Intraspecific Trait Variation Regulates Biodiversity and Community Productivity of Shrublands in Drylands

Intraspecific variation (Intra-V) has played an important role in determining the responses of ecosystem functions to climate change. However, its specific role in the regulation of ecosystem functions during community assembly is less investigated. In this study, we conducted a transect survey in northwest China and determined different plant functional types, namely resource-conservative, medium, and resource-acquisitive strategies, which describe resource-use strategies of plants in multi-functional dimensions. Plant functional traits including canopy, wood density (WD), height, specific leaf area (SLA), and leaf nitrogen (N) and phosphorus (P) concentrations were determined. Ecological filters, including external filtering (assembly processes at the regional scale), internal filtering (assembly processes within a certain community), and functional redundancy, were employed to examine plant environment interactions. We found that with the decrease in environmental pressure, dominant shrub plants changed from conservative to acquisition species in drylands. Specifically, a benign environment (such as stable and adequate precipitation, loose soil, and increased acid deposition) significantly increased plant mean traits, such as SLA and WD of shrubs, especially for conservative strategy plants. In addition, a benign environment mainly reduced the functional redundancy of SLA (FRed_SLA) by strengthening internal filtering and, ultimately, increased aboveground biomass but decreased species richness. Our results suggest that conservative strategy plants with stronger adaptability to the external environment may exhibit more competitive advantages and play a more important role in community construction under future climate scenarios of gradual warming and wetting in northwest China. Our results also revealed that trait-based Intra-V may be a more reasonable ecological filter than plant mean traits for predicting the structure and function of dryland ecosystems.