摘要
高寒草甸在青藏高原畜牧业发展中占有重要地位,然而气候和人为活动的干扰对原本脆弱的生态系统产生了深刻影响。虽然封育是被广泛采用的草地恢复有效措施之一,但封育年限对群落组分和多样性的影响一直是受关注的核心问题,探明这一问题对高寒草甸的可持续发展具有重要意义。研究了封育2、7、17a的高寒矮嵩草(Kobresia humilis)草甸的群落组分和物种多样性变化特征,并探讨了不同封育年限影响物种多样性的可能原因。结果表明:1)随封育年限延长,群落上层禾本科植物的总体重要值明显增加,其中异针茅(Stipa aliena)最为显著,其重要值封育2a(13.87%)<封育7a(21.76%)<封育17a(23.95%),而豆科植物总体重要值显著降低,莎草科和杂类草植物变化不明显;2)α多样性:随封育年限延长,高寒草甸群落物种丰富度指数(Patrick和Margalef指数)没有发生显著变化,然而物种多样性指数(Simpson、Shannon-Wiener和种间相遇机率指数)及均匀度指数(Alatalo和Pielou指数)均表现为封育2a>封育7a>封育17a,且封育2a与封育7、17a呈显著性差异(P<0.05);3)β多样性:Cody指数和Morisita-Horn相似指数的变化表明,封育2a与封育7、17a之间的物种差异较大,而封育7a和17a之间的物种差异较小;4)封育后凋落物的覆盖时间及其分解引起的土壤养分变化是导致物种多样性降低的重要原因之一,土壤碳氮比(C/N)与物种均匀度指数(Alatalo指数)和多样性指数(Simpson指数和种间相遇机率指数)均呈显著性负相关关系(P<0.05),说明土壤养分元素之间的耦合效应对物种多样性变化具有重要影响。本研究说明,虽然物种丰富度指数随封育年限的延长没有变化,但物种均匀度和多样性指数均降低,且封育前期对物种多样性的影响大于后期,就物种多样性而言,该高寒草甸不宜进行长期封育。该研究以期为高寒草甸生物多样性的保护和可持续利用及管理提供科学依据。
The Qinghai-Tibet Plateau is one of the richest areas in terms of biodiversity in China. The alpine meadow is the most widespread vegetation type on this plateau and plays an important role in the carbon cycle, conservation of biodiversity,and livestock husbandry. However,climate change and human activities have greatly affected this already fragile ecosystem. Although exclosure,one of the effective measures,has been widely applied in grassland restoration,the impact of exclosure duration on community structure and species diversity is of particular interest. Therefore,determining the influence of exclosure duration on the alpine meadow is important for the development of sustainable livestock husbandry. We examined the community structure and species diversity in patches of Kobresia humilis alpine meadow,which had been enclosed for 2,7,or 17 years. We have discussed possible reasons for the changes in community structure and species diversity. The results indicated the following： 1） With increase in exclosure duration,the percentage of grass species in the upper community increased significantly,especially of Stipa aliena. The percent change was 13. 87% for2-year,21. 76% for 7-year,and 23. 95% for 17-year exclosure. The percent change of leguminous species significantly decreased,whereas sedge and forbs species exhibited no obvious change in exclosure duration. 2） The α-biodiversity,Patrick index,and Margalef index of the plant communities indicated no significant changes in exclosure duration. In contrast,the Simpson index,Shannon-Wiener index,probability of interspecific encounter index,Alatalo index,and Pielou index decreased in exclosure duration（ 2-year 7-year 17-year enclosures）; there were significant differences between the 2-year and 7-year exclosures and between the 2-year and 17-year exclosures（ P 0. 05）. 3） The β-biodiversity,Cody index,and Morisita-Horn similarity index indicated that differences inspecies were greater between 2-year and 7-year exclosures,as well as 2-year and 17-year exclosures,than that between 7-year and 17-year exclosures. 4）The amount of plant litter decreased in exclosure duration,but differences were not significant. Litter coverage time appeared to be one of the reasons for the decrease in species diversity because the litter layer could prevent the seeds from falling to the ground. 5） Soil organic carbon（ SOC）,soil total nitrogen（ STN）,and soil total phosphorus（ STP） increased in exclosure duration due to litter decomposition,but we observed no effect on species diversity. We found that the ratio of soil carbon to nitrogen（ C / N） showed significantly negative correlation with the Alatalo index,Simpson index,and probability of interspecific encounter index（ P 0. 05）,indicating that the coupling relationship between soil carbon and nitrogen was possibly the most important factor influencing species diversity. Our results suggested that species diversity decreased in exclosure duration because of the effects of litter accumulation,litter decomposition,and plant competition for light. The influence of exclosure on species diversity in the early stage was greater than that in the later stage,and thus,long-term exclosure was unnecessary for species diversity in this alpine meadow. We hope that our study will provide a scientific basis for biodiversity protection,sustainable utilization,and management of alpine meadow ecosystems.
出处
《生态学报》
CAS
CSCD
北大核心
2016年第16期5150-5162,共13页
Acta Ecologica Sinica
基金
国家自然科学基金项目(31070433
31570478
31270523
31300385)
