东江中上游4树种水势日变化特征及其与环境因子的关系

Diurnal Changes of Water Potential of the Four Tree Species and Its Relationships with Environmental Factors in the Upper and Middle Reaches of Dongjiang River

在东江中上游,以6a生树种木荷、红锥、火力楠和藜蒴为材料,采用PSYPRO露点水势仪对4树种在旱季与雨季的土水势、根水势、茎水势和叶水势日变化过程进行了测定,探讨了4树种在自然生境下的水势梯度变异及叶水势与气象因子的关系。结果表明,叶水势日变化均呈"单峰"型曲线,日均值表现为木荷>火力楠>红锥>藜蒴,旱季叶水势明显低于雨季;叶水势与大气温度(Ta)和光合有效辐射(PAR)呈极显著负相关(P<0.01),而与空气相对湿度(RH)和大气水势(Фa)呈极显著正相关(P<0.01),气象因子对东江流域主要造林树种叶水势直接作用由大到小结果如下:火力楠和藜蒴(Ta>RH>Фa>PAR),红锥(RH>Фa>Ta>PAR),木荷(Ta>Фa>RH>PAR)。

By using PSYPRO water potential apparatus,six-year-old Schima superba,Castanopsis hystrix,Michelia macclurel,and Castanopsis sfissa,in the upper and middle reaches of Dongjiang River were selected as experimental materials to measure diurnal changes of soil water potential,root water potential,stem water potential,and leaf water potential of four tree species in rainy and dry season,and study on the variations of water potential gradient,and analyze the relationship between leaf water potential and meteorological factors of four tree species in natural habitats.The results showed that the daily water potentials of leaves of four tree species presented single-peak curve.The means of daily water potential of Schima superba was the highest,followed by Michelia macclurel,Castanopsis hystrix,and Castanopsis sfissa respectively.The leaf water potential of four tree species was significantly lower in dry season than that in rainy season（P0.05）.Leaf water potential showed significantly negative correlations with air temperature（Ta） and Photosynthetic Active Radiation（PAR）,and significantly positive correlations trend with relative air humidity（RH） and air water potential（Фa）,respectively（P0.01）.In addition,the meteorological factors which had a directly effect on the leaf water potential of the four species in Dongjiang watershed showing the following order： TaRHФaPAR for Michelia macclurel and Castanopsis sfissa,RHФaTaPAR for Castanopsis hystrix,and TaФaRHPAR for Schima superba.