河西绿洲边缘积沙带形成的典型相关因子

Canonical correlation factors causing the formation of accumulated sand-belts along the oasis fringe in Hexi corridor

绿洲边缘积沙带的形成因素及其生态效应是一个新的科学问题。为了研究河西绿洲边缘积沙带的形成原因,运用方差分析、相关分析以及典型相关分析等方法,对河西绿洲边缘积沙带的21个样点的观测资料进行了分析。结果表明:河西绿洲边缘积沙带的分布趋势大致为东高西低、东宽西窄,大部分地段目前处于稳定阶段;积沙带上的优势种植物以天然柽柳最多,不同优势种植物的积沙带的迎风坡植被盖度及植被纯盖度差异较显著。典型相关分析结果表明:积沙带的高度和宽度是降水量、到沙源的距离、背风坡植被盖度和年平均风速等气候环境因子共同作用的结果。积沙带的生态效应:一是自身作为一种障碍物的防护作用,二是阻截、减少流沙流沙进入农田的作用。

Accumulated sand-belts refer to those formed along the oasis fringe,especially at the upwind location,due to the accumulation of sand blocked by farmland windbreak. In the 60 years since the foundation of new China,a lot of trees have been planted for desertification combating in northwest and north China,thus,accumulated sand-belts were formed at the upwind location. The formation and the ecological effects of the accumulated sand-belts along the oasis fringe is a new scientific concern. To study the formation causes of these belts in Hexi corridor,21 samples were selected,and the height /width of the belts,as well as the vegetation,soil,soil moisture and climatic factors were investigated. This paper analyzed the correlation between the height / width of the belts and the vegetation,soil,soil moisture and climatic factors using the methods of variance analysis, correlation analysis and canonical correlation analysis. The results indicate that： the accumulated sand-belts take a trend of being high and wide in the east whereas low and narrow in the west,and most of the parts tend to be stable; the species on the belts are dominated by Tamarix austromongolica,the vegetation cover and the pure vegetation cover of different dominant species on the leeward slope of the accumulated sand-belts vary significantly. The canonical correlation analysis shows that： the height and width of accumulated sand-belt is the interaction of precipitation,distance to the sand source,leeward vegetation cover and annual average wind speed. Moreover,the height of accumulated sand-belts are negatively correlated to the soil moisture at the depth of 30—50cm,air humidity and leeward vegetation cover,and the width of the belts is also negatively correlated with the distance to the sand source. The ecological effects of the accumulated sand-belts are both positive（ stopping sands from moving into farmland,protective role as an obstacle） and negative（ when the belts decay and activate one day,they will become the new sand sources）. At present,there are no signs showing the negative effects of the belts. The ecological effects of the accumulated sand-belts are： firstly the protective role as an obstacle,and secondly to intercept and reduce the sands moving into farmlands. Whether by use single correlation analysis method or by use canonical correlation analysis method,the results show that the accumulated sand-belt height and width are closely related with annual precipitation,by use principal factor analysis method,the results also show that the contribution of annual precipitation in climatic and environmental factors in the maximum rate. In Hexi oasis edge,accumulated sand-belt distribution trends roughly east accumulated sand-belt higher and wider than west accumulated sandbelt,accumulated sand-belts discontinuous distribution with oasis distribution,most of the area is currently in a stable stage,if as long as no damage,then after 70—80 years that accumulated sand-belt is still not activated to cause harm.