新疆肖塘冬季土壤呼吸特征及影响因素

Characteristics and Affecting Factors of Soil Respiration in the Northern Margin of the Taklimakan Desert

采用LI-COR8150多通道土壤碳通量观测系统对塔克拉玛干沙漠北缘肖塘地区盐碱地和流沙地土壤的冬季呼吸速率、土壤温度、含水量的日变化动态进行定位连续监测,并深入分析土壤水热因子对呼吸速率的影响。结果表明:(1)肖塘地区盐碱地和流沙地的土壤呼吸速率较低,具有明显的日变化规律,并会因土壤类型的不同而有微弱差异,总体上均呈不对称"钟形"的单峰型曲线。(2)夜间及凌晨2类土壤的呼吸速率多为负值,表明该时段土壤成为碳元素的汇集区,然而在日尺度上沙漠地区仍属于碳源,但相对较为微弱。(3)盐碱地和流沙地的土壤呼吸速率与土壤表层0~5cm平均温度均具有较为一致的昼夜变化趋势,且分别存在极显著的线性和指数回归关系。温度敏感性指数Q10在2类土壤中均较小,其中盐碱地Q10相对较大。(4)土壤呼吸速率与土壤表层0~5cm平均含水量在盐碱和流沙两地昼夜变化趋势均较为一致,且存在极显著的线性关系。(5)相对于单因素影响下的一维回归方程,土壤温度和含水量对土壤呼吸速率的二维回归方程能够更好地解释土壤呼吸随时间的变化情况,且土壤温度和含水量对于土壤呼吸速率均表现出明显的时滞效应。

Soil respiration is one of the most sensitive ecosystem processes to climate change,but is little known in desert ecosystems.The spatial and temporal changes in soil respiration directly influence the local and regional carbon budgets.In order to understand the controlling factors of soil respiration in desert ecosystem,we selected Xiaotang,in the northern margin of the Taklimakan Desert,as a site to analyze daily variation of soil respiration and its relationship with soil temperature and soil water content for two soil types(saline-alkali land and shifting sandy land).Soil respiration was measured by a LI-8150 soil CO2 efflux system from21 January to 31 January in 2013.The observation indicated that:(1)Soil respiration rates for the two types of soil were relatively slow,but showed obvious diurnal patterns,which displayed a single peak curve with the maximum rate occurring between 13:00-15:00.(2)On nights,most of the soil respirations were negative at the two types of soil,which indicated that soil had evident carbon sink functions.But in days,the desert soil was a weak carbon source.(3)The daily variation trends of soil respiration rates were fairly consistent with soil temperature at 0-5 cm depth for the two types of soil.Linear and exponential model could effectively describe the relationship between soil respiration rate and soil temperature at 0-5 cm depth in saline-alkali land and shifting sandy land,respectively.The Q10 values for the two types of soil were kept at a lower level,among them the Q10 values of saline-alkali land was relatively larger.(4)There was a significant linear relationship between soil respiration rate and soil water contents at 0-5 cm depth.(5)Two-dimensional regression of soil temperature and soil water content could better explain daily variation of soil respiration than one single factor regression.Moreover,the soil temperature and soil water content on soil respiration rate were respectively showed the significant hysteresis effect.