半干旱区流沙固定初期不同植被类型的土壤湿度特征

利用科尔沁沙地奈曼生态网络研究站1983～1990年土壤水分定位观测数据,分析了不同类型植被土壤湿度的时间变化特征及其受降水的影响。结果表明:植被建立对沙地土壤湿度影响是显著的,与流动沙丘(多年平均土壤含水量3.56%,变异系数为0.074)相比,生长在沙丘顶和丘间低地的乔木树种小叶杨和樟子松,10～15年后平均土壤含水量分别为2.73%和3.08%,但在较短的时间尺度上变异较大,变异系数分别为0.127和0.347,下降最明显的是生长在沙丘顶部的灌木、半灌木,如小叶锦鸡儿和差巴嘎蒿 樟子松等植被区,平均土壤含水量均低于2.5%,变异系数分别为0.179和0.262。半干旱土壤湿度除了受植被影响外,降水也是主要控制因子。欠水年,土壤旱化现象严重,在固沙植被区,特别是沙丘顶部会出现暂时性土壤干层,并且不同类型植被区土壤湿度差异显著;丰水年,土壤水分好转,干层消失。

Characteristics of Soil Moisture of Different Vegetation Types in Initial Stage of Fixed Sand Dune of Semi-arid Region

Soil moisture data from May to October during 1983 to 1990 at Naiman on Horqin sandy land are applied to study in temporal and spatial variant characteristic ofsoil moisture and effect of precipitation in the different type vegetation. The results showed that the influence of vegetation is significant, soil moisture of shifting sand dune is best, its average value is 3.56% and variation coefficient is 0.074. Second is soil moisture of arbor area which grew in the lower part of sandy dune, its average value is from 2.73% to 3.08%, but soil moisture have not stability, variation coefficient is 0.127 and 0.347, respectively. Soil moisture of semi-bush and bush areas which grew on top of sandy dune are worst, its average values are less that 2.5%, variation coefficient are (0.179) and 0.262, respectively. Soil moisture has also been controled by precipitation,sandy land would appear dried soil layer when vegetation and dry climate influence in the same time, but not in the normal or wet years in the desert region of semi-arid.