塔克拉玛干沙漠腹地流沙下垫面土壤呼吸特征及影响因素分析

通过LI-COR8100A土壤碳通量观测系统分别于2013年1月、5月、10月和11月进行了塔克拉玛干沙漠腹地塔中流沙下垫面土壤呼吸速率测定试验,并分析了相应的土壤水热因子对呼吸速率的影响。结果表明:塔克拉玛干沙漠腹地土壤呼吸速率整体偏低,但具有明显的昼夜波动性和季节变化特征。研究区流沙土壤中可能存在的无机碳过程是导致夜间及凌晨的土壤呼吸速率为负值,白天为正值的主要原因。不同时段的土壤呼吸速率(Rs)分别与土壤表层0~5 cm平均土壤温度(T)和湿度(W)间存在较为同步的昼夜变化趋势且具有良好的回归关系。相对于单因素影响的回归分析,土壤温、湿度的协同作用能够从整体角度更好地解释土壤呼吸速率的变化情况。回归方程Rs=a+bT+cW和Rs=a+bT+cW+dTW可解释不同时段土壤呼吸速率76.0%以上的变化情况。这说明土壤温、湿度是控制土壤呼吸速率的主要环境因子。沙漠腹地土壤极低的水分条件成为土壤呼吸的限制性因子,呼吸速率对于作为限制性因子的土壤湿度的变化响应则更加直接,而对于土壤温度变化的敏感性就有所下降,导致土壤呼吸速率与土壤温度回归关系出现明显的时滞环现象。

Analysis on characteristics and effects factors of soil respiration with different time periods in the hinterland of the Taklimakan Desert

In this paper, an automated soil CO2 flux system (model LI-8100A fitted with a LI-8150 multiplexer, LI-COR, NE, USA) was used to measure soil respiration of shifting sandy land in the Tazhong area in the hinterland of the Taklimakan Desert in January, May, October and November of 2013. The effects of soil temperature and soil water content at 0-5 cm depth on soil respiration rates were also analyzed. The results showed that the soil respiration rates of shifting sandy land in the different time periods were low, and had obvious diurnal fluctuation and seasonal variation. There could be hiding the process of inorganic carbon in the sandy soil, which was probably the main reason for the desert hinterland was a carbon sink at night and early morning, and a carbon source in the day. The daily variation trends of soil respiration rates in the different time periods were fairly consistent with soil temperature and soil water content at 0-5 cm depth. And soil temperature and soil water content at 5 cm depth both have good regression relationships with soil respiration rates for the different time periods. From the overall perspective, two-dimensional regression of soil temperature and soil water content could better explain daily variation of soil respiration than one single factor regression. The equations Rs=a+bT+cW and Rs=a+bT+cW+dTW could explain >76.0% of the variation of soil respiration in the different time periods. This showed that soil temperature and soil water content were the main environmental factors controlling soil respiration. In the Taklimakan desert hinterland, the extremely low soil water content was identified as a limiting factor affecting the variation of soil respiration. Soil respiration was more directly responsive to variation of soil water content, but low sensitive to soil temperature, resulting in a distribution of regression points between soil respiration and soil temperature indicating a hysteresis loop at some times.