Figure 4 The effects of different trophic species diversity on ecosystem
functions: (a) water conservation; (b) soil fertility; (c) nutrition
cycling and transformation; (d) community productivity; (e) ecosystem
multifunctionality. The solid lines indicate significant relationship
and the dashed lines indicate no significant relationship.
3.4 Contribution of multitrophic species diversity in explaining
ecosystem multifunctionality
Variation partitioning analysis was used to quantify the relative
importance of biotic variables of multitrophic diversity (plant
diversity, bacterial diversity, fungal diversity, and rodent diversity)
and the abiotic variables of altitude and soil environment (pH).
Multitrophic diversity and abiotic variables (pH and altitude) accounted
for 35% and 27% of the variation in water conservation and soil
fertility, respectively (Figures 5a and b). Compared with altitude and
pH, multitrophic diversity accounted for a higher proportion to predict
nutrition cycling and transformation, and community productivity
(Figures 5c and d). More importantly, multitrophic diversity and
altitude accounted for a similar proportion (26%) of the explained
ecosystem multifunctionality (Figure 5e). The results suggested that
multitrophic diversity and altitude were more important in supporting
specific ecosystem functions. Accordingly, we constructed a Piecewise
SEM which explained 76% of variation in ecosystem multifunctionality.
Effects of biotic and abiotic variables on ecosystem multifunctionality
followed two paths: first, pH and altitude had direct negative and
positive effect on ecosystem multifunctionality respectively; Second, pH
had an indirect positive influence on ecosystem multifunctionality via
its negative effects on niche breath and multitrophic diversity. (Figure
6).