晋西黄土丘陵沟壑区油松刺槐混交林蒸腾耗水

 为了研究黄土丘陵沟壑区主要造林树种和林分蒸腾耗水规律,以位于山西省吉县蔡家川流域内密度为2 450株/hm2的16a油松刺槐混交林为对象,在2008年7—10月,应用热扩散探针技术(TDP)对油松和刺槐4个径阶共17株样木进行蒸腾液流野外实地定位连续观测,同时对环境因子进行同步连续动态观测。结果表明:典型晴天条件下,油松和刺槐树干液流速率在液流启动时间、达到峰值时间、开始快速下降时间和峰值波动范围上有较为显著的差异;2树种不同径阶单木日均蒸腾量的大小排序为油松12 cm>10 cm>6 cm>8 cm,刺槐12 cm>8 cm>6cm,呈现出日蒸腾量随胸径增加而增加的趋势;太阳辐射和水汽压差是影响油松和刺槐树木冠层蒸腾的主要因子;2008年7—10月油松刺槐混交林月蒸腾耗水量分别为30.8、24.1、26.3和18.4mm,总蒸腾量小于同期降雨量。

Transpiration of a Pinus tabulaeformis and Robinia pseudoacacia mixed forest in Hilly-gully region of the Loess Plateau, West Shanxi Province

Understanding of the relations between plant and water is the key to successfully implement protective afforestation programs in the Hilly-gully region of the Loess Plateau,West Shanxi Province.Our study measured sap flow of 17 trees covering 4 diameter classes in a 16 years old Pinus tabulaeformis and Robinia pseudoacacia mixed forest stand from July to October in 2008 using Thermal Dissipation Probe（TDP） in Caijiachuan watershed in Jixian County,Shanxi Province.At same time,we also measured the changes of environmental factors.The diurnal fluctuation of sap flow velocity of Pinus tabulaeformis and Robinia pseudoacacia was experienced a significant difference in the starting time,time to peak,dramatic decreasing time,and lasting time duration of sap fow velocity.The diurnal transpiration rate increased against the diameter of breast height except for 6 and 12cm pine trees.We found that the solar radiation and vapor pressure deficit were the major factors to control the canopy transpiration of Pinus tabulaeformis and Robinia pseudoacacia.In addition,monthly stand transpiration scaled up from sapwood area were 30.8mm,24.1mm,26.3mm,and 18.4mm for July,August,September,and October,2008,respectively.The total transpiration amount during this four months period was less than the total rainfall amount during the same time.