极端干旱区柽柳林地蒸散量及能量平衡分析

运用波文比-能量平衡法对极端干旱区柽柳林地的蒸散量及能量通量进行了连续的测定和估算,并对柽柳林地蒸散特点和能量平衡进行了分析和探讨。结果表明:柽柳林地的日平均蒸散量为1.6 mm/d,整个生长季的蒸散量为248.2 mm,蒸散量的季节变化系数为47%±3%。柽柳林地蒸散量的季节变化与土壤水分条件密切相关。柽柳林地蒸散量受气象因子和下垫面条件的影响和制约。在极端干旱区,感热通量消耗了绝大多数的能量,潜热通量在整个生长季只占很小的一部分,夜间,土壤储存的能量是大气能量的主要来源,而白天土壤是能量的主要汇源。

Evapotranspiration and energy balance analysis for Tamarix ramosissima stands under extreme arid conditions

Given the increasing threat of water shortages in the extremely arid regions(rainfall < 50 mm yr-1) of northwestern China,growing season evapotranspiration(ET) associated with native species such as Tamarix ramosissima is of particular interest.Consequently,this study sought to evaluate the accuracy of daily ET estimates using Bowen ratio data,as well as measuring seasonal ET and development of an energy balance for a stand of T.ramosissima.Bowen ratio apparatus measurements of ET were carried out on a stand of T.ramosissima in a 2.04 km2 field,which are all covered with T.ramosissima near Erdaoqiao,Ejina Province,Inner Mongolia Autonomous Region,China.Soil moisture content and green area index were also monitored.Daily ET could be accurately estimated from Bowen ratio data on a continuous basis over the 153-day growing season.The mean daily T.ramosissima ET over this period was 1.62 mm d-1,for a seasonal total of 248.2mm.In this extremely arid locale,the great majority of available energy dissipated over the growing season was a result of sensible rather than latent heat fluxes.While the heat storage term was the main source of energy at night and a considerable sink of energy during the daytime,the magnitude of the daily mean soil heat flux was small.Such a determination of temporal and ecosystem specific ET patterns allows an improved prediction of ET in the desert riparian zone.