摘要
为了解放牧干扰对藏北高寒草甸的影响,以及连续围封措施对草地的恢复作用,2013—2015年连续3年对那曲县围封、自由放牧天然高寒草甸土壤线虫群落进行取样调查及数据分析。结果表明:围封、放牧样地的线虫个体数量在年际间的变化均较明显,植食性线虫是整个线虫群落个体数量变化的主要贡献者;围封样地的线虫个体密度、多样性指数H′、丰富度指数SR,以及优势度指数λ的年际变化幅度均大于放牧样地;食细菌性线虫个体数量及线虫通路比值(NCR)表明放牧样地的有机质转化效率高于围封样地;成熟度指数(MI)、植物寄生线虫指数(PPI)分析表明,所研究区域经5年围封,高寒草甸生态系统稳定性没有明显的提高,相反,现有放牧强度维持或者增加了线虫群落的物种多样性,利于物种共存和草地生态系统稳定性的维持。
【Objective】The North Tibet Prairie lies in the inland of the Qinghai-Tibet Plateau and is one of the most important grassland ecosystems in China.Recent years have witnessed an apparent rising trend of the expansion of severely degraded grassland in area.According to relevant data available,in 2013,the area of slightly degraded grassland expanded to cover 62.0% of the total of the prairie.【Method】During the initial period of this research project,an investigation was carried out of soil nematode communities under different plant communities in the alpine meadow of Nagqu County of North Tibet.It was found that soil nematode communities responded significantly to degradation of grassland.On such a basis,the research went on with colleting soil samples from two tracts of natural grassland in the same area,one enclosed and the other exposed to free grazing for 3 years in a row(2013—2015),for analysis of changes in soil nematode communities along the soil profile(0~25 cm),with soil moisture and temperature taken into account,in an attempt to explore effects of grazing on alpine meadow,and effects of enclosure on degraded alpine meadow.Soil nematodes in the soil samples were collected using the shallow basin method and analyzed for composition,number of individuals,and diversity of the nematode communities,and their relationships with soil temperature and water content.【Result】Results show that the two tracts of grasslands differed sharply in all the indices of soil nematode community.The nematode community in the enclosed tract were higher than that in the grazing tract in nematodes individual density,diversity index(H′),species richness(SR),and dominance index(λ).The number of nematode individuals varied greatly from year to year in both tracts.Phytophagous nemitodes are the major contributor to the changes in nematode population of the community.The number of bacterivores and nematode channel ratio(NCR)value shows that the grazing tract was higher than the enclosed tract in organic matter conversion efficiency.In the studied area under the same grazing intensity as it has,maintaining or increasing species diversity of the nematode community is conducive to species coexistence and ecosystem stability of the grassland.Maturity index(MI)and plant parasite index(PPI)values demonstrate that the five years of enclosure did not have any obvious positive effect on stability of the ecosystem.【Conclusion】 Composition,individual density,diversity index and other indexes of soil nematode communities may reflect to a certain extent conditions of the environment they live in.All the findings in this study indicate that in the studied region,the current grazing practices are still within the reasonable extent do not have any pressure forcing the grassland to degrade.So free grazing controlled within a certain intensity may contribute to maintenance of the stability of the grassland ecosystem.
出处
《土壤学报》
CAS
CSCD
北大核心
2017年第2期480-492,共13页
Acta Pedologica Sinica
基金
国家自然科学基金项目(31260144
31660155)
西藏特色农牧资源研发协同创新中心高原生态项目资助~~
关键词
土壤线虫
生物多样性
高寒草甸
西藏
Nematode
Biodiversity
Alpine grassland ecosystem
Tibet