塔里木河下游物种多样性与地下水位灰色关联分析

Grey Incidence Analysis between Species Diversity and GroundwaterLevel in the Lower Reaches of the Tarim River

根据植被样地资料和地下水埋深观测资料,运用灰色关联法对物种多样性与地下水埋深的关系进行了分析.结果表明:在塔里木河下游,物种多样性与地下水埋深变化关系密切,Shannon Weiner指数、Simpson指数、Margalef指数、Menhinick指数、JSW指数和JSI指数与地下水埋深之间的灰色综合关联度都在0.70以上,其中物种多样性指数Simpson指数与地下水埋深变化的灰色综合关联度最高,为0.866,其关联度数值体现了地下水埋深对物种多样性变化的主导性.

The intensive exploitation and utilization of water resources in the upper researches of the Tarim River lead to cutting off of the river from the Daxihaizi Reservoir to the Taitema Nor for 30 years. Without the supply of surface runoff, the groundwater table lowers continuously and vegetation degenerates. Based on the data of stationed plant plots and groundwater table in five sections in the lower reaches of the Tarim River, the features of groundwater table changing and species diversity are analyzed. Before the water conveyance to the lower researches, the depth of groundwater table is below 8 m at Yinsu section, and below 10 m at Yiganbujima section. The coverage of vegetation decreases obviously from upper section to lower section. The distribution features of plant communities in sections of the lower researches of Tarim River are as follow: (1) The community type of Yinsu section and Abudali section is Populus euphratica and Tamarix community. In the constitution of this community, arbor layer is composed of Populus euphratica; shrubbery layer is composed of Tamarix ramosissima, T. hispida, Lycium ruthenicum and Halimodendron halodendron; herbage layer is composed of Glycyrrhiza inflata, Apocynum venetum, Alhagi sparsifolia, Phragmites communis and a litter of Karelinia caspica and Salsola sp. Populus euphratica and Tamarix sp are dominant species among this community. At the angle of vertical structure of community, this community can be divided into arbor layer, shrubbery layer and herbage layer, but relative density and relative coverage of each layer among the whole community are different with each other. At the angle of horizontal structure of community, the distribution of plants is sparse and the distribution of herbage plants takes on fragmentation; the kind and number of species decrease from upper to lower at the lower researches of the Tarim River. (2) The community type of Kardayi section, Alagan section and Yiganbujima section is Populus euphratica and Tamarix community. This community is composed of Populus euphratica, Tamarix accompanied with Lycium ruthenicum and a little of Halimodendron halodendron. Because the groundwater table is too deep to be absorbed by the herbage with shallow root system, there hardly exists herbage except Alhagi sparsifolia with deep root system. Most plants take on degradation. The type of vegetation is mainly desert Tamarix scrub, Tamarix scrub and desert Populus euphratica forest. At the angle of horizontal structure of community, the whole community takes on compound distribution, i.e., three types of Populus euphratica forest, Populus euphratica forest + Tamarix scrub and Tamarix scrub are combined together. (3) The community type of Yiganbujima section and Kaogan section is simple \%Tamarix community. Here Vegetation is more degraded than in other regions for the deeper groundwater table. The vegetation type is desert Tamarix scrub and naked unstable dunes. (4) The region from Kaogan to Taitema Nor has become depositional saline plain, with less vegetation.After 4 times of ecological water conveyance to the lower researches, the groundwater table near the riverbed rises to some extent. The degraded Populus euphratica community and Tamarix community take on rehabilitation. At some washes near the river, Salsola sp, Hexinia polydichotoma and Scorzonera sp grow and thrive. According to an investigation, after 4 times of water conveyance, the kind of herbage species increases at the places where water has overflown, which take on a landscape different from the region away from the river. According to the Grey incidence analysis between species diversity and depth of groundwater, there is close relationship between species diversity and change of depth of groundwater in the lower reaches of the Tarim River: The Grey integrated incidence degrees between species diversity index, including the Shannon-Weiner index, Simpson index, Margalef index, Menhinick index, JSW index and Jsi index, are all above 0.70. The Grey integrated incidence degrees between Simpson