关键词: 库布齐沙地, 油蒿, 光合作用, 环境因子

Abstract:

The photosynthesis of Artemisia ordosica as a dominant species and other principal species, and their relations to environmental factors have been studied by us using portable LI 6000 photosynthesis measure system in Hobq desert form June to September in 1996. Results show that the photosynthesis of Artemisia ordosica and others have similar diurnal variation and trend which have bi peak and noon depression. The rate of photosynthesis (PH) of A. ordosica increases as environmental factors such as active radiation and air temperature increase, but relative air humidity factor is not including. The first peak of photosynthesis of A. ordosica emerges during 10~12 a.m., and its second peak appears during 14~16 p.m.. There is a depression between two peaks at the photosynthesis curve of A. ordosica, which followed the second peak PH of A. ordosica decreases gradually. A. ordosica and other species similarily acclimatized to environmental conditions, but there are still some differences in different species. For example, different plant's PH noon depressions are dramatically changeable, meanwhile peaks emerging time vary in spite of their lying same period. Noon depression maybe relate to high active radiation, hight air temperature and low air humidity because these factors can result in stoma closing, and CO₂ exchange is also handicapped by these. PH of A. ordosica has obviously seasonal variation, it rises from April and reaches the highest in August, then declines gradually. The above ground biomass (AGB) of A. ordosica reaches the highest value in September and it is behind the PH peak (August). We consider that AGB represents the accumulation of photosynthesis, but PH is only instant value which indicates plant's photosynthesis trait in measuring time. The photosynthesis is affected by lots of environmental factors, meantime the environmental factors influence each other. The importance of the factors are active radiation (PAR) relative humidity (RH) air temperature (AT) by pathanalysis, and the multiple regression equation is PH=0.295+0.000994PAR+0.00174RH-0.0011AT(P=0.0000001).

Key words: Hobq sandy land, Artemisia ordosica, photosynthesis, environmental factors