Soil Respiration Dynamic Change Of Oasis Cotton Field And Desert Vegetation In Ebinur Lake Basin

The arid area is special and important geography unit, which is more sensitive to the climatic change. Study of the respiration and its affecting factors in the arid for in-depth understanding the global carbon cycle has the great significance.The soil respiration rate and environmental factors were determined in the cotton field, Populus euphratica, Phragmites australis community of desert ecosystem in the Ebinur Lake Basin, using a LI-8100 automated soil CO2 flux system during the plant growing period(June and September),we also evaluated the influence of temperature and soil moisture on soil respiration rate, eventually reveal the soil respiratory change rule of desert area for the moisture content to lacks and the soil more barren, and provides the foundation experimental datum of the desert ecosystem in china for the global carbon cycle research. The major results were summarized as follows:⑴After the desert land was cultivated and became oasis, the content of soil organic matter and soil moisture increased,total salt decreased significantly, pH value didn't change that significant. The microbial community composition and microbial numbers were resulted in a significant difference. Soil total salt is the main factor in this area.⑵In the cotton field, diurnal variation of soil respiration rate showed a single peak, the soil respiration rate reached the highest at 11:00 to 15:00.In the desert plants community, the soil respiration rate showed rule less diurnal variation, sometimes showed a single peak, the soil respiration rate reached the highest at 9:00 to 13:00.According to the mean soil respiration rate and seasonal amplitude during the plant growing season, its pattern was observed in order of thirty-year cotton field >three-year cotton field>sixteen-year cotton field>Populus euphratica community>Phragmites australis community. The soil respiration rate of several communities showing a similar diurnal variation dynamics with air temperature and soil surface temperature.Soil respiration increased congruously with increasing soil temperature, but the time appearing of maximum temperature lagged that of maximum respiration rate.⑶The mean soil respiration of cotton field is about 4.93 times than desert plants communities. That's means after the desert land was cultivated and became oasis, the soil respiration rate was increased. From the diurnal variation and season variation, cotton field was higher than desert plants communities.Phragmites australis community showed negative during night in soil respiration.⑷Through the research,we find the soil respiration rate showed high correlation with soil temperature(10~15cm) and air temperature(10cm).The fitting curve of soil respiration rate in desert plant communities indicate those result three times polynomial model preferably descript the change situation of soil respiration rate. So the air temperature is main factor to soil respiration change in various plant communities. The value of Q10 was different which range were between 1.196~1.908 according to the air temperature (10cm).⑸The humidity of the plant communities in September is higher than in June, the soil respiration rate and air relative humidity showed a negative correlation. The soil respiration rate and air relative humidity(10cm) was related more closely, the correlation coefficient were reach more than 0.9. The peak and low value of soil respiration rate with soil moisture content(0~20cm) is almost changes in synchronization, there is a significant positive correlation, but the relevance of non-obvious impact on the temperature.⑹In order to analyze soil respiration synergies, we select surface temperature, soil temperature and air relative humidity (10cm) as variables. The results showed that the air relative humidity (10cm) is the closest factor for the soil respiration rate, fitting model can explain over 90% of the plant community changes in soil respiration.⑺The content of soil nutrients in five different sites was ranked as follow: thirty-year>Populus euphratica>three-year>sixteen-year>Phragmites australis.The amount of microorganism was ranked as follow: thirty-year>sixteen-year>three-year>Populus euphratica>Phragmites australis.The biomass in cotton field was ranked as follow: thirty-year>sixteen-year>three-year, which are the same with amount of microorganism.