicting the impacts of land use changes.