水热因子对沙漠地区土壤呼吸的影响

利用Li-6400-09土壤呼吸室和Li-6400便携式光合测定仪,在植物生长季对腾格里沙漠东南缘植被区和流沙区的土壤呼吸进行了连续测定,并分析了温度和水分对土壤呼吸的影响.结果表明:(1)植被区和流沙区土壤呼吸速率的日变化特征相似,即夜间土壤呼吸速率保持在较低的水平,而白天则呈现单峰变化趋势;而季节变化趋势明显不同,即植被区内的土壤呼吸有明显的季节变化,流沙则没有明显的季节变化;(2) 植被区和流沙区0～5cm土壤含水量与土壤呼吸速率均呈显著的线性关系,但植被区的相关性好于流沙区.当0～5cm土壤含水量大于测定期间的平均值 (植被区为6.78%、流沙区6.94%)时,植被区和流沙区的土壤呼吸速率都明显高于土壤含水量小于平均值时的土壤呼吸速率,其土壤呼吸速率平均值之比分别为:2.6、1.5;(3) 土壤呼吸速率与地表5cm处土壤温度呈显著的指数关系,当土壤含水量小于测定期间的平均值时,植被区与流沙区的Q10值分别为1.23和1.43;当土壤含水量大于测定期间的平均值时,植被区与流沙区的Q10值分别为2.23和1.72.由此可见,土壤水分不仅影响了土壤呼吸速率的大小,而且还影响了土壤呼吸速率的温度敏感性.

Effects of heat and water factors on soil respiration in desert area

To investigate the effects of soil temperature and soil moisture on soil respiration, we measured soil respiration rates of a revegetated area and a shifting sand area in the Tengger Desert using the Li-6400-09 soil respiration chamber technique. Results showed that: (1) soil respiration rates remained low at nighttime and exhibited a single-peak curve at daytime from April to October, and compare to the shifting sand area, a remarkable seasonal variation occured in the revegeteated area; (2) soil respiration rate was linearly correlated with volumetric soil moisture in the 0-5 cm layer, and a more significant correlation was obtained in the revegetated area than in the shifting sand area (R2=0.27, p<0.01, revegetated area; R2=0.10, p=0.03, shifting sand area). In addition, when the volumetric soil moisture was higher than its mean value during the experiment period (6.78% for revegetated area; 6.94% for shifting sand area), soil respiration rates were distinctly higher than when the volumetric soil moisture was belowed the mean value, with the ratios between them were 2.6 and 1.6 for the revegetated area and the shifting sand area, respectively; (3) an exponential model can be used to describe the relationship between soil respiration and soil temperature at depth of 5 cm. The calculated Q10 values were 1.23 and 1.43 when the soil moisture was lower than its mean value, and 2.23 and 1.72 when it was higher than its mean values for the revegetated area and the shifting sand area, respectively. Thus, we conclude that the soil moisture affects not only the soil respiration rates, but also the sensitivity of soil respiration to temperature in the Tengger Desert