Data from: Nitrogen enrichment and warming shift community functional composition via distinct mechanisms: the role of intraspecific trait variability and species turnover

1. Global change factors may shift community functional composition by
driving species turnover (species occurrence and species relative
abundance) and intraspecific trait variability. However, their relative
contribution in determining the functional response of community to global
change, especially nitrogen enrichment and warming, remains unclear. 2. We
conducted a fully factorial field experiment in a Tibetan alpine meadow to
examine responses of plant community functional composition to nitrogen
enrichment and warming by quantifying seven plant functional traits in
each plot. Using the sum of squares decomposition, we further disentangled
the relative contribution of intraspecific trait variability and species
turnover to changes in community functional composition. 3. We found that
nitrogen enrichment caused a shift of plant community toward a more
resource-acquisitive strategy, while warming resulted in a shift toward a
more resource-conservative strategy. Plant intraspecific trait variability
controls shifts in community functional composition in response to
nitrogen enrichment, whereas species turnover (especially change in
species relative abundance) mainly explains warming-induced shifts.
Nitrogen enrichment and warming did not show significant interactive
effects on plant functional composition. 4. These findings suggest that
nitrogen enrichment and warming can alter community functional composition
of alpine meadow through distinct mechanisms. Plant intraspecific trait
variability confers functional resilience of Tibetan alpine meadows under
nitrogen enrichment, but warming could induce significant turnover of
species that pronouncedly impacts community functioning in this highland
ecosystem.

1. 全球变化因子可通过驱动物种周转（species turnover，涵盖物种出现与相对多度）与种内性状变异（intraspecific trait variability）来改变群落功能组成。然而，二者在决定群落对全球变化的功能响应方面的相对贡献，尤其是针对氮富集与增温这两类因子，仍尚不明确。
2. 本研究在青藏高原高寒草甸开展了完全析因野外实验，通过对每个样地内7种植物功能性状进行量化，探究植物群落功能组成对氮富集与增温的响应。借助平方和分解法（sum of squares decomposition），本研究进一步拆解了种内性状变异与物种周转对群落功能组成变化的相对贡献。
3. 研究结果显示，氮富集会使植物群落朝着更为资源获取型的策略方向转变，而增温则会使其转向更为资源保守型的策略。植物种内性状变异主导了氮富集驱动下的群落功能组成变化，而物种周转（尤其是物种相对多度的变化）则主要解释了增温引发的群落转变。氮富集与增温对植物功能组成未表现出显著的交互效应。
4. 上述研究结果表明，氮富集与增温可通过不同的作用机制改变高寒草甸的群落功能组成。在氮富集情境下，植物种内性状变异赋予青藏高原高寒草甸以功能韧性，而增温则可能引发显著的物种周转，该过程会对该高原生态系统的群落功能产生显著影响。