天山北麓典型地段植被对景观格局和动态的指示意义

Indication of desert vegetation to landscape patterns and dynamics at the northern edge of Tianshan Mountains

景观是由气候、地貌、水文、土壤、植被等组分构成的综合体。这些组分之间相互影响、相互作用 ,其中植被对其它组分的反映最为敏感。研究了天山中段北坡从中山开始 ,向下经准噶尔盆地南缘壤质和黏土荒漠 ,到古尔班通古特沙漠南缘的范围内 ,以典型温带荒漠植被为主的天然植被格局及其与环境梯度的关系 ,并以此为基础探讨了干旱区荒漠植被对于景观格局及相应的景观过程的指示意义。结果表明 ,土壤质地对研究区植被类型有显著的影响 ,白梭梭 -梭梭群落、梭梭群落、琵琶柴群落对细粒物质的偏好依次增大 ,对粗粒物质含量则有相反的规律 ;研究区壤质和黏土荒漠中的白梭梭 -梭梭群落可以作为景观中土壤沙化过程的指示体。在对土壤含盐量的适应性方面 ,琵琶柴群落高于梭梭群落 ,分布在总盐含量更高的生境中 ,柽柳群落则对土壤盐分没有明显的偏好 ;盐生矮半灌木群落可以作为土壤盐渍化过程的指示体。在对土壤水分与地下水位的适应性方面 ,柽柳群落表现出较明显的对高的土壤含水率的偏好 ,可以指示景观中具有优良生境的斑块。荒漠化过程是干旱区重要的景观生态过程 ,主要表现为土壤沙化和土壤盐渍化 ,而这两个过程都有非常明显的植被表征 ,因此 ,在以荒漠化动态为目标的干旱区景观动态分析中 ,可以通过植被的演化?

Landscape is an integrated earth surface unit composed of interacted landscape components such as climate, landform, hydrological condition, soil and vegetation. Vegetation is sensitive to other landscape components in a landscape and was usually employed to indicate the dynamics of other landscape components. In this paper, vegetation patterns with environmental gradients and their indication to landscape patterns and processes were studied in a typical area from middle mountainous zone of the northern slope of Tianshan Mountains, through the clayey desert at the southern edge of Jungar Basin, to the southern margin of Gurban Tonggut Sandy Desert. 10 transects were set in the study area. 43 relevés of plant communities were recorded and soils at the depth of 15 cm and 45 cm for each relevé were taken. TWINSPAN was adopted to distinguish plant community types and DCCA to reveal links between plant communities and habitat conditions. 10 types of plant communities were divided. Although the effects of soil salinity and water table upon vegetation in arid land have been convinced by previous work in this region, our results implied that physical composition of soils in the study area is also closely linked to various plant community types remarkably. As to the preference to fine grain, the order is concluded as H. persicum-H. ammodendron community > H. ammodendron community> R. soongorica community, and an opposite order for coarse grain, therefore the H. persicum-H. ammodendron community on clayey desert in the study area is regarded as an indicator of sandy desertification. R. soongorica community has higher adaptability to saline soil than H. ammodendron community, and exist in habitat of higher salinity, while halophyte community indicates soil salinization. T. ramosissima community doesn't show obvious preference to salinity or water table depth, but a quite remarkable preference to a high soil moisture content. Vegetation patterns interpreted from ETM satellite images well reflects the spatial patterns of physical composition and total salt content of soils, which further demonstrated that vegetation well indicates landscape patterns in the study area. It is inferred from this study that dynamics of two types of desertification, sandy desertification and saline desertification, can be revealed by studies on vegetation dynamics in the study area.