青冈常绿阔叶林主要植物种叶片的光合特性及其群落学意义

 青冈(Quercus glauca)林乔木层主要树种叶片的净光合速率日进程在春夏季晴天均有明显午休。常绿树种的光合速率在秋季最高，大量换叶期最低，冬季仍有一定的净光合量。落叶树种的光合速率和光合产量低于常绿树种，随着群落的发育其地位将降低。青冈和石栎(Lithocarpus glaber)的光合速率接近，但青冈能够利用较弱的光，因而其高叶量的树冠具有较高的光合总量，以保持其在群落中的优势种地位；石栎主要利用较强的光，其较低叶量的树冠可以维持较高的光合总量，以保证其次优势种地位。灌木、草本层种类光合日进程均为单峰型。灌木种类对光的需求较高。蕨类植物耐荫强，因而在林中能占有稳定的伴生地位。

CHARACTERISTICS OF THE LEAF NET PHOTOSYNTHESIS OF THE EVERGREEN BROAD LEAVED FOREST DOMINATED BY QUERCUS GLAUCA AND THEIR SIGNIFICANCE IN COENOLOGY

The diurnal courses of the net photosynthesis(Pn)of the main tree species in the evergreen broad leaved forest dominated by Quercus glauca under clear day in spring and summer showed significant midday decrease.The net photosynthesis of the evergreen species was the highest in autumn and the lowest when the plants were in the period of concentrate change of leaves.They still had Pn in winter.The photosynthetic rate of summer green species was the highest in autumn too,but it began to defoliation in the end of October,when the environment was still suitable for photosynthesis.That caused the summed lower Pn in the year of summer green species compared with the evergreen species,and their status would decrease in the development of the community.Between the two evergreen species, Quercus glauca can use the weaker light,that would ensure the dense crown having a higher Pn and keeping its dominated status in the community. Lithocarpus glaber Preferred to use stronger light.Their fewer leaves and the relative sparse crown could meet the require for light so as to get high photosynthesis and keeping its status of subdominant species.The diurnal course of Pn of the shrub and herb species in the community were the single peak type.Two shrub species, Loropethalum chinense and Lindera aggregata required relatively high light.The pteridophyta Woodwaria japonica had stronger shade tolerance and higher Pn,so it would become the stable accompany species in the community.