西双版纳5种乔木对CO_2摩尔分数倍增的响应

Ecophysiological Responses of Five Tree Species to Elevated Carbon Dioxide Concentration in Xishuangbanna,China

使用LI-6400便携式光合作用测定仪测定了西双版纳地区5种乔木在CO2摩尔分数从360μmol.mol-1倍增加到720μmol.mol-1倍生理生态指标的变化。结果表明:5种植物光合作用都有明显提高趋势,但提高幅度不同,幅度范围25%～118%,耐荫树种(云南玉蕊、大叶白颜树)提高幅度高于喜光树种。表观量子效率均提高,幅度范围7.8%～45.7%。华南石栎、红木荷和大叶白颜树发生光抑制,发生光抑制时的叶温和饱和水汽压差(VDP)较其他热带地区叶温和饱和水汽压差(VDP)小。水分利用效率(WUE)均明显提高,其中红木荷提高幅度最大为367%,千果榄仁最小为77%。气孔导度均降低,其中红木荷降低幅度最大为70%,大叶白颜树降幅最小为25%。暗呼吸作用均下降。要全面认识森林生态系统对CO2摩尔分数升高的响应程度,应在更大空间和时间尺度上进行环境因子与植物生理研究。

An experiment was conducted to study the changes in ecophysiological indexes of five tree species in Xishuangbanna using portable LI-6400 photosynthesis system when carbon dioxide concentration varied from 360 to 720 μmol·mol-1.Result showed that the net photosynthetic rates of the five tree species all increased with the elevation of carbon dioxide concentration,with an increase in the range of 25 percent and 118 percent.The increasing range of the shade-tolerant tree species was higher than that of the intolerant tree species.Apparent quantum yield of photosynthesis of the five tree species increased,with an increase ranging from 7.8 percent to 45.7 percent.Photosynthetic light responses of Lithocarpus fenestrate,Schima wallichii,Gironniera subaequalis were inhibited under high leaf temperature（Tl） and vapor pressure deficit（VPD）.However,the values of Tl and VPD resulted in photoinhibition of L.fenestrate, S.wallichii,G.subaequalis were lower than those of some tree species in other tropical zones.Water use efficiency of all the tree species increased obviously with the increase of carbon dioxide concentration,and the increasing range for S.wallichii was the maximum（367%） and that for T.myriocarpa was the minimal（77%）.Stomatal conductance of all the tree species decreased,and S.wallichii exhibited the maximum increasing range（70%） and G.subaequalis showed the minimal one（25%）.Dark respiration rate of all the tree species also decreased.Studies on environmental factors and plant physiology at large time-space scales should be carried out to make a full understanding of responses of forest ecosystems to the elevated carbon dioxide concentration.