Effects of yak dung deposition on community characteristics and niche parameters in alpine meadow

To provide foundation for researches on vegetation succession and mechanism of heterogeneity formation in alpine meadow, changes of vegetation composition, forage nutrients, plant importance value, plant niche breadth and plant niche overlap in Tibet Plateau alpine meadow with yak dung depositing were quantitative analyzed in this study. The results showed that, yak dung deposition significantly increased herbage biomass, green matter weight, plant height, coverage and K content of herbage, but had no significant influence on dead matter biomass and number of species. For dominant species, yak dung deposition decreased importance values of Stipa purpurea, Koeleria cristatav and Kobresia humilis, increased niche breadth values of these three species, and increased importance values of K.capillifolia and Agropyron cristatum. So yak dung deposition made these dominant species become to generalization species. For accompanying species, yak dung deposition decreased importance value of S.aliena, increased importance vale of S.krylovii, and decreased importance value and niche breadth value of Polygonum viviparum. For few species, yak dung deposition increased niche breadth values of Elymus nutans, Aremisia Smithii, A. capillaries, A. frigida, Allium sikkimense and Stellera chamaejasme. Beside, yak dung increased the whole niche overlap value of plants, increased species pairs, whose overlap values were 0.85, by increased 13.8%, while decreased species pairs, whose overlap values were0.45, by 42.9%. In a word, yak dung deposition increased the proportion of grasses, and promoted the meadow transformation from sedge+grasses community to grasses community or grasses+sedges community.