Explaining productivity variation in response to nitrogen addition and warming requires intraspecific variability

1. Recent studies have shown that intraspecific trait variability is an important source of total trait variation. However, the contribution of intraspecific variability to ecosystem functions in the face of global change remains unknown.
2. We measured plant height, leaf area, specific leaf area, leaf dry matter content and leaf thickness of 26 species at individual or leaf level and aboveground net primary productivity in 48 subplots subjected to 8 years of nitrogen addition and warming in a Tibetan alpine meadow. We split community weighted mean (CWM) and Rao’s quadratic entropy (Rao) of individuals’ traits within a given community into “fixed value” (only caused by interspecific difference of traits) and intraspecific variability (only caused by intraspecific difference), respectively, using a variance partitioning method.
3. We found that productivity showed a humped back response to nitrogen addition: it was highest at intermediate levels of nitrogen fertilization. The response tr..., ,