大型土壤动物群落对高寒草甸退化的响应

RESPONSE OF SOIL MACROFAUNA COMMUNITIES TO DEGRADATION OF ALPINE MEADOW

为了查明大型土壤动物群落对高寒草甸退化的响应,2009至2010年间对青藏东缘若尔盖湿地的沼泽草甸、草原草甸、退化草甸和沙化草甸4个退化阶段的大型土壤动物群落进行了7次调查。结果表明:高寒草甸的不同退化阶段大型土壤动物群落的类群组成和优势类群存在差异,且退化和沙化对大型土壤动物群落的丰富度、密度、Shannon多样性和群落结构均有显著影响(p<0.01或p<0.05)。其中退化可使带马陆目(Polydesmida)和鞘翅目幼虫(Coleoptera)等多个类群的密度显著增加(p<0.05),而沙化则使优势类群密度显著降低(p<0.05)、常见类群和稀有类群消失。植物种类、生物量和土壤理化性质,尤其是有效磷和速效钾含量与大型土壤动物的丰富度、密度和多样性间存在显著相关关系(p<0.01或p<0.05)。季节变化对大型土壤动物的群落密度和多样性有显著影响(p<0.01或p<0.05),但不同退化阶段的大型土壤动物对季节变化的响应存在差异。研究结果表明高寒草甸的中度退化能够增加大型土壤动物群落多样性,而严重退化(即沙化)则显著降低土壤动物群落多样性,且不同退化阶段大型土壤动物群落的季节动态不同。

Zoige alpine wetland meadow, located on the eastern edge of the Qinghai-Tibetan Plateau, is degrading under the impact of global climate change and the increasingly heavy burden of livestock in recent years, demonstrating four typical phases,i, e. swampy meadow, grassland meadow, degraded meadow and desertifying meadow in the process. From April 2009 to October 2010, seven investigations were conducted of soil maerofauna communities in the four phases for analysis of impacts of the degradation on soil macrofauna. Results show that differences existed between the phases in taxonomic composition and dominant groups of the soil macrofauna communities. Statistical analysis shows that the impacts of the degradation on richness, density and Shannon diversity index of the soil macrofauna communities were extremely sig- nificant （p 〈0.01 or p 〈0.05） in the last two phases. Principal Component Analysis （PCA） shows that in the phase of graded meadow, Polydesmida and Coleoptera larvae increased significantly （p 〈 0.05 ） , while in the phase of desertifying meadow the dominant groups decreased significantly in density （p 〈 0.05 ） and some common and rare groups disap- peared. Correlation analysis shows that richness, density and diversity of soil maerofauna communities were closely related to species and biomass of the plants and physical and chemical properties of the soils （p 〈 0.01 or p 〈 0.05 ） , especially available phosphorus and readily available potassium, in the meadows. And soil macrofauna communities also responded to changes in season significantly in abundance and diversity, and the responses varied from phase to phase of the degrada- tion process （p 〈0.01 or p 〈0.05）. All the findings indicate that moderate degradation of alpine meadows may increase soil macrofauna community in diversity, whereas severe degradation （desertification） significantly reduces the diversity, and moreover, seasonal dynamics of soil macrofauna communities varies from phase to phase of the degradation process.