The Daily And Seasonal Change Research Of Strong Alkaline Soil Respiration In Qitai County

There is a huge capacity of soil inorganic carbon in arid and semi-arid region. It is the role of the whole area and even the global carbon cycle can not be ignored. This research adopts the LI- 8100 open type soil carbon flux measurement instrument measured soil respiration of strong alkaline soil where no vegetation growth, rarely organic matter content. Soil columns were gathered in field and sterilized in laboratory. By comparing the proportion of inorganic and organic soil respiration, determine the dominant way about soil respiration of strong alkaline soil. In the mean time, observed the soil respiration rate, temperature(air temperature and ground temperature), humidity(air relative humidity and soil moisture) in spring, summer and autumn. By analyzing the relationship between them, and through the pass analysis, got different seasons for the greatest impact on soil respiration directly impact factors and indirect factors. And then built different kinds of regression models. On the basis of the accuracy test and simple principle, got the optimal model of soil respiration in each season. And based on modeling factors discuss the mechanism of soil respiration seasonal change about strong alkaline. In addition, simulated soil respiration under winter low temperature environment in the indoor, and the changes under different rainfall intensity in the wild. Finally to show the soil respiration characteristics of strong alkali soil in different environments.The main results were as follows:(1)In strong alkali soil respiration, the inorganic part account for 99.37% of the total respiration. It dominated the daily variation and seasonal variation, so the influence of the organic part respiration can be ignored.(2)In spring and autumn, the highly significant correlation have achieved between soil respiration, air temperature, air relative humidity and soil moisture, and the strongest correlation is the soil respiration with air temperature. The soil respiration with four factors of temperature and humidity relationship were highly significant in the summer, and the correlation with ground temperature is the highest. Pass analysis shows that, the air temperature is the biggest direct impact factor in spring and autumn, but ground temperature is in summer. And the biggest indirect effect factor is the soil moisture in the three seasons. In addition, the coupling of temperature and humidity control the variation of soil respiration, The best prediction model is built by air temperature and soil moisture at 10 cm in spring and autumn, the estimate accuracy is 92.67% and 77.23%. However, the best prediction model of soil respiration in summer is four factor equation built by air temperature, ground temperature, air relative humidity and soil moisture at 10 cm. And the estimate accuracy is 84.99%.(3)The diurnal variation characteristics of soil respiration rate in spring and autumn presented a simple peak,its peaks appeared at 14:00 and 10:00,its release CO2 in daytime and absorb CO2 in nighttime,but as a whole its mainly release CO2 in spring(The emission is 0.07μmol·m-2·s-1),mainly absorb CO2 in autumn(The emission is 0.05μmol·m-2·s-1). The diurnal variation characteristics of soil respiration rate in summer presented double peaks, the first peak appear at 9:00~10:00, the second peak appear about 21:00, positive respiration at 5:00~11:00 and around 21:00, negative respiration at other times, as a whole its release 0.14μmol·m-2·s-1 CO2. Simulated soil respiration in the low temperature of winter, found that strong alkali soil can absorb large number of CO2, and the lower temperature, the greater amount of absorption.(4) For the mechanism of soil respiration change about strong alkali soil, mainly because of the chemical reaction in the soil carbonate(CaCO3) and H2O-CO2, it generate bicarbonate and absorb CO2, this let the night and low temperature during the day time soil respiration rates are negative. And high temperature period in the daytime, the bicarbonate can thermal decomposition releases CO2, but when the temperature reached a certain limit(air and ground temperature is 30℃ and 26℃ in 10 cm), high temperature inspired chemical reaction rate of carbonate and H2O-CO2, and absorb a large number of CO2, but the premise is the soil humidity shall be maintained at a high level.(5)The light rain inspired soil respiration, in the process of precipitation, it increased 320.69% than contrast, after precipitation that growth of 58.82%. 22 h later, the soil respiration rate back to the contrast. Moderate rain process in the precipitation process, it was down more than 48.27% than contrast, but after the precipitation that increased by 29.41%. 37 h later, the soil respiration rate back to the contrast. The heavy rain process makes strong alkali soil can absorb more CO2, precipitation process and after the precipitation of the soil respiration rate, decrease by 306.89% and 188.24% compared with contrast.