The links between ecosystem multifunctionality and above- and belowground biodiversity are mediated by climate

Abstract

Plant biodiversity is often correlated with ecosystem functioning in terrestrial ecosystems. However, we know little about the relative and combined effects of above- and belowground biodiversity on multiple ecosystem functions (for example, ecosystem multifunctionality, EMF) or how climate might mediate those relationships. Here we tease apart the effects of biotic and abiotic factors, both above- and belowground, on EMF on the Tibetan Plateau, China. We found that a suite of biotic and abiotic variables account for up to 86% of the variation in EMF, with the combined effects of above- and belowground biodiversity accounting for 45% of the variation in EMF. Our results have two important implications: first, including belowground biodiversity in models can improve the ability to explain and predict EMF. Second, regional-scale variation in climate, and perhaps climate change, can determine, or at least modify, the effects of biodiversity on EMF in natural ecosystems.

Figure 1. Relationships between below- and aboveground biodiversity and ecosystem multifunctionality.

Relationships between soil bacterial (a) soil faunal (b) soil archaeal (c) soil AM fungal (d) plant (e) and soil (f) biodiversity and ecosystem multifunctionality (EMF). There were no significant linear relationships between EMF and soil archaeal biodiversity or soil AM fungal biodiversity. The red fitted lines are from OLS regression. Only significant fitted lines are displayed on the graphs. Shaded areas show 95% confidence interval of the fit.

Figure 2. The relative effects of below- and aboveground biodiversity on ecosystem multifunctionality.

The relative effects of soil biodiversity (a) and plant species richness (b) on ecosystem multifuncitonality (EMF).The red fitted line is from a partial linear regression. Only significant fitted lines are shown on the graphs. The results of variance partitioning for soil biodiversity and plant species richness are shown by the R² on this graph. Shaded areas show 95% confidence interval of the fit.

Figure 3. Structural equation models of climate, soil and biodiversity as predictors of ecosystem multifuncitonality (EMF).

Solid red arrows represent positive paths (P<0.05, piecewise s.e.m.), solid black arrows represent negative paths (P<0.05, piecewise s.e.m.) and dotted grey arrows represent non-significant paths (P>0.05, piecewise s.e.m.). We report the path coefficients as standardized effect sizes. Overall fit of piecewise s.e.m. was evaluated using Shipley's test of d-separation: Fisher's C statistic (if P>0.05, then no paths are missing and the model is a good fit) and Akaike information criterion (AIC). MAP, mean annual precipitation; MAT, mean annual temperature; SM, soil moisture, plant SR, plant species richness.