热带季节雨林生态系统净光合作用特征及其影响因子

以西双版纳热带季节雨林生态系统为对象,利用涡度相关系统定量分析了2003-2006年该生态系统光合作用特征及其环境控制因子.结果表明： 2003-2006年西双版纳热带季节雨林生态系统净光合作用年际变化较小,其最大光合速率(P_eco,opt)、昼间呼吸速率(R_eco,d)和表观量子效率(α)平均值分别为-0.813 mg·m^-2·s^-1、0.238 mg·m^-2·s^-1和-0.0023 mg·μmol^-1受气温(T_a)和饱和水汽压差(VPD)等环境因子的交互影响,不同季节生态系统光合作用特征有所差异.雨季的降水量大、气温较高,生态系统的光合能力最强;雾凉季的浓雾为植物提供了部分水分,其光合水平仍较高;干热季气温较高、降水少,T_a和VPD升高,P_eco,opt和α下降.净生态系统CO₂交换主要受>20 ℃的T_a和>1 kPa VPD的影响.

Net photosynthesis and its affecting factors in a tropical seasonal rainforest ecosystem in Southwest China

By using eddy covariance technique, this paper quantitatively analyzedthe photosynthetic characteristics of tropical seasonal rainforest ecosystem and related environmental controlling factors in Xishuangbanna in 2003-2006. In the study period, less interannual difference was observed in the net photosynthesis of the ecosystem, with the maximum photosynthesis rate (P_eco,opt), respiration at daytime (R_eco,d), and apparent quantum yield (α) averaged by 0.813 mg·m^-2·s^-1, 0.238 mg·m^-2·s^-1, and 0.0023 mg·μmol^-1, respectively. As affected by the interaction of air temperature (T_a) and vapor pressure deficit (VPD）, the photosynthetic characteristics had some seasonal differences. In rainy season, the ecosystem had the strongest photosynthetic capacity because of the higher precipitation and warmer air temperature; in foggy and cool season, fog drip played an important role in the water relations of plants, and thereby, the ecosystem photosynthetic capacity was still higher; in dry and hot season, due to the limited precipitation and high temperature, the T_a and VPDincreased, inducing a decrease of ecosystem α and P_eco,opt. The net CO₂ exchange of the ecosystem strongly depended on the T_a above 20 ℃ and the VPD above 1 kPa.