极端干旱区不同下垫面土壤凝结水试验研究

为了探讨极端干旱区植被生长季的土壤凝结水特征，采用微渗计和中子仪，于2010年6-7月对塔里木河下游地区胡杨林、柽柳丛和裸地3种典型下垫面密封和不密封处理的土壤凝结水的变化特征、形成时间及其影响因素进行了研究。结果表明：微渗计和中子仪观测结果均显示观测期间裸地产生的土壤凝结水总量最大，其次为柽柳丛，而胡杨林形成的土壤凝结水总量最小。观测期间研究区凝结现象从21：00-22：00左右开始，02：00-03：00左右达到第一个峰值前，随着近地表气温和地温的降低，土壤凝结水量呈增加的趋势。不密封处理产生的土壤凝结水量显著大于密封处理的（t〈0．01）。柽柳丛土壤日均凝结水量最大，其次为裸地，胡杨林最小。方差分析显示，不同下垫面类型土壤的日均凝结水量之间存在极显著差异（P〈0．01）。3种下垫面土壤凝结水量的变化趋势基本一致，均呈双峰曲线。凝结过程一般从22：00左右持续到次日09：00左右。土壤凝结水量主要受气温、大气相对湿度、表层地温、风速以及下垫面等因素的影响。研究结果可以为生态退化区的植被恢复提供一定的理论依据。

Measurements of Soil Condensation Water on Different Types of Underlying Surfaces in Extreme Arid Region

Condensation water is an important water source in arid ecosystems.To understand the characteristics of soil condensation water during growing season in extreme arid regions,micro-lysimeters and neutron probe were used to measure the amounts and duration of soil condensation water on different types of underlying surfaces(Populus euphratica forest,Tamarix bushes and bare land) in the lower reaches of the Tarim River.The results showed that the maximum total soil condensation amount occurred on the surface of bare land.The minimum total soil condensation amount was accumulated on the underlying surface of Populus euphratica forest.Soil condensation amounts of the connected treatment were significantly larger than those of the unconnected treatment(t<0.01).The average daily soil condensation amount varied with types of underlying surfaces with the maximum condensation amount occurred on the underlying surface of Tamarix bushes,while the minimum condensation amount was created on the underlying surface of Populus euphratica forest.ANOVA analysis results indicated that the average daily soil condensation amounts on different types of underlying surfaces were significantly different(P<0.01).Diurnal dynamics trend of soil condensation amounts on different types of underlying surfaces showed a clear double-peak curve.Soil condensation water began at 22:00 and ended at 09:00 the next morning.The formation of soil condensation water was mainly affected by atmospheric temperature,relative humidity,soil surface temperature,wind speed and types of underlying surfaces.The results may assist in the calculation of rational ecological water demand and provide scientific supports for ecological restoration in the lower reaches of the Tarim River.