湿地松改造林分冠层结构及树种光合特征研究

Study on the Tree Photosynthesis Characteristics and Canopy Structures of Pinus elliottii Transformation Forests

低效林林分改造是提高森林效益的重要技术。为探讨南亚热带湿地松林分改造在冠层结构和光能利用上的效益,对广东省中山市五桂山区长命水村2个湿地松(Pinus elliottii)与乡土阔叶树种改造的混交林和对照湿地松纯林的冠层结构和光合作用进行了对比研究,结果表明,(1)在林冠结构方面,湿地松-荷木(Schima superba)等7种阔叶树种混交林改造效果明显,光能利用较为充分;林冠开度以对照样地最大,达38.75%,显著大于2个林分改造样地;叶面积指数以湿地松-荷木等7种阔叶树种混交林最大,达2.26,显著高于其他样地。(2)在光合作用方面,各改造树种之间各项光合指标均呈现显著差异。光能利用率以樟树(Cinnamomun camphora)和黎蒴(Castanopsis fissa)最好,樟树的净光合速率、气孔导度、蒸腾速率、环境光合有效辐射分别为12.08μmol·m^(-2)·s^(-1)、0.18 mmol·m^(-2)·s^(-1)、2.43 mmol·m^(-2)·s^(-1)、302.60μmol·m^(-2)·s^(-1),黎蒴的净光合速率、气孔导度、环境光合有效辐射分别为7.98μmol·m^(-2)·s^(-1)、0.11 mmol·m^(-2)·s^(-1)、309.66μmol·m^(-2)·s^(-1),这两个树种的这些光合指标在各树种中都排前两名。对照地湿地松光能利用率比改造地湿地松好,对照地湿地松的净光合速率、气孔导度、胞间CO_2浓度、蒸腾速率、环境光合有效辐射分别为3.13μmol·m^(-2)·s^(-1)、0.06 mmol·m^(-2)·s^(-1)、267.19μmol·mol-1、0.83 mmol·m^(-2)·s^(-1)、85.87μmol·m^(-2)·s^(-1),均大于改造地湿地松。

Stand improvement plays an important role in promoting ecological benefits of low-efficiency forests.In order tounderstand the effects of forest transformation on south subtropical Pinus elliottii forests,canopy structures and photosynthesis of twomixed forests of P.elliottii with native broad-leaved tree species and a P.elliottii pure forest were investigated in Chang mingshuivillage,Wuguishan district,Zhongshan city,Guangdong province.Results showed that,(1)the mixed forest of P.elliottii and sevenbroad-leaved tree species(Schima superba,etc)showed a significant improvement effect and higher utilization of light energy in thecanopy structure.Canopy openness of the pure forest(38.75%)was significantly higher than that of two transformed stands,and thelargest leaf area index was observed in the mixed forest of seven broad-leaved tree species,which was significantly higher than that ofother stands.(2)Photosynthetic physiological indices significantly differed among transformation tree species.Light utilizationefficiency was highest in Cinnamomun camphora and Castanopsis fissa trees,and the net photosynthetic rate,stomatal conductance,transpiration rate and photosynthetically active radiation of Cinnamomun camphora were12.08μmol·m-2·s-1,0.18mmol·m-2·s-1,2.43mmol·m-2·s-1,302.60μmol·m-2·s-1,respectively;the net photosynthetic rate,stomatal conductance,transpiration rate andphotosynthetically active radiation of Castanopsis fissa were7.98μmol·m-2·s-1,0.11mmol·m-2·s-1,309.66μmol·m-2·s-1,further more,the above photosynthetic indices ranked the top two among all the species.The light utilization efficiency of P.elliottii in the purestand was higher than that of transformed stands.The net photosynthetic rate,stomatal conductance,intercellular CO2concentration,transpiration rate and photosynthetically active radiation of P.elliottii in the pure stand were3.13μmol·m-2·s-1,0.06mmol·m-2·s-1,267.19μmol·mol-1,0.83mmol·m-2·s-1,85.87μmol·m-2·s-1,respectively,which were higher than those in the transformed stands.