Middle Reaches Of The Xilin River Floodplain Wetlands Of Different Communities Of Photosynthesis Research

In this paper,the methods of the determination for CO₂ absorption of different communities in high humidity climates were preliminarily studied in July and August 2007.On this basis,by means of connecting LI-7000CO₂/H₂O analyzer to the chamber,we studied the changes of CO₂ absorption of different communities in different bands throughout a day and seasons in Xilin river floodplain wetlands in July and August 2008.Based on a model,we also calculated the results of the CO₂ absorption of different communities and the relationship between the CO₂ absorption of different communities and specific environment.Therefore,we came to the following conclusions:1.In different communities of each band in wetland,the curves of diurnal variation of CO₂ absorption appear as either one-peak Gaussian or two-peak Gaussian.The general variation tendency of CO₂ absorption shows as follows:the CO₂ absorption was increased with the rise of the temperature and light intensity, arriving the peak around noon.After the light saturation point,it begin to declined with the further rise of the temperature light intensity.Then,it continues to decline with the falling of the temperature and light intensity.Two-peak Gaussian is usually resulted from water deficit. 2.There is no significant correlation between the CO₂ absorption of communities and aboveground biomass,so the standing crop can't be used to reflect the CO₂ absorption of communities in wetland.3.The CO₂ absorption of communities was measured after a restoring period when using the cutting method to stimulate grazing.The results show that moderate grazing can improve the photosynthetic rate,and,therefore,it improves the photosynthetic substances accumulation,eventually making the whole wetland community grow better.4.As two important environmental factors affecting the CO₂ absorption,the light intensity and the air temperature both show significant positive correlation with it.Based on this,letting light intensity and temperature as independent variables and CO₂ absorption as dependant variable,we established the optimal regression model of the CO₂ absorption and the environmental factors,which can be used to calculate the integrated CO₂ absorption of the whole growth season in the region.5.By stimulating and fitting the Matlab and Eviews models,we determined the total CO₂ absorption of the following different communities of the wetland from July to August in growing season:Poa subfastigiate Trin and Equisetum arvense community,Glyceria triflora and Equisetum hyemale community,Form Glyceria triflora+Carex appendiculata Community are flooding communities of complex communities,and Form Lathyrus quinguenervius community,Polygonum alopecuroides community,Competitive community,Cirsium esculentum community.the total CO₂ absorption of above communities respectively is: 7.79×10⁵,7.33×10⁵,8.83×10⁵,7.24×10⁵,7.78×10⁵,5.47×10⁵,5.42×10⁵(Units: mg.m^-2.77d^-1) Low floodplain plant communities of CO₂ absorption was significantly higher than that of the high floodplain plant communities.