青海大通退耕还林工程区的林木耗水特性

 为了给退耕还林工程建设的树种选择提供依据,2002—2003年,通过实地观测并应用PenmanMonteith方程和定位通量法,对青海大通黄土高寒区自20世纪80年代陆续退耕还林后营造的青海云杉、紫果云杉、华北落叶松、白桦、青杨和沙棘进行了林木耗水特性研究。结果表明:2种方法测算林地蒸散的月平均相对误差是57%。中龄林的青杨沙棘混交林、白桦纯林、青杨灌木混交林和白桦青海云杉沙棘混交林的生长季蒸散总量为488～538mm,其中蒸腾量占蒸散总量的74%～79%,林地土面蒸发总量占蒸散总量的10%～12%,林地无地表径流产生;处于幼龄生长阶段的紫果云杉、青杨、华北落叶松、青海云杉混交林生长季蒸散总量为450～510mm,其中蒸腾总量占蒸散总量的45%～69%,林地土面蒸发总量占蒸散总量的16%～44%,地表径流量占林地降水量的1%～6%。大部分林分6—8月的蒸腾耗水量占全年的80%。

Water consumption of forests in project area of returning farmland to forests in Datong county, Qinhai province

In order to provide proof for tree species selection in returning farmland to forest project, based on Penman-Monteith equation and oriented flux method, the paper has studied the seasonal changes of water consumption of forests in 2002 and 2003.The studied tree species are Picea crassifolia, Picea purpurea, Larix principis-rupprechtii, Betula platyphylla, Populus cathayana, Hippophae rhamnoides, which were planted for returning farmland into forests since early 1980s. It was concluded that: The month avenge relative error of two calculating stands evapotranspiration methods is 5.7%. The total evapotranspiration of middle stand of mixed forests composed of Populus cathayana with Hippophae rhamnoides,pure forest of Betula platyphylla, mixed forest of Populus cathayana with shrubs, mixed forest of Betula platyphylla with Picea crassifolia and Hippophae rhamnoides is 488～538mm, the total evaporation accounting for 74%～79% of total evapotranspiration, the total vaporation is 10%～12% of that and no surface runoff. However, the avenge total evapotranspiration of young aged stands of pure forest of Picea purpurea, Populus cathayana, Larix principis-rupprechtii, mixed forests composed of Picea crassifolia is 450～510mm, the total evaporation accounting for 45%～69% of total evapotranspiration, the total evaporation is 16%～44% of that and a surface runoff is 1%～6% of precipitation. The transpiration of the most stands in the period from June to August accounts for 80% of that in total year.