西双版纳季节雨林网脉核实幼树光合特性的季节动态

Seasonal dynamics of photosynthetic characteristic for sapling of Drypetes perreticulatain the understory of tropical seasonal rain forest in Xishuangbanna,China

【目的】揭示热带季节雨林中幼树个体的生物学特性及林下更新的适应机制,为全球气候变化下山地森林资源的开发与保护提供科学依据。【方法】选择西双版纳热带季节雨林中生长于林下的网脉核实幼树,分别在雾凉季(1月)、干热季(4月)和雨季(7月),利用Li-6400光合作用测定仪,测定其光合光响应特征及光合速率日变化的季节动态特征。【结果】林下网脉核实幼树叶片的最大净光合速率(Pnmax)为雨季>干热季>雾凉季,分别为4.105,3.021和2.125μmol/(m2.s),季节间存在显著差异;在人工光源下,雨季的气孔导度(Gs)、蒸腾速率(Tr)和水分利用效率(WUE)均相对更高,最大值分别达到0.149,1.733mmol/(m2.s)和7.632mmol/mol。网脉核实幼树在林下自然光照环境中,雾凉季、干热季、雨季一天中净光合速率(Pn)最大值分别为0.652,1.192和1.975μmol/(m2.s);各季节中,Pn、Gs、WUE等的日变化进程均表现为双峰型特征,但峰值出现的时间存在差异。【结论】热带季节雨林网脉核实幼树在林下的光合作用受季节变化的影响较大,Pn、Gs、Tr、WUE等总体上呈现出雨季最大、雾凉季最小的特征。

【Objective】 The study revealed the biological characteristics of saplings in tropical seasonal rain forest and its adaptive mechanism of update in the understory,which can provide scientific foundation for mountainous forest resources development and protection under global change.【Method】 The light response curves and diurnal change of photosynthesis for sapling of Drypetes perreticulata were measured with Li-6400 in understory in tropical seasonal rain forest in Xishuangbanna.This experiment was developed in fog-cool season,dry-hot season,and rainy season respectively.【Result】 The maximum net photosynthetic rate（Pnmax） for sapling of D.perreticulata in understory was 4.105 μmol/（m2·s） in rainy season〉3.021 μmol/（m2·s） in dry-hot season〉2.125 μmol/（m2·s） in fog-cool season.There existed marked differences among seasons;The stomatal conductance（Gs）,transpiration rates（Tr） and water use efficiency（WUE） were higher in rainy season than in other seasons,and their max values were 0.149,1.733 mmol/（m2·s） and 7.632 mmol/mol respectively.When at an environment of natural illumination in the understory,the maximum of net photosynthetic rate（Pn） for sapling of D.perreticulata was 1.975（rainy season）,1.192（dry-hot season） and 0.652（fog-cool season） μmol/（m2·s） respectively;The diurnal process of Pn,Gs and WUE showed a ＂bimodal pattern＂ in every season,but the occurrence timing of peaks value was different among seasons.【Conclusion】 The photosynthesis of sapling of D.perreticulata was largely influenced by change of seasons.Overall,Pn,Gs,Tr and WUE were the highest in rainy season and the lowest in fog-cool season.