青藏高原东缘林线交错带4种不同功能型物种的光合特性

Photosynthetic Characteristics of Different Functional Types in a Timberline Ecotone on the Eastern Tibetan Plateau

【目的】初探青藏高原东缘林线交错带4种不同功能型植物糙皮桦(Betula utilis)、金顶杜鹃(Rhododendronfaberi)及中华羊茅(Festuca sinensis)和羽裂凤毛菊(Saussurea bodinieri)的叶氮浓度和光合特征。【方法】使用Li-6400便携式光合测定仪器测定4种不同功能型植物光合特征,使用单因素方差分析检验物种间变量差异显著性。【结果】4种植物的叶氮浓度都较高;光响应曲线相对一致;最大同化速率、暗呼吸速率和光补偿点都表现为糙皮桦显著高于其他3者;表观量子效率在4种植物间没有明显差异;而金顶杜鹃和中华羊茅的光饱和点远高于糙皮桦和羽裂凤毛菊的;4种植物CO2响应曲线存在一定差异,最大羧化速率和电子传递速率都表现为木本>草本,而磷酸丙糖利用率、CO2补偿点及羧化效率没有一致规律。【结论】相对于草本和灌木,乔本对环境变化的响应更为敏感。

[Objective] The aim of the present study was to investigate leaf photosynthetic charac- teristics of four different functional types （Betula utilis, Rhododendron faberi, Festuca sinensis and Saussurea bodinieri） in a timberline ecotone on the eastern Tibetan Plateau. [Method] The gas exchange of four functional types was measured with an Li-6400 portable photosynthesis sys- tem. Comparisons of variables among species were analyzed by one-way ANOVA. [Results] All of four species had relatively high leaf nitrogen concentration. Their light response curves were similar. The maximum net assimilation rates （A ）, dark respiration rates （Rd） and light com- pensation points （LCP） of B. utilis were significantly higher than ones of the other three species, respectively. There was no significant difference in apparent quantum yield （AQY） among the species. However, the light saturation points （LSP） of R. faberi and F. sinensis were significant- ly higher than those of B. utilis and S. bodinieri. Additionally, The CO2 response curves of four species exhibited slight differences. The maximum carboxylation rates and rates of photosyntheticelectron transport of woody plants were significantly higher than those of herbs, respectively. Nevertheless, there were no uniform patterns in triose phosphate use （TPU）, carbon dioxide compensation point and carboxylation efficiency （CE） among different functional types. [Conclu- sion] The results obtained in our study indicated that responses of trees to environmental changes are more sensitive in comparison with shrubs and grasses.