羊草和大针茅群落光合速率的比较研究

本研究用同化箱法，在野外条件下测定了羊草群落和大针茅群落的光合速率日进程和季节变化。得到如下结果：1；在整个生长期中，测得羊草和大针茅两群落光合速率的日进程都属双峰型，上、下午，各有一个高峰，但一般以上午峰值较高。2．羊草和大针茅两群落日净光合量的季节变化趋势是相似的。自返青后迅速的提高，到7月上旬达最大值，羊草和大针茅两群落的日净光合量分别为31.68和11.5 gCO2／m2d，随后逐渐降低。3.两群落光合能力的大小，峰值的高低和出现的早晚、中午光合降低的幅度以及季节变化的特点等都与植物生长发育阶段和环境条件有密切的关系。 4．羊草群落各阶段的瞬时光合、日净光合，LAI和生物量等都高于相近时期的大针茅群落。但在环境条件较差(干旱)时，羊草群落光合增加的幅度要比环境条件好时小。5．大针茅群落要比羊草群落耐旱，对不良环境的适应能力强，但在条件较好时增产幅度小。

A COMPARATIVE STUDY OF THE COMMUNITY PHOTOSYNTHESIS OF ANEUROLEPIDIUM CHINENSE AND STIPA GRANDIS

In natural condition, the diurnal and seasonal changes in the photosyn-thetic rates of Aneurolepidium chinense and Stipa grandis were measuredby means of a simulation chamber. The chief results obtained are as fo-llows: 1. The types of diurnal changes in the photosynthetic rates of Aneuro-lepidium chinense and Stipa grandis all showed double peak curves. Thehigh peak appeared in the morning and afternoon respectively. But thepeak values in the morning always were higher than those of the afterno-on. 2. The trends of seasonal changes in the diurnal net photosynthesisof two the communities were similar. The diurnal net photosynthetic rateincreased rapidly from the period of turning green to the beginning ofJuly, their maxmum values were 31.68 and 11.5gCO_2/m~2d respectively,and after then they gradually decreased. 3.The photosynthesis abilities of the plants, the values of the peaksand their appearance times, the fall range of photosynthesis at noon andthe characteristic of the seasonal changes etc. of the two communitieswere closely correlated with the characteristics of the plants growth andenvironmental conditions. 4. The instantaneous photosynthetic rate, diurnal net photosynthe-sis, LAI and biomass of the Aneurolepidium chinense community were hi-gher than those of the Stipa grandis one,but under poor(drought) enviro-nmental conditions, the increase of the photosynthesis of Stipa grandiswas less than under good conditions. 5. Stipa grandis community was more drought resistant than Aneurole-pidium chinense commumity, but its productivity increase under good co-nditions was less.