科尔沁沙地黄柳和小叶锦鸡儿茎流及蒸腾特征

利用Dynamax茎流测量系统、Li-6400光合作用仪和自动气象站分别对科尔沁沙地两种灌木树种黄柳和小叶锦鸡儿的液流变化、蒸腾速率及其周围的环境因子进行检测.研究结果表明：（1）黄柳、小叶锦鸡儿茎干液流通量密度日变化趋势基本相同,呈多峰曲线;液流启动时间分别为4：30、5：30,在13：00左右到达各自液流峰值,峰值大小为81.2～91.7mg/h、17.3～27.1mg/h,20：30降为最低,晚间均具有明显的液流活动现象.（2）灌木的茎流日变化曲线与蒸腾速率日变化曲线并不吻合,实验测得的叶片蒸腾速率不能同步反映茎干液流的动态变化特征;黄柳的叶片蒸腾速率和单枝蒸腾耗水量均大于小叶锦鸡儿,耐旱性相对较低.（3）黄柳、小叶锦鸡儿白天液流通量密度变化趋势与环境因子变化趋势相吻合.相关性分析表明,影响灌木液流变化的主要因子依次是太阳有效辐射、相对湿度、大气温度、风速、10cm和20cm土壤温度.

Characteristics of sap flow and transpiration of Salix gordejevii and Caragana microphylla in Horqin Sandy Land, northeast China

Both Salix gordejevii and Caragana microphylla are dominant shrub species on moving and semi-moving dunes in Horqin Sandy Land which are well adapted to the arid and infertile condition. There is still poorly understand concerning the differences and dynamics on the sap flow and transpiration of the two shrub species. Dynamax Sap Flow Measuring System, Li-6400 Portable Photosynthesis System and Automatic Weather Station System were used to simultaneously measure and monitor the sap flow velocity, leaf transpiration and related environmental factors of the two shrubs. Based on the analysis of the diurnal variations of stem sap flow and leaf transpiration, the results showed that the diurnal variations of sap flow velocity of the two species were as a multi-peaked curve. The sap flow of Salix gordejevii and Caragana microphylla started at 4:30 and 5:30 while stopped at 20:30, respectively. The maximum value of the sap flow velocity of Salix gordejevii was 81.291.7 mg/h, and that of Caragana microphylla was 17.327.1 mg/h in field situation. The diurnal sap flow of unit cross-section area of stem of Salix gordejevii and Caragana microphylla were 0.881.56 g/cm~2 and 0.641.34 g/cm~2, respectively. The diurnal variation curves of the sap flow and the transpiration velocity of the two shrubs were non-synchronous to each other, which implied the dynamic variation of the sap flow could not be substituted by that of their the transpiration velocity. The leaf transpiration and the water assumption of Salix gordejevii were more than that of Caragana microphylla, which implied that the drought tolerance of the Salix gordejevii was lower than that of the Caragana microphylla. The sap flow density of the two species was positively correlated with some ambient environmental factors. The order of their coefficient from correlation analysis was PAR (photosynthesis available radiation) > air relative humidity > air temperature > wind speed > soil temperature at 10cm depth > soil temperature at 20cm depth. These results are of importance for clarifying the principle of plant's water consumption and for explaining the adaptation processes and mechanisms of plants in arid and sandy environment.