It is known that the dominance of graminoid species is promoted by N addition; however, there has been relatively little effort to examine the pattern induced by natural N fertility. Since nutrie nt use e fficiency (NUE) is an important trait determining plant competitive ability, we expected that the species guild with higher NUE (lower nutrient content) may be more competitive on infertile soils. We explo red t he relationships between relative forbs biomass share , soil N and productivity by the linear regressi on analysis on a natural alpine meadow in northeast of Qinghai- Tibetan Plateau (3600 m a.s.l.). To test the variety of leaf N:P stoichiometry, paired t test and general linear model multivariate (GLM) analysis were also used. We f ound that the leaf N:P ratios of the whole community were below 13 in studied sites, which may be consistent with the N limitation on the veget ation. Graminoids re tained lower concentrations of leaf N and P than forbs in community on the Nlimited grassland. Consistent with our prediction, we found that the biomass fraction of graminoids declined with soil N content and aboveground production on the grassland. Different from the pattern along fertility gradients induced by N fertilization, our results showed that gr aminoids with lower internal nutrient content w ere able to resist low levels of nutrient availability on the natural alpine grassland when compared to forbs.
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