广西典型水库集水区巨尾桉和马尾松蒸腾作用

Transpiration of Eucalyptus grandis × E. urophylla and Pinus massoniana in typical reservoir watershed in Guangxi

选择广西公净水库,开展集水区范围内2种主要木本植物巨尾桉(Eucalyptus grandis×E.urophylla)和马尾松(Pinus massoniana)群落蒸腾速率(Tr)、叶面积指数(LAI)和相关环境因子的现场观测,结果表明:马尾松蒸腾速率的季节变化为0.14~0.69μmol·m-2·s-1,<2年龄巨尾桉为1.65~3.76μmol·m^(-2)·s^(-1),>4年龄巨尾桉为1.05~2.04μmol·m-2·s-1,<2年龄巨尾桉和>4年龄巨尾桉年均蒸腾速率均高于马尾松,分别是马尾松的6倍和3.4倍。2种植物蒸腾速率均是夏季最高,冬季最低,夏季蒸腾速率约是冬季的2倍。相关分析结果显示,2种植物蒸腾速率均与叶面积指数、土壤含水率和林下空气温度呈极显著正相关(P<0.01),但各影响因素并不是独立作用于蒸腾速率的。通径分析结果表明,林下空气温度和土壤含水率对马尾松蒸腾速率起主导作用,是主要决策变量;叶面积指数和土壤含水率分别是<2年龄和>4年龄巨尾桉蒸腾作用的主要决策变量。

Field measurements of transpiration rate（ Tr）,leaf area index（ LAI）,and related environmental factors were conducted for two typical woody plant communities（ Eucalyptus grandis× E. urophylla and Pinus massoniana） in the watershed of the Gongjing Reservoir in Guangxi,China. Results showed that the seasonal change of Trof Pinus massoniana was 0.14-0.69 μmol·m-2·s-1,and that of 〈2-year-old and 〉4-year-old Eucalyptus was 1.65-3.76 μmol·m^（-2）·s^（-1） and 1.05-2.04 μmol·m^（-2）·s^（-1）,respectively. The Trof 〈2-year-old and 〉-year-old Eucalyptus was 6 times and 3.4 times that of P. massoniana,respectively. The Trwas highest in summer and lowest in winter for all plants,and Trin summer was nearly twice as high as in winter. Significant positive correlations were found between Trand LAI,soil water content and air temperature（ P0.01）; all factors influencing transpiration were not independent. Path analysis results showed that air temperature and soil water content were the key variables for transpiration in P. massoniana. LAI had the greatest effect on transpiration of younger Eucalyptus,while soil water content was the key variable for older Eucalyptus.