The Study Of Evapotranspiration And CO₂ Absorption In Different Steppe Communities

Applying means of connecting LI-6262CO2/H2O analyzer to the chamber,this paper studied on the changes of evapotranspiration and CO2 absorption of different communities across a day and growing season in typical steppe July and August 2003 .Analysing the relationships among evapotranspiration, CO2 absorption and their environment by statistic means ,we came to such conclusions:1 Degraded communities were characterized by physical process evaporation and lower water efficiency,while communities with good vegetations were distinguished by their biological process evapotranspiration and higher water efficiency. There was water resources not used in degraded communities because of their less evapotranspiration under the similar precipitation conditions.2 Light intensity and temperature were the two important environmental factors affecting evapotranspiration.Let light intensity and temperature as independent variables and evapotranspiration as dependant one,establish model among them in order to calculate evapotranspiration of the whole growth season across the region.3 Capacity of water use, evapotranspiration and ecological use of water decreased along with the deterioration of communities so that the minimum values existed in the communities degraded seriously and increased along with the recovery successionof degraded communities and came to the maximum values in the climax ones.For those reasons,we could regard them as standard that weigh the degree how the communities degraded and how they recovered.4 Quantity of CO2 absorption was mainly affected by vegetation conditions.Initial communities that had little dead litter were the sink of CO2 across the whole growth season,while the ones that degraded seriously were the source of itlnitial communities had dead soil covering were the sink of CO2 only when their photosynthesis got to the peak.