Characteristic Of Carbon Exchange And Its Response To Environmental Factors Of Saline Desert Ecosystem

Saline desert has high vegetation coverage and soil salinization degree, with zonal and broadly representative. As in previous studies, most of the studies are on the grassland, forest, farmland ecosystem,less on the study of the desert ecosystem. Based on the in situ measurement of soil CO₂ flux and laboratory experiments, we studied the characteristics of carbon exchange and its influence factors at saline desert.The study was conducted at Hutubi station of ecological and grassland, Xinjiang Agricultural University.Soil respiration and carbon exchange was measured with Li-8100 Automated Soil CO₂ Flux System and Li-840 CO₂/ H₂ O Infrared analyzer, measuring temperature and soil moisture content at the same time; The change characteristics of inorganic CO₂ flux in soil after sterilization was measured by LI-840 CO₂/ H₂ O Infrared analyzer and analysis the correlations between temperature and inorganic CO₂ flux. The main conclusions are as follows:1 soil respiration under the canopy were significantly higher than that in bare land?P<0.05? at saline desert, soil respiration under the canopy and bare land showed a different diurnal variation, Except the night fluctuation, In addition to the October bare land showed a single apex curve at daytime, the rest is double apex curve, while soil respiration under the canopy showed single apex curve, however, due to sudden increase of CO₂ flux At night, So there was another peak in the night from July to September.2 soil respiration was weakly correlated with temperature and soil water content. However, under the suitable conditions of temperature and soil moisture, soil respiration was highly correlated with temperature,the correlation between soil respiration and air temperature in September was 0.973, which was extremely significant correlation?P<0.01?. In May, due to the reason of the rain and the high temperature at noon, the soil respiration was negatively correlated with the temperature.3 The ecosystem respiration?Re? and plant autotrophic respiration?Ra? showed a apex curve; Net ecosystem carbon exchange?Nee? in June, July and September owed a different trend with May and August. Due to the high temperature, the growing season in July and June showed a weak carbon source.Although August has a higher soil water content, but diurnal average ecosystem respiration in both Juneand July are higher than that in August, this shows that the temperature plays a leading role of ecosystem respiration?Re? and plant autotrophic respiration?Ra?. Except August, plant autotrophic respiration?Ra?accounted for the proportion of total respiration was higher in the daytime than at night.4 The ecosystem respiration?Re? respiration and plant autotrophic?Ra? showed a high correlation with temperature, the correlation between the two and the air temperature was the highest, followed by 5 cm soil temperature, 10 cm soil temperature. Plant autotrophic respiration?Ra? in the monthly variation and diurnal variation showed higher correlation than the ecosystem respiration?Re? with temperature. Due to the high temperature and the changes in soil respiration at night, the net ecosystem carbon exchange?Nee? is not related to the temperature.5 During the In situ measurement of soil CO₂ flux, during the night, the negative value of soil CO₂ flux increased to positive value from the previous period, compared with the two time periods, the temperature increased during the night. In the laboratory, the inorganic CO₂ flux was absorbed at sterilized soil when temperature decreased and constant, and released in the heating up state. Inorganic CO₂ flux has a very significant positive correlation with the change of temperature, the faster the temperature falls, the higher the CO₂ absorption, the faster the temperature rise, the faster the inorganic CO₂ release. In the constant temperature state, the inorganic CO₂ flux is mainly derived from the reaction of inorganic salts.