关键词: 林线交错带, 功能型, 光响应曲线, CO2响应曲线

Abstract: [Objective] The aim of the present study was to investigate leaf photosynthetic characteristics 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 system. 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_max), dark respiration rates(R_d) and light compensation 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 significantly 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 photosynthetic electron 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. [Conclusion] The results obtained in our study indicated that responses of trees to environmental changes are more sensitive in comparison with shrubs and grasses.

Key words: timberline ecotone, functional type, A-PAR curve, A-C_i curve