Soil Respiration And Affecting Factors Of The Desert Plant Communities In The Northwest Junngar Basin

The arid area is the special and important geography unit, which is more sensitive to the climatic change. Study of the soil respiration and its affecting factors in the arid area for in-depth understanding the global carbon cycle has the great significance.The soil respiration rate and environmental factors were determined in the Haloxyon ammodendron, Anabasis sp, Halostachys Caspica, Tamarix ramosissima - Phragmites communis community of desert ecosystem in the northwest Junngar Basin, using a LI-8100 automated soil CO2 flux system during the plant growing period (from May to October in 2006), 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:â‘ In the Haloxylon ammodendron community, diurnal variation of soil respiration rate showed a double peak in July, the soil respiration rate reached the highest at 10:00 and 16:00, the rest month showed a single peak ; In the Anabasis aphylla L community, the soil respiration rate showed ruleless diurnal variation in July,August and October,the time of the peak and nadir value is different, the rest month showed a single peak;In the Tamarix ramosissima - Phragmites communis community, diurnal variation of soil respiration rate showed a fluctuant curve that both single peak and double peak; In the Halostachys caspica community, the soil respiration rate showed a well-regulated single peak. In the every community, maximum rate of CO2 emission appeared at 12:00-14:00 and minimum at 8:00 in the early morning or 20:00 at night when it showed a single peak. 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.â‘¡Soil respiration rate of four plant communities had significant seasonal dynamics, they all showed a single-peak curve. The soil respiration rate of three desert communities reached the highest in June, soil respiration rate of Tamarix ramosissima - Phragmites communis community reached the highest in July, and soil respiration rate of all communities reached the lowest in October. In the plant growth season,the seasonal dynamics of soil respiration rate in all communities had quite similar dynamic patterns with soil temperature.Soil respiration rate was higher in summer and lower in autumn. According to the mean soil respiration rate and seasonal amplitude during the plant growing season, its pattern was observed in order of Tamarix ramosissima-Phragmites communis community >Haloxyon ammodendron community > Anabasis sp community > Halostachys Caspica community.The soil respiration rate had significant difference between the different community and not significant within the same community.â‘¢There existed a distinct relation between soil respiration and soil temperature of each layer in the Tamarix ramosissima - Phragmites communis community, and nearly no relations in the Haloxylon ammodendron community.Correlation analysis showed that soil respiration rate of Anabasis sp, Halostachys Caspica community significantly correlated with air temperature, soil temperature at surface, 5cm and 10cm depth .The relationship between soil respiration rate (Y) and air temperature, soil surface temperature (X) could be described by the Cubic regression equation(P<0.01),which soil surface temperature and soil respiration is better correlation.â‘£Soil water content was another important factor affecting soi1 respiration rate,but in this region, the relationship between soil respiration and soil moisture was poor.Correlation analysis showed that soil respiration rate correlated with 20~30cm,30~40cm of soil moisture significantly in the Haloxyon ammodendron and Halostachys Caspica community, and no distinct relationship was shown in the Tamarix ramosissima - Phragmites communis and Anabasis L community.