晋西黄土残塬沟壑区防护林热收支特性及蒸散研究

Heat Energy Budget Characteristics and Evapotranspiration of Protection Forest in the Loess Region of Southwestern Shanxi Province

应用自记综合气象观测塔，对刺槐和油松林进行了以蒸散研究为目的的防护林热收支特性研究．结果表明：１９９４年生长季日平均实际太阳辐射量为７～２４ＭＪ·ｍ－２；刺槐林林冠对太阳辐射的反射率为１５％，油松林的反射率在１０％以下，反射率的差异是造成两林分净辐射收支相差１～３ＭＪ·ｍ－２的主要原因．春夏两季林分获取的净辐射均由约７０％～８０％的太阳辐射转换而来；秋季的转换率约为６０％，油松林的转换比刺槐约大１％～５％；防护林地区每天获取的净辐射量中，消耗于蒸散的潜热通量部分，在春夏秋三季分别为６５％，８２％和８５％，油松林比刺槐林偏高１％左右；用于气温变化的显热通量部分在春季约占３２％，夏秋为１５％左右，其中刺槐林中显热通量部分在春夏两季所占的百分比相对油松要高出４％～５％；刺槐林地用于土壤热流量部分的热量在５～９月约占净辐射的１％～３％，油松林为２％～５％；１９９４年生长季刺槐林蒸散量为５１９ｍｍ，油松林为５９７ｍｍ．

Based on the observation of micrometeorological tower at Robinia pseudoacacia and Pinus tabulaeformis stands in Jixian Country,Shanxi Province,a research on heat energy budget characteristics was carried out form May to Oct.in 1994.The results are as follows: In growing season the actual daily solar radiation was 7～24MJ·m -2 ; the albedo of Robinia pseudoacacia canopy was 15% and Pinus tabulaeformis below 10%.This diversity led to a difference of net radiation budget about 1～3MJ·m -2 between these two stands. Net radiation corresponded to approximately 70%～80% of total solar radiation in both stands in spring and summer, 60% in autumn. Among daily net radiation budget, the part of latent heat be used up in evapotranspiration was 65% in spring, 82% and 85% in summer and autumn respectively, 1% more at Pinus tabulaeformis stand that Robinia pseudoacacia stand. The part be expended in sensible heat was 32% in spring, 15% in other seasons. The soil thermal flux was 1%～3% of net radiation in Robinia pseudoacacia stand and 2%～5% in Pinus tabulaeformis stand.The evapotranspiration in growing season was, 519 mm in Robinia pseudoacacia stand and 597 mm in Pinus tabulaeformis stand.