塔河中游不同生境天然胡杨林木的光合与蒸腾特性

Photosynthetic and Transpiration Characteristics of Natural Populus euphratica Forests in Different Habitats in the Middle Reaches of the Tahe River

利用CIRASⅡ光合测定系统对塔河中游不同生境下生长的中龄林天然胡杨林光合生理参数进行测定比较,探究天然胡杨林对不同生境适应和响应机制。结果表明,中生生境条件下的天然胡杨林最大净光合速率(Pnmax)极显著高于其他生境下生长的胡杨林,旱生生境下天然胡杨林LSP、LCP和Rd显著低于中生和水淹生境。天然胡杨林除了Tr外,Pn、胞间CO_(2)浓度、Gs和WUE对光强敏感,其中胞间CO_(2)浓度与光强呈显著线性负相关;不同生境下Tr、胞间CO_(2)浓度和Gs之间差异极显著(P<0.01),而Pn和WUE差异不显著(P>0.05),但其大小有差别。中生生境下天然胡杨林表现较强的生活力,表现为更高的光合速率(16.71μmol·mol^(-2)·s^(-1))、水分利用效率(2.40μmol·mmol^(-1))以及低蒸腾速率(6.33 mmol·m^(-2)·s^(-1));旱生生境下通过关闭气孔来降低水分散失并使通过气孔进入叶片的CO_(2)减少、引起Ci下降,致使Tr下降(17.18%)大于Pn降幅(7.20%),从而提高水分利用效率来适应干旱环境;水淹生境下天然胡杨林的大部水用以维持其较高蒸腾,用于合成有机物的水分较少,降低水分利用效率。因此,塔河中游的天然胡杨林在高温、高湿、光照强烈和干旱的生境呈现出不尽相同的生态适应策略。

The photosynthetic and physiological parameters of the naturally occurring Populus euphratica forests occurring in the middle reaches of the Tahe River were compared and studied by using photosynthesis measurement system CIRAS II(Hansha UK).We explored the adaptation and response mechanism natural P.euphratica forests in different habitats.The results showed that the maximum net photosynthetic rate(Pnmax)of of the forests under the moderate habitat was significantly higher than that of other habitats.The 1ight saturation point(LSP),1ight compensation point(LCP)and dark respiration rate(Rd)of the forests under the of xerophytic habitat were significantly lower than those of the moderate and flooded habitats.In addition to transpiration rate(Tr),Pn,intracellular CO_(2) concentration(Ci),stomatal conductance(Gs)and water use efficiency(WUE)were sensitive to light intensity.The Ci and light intensity had significant linear negative correlation.The Ci and Gs of Tr were significantly different in the three habitats(P<0.01),while Pn and WUE were not significantly different(P>0.05).However,there were differences in their sizes.In the moderate habitat,the forests showed stronger living capacity,with higher values of Pn(16.71μmol·mol^(-2)·s^(-1)),WUE(2.40μmol·mmol^(-1))and lower transpiration rate(6.33 mmol·m^(-2)·s^(-1)).In xerophytic habitat,the forests could reduce the loss of water by closing the stomata and decreasing the CO_(2) that entered the leaves which caused the decrease of Ci.On this condition,Tr decreased by 17.18%,7.20%greater than Pn,thus improving WUE to adapt to arid environment.In the flooded habitat,most of the water in the forest was used to maintain its high transpiration,while less water was used to synthesize organic matter,which reduced WUE.Therefore,the natural P.euphratica forests in the middle reaches of the Tahe River presented different ecological adaptation strategies in the habitats of high temperature,high humidity,intense light and drought.