三种温带树种叶片呼吸的时间动态及其影响因子

为认知叶片呼吸(RL)的季节变化格局及其影响因子,以东北东部山区3个主要树种(红松Pinus koraiensis、樟子松P.sylvestris var.mongolica和白桦Betula platyphylla)为对象,采用红外气体分析法在2011年生长季(常绿树4月至10月;落叶树6月至9月)测定了自然条件下叶片气体交换及其相关生理特征的季节变化,探索了RL与空气温度(Tair)和相关叶片特征之间的关系.结果表明:红松和樟子松基于叶面积的RL(RL-area)表现为生长季初期和末期较大,而白桦RL-area则随生长季进程而逐渐减小.在生长季中,RL-area与叶片总光合之比的时间动态明显.红松、樟子松RL-area与Tair关系显著,而白桦RL-area与Tair关系不显著;但3种树种基于叶质量的RL(RL-mass)与Tair均呈显著的指数函数关系.叶片特征(包括可溶性糖、淀粉、氮、比叶面积等参数)也有明显的季节变化.影响RL的叶片特征参数因树种而异,其中可溶性糖浓度对3种树种的RL均有显著影响.可见,RL的季节变化格局受树木的生长节律、温度和叶片特征的联合控制.

Temporal dynamics and influencing factors of leaf respiration for three temperate tree species

To understand the factors influencing seasonal variation in leaf respiration (R_L), the leaf gas exchange characteristics and related leaf traits were examined for three tree species in northeastern China. The species were Korean pine (Pinus koraiensis), Mongolian pine (P. sylvestris var. mongolica) and white birch (Betula platyphylla). The R_L, net photosynthetic rate, and air temperature (T_air) were measured in situ with an infrared gas exchange analyzer (LI-6400 IRGA) twice per month throughout the growing season in 2011 (from April to October for the pines; from June to September for the birch). Specific leaf area (SLA) was calculated from oven-dried leaf weight and projected leaf area; nonstructural carbohydrates (NSC) concentrations were determined by a modified phenol-sulfuric acid method; and leaf nitrogen concentrations were measured by the Kjeldahl method. A stepwise multiple regression procedure was applied to explore the relationships between R_L and leaf traits. The area-based R_L (R_L-area) of Korean pine and Mongolian pine peaked in early and late growing seasons, while the R_L-area of white birch declined gradually with the growing season proceeding. The ratio of R_L-area to total photosynthesis and leaf trait parameters (i.e., soluble sugar concentration, starch concentration, SLA, leaf nitrogen concentration) also exhibited seasonal variations for the three species. The R_L-area of pines were positively correlated with T_air, while that of the birch was not. The mass-based R_L (R_L-mass) of the three tree species, however, were all positively related with T_air in an exponential function. The leaf trait parameters affecting the R_L varied with species, and the soluble sugars concentration significantly influenced the R_L for all the species. These results suggest that seasonal variation in R_L jointly controlled by growth rhythm, temperature and leaf traits.