三种植被恢复树种的冠层气孔导度特征及其对环境因子的敏感性

Characteristics of canopy stomatal conductance in plantations of three re-vegetation tree species and its sensitivity to environmental factors

应用Granier热消散探针,长期监测华南地区荷木、大叶相思和柠檬桉林不同径级样树的树干液流,结合同步观测的气象数据,求算冠层气孔导度(gc),并分析其对环境因子的响应方式及敏感性.结果表明:不同季节荷木林日间平均gc显著高于大叶相思和柠檬桉(P<0.05)(除3月外).在干季和湿季,gc与光合有效辐射(PAR)呈现对数正相关关系(P<0.001),湿季gc对PAR响应比干季更敏感.gc与水汽压亏缺(VPD)在干湿季均呈现对数负相关关系(P<0.001),同样在湿季表现出更高的敏感性.湿季gc与VPD的偏相关系数高于干季,VPD对气孔行为的调控作用在湿季更为明显.随着土壤含水量的降低,gc对VPD的敏感性下降,荷木和柠檬桉林下降的幅度大于大叶相思林,荷木和柠檬桉林下降的幅度相当.通过综合分析gc对环境因子(PAR和VPD)的敏感性及其对土壤含水量变化的响应规律,发现乡土树种荷木作为植被恢复树种比外来引种的大叶相思和柠檬桉更为适宜.

In plantations of three different re-vegetation tree species（ Schima superba,Acacia auriculaeformis and Eucalyptus citriodora） in southern China,the stem sap flow of individuals at different DBH classes were monitored using Granier＇s thermal dissipation probes. With synchronouslymeasured meteorological data,the canopy stomatal conductance（ gc） was determined and the responses of gcto environmental variables were analyzed. We found that daytime mean gcin S. superba forest on average was significantly higher than those of A. auriculaeformis and E. citriodora plantations du-ring a year（ except in March）. In the three plantations,gcwas positively logarithmically correlated with photosynthetically active radiation（ PAR）（ P〈0.001）,with a higher sensitivity of gcto PAR during wet season than that of dry season. By contrast,a negative logarithmical correlation between gcand vapor pressure deficit（ VPD） was observed,with a higher sensitivity of gcto VPD during the wet season. Additionally,a higher partial correlation coefficient between gcand VPD was observed during wet season,indicating that VPD played a more important role in regulating the behavior of stomata during wet season. In general,the sensitivity of gcto VPD decreased with the decreases of soil water content,but more manifest decreases were found in S. superba and E. citriodora forests than in A. auriculaeformis plantation,while the descend degree in S. superba and E. citriodora forests were equal. Overall,our results demonstrated that the native species S. superba is more suitable for re-vegetation in southern China than the exotic species A. auriculaeformis and E. citriodora.