| Summary: | Although ecologists have documented the effects of nitrogen enrichment on productivity, diversity and species composition, we know little about the relative importance of the mechanisms driving these effects. We propose that distinct aspects of environmental change associated with N enrichment (resource limitation, asymmetric competition, and interactions with soil microbes) drive different aspects of plant response. We test this in greenhouse mesocosms, experimentally manipulating each factor across three ecosystems: tallgrass prairie, alpine tundra and desert grassland. We found that resource limitation controlled productivity responses to N enrichment in all systems. Asymmetric competition was responsible for diversity declines in two systems. Plant community composition was impacted by both asymmetric competition and altered soil microbes, with some contributions from resource limitation. Results suggest there may be generality in the mechanisms of plant community change with N enrichment. Understanding these links can help us better predict N response across a wide range of ecosystems. Plant community data from three greenhouse mesocosm experiments (tallgrass prairie, alpine tundra, desert grassland) manipulating nitrogen, competition, and soil microbesData are from three greenhouse mesocosm experiments representing three different systems: tallgrass prairie, alpine tundra, desert grassland. Treatments were nitrogen fertilization, competition (planting density), and soil microbes (microbes from control or fertilized field plots). Each mesocosm consisted of a mix of 9 species. Data collected were the following: biomass (above + below ground) of each species in each mesocosm, total mesocosm biomass, diversity, evenness, richness.KNZ_NWT_SEV_greenhouse_exp_Dryad.csv
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