日本落叶松冠层光合生理参数的空间异质性研究

目的]比较日本落叶松不同冠层和方位光合生理参数的差异,探讨冠层及方位变化对光合生理参数的影响,为构建冠层生产力模型及估算冠层生产力提供理论参考。方法]以7年生和19年生日本落叶松单木为研究对象,将树冠分为上、中、下3层,东、西、南、北4个方位,测定冠层每一部位的光响应曲线、CO_2响应曲线和光合色素含量,并分析不同冠层及方位的光合生理特性。结果]表明:垂直方向上,2种林龄样木冠层对大多数光合生理参数影响显著;最大净光合速率(A_(max))、光饱和点(LSP)、光补偿点(LCP)和暗呼吸速率(R_d)随冠层的升高而增大;最大羧化速率(V_(max))、最大电子传递速率(J_(max))、磷酸丙糖利用率(TPU)和羧化效率(CE)均为下冠层最小,而CO_2补偿点(CCP)均为冠层下部最大;不同冠层针叶光合色素含量差异显著,且叶绿素a(Chla)、叶绿素b(Chlb)和类胡萝卜素(Car)均随冠层的升高而降低。水平方向上,方位对2种林龄树木光合生理参数均影响不显著,南向和东向光合参数均值分别反映了7年生和19年生样木全冠层的光合特性。光合生理参数在林龄间无显著差异。结论]日本落叶松冠层光合生理参数具有空间异质性,冠层对树木多数光合生理参数的影响显著,而方位和林龄对以上参数影响不显著。

Spatial Heterogeneity of Photosynthetic and Physiological Parameters in Larix kaempferi Crown

Objective] To compare the differences of photosynthetic and physiological parameters among crown layers and orientations, and then study the effects of crown layers and orientations on photosynthetic characteristics in Larix kaempferi, and to provide a sound theoretical foundation for developing canopy productivity model and accurately evaluating canopy productivity.Method] 7-year-old and 19-year-old Larix kaempferi were selected for researching gas exchange. The canopies of Larix kaempferi were divided into 3 layers equally and each layer was divided further into 4 orientations-east, west, south and north. The photosynthetic and physiological parameters, including light response curve, CO₂ response curve and photosynthetic pigment content, were measured on the needles in different canopy layers and orientations. Then the data were analyzed according to crownlayer.Results] Vertically, all photosynthetic parameters showed significant differences among canopies except apparent quantum yield in the sampled trees. The maximum net photosynthetic rate, light saturation point, light compensation point and dark respiration rate increased with raising crown in both stand ages of L. kaempferi. The maximum carboxylation rate, maximum electron transport rate, triose phosphate utilization and carboxylation efficiency in lower crown were lowest in all measured trees, while the maximum values of CO₂ compensation point existed in lower crown. There were significant differences exist in all photosynthetic pigments of different canopies in the selected trees. The Chla, Chlb and Car increased with declining crown in both stand ages. Horizontally, Orientation had no significant effect on photosynthetic and physiological parameters for the sampled trees. The mean values of photosynthetic parameters in the south and east represented photosynthetic characteristics of the whole crown of 7-and 19-year-old trees, respectively. There were no significant differences in photosynthetic and physiological parameters between 7-year-old and 19-year-old L. kaempferi.Conclusion] There are considerable spatial heterogeneity of photosynthetic and physiological parameters in L. kaempferi crown, and most of these parameters are affected significantly by crown layer, but not by orientation.