Aims Theories based on resourceadditions indicate that plant species richness is mainly determined by the number of limiting resources. However, the individual effects of various limiting resources on species richness and aboveground net primary productivity (ANPP) are less well understood. Here, we analyzed potential linkages between additions of limiting resources, species loss and ANPP increase and further explored the underlying mechanisms. Methods Resources (N, P, K and water) were added in a completely randomizedblockdesignto alpinemeadowplots in theQinghai-Tibetan Plateau. Plant aboveground biomass, species composition, mean plant height and light availability were measured in each plot. Regression and analysis of variance were used to analyze the responses of these measures to the different resource-addition treatments. Important Findings Species richness decreased with increasing number of added limiting resources, suggesting that plant diversity was apparently determined by the number of limiting resources. Nitrogen was the most important limiting resource affecting species richness, whereas PandK alonehad negligible effects.Thelargest reductioninspecies richness occurred when all three elements were added in combination. Water played a different role compared with the other limiting resources. Species richness increased when water was added to the treatments with N and P or with N, Pand K. The decreases in species richness after resource additions were paralleled by increases in ANPPand decreases in light penetration into the plant canopy,suggestingthatincreasedlightcompetitionwas responsible for the negative effects of resource additions on plant species richness.