The relative importance of intraspecific trait variation (rITV) for functional diversity (FD) in plant communities is increasingly apparent, but the influence of abiotic factors on the balance between intraspecific and interspecific effects in contrasting environments is uncertain. We predicted that rITV would increase with environmental harshness as a result of decreasing interspecific variation (Inter_FD) and concomitant increases in between-population ITV(Intra_FD). We empirically tested this prediction in a comparison of rITV for five traits (mature plant height, SLA: specific leaf area, leaf dry matter content, and the foliar concentrations of nitrogen and phosphorus) characterizing species in Tibetan alpine meadow communities from contrasting environmental regimes(i.e. valley floor at the base of the ridge, northern- and southern-slopes at mid-elevation, and ridge top) on each of three sites (ridges). We found that across plots: i) rITV for all five traits increased with environmental harshness not only through decreasing Inter_FD but also increasing Intra_FD; ii) increases in rITV were mostly attributable to declines in soil resources, especially soil phosphorus, with lower soil P significantly associated with lower Inter_FD but higher Intra_FD for most traits; and iii) although neither Intra_FD nor Inter_FD were significantly impacted by species richness for any traits, a higher rITV for SLA was significantly associated with low species richness.