准噶尔盆地典型地段植物群落及其与环境因子的关系

沿88°E线,南北纵穿新疆北部准噶尔盆地,选择环境梯度明显的典型地段,设置33个具有代表性的野外样方,应用TWINSPAN与DCCA分析样方的物种数据和环境数据。研究结果表明:(1)样方TWINSPAN分类结果的第一级分类将分布于流动、半流动沙丘(垄)上的白梭梭群落与固定、半固定沙地上的梭梭群落区分开来,进一步的分类,可将33个样方划分为12个组。35种优势植物种TWINSPAN第1级分类把沙漠内部植物种与外缘物种分开。第2级分类把沙漠内部垄上与垄间植物种以及沙漠外缘旱生、中生和盐生植物种分开。(2)在各种环境因子中,土壤水分与相对高度(或地面活动性)是影响植物群落分布的最主要环境因子,DCCA第一排序轴反映生境水分环境条件,第2轴反映土壤结构梯度的变化。(3)除相对高度(或地面活动性)与土壤水分外,在沙漠南部外缘的山前冲积、洪积扇扇缘,土壤盐分状况亦为植物生长的重要胁迫因子;在沙漠北部外缘的砾石戈壁平原,基质的机械组成对群落分布格局有重要影响;在沙漠内部,土壤质地、地面坡度对植物群落的分布有较大影响。(4)以沙漠为中心的准噶尔盆地地势相对高度与地面活动性、土壤有机质与土壤粘粒、土壤水分与土壤总盐、pH值、有机质、相对高度之间存在显著相关关系。

Relationships between plant community characteristics and environmental factors in the typical profiles from Dzungaria Basin

Dzungaria Basin, located in Northern Xinjiang, is one of the desert regions in China with a mid-latitude arid climate where the mean annual precipitation is around only 70-150 mm. The ecosystems in the basin are extremely fragile to resist any severe disturbance. With the exploitation and exploration of oil and gas resources, parts of the ecosystems in Dzungaria Basin have been degraded or even damaged. In order to provide background data for restoring the damaged desert ecosystems, a survey of the desert vegetation to reveal its relationships with environment factors was conducted in the basin. 33 sampling plots, with each 10 m×20 m in size and following the contour of the land, were set up at the typical transect with distinct environmental gradients along 88°E across the Dzungaria Basin. The species and coverage of trees and shrubs of desert vegetation were surveyed in each plot. Each plot was further sub-divided into fifty 2 m×2 m quadrats, and the species and coverage of herbs were then surveyed in three randomly selected quadrats per plot. Meanwhile, the environmental data of the 33 plots, including ground activity, relative altitude, ground slope, slope aspect, and physical-chemical features of topsoil like total salts, pH, organic matter, water content, medium-coarse grain and clay grain, etc. were collected. The quantitative ordination and classification approaches as DCCA and TWINSPAN were used to analyze the collected species and environmental data so as to explore and reveal the distribution pattern of plant community influenced by environmental factors. The results were shown as follows. (1) There are two main types of desert vegetation sparsely distributed along the transect. One is Formation Haloxylon persicum scattered on mobile and semi-mobile dunes, while the other is Formation Haloxylon ammodendron emerged only on fixed and semi-fixed sandy land. Those two main vegetation types can be further divided by TWINSPAN until the sixth level into 12 vegetation groups, each of which shows more or less distinct features including distribution preferences from others. 35 dominant plant species can be roughly divided into two categories, namely the inner and the outer species of the basin, at first level by TWINSPAN. The inner species can be further divided into species on the upper or the lower slopes of dunes, and the outer species can be further divided into categories of xerophyte, mesophyte and halophyte at second level by TWINSPAN. (2) The ordination results of the 33 plots with 35 dominant plant species by DCCA showed the distribution pattern of plant communities changed apparently with the gradient of environment factors. The first axis of the DCCA ordination chiefly reflected the gradient of soil water content, and the second axis mainly related to soil structure gradient, which indicated that of all the environmental factors examined, soil water content and relative altitude (or ground activity) were the two most prominent environmental factors controlling the community distribution pattern. (3) Apart from relative altitude (ground activity) and soil water content, soil salinity also emerged as an environmental factor stressing vegetation, especially at the marginal zone of piedmont diluvial fans in the southern fringe of the desert. Soil texture was another factor influencing the vegetation features as well as distribution, particularly in the gobi plain along the northern outskirt of the desert. Meanwhile, soil texture and dune slope also contributed to the plant distribution pattern in inner desert as two extra environmental gradients. (4) Significant correlations can be found between relative altitude and ground activity, between soil organic matter and soil clay content, or between soil water content and total soil salts, pH, relative altitude, and soil organic matter in Dzungaria Basin.