关键词: 氮沉降, 氮梯度, 地上生物量, 沙质草地, 生态系统过程, 滨海湿地生态系统, 物质循环, 重金属, 互花米草, 生物群落

Abstract: Species diversity and productivity are the important indices of the structure and functioning of ecosystems. With Keerqin sandy grassland as test object, this paper studied its species composition, species diversity, and productivity under effects of different level nitrogen (N) addition. Nitrogen addition altered the species composition and the dominant species in the community, increased the vegetation height and coverage, and decreased vegetation light penetration. With the increase of N addition, both the species richness and the diversity decreased. Nitrogen addition increased the aboveground biomass significantly (P<001). There was a significant positive relationship between species richness and vegetation light penetration (P<001), and a significant negative relationship between species richness and vegetation coverage (P<001). It was suggested that  nitrogen deposition and artificial nitrogen addition would affect the species composition, species diversity, and productivity of sandy grassland ecosystem.

Key words: nitrogen deposition, nitrogen gradient, aboveground biomass, sandy grassland, ecosystem process, heavy metal, biological community., material cycling, Spartina alterniflora, coastal wetland ecosystem