Soil water availability strongly drives the differentiation of acquisitive and conservative strategies for coexisting woody species in a Chinese subtropical evergreen forest

Abstract

Questions

Trait–environment relationships hold great promise for elucidating the mechanisms that drive community assembly. We asked to what extent does functional trait coordination underlie the differentiation of acquisitive–conservative strategies along environmental gradients? Also, to what extent does soil water availability determine trait combinations and subsequently shape microhabitat preferences for species with distinct ecological strategies?

Location

Yunnan Province, southwest China.

Methods

Pearson correlation and trait network analyses were used to quantify trait associations. A combined RLQ–fourth-corner analysis and a spatial autoregressive error model were employed to examine trait–environment relationships and explain species distribution along environmental gradients.

Results

Leaf and stem traits were tightly coordinated along the first RLQ axis. Herein, traits representing construction cost exhibited trade-offs against traits representing resource acquisition rate, underlying an acquisitive–conservative strategy differentiation along the environmental gradients. Significant overall and bivariate trait–environment relationships were found. In addition, the topographic wetness index contributed substantially to the environmental variation, and significantly influenced most traits alone. These results supported the hypothesis that soil water availability was the key environmental factor in selecting trait combinations and driving the differentiation of acquisitive and conservative strategies for coexisting species compared with other environmental factors. Finally, deciduous and a proportion of the evergreen species were acquisitive, whereas the remaining evergreen species were conservative, preferring wetter and drier microhabitats, respectively.

Conclusions

Our findings indicate that soil water availability plays a central role in shaping both the trait combinations and microhabitat preferences of species with different ecological strategies rather than different leaf habits. These findings also highlight the fundamental significance of functional traits in facilitating the differentiation between acquisitive and conservative strategies along environmental gradients.