Abstract: The experiment with three levels of N fertlizer (0.150 and 300kg N/hm²) was conducted for three years at alpin Kobresia humilis meadow to study responses of different plant groups and some species. The response of grasses was more significance than Non leguminous forbs to nitrogen addition. The synthetic dominated ratio (SDR) of grasses increased, and that of non leguminous forbs decreased with the increase of nitrogen, whereas the SDR of sedges and leguminous forbs were not significantly affected by N fertilizer. Plant diversity decreased and forage quality increased with the increase of nitrogen. Index of meadow quality (IMQ) was the highest at 150kg N/hm² plot, and showed no significant difference between 150 and 300kg N/hm² plot. Excessive nitrogen application did not improve the IMQ. Response of above ground biomass of plant groups was lagged when compared with plant diversity and IMQ. Total above ground biomass was significant increased with the nitrogen application. There were different responses of above ground biomass among plant groups to the nitrogen application. The results showed that the above ground biomass of grasses was significantly increased with N fertilizer application, and that of forbs was decreased. The responses of plant grounps to nitrogen application were more affected by precipitation and its distribution in July, therefore, the status of soil water after nitrogen application was a key factor to the responses of plant groups.

Key words: Alpine Kobresia humilis meadow, Nitrogen fertilization, Diversity, Meadow quality, Above ground biomass

摘要： 研究高寒矮嵩草草甸高强度施氮试验(150和300kgN/hm²)对不同植物类群的影响.结果表明,禾草类植物的反应较大,其综合优势比呈明显增大趋势,非豆科杂草次之,莎草类和豆科杂草的反应不显著.增施氮肥能明显降低矮嵩草草甸的植物多样性,其草甸质量指数以施氮150 kg/hm²最高,过量施氮(300/hm²)并不再提高草甸质量.其地上生物量对施氮的反应比多样性和草甸质量指数的变化滞后,地上生物总量在施氮后明显增加,其中禾草类明显增加,杂类草则明显降低.7月的降水量及其分布对施氮的效果影响较大.土壤水分状况对施肥效果十分重要.

关键词: 高寒矮嵩草草甸, 施氮, 多样性, 草甸质量, 地上生物量