塔里木河下游地区胡杨蒸腾耗水规律及其对生态输水的响应

本文结合塔里木河下游地区地下水住埋深的变化,运用先进仪器,对不同监测断面的胡杨液流变化特征进行了测定,结果表明:塔里木河下游地区胡杨液流日变化表现出单峰值和双峰值两种形式,且有明显的昼夜节律变化;胡杨液流在树干2个方位上,东南面液流速率高于西北面,且液流速率随木质部深度的增加而减小;具有较大直径的胡杨,其液流速率、耗水量相对较大;空气湿度、太阳辐射和大气温度是影响塔里木河下游地区胡杨蒸腾耗水量变化的主要环境因子;塔里木河下游地区高温干旱的环境特征,以及生态输水提供的较为充分的水分来源,决定了该区胡杨日水耗量较其他地区胡杨大,2005年2次生态榆水后,河岸两侧地下水位明显抬升,胡杨液流和水势作为两项生理指标都对地下水位变化灵敏响应.

Analysis of the Variation of Transpiration of Popular Euphratica and Its Response to Ecological Water Supply at the Lower Reaches of Tarim River

Having combined the change of water table with employed advanced tools, we investigated the sap flow rate of populus euphratica distributed in different sections at the lower reaches of Tarim River. The results showed that: being influenced by solar radiation, the daily variation of sap flow rate of populus euphratica showed two different styles, which were single-peak and multi-peaks. Also, there was a clear day-night shift. There were obvious differences in the changing patterns of sap flow in different directions and different depths in the trunk of populus euphratica. On the one hand, the sap flow rate in the southeast was higher than that in the northwest. On the other hand, the sap flow rate decreased with the increase of xylem depth. Sap flow rate of populus euphratica branches differed dramatically among different stem diameters. In general, the larger the stem diameters were, the higher the sap flow rate and water consumption amount were. Air humidity, solar radiation and air temperature were the three main environmental factors that affected the sap flow rate of populus euphratica. the daily water use of populus euphratica at the lower reaches of Tarim River were higher than those in other areas. The main reasons were the high temperature, arid climate and the relatively enough water resource supplied by ecological water. The water table on both sides of the main watercourse increased after twice stream water supplies in 2005, which strongly affected the sap flow and water potential of populus euphratica. The sap flow rate and water potential of populus euphratica were sensitive to the change of ground water table. The study results can be used as a reference to understanding the effects of different environmental factors on the water consumption of populus euphratica in order to improve ecological water supply to suit local climate in the lower reaches of Tarim River.