黄土高原常见造林树种光合蒸腾特征

Characteristics of photosynthetic and transpiration of three common afforestation species in the Loess Plateau

为改善黄土丘陵沟壑区水土流失现状,该区长期以来开展了大量的植被建设,但是,植物的适应性及生长状况如何,还不十分清楚。为探讨造林树种对环境的适应性,从光合、蒸腾和生理生态指标出发,对黄土高原3个主要退耕还林树种:刺槐、沙棘、山杏的适应性进行了研究,并对其适宜性进行了评价。研究结果表明:沙棘不同坡位最大净光合速率Pmax、光补偿点LSP较其它两个树种占明显优势,特别是在上坡位Pmax、LSP分别达到了22.8μmol·m-·2s-1、520μmol·m-·2s-1,具有较高的同化代谢能力,该物种较适应该地区的强光环境,适宜种植于阳坡或坡顶;山杏LSP相对较低,而表观量子效率α明显高于沙棘、刺槐,并在下坡位达到最大值0.069,说明它主要利用弱光进行光合作用,适宜种植于阴坡或坡脚等弱光环境中,但由于山杏水分利用效率WUE较低,可能对环境带来不良影响,山杏叶片含水量为65.1%,明显高于其它两个树种,而叶绿素含量仅为0.94mg/g与刺槐沙棘的2.34mg/g和2.00mg/g相差很大,这可能是导致其WUE较低的一个原因;刺槐在上坡位的光合生理参数与山杏相差不大,但是随坡位下降其α、净光合速率Pn较山杏明显偏低各个坡位受限明显,容易形成老头树。

The characteristics of photosynthetic and transpiration of three common afforestation species （Robinia pseudoacia, Hippophae rhamnoides, Prunus arrneniaca） were studied in order to reveal their adaptability to environment in the Loess Plateau. Results showed that： All the tree species are sun plants. Pmax （Maximum net photosynthetic rate） and LSP （ Light saturation point） of Hippophae rhamnoides in different slope aspects were obviously higher than the other two species. Hippophae rhamnoides With low a could not efficiently use the light of low intensity （ 〈 200μmol· m^-2·s^-1）, and a high WUE in upper slopes allowed it to appropriate use the limited water resources, Therefore this species was acclimated in upper and sunny slopes. With intensity. It was acclimated in 1 low LSP and high α, Prunus armeniaca tended to carry out photosynthesis with light of low ower or shaded slopes. But the low WUE implied potential a harm to environment. In contrast to Prunus armeniaca, αand Pn of Robinia pseudoacia decreased obviously downslope, while they were almost the same at the upper slope. The WUE exhibited a shape of parabola along with photosynthetic active radiation （Ⅰ） with a peak between 400 and 800 μmol· m^-2·s^-1 Leaf water content in Prunus armeniaca was significantly higher than in the others, while the chlorophyll content was relatively low. This is the reason of low level WUE of Prunus armeniaca.