Decadal dynamics of dry alpine meadows under nitrogen and phosphorus additions

Plants often exhibit positive responses to multiple nutrient additions, but generalities about the life form and traits of the most responsive species are few. Findings from long-term experiments in dry meadow alpine tundra in Colorado, USA, were used here to examine univariate and multivariate analyses of plant and plant trait responses. We found transient responses for community richness-biomass relationships, but a consistent increase in forb dominance in nitrogen (N) and phosphorus (P) addition plots. The response seen in the N + P plots was not affected by additions of micronutrients or potassium. Multivariate analyses corroborate transient responses in community shifts over shorter-time scales, and directional shifts in N + P over two decades. Using species-level aboveground trait data when available, we found N + P may favor species with resource-acquisitive traits, regardless of their lifeform, as well as relatively tall grasses, regardless of their resource strategy. In the absence of N and P limitation but with the environmental constraints found in dry alpine meadows, plant richness and community structure continued to exhibit transient states for decadal time frames.