牦牛粪对高寒草甸植被群落特征和生态位参数的影响

本研究定量分析了青藏高原高寒草甸牦牛粪斑与对照处植被构成、牧草养分、植物种重要值、生态位宽度和生态位重叠值的变化,为高寒草甸植被演替和异质性形成机制的揭示提供科学依据。结果表明,牦牛粪沉积增加植物总生物量和活体质量,使草层高度、盖度和牧草K含量增加,而对死物质质量和物种数无影响。粪沉积降低优势植物紫花针茅(Stipa purpurea)、艹洽草(Koeleria cristata)和矮嵩草(Kobresia humilis)的重要值,增加其生态位宽度,并提高线叶嵩草(Kobresia capillifolia)和扁穗冰草(Agropyron cristatum)的重要值,使优势种植物更倾向于泛化种。粪沉积使伴生种异针茅(S.aliena)的重要值降低,西北针茅(S.krylovii)的重要值增加,珠芽蓼(Polygonum viviparum)的重要值和生态位宽度均降低,使少量种垂穗披碱草(Elymus nutans)、球花蒿(Artemsia pratensis)、茵陈蒿(A.capillaries)、冷蒿(A.frigida)、高山韭(Allium sikkimense)和狼毒(Stellera chamaejasme)的生态位宽度增加。粪沉积使草地植物的整体生态位重叠值增大,使生态位重叠值0.85的种对增加13.8%,生态位重叠值0.45的种对降低42.9%。总之,粪沉积使草地禾草比例增加,促进高寒草甸草地由莎草+禾草群落向禾草群落或禾草+莎草群落转化。

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.