热带季节雨林生态系统净光合作用特征及其影响因子

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

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(Peco,opt)、昼间呼吸速率(Reco,d)和表观量子效率(α)平均值分别为-0.813mg·m-2·s-1、0.238mg·m-2·s-1和-0.0023mg·μmol-1.受气温(Ta)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,Ta和VPD升高,Peco,opt和α下降.净生态系统CO2交换主要受>20℃的Ta和>1kPaVPD的影响.

By using eddy covariance technique,this paper quantitatively analyzed the 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 ob- served in the net photosynthesis of the ecosystem,with the maximum photosynthesis rate （ Peco,opt） , respiration at daytime （ Reco,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 （ Ta） 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 Ta and VPD increased,inducing a decrease of ecosystem α and Peco,opt. The net CO2 exchange of the ecosystem strongly depended on the Ta above 20 ℃ and the VPD above 1 kPa.