UPTAKE AND ALLOCATION OF N-15 IN ALPINE PLANTS - IMPLICATIONS FOR THEIMPORTANCE OF COMPETITIVE ABILITY IN PREDICTING COMMUNITY STRUCTURE IN A STRESSFUL ENVIRONMENT

Several potential components of competitive ability were determined fo r 13 plant species in a N-limited alpine moist meadow community in ord er to determine if competition had an influence on relative abundance in this stressful environment. The components of competitive ability e xamined were N-15 uptake rate, N-15 allocation, whole pliant biomass, root:shoot ratio, and tissue N concentrations. It was hypothesized tha t N-15 uptake rate would be the component most correlated with relativ e abundance. However, N-15 uptake rate was negatively correlated with percent cover in the community. In contrast, whole plant biomass and r oot:shoot ratio were positively correlated with relative abundance. Ti ssue N concentrations and N-15 allocation were not important predictor s of relative abundance. These results suggest that in a harsh environ ment, high resource uptake rates are not indicative of competitive abi lity, but may instead be a mechanism by which rare species are able to coexist with competitive dominants.