古尔班通古特沙漠植被与环境的关系

Vegetation-environment relationships in Gurbantunggut Desert

对古尔班通古特沙漠进行了纵向及横向的路线调查,植被测度和土壤理化性质分析。对比发现该沙漠地貌形态纵、横向上的显著差异,使沙漠植被分布格局存在着异质性,即植物群落的物种多样性、优势度及盖度在纵、横向上明显不同。CCA排序结果显示,土壤的有机质含量、全盐含量、分选系数、含水量和pH值等微生境使植被沿其变化梯度以不甚耐盐碱的短命、类短命草本和小半灌木、半灌木为主的群落逐渐向耐盐碱的灌木、小乔木类群落转变。地形和土壤质地可使横向上相当数量的植物种产生空间分化,而这种分化在纵向上不明显。沙漠植被物种在各生境梯度作用下形成3类组合,其在横向上对应3个地段,但在纵向上没有清晰的对应空间(除南北边缘区外),原因是多数植物的生境处于沙漠纵向微生境梯度的中间序位。

The paper reports on marked heterogeneity found in vegetation and soil in the Gurbantunggnt Desert, Western China related to landform position and orientation. Vegetation and soil data were collected on north-south transects in the area 44°14′00″-45°41 ′52″N and 87°37′09″- 88°24′04″E, and were compared with vegetation and soil data collected on east-west transects in the area 44°56′40″-45°29′55″N and 85°30′35″- 88°45′12″E. The sand dunes of the survey area are mainly of the longitudinal form from south to north, but checkerboard-shaped and honeycomb-shaped forms are also present, with the height of 10 -50 m. Analysis revealed that the varying trend and strength of the species diversity, dominance and cover of the plant communities in the longitudinal and transverse directions across the landscape are significantly different. The results of CCA ordination show that the microhabitats of soil organic matter （OM） , soil salts （TS）, sorting index （σ） , topsoil water-content （SM） and pH relate to the differences in vegetation observed as differences in species assemblage from salt-intolerant ephemerals, micro-subshrnbs and subshrnbs to salt-tolerant shrubs and micro-arbors. The terrain （alt.） and soil texture （ the contents of Mz and Ф1 ） affect the spatial differentiation of many species. However, this spatialdifferentiation is not so marked on transects running longitudinally with the landscape, in the same direction as the dunes. The species of the desert vegetation have formed three assemblages under the action of habitat gradients, relating to three sections running transversely across the landscape, at right angles to the direction of the dune crests. In the mid-east section of the study area the topography is higher, with sand-lands or dune-slopes with coarse particles. Here the dominant vegetation comprises shrubs and subshrubs of Seriphidium santolinum and Ephedra distachya, with large numbers of ephemeral and ephemeroid plants of Senecio subdentatus, and Carex physodes in spring and summer. On the soil of the dune-slopes in the mid-west of the study area, with coarse particles and abundant TK, the plant assemblage of Haloxylon persicum, Soranthus meyeri, Agriophyllum squarrosum is developed. The species composition in the east marginal belt of the study area has similar characteristics to the mid-west section. There is no corresponding section in the north-south transect （except for the north and south margins）. This is because the habitats of most plants are located in the middle of the microhabitat gradients in the north-south direction in the desert.