塔里木河中游荒漠绿洲过渡带土壤水分与植被空间格局变化关系研究

Variable Relationship of Soil Moisture and Spatial Pattern along Desert Oasis Transition Zone in the Tarim River Middle Reaches Basin

土壤水分含量的高低决定了荒漠绿洲过渡带的植被种类及群落构成,因此,掌握植被特征随土壤水分的变化规律,能为干旱区生态环境建设提供科学的理论依据。选择典型的干旱区塔里木河中游流域作为样区,定点采集土壤样品测定其含水量,并调查植被特征,分析了干旱区荒漠绿洲过渡带土壤水分与植被空间格局的关系,进行荒漠生态系统土壤水分对植被空间格局的影响研究。结果表明,荒漠绿洲过渡带20~40cm土层土壤湿度、草本密度及植被密度在研究区尺度上具有中等空间自相关,其0~20、40~60、60~80、80~100cm土壤湿度、灌木个数、灌木密度、幼苗个数、胡杨个数、郁闭度和植被群落物种数,在研究区尺度上表现出强空间自相关;土壤水分和植被特征均具有相似且明显的空间分布格局,其数值均呈先升高后降低的趋势即呈M型分布;灌木密度与20~40cm和40~60cm土层的土壤含水量呈显著相关,80~100cm土壤水分与胡杨个数、郁闭度、植物群落物种数有极显著相关关系,研究区生态系统脆弱,植被群落物种数较为单一,土壤水分和植被特征的空间变异性主要是结构性因素作用的结果;由于荒漠河岸林的主要建群树种为胡杨,研究表明20~60cm土层的土壤含水量对灌木的生存与生长起关键作用,而植被空间格局主要由80cm以下的土壤含水量决定。

The soil moisture plays an important role in the desert ecosystem in arid area because it deter- mines the vegetation species and community composition of desert oasis transition zone. Therefore,it will provide scientific theoretical basis for the construction of ecological environment in arid area if the variation of vegetation characteristics with soil moisture is understood. The typical arid area in the middle reaches of the Tarim River Basin was selected as a sample area. Soil samples were collected to measure soil moisture. The vegetation characteristics were investigated. The relationship between soil moisture and spatial pattern of vegetation in the transitional zone of desert oasis in arid area was analyzed. Effect of soil moisture on vegetation spatial pattern in desert ecosystem was studied. The results showed the moisture of 20--40 cm deep soil,herbaceous density and vegetation density had moderate spatial autocorrelation in the study area of desert oasis transitional zone. The spatial distribution pattern of soil moisture and vegetation characteris-tics was obvious. It showed the M-type distribution trend： increased first and then decreased. Significant relationships were found between shrub density and moisture of 20--40 cm and 40--60 em deep soils, re- spectively. Soil water content of 80--100 cm soil layer was highly and significantly correlated to Populus number, canopy density and plant species number, respectively. The ecological system of the study area was fragile. The number of species of vegetation communities was relatively simple. The spatial variability of soil moisture and vegetation characteristics was mainly the result of structural factors. Populus is the main constructive species of the desert riparian forest. Therefore, soil water content of 20-- 60 cm soil layer played a key role in the survival and growth of shrubs. The vegetation spatial pattern was mainly deter- mined by the moisture of soil below 80 cm.