Reduced soil moisture caused by human disturbance mediates the biodiversity effects on ecosystem multifunctionality across stand ages in the temperate forests of North-Eastern China

Human-influenced soil moisture significantly shapes the biodiversity effects on ecosystem functions in temperate forests. However, its role in regulating the biodiversity effects on ecosystem multifunctionality at different stages of stand development remains unclear. Accordingly, this study aims to explore how the soil moisture mediates the biodiversity effects on ecosystem multifunctionality across stand ages in a temperate forest region. Based on a set of forest survey data in northeastern China, we used structural equation models to quantify the direct and indirect effects of predictors on ecosystem multifunctionality. Linear mixed-effects models were fitted to assess the effects of soil moisture and other factors on the biodiversity-ecosystem multifunctionality relationships. The results show that human disturbance indirectly decreases biodiversity and ecosystem multifunctionality by affecting the soil moisture. Soil moisture, stand age and their interactions are significantly correlated with the biodiversity effects on ecosystem multifunctionality. It is concluded that reduced soil moisture caused by human disturbance decreases the biodiversity effects on ecosystem multifunctionality in middle-aged and old-growth stands, but increases the biodiversity effect in young-growth stands. The findings suggest that the contribution of biodiversity to ecosystem multifunctionality can be enhanced by regulating the human activities in temperate forests.