Resource co-limitation of community biomass but not structure of an
alpine grassland
Abstract
Anthropogenic environmental changes are influencing the structure and
function of many ecological communities, but their underlying mechanisms
are often poorly understood. We conducted a seven-year field experiment
to explore the ecological consequences of nitrogen (N) and phosphorous
(P) enrichment in a high-altitude Tibetan alpine grassland. The
enrichment of both N and P, but not either alone, resulted in increased
plant above- and below-ground biomass. By contrast, N, but not P,
enrichment reduced species richness, and altered plant phylogenetic
diversity and structure. The observed decline in species richness under
N addition was driven by the loss of species characterized by high leaf
nitrogen content, and associated with higher soil manganese level and
greater belowground competition. Our study highlights resource
co-limitation of community biomass but not structure of the study
grassland, while also identifying soil metal toxicity and belowground
competition as important mechanisms driving community changes after
nutrient amendment.