Abstract: We conducted a nitrogen addition experiment in a desert steppe of Ningxia, northwestern China, to explore the effects of different addition levels (0, 5, 10, 20 and 40 g·m^-2·a^-1, designated as CK, N5, N10, N20 and N40 respectively) on plant species diversity, biomass, and community stability. Shortterm nitrogen addition significantly affected Shannon diversity index, Patrick richness index, and community coverage, but did not affect Pielou evenness index. The values of Shannon diversity index, Patrick richness index and community coverage reached the maximum under the N10 treatment, which were 2.05, 10 and 70.75%, respectively. The Pielou evenness index reached the maximum (0.92) under the N20 treatment. Shortterm nitrogen addition significantly increased aboveground, belowground, and total biomass of desert steppe, but significantly reduced the roottoshoot ratio at community level. Shortterm nitrogen addition improved community stability of desert steppe, with higher community stability under medium nitrogen addition treatment (N10). Therefore, plant diversity, biomass and community stability could be increased by nitrogen addition with a proper level.

Key words: desert grassland, nitrogen addition, species diversity, biomass, community stability.