title: Environmental controls of evapotranspiration in a mixed plantation in North China.
abstract: 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.
authors.affiliation: College of Forestry, Beijing Forestry University, Beijing, 100083, China. tongxj@bjfu.edu.cn.
authors.forename: Xiaojuan
authors.initials: X
authors.lastname: Tong
authors.affiliation: Key Laboratory of Tree Breeding and Cultivation of State Forestry Administration, Research Institute of Forestry, Chinese Academy of Forestry, Beijing, 100091, China.
authors.forename: Jinsong
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Tree Breeding and Cultivation of State Forestry Administration, Research Institute of Forestry, Chinese Academy of Forestry, Beijing, 100091, China.
authors.forename: Ping
authors.initials: P
authors.lastname: Meng
authors.affiliation: Key Laboratory of Water Cycle and Related Land Surface Processes, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, 100101, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Li
authors.affiliation: Key Laboratory of Tree Breeding and Cultivation of State Forestry Administration, Research Institute of Forestry, Chinese Academy of Forestry, Beijing, 100091, China.
authors.forename: Ning
authors.initials: N
authors.lastname: Zheng
mesh_terms: D002681:China; D029779:Cupressaceae / Q000502:physiology; D065928:Forests; D019684:Magnoliopsida / Q000502:physiology; D008834:Microclimate; D008962:Models, Theoretical; D018526:Plant Transpiration; D011891:Rain; D012621:Seasons; D012987:Soil / Q000737:chemistry; D014867:Water / Q000032:analysis
chemical_list: D012987:Soil; D014867:Water
keywords: Canopy conductance; Decoupling factor; Eddy covariance; Evapotranspiration; Mixed plantation; Priestley–Taylor coefficient