Tong Xiaojuan, Zhang Jinsong, Meng Ping, Li Jun, Zheng Ning
College of Forestry, Beijing Forestry University, Beijing, 100083, China.
Key Laboratory of Tree Breeding and Cultivation of State Forestry Administration, Research Institute of Forestry, Chinese Academy of Forestry, Beijing, 100091, China.
Int J Biometeorol. 2017 Feb;61(2):227-238. doi: 10.1007/s00484-016-1205-0. Epub 2016 Jul 5.
The mixed plantation plays an important role in the water cycle in the hilly area of North China. To evaluate the effect of afforestation on the water balance in this region, the temporal variation of evapotranspiration (ET) and environmental controls were investigated based on the eddy flux measurement of water vapor in a 31-year-old mixed plantation from 2006 to 2010. During 5 years, annual ET ranged from 513 to 680 mm, with an average of 579 mm. Growing season ET accounted for 72-82 % of annual ET during the 5-year period and its interannual variation was determined by the number of rainy days. In the non-growing and growing seasons, monthly ET was primarily dependent on monthly mean soil water content and monthly mean net radiation, respectively. Annual mean Priestley-Taylor coefficient (α) was 0.64, and the decoupling factor (Ω) was 0.48. High values of α and Ω implied that ET was energy limited in the growing seasons of 2006-2010. The mean annual ratio of ET to precipitation (ET/P) was 1.10. The density of the mixed plantation was around 50 % higher than the optimal value determined by local water capacity, leading to a large ET/P ratio. The dense plantation needs to be thinned to prevent excessive water loss in the hilly area of North China.
混交林在中国北方山区的水循环中起着重要作用。为了评估造林对该地区水平衡的影响，基于2006年至2010年一片31年树龄混交林水汽的涡度通量测量，研究了蒸散量（ET）的时间变化及其环境控制因素。在这5年期间，年ET范围为513至680毫米，平均为579毫米。生长季ET占5年期间年ET的72% - 82%，其年际变化由雨日数决定。在非生长季和生长季，月ET分别主要取决于月平均土壤含水量和月平均净辐射。年平均普里斯特利 - 泰勒系数（α）为0.64，解耦系数（Ω）为0.48。α和Ω的高值表明在2006 - 2010年生长季ET受能量限制。年平均ET与降水量之比（ET/P）为1.10。混交林的密度比当地水分容量确定的最佳值高出约50%，导致ET/P比值较大。在华北山区，需要对密集的树林进行间伐以防止过度的水分流失。
