【摘要】 林分蒸腾是森林生态系统中水循环的重要环节，占森林总蒸散量的40%～70%,直接影响着区域小气候及下游用水安全。预测变化环境下的林分蒸腾量(T),分析林分蒸腾的影响因子及其对这些因子的响应，对于森林水分调控和林水综合管理有着重要意义。于2019年生长季(5-10月),在宁夏六盘山半湿润区香水河流域，选取1块林龄38 a、林分密度为746株/hm~2、平均胸径19.94 cm、平均树高17.54 m的华北落叶松纯林，通过观测其树干液流，经尺度上推得到林分蒸腾量，并对生长季内的潜在蒸散量(ET_o)、土壤水分相对可利用度(RSWC)以及冠层叶面积指数(LAI)进行监测。研究表明，生长季内林分蒸腾变化范围为0.031～1.191 mm/d,呈现出先增后减的波动趋势，平均值为0.572 mm/d。利用外包线法确定的林分蒸腾单因素响应规律表明，T与ET_o之间为二次函数关系，阈值为1.191;T与RSWC之间为饱和指数函数关系，阈值为1.094;T与LAI之间为线性增长关系。基于单因素响应函数研究，进一步构建了T的多因素耦合模型，且得到了良好的拟合效果(R~2=0.85,NSE=0.83,P<0.01)。通过T模型计算各主要影响因素的贡献率发现，无雨日ET_o是T变化的主要贡献因素(13.35%),LAI次之(-4.63%),RSWC最小(-0.03%);有雨日LAI是T变化的主要贡献因素(6.95%),RSWC次之(0.05%),ET_o最小(-23.60%)。对T随各主要因素动态变化的研究表明，在高ET_o、RSWC和LAI水平下，T的变化幅度最大。研究确定了T对潜在蒸散量、土壤水分相对可利用度的单因素响应关系以及T与叶面积指数的关系，并构建了多因素T模型，可用于评估和预测林分蒸腾量，量化各因素的影响。更多还原

【Abstract】 Forest transpiration(T) is an important link of water circulation in forest ecosystem, accounting for 40%-70% of the total evapotranspiration of forests, which profoundly affects regional microclimate and downstream water security.To predict the transpiration of stand under changing environment, analyze the influence factors of stand transpiration and its response to these factors are of great significance for forest water regulation and comprehensive forest-water management.This study was conducted out in the growing season of 2019(May to October) in the Xiangshui River Basin, a semi-humid area of the Liupan Mountain.A pure Larix principis-rupprechtii plantation with the age of 38 years, stand density of 746 trees/hm~2,average DBH(diameter at breast height) of 19.94 cm, and average tree height of 17.54 m was selected as the research object.By observing the liquid flow of the tree trunk, the transpiration of the forest stand was estimated through the scale, and the potential evapotranspiration(ET_o),soil relative available water(RSWC) and leaf area index(LAI) during the growing season were monitored.The results indicated that the variation range of stand transpiration in the growth season was 0.031-1.191 mm/d, showing a fluctuation trend of first increasing and then decreasing, with an average value of 0.572 mm/d.The univariate response law of stand transpiration was determined by the outer line method, which showed that there was a quadratic function relationship between T and ET_o with a threshold of 1.191.The relationship between T and RSWC was in an exponential saturation function with a threshold of 1.094,and a linear growth relationship was found between T and LAI.Based on the single-factor response function, the multi-factor coupling model of T was further constructed and the fitting effect was good(R~2=0.85,NSE=0.83,P<0.01).The contribution rate of each major influencing factor was calculated by the T model, and it was found that ET_o was the main contributor to T change on a rainless day(13.35%),followed by LAI(-4.63%),and RSWC was the smallest(-0.03%),while LAI on a rainy day was the main contributor to T change(6.95%),followed by RSWC(0.05%),and ET_o was the smallest(-23.60%).The study of the dynamic change of T with each major factor showed that the change amplitude of T was the largest at high ET_o,RSWC and LAI levels.It is concluded that the single-factor response relationship of T to potential evapotranspiration, soil relative available water and leaf area index are determined, and a multivariate T model is constructed, which can be used to evaluate and predict the transpiration of stand and quantify the influence of various factors.更多还原