ABSTRACT Aim Climate change affects Arctic vegetation directly through increasing temperatures and indirectly through changes in nutrient availability. Here, we tested the long‐term effects of nitrogen (N) and phosphorus (P) additions on tundra plant communities across an elevational gradient. We aimed to explore the interactive effects of nutrient addition, elevation‐associated changes in temperature and vegetation type for plant community dynamics in tundra landscapes. Location Abisko, northern Sweden. Methods We measured plant community properties in a 14‐year‐long fully factorial N and P addition experiment in subarctic heath and meadow at three elevations. We used linear mixed effects models and non‐metric multidimensional scaling to analyse the main and interactive effects of nutrient addition treatments, vegetation type and elevation over time on community responses. Results Plant community properties often responded to the interactions between N addition, P addition, vegetation type, elevation and time. Nitrogen was the main limiting nutrient, but N added with P generated the greatest change in plant community composition over time. Community responses to nutrient additions were largely driven by an increase in the abundance of graminoids and a decrease in species richness. The greatest change in plant community composition and species richness occurred in heath at the lower elevation and in the meadow at higher elevations, and the responses of species richness to N and N + P addition became stronger after 7 years. Conclusions Our results show that significant and relatively fast context (vegetation type and elevation) dependent responses of plant communities to increased N and P availability persist, but in several instances become stronger with time. They highlight the need to account for drivers of spatial and temporal variability in plant community dynamics when predicting plant community and diversity patterns under changes in climate and nutrient supply in tundra landscapes.
Kate et al. (Sun,) studied this question.