温度和水分对羊草草原土壤呼吸温度敏感性的影响

采用静态暗箱-气相色谱法对内蒙古锡林河流域羊草(Leymus chinensis)草原土壤呼吸进行测定,研究了温度和水分条件对土壤呼吸温度敏感性系数Q_(10)值的影响.结果表明羊草草原土壤呼吸与5cm地温具有很好的指数关系(r~2=0.338～0.858,P<0.001～0.08),Q_(10)介于1.15～2.25之间,均值为1.72.Q_(10)值与5 cm地温呈负相关关系(r~2=0.407),而与0～10 cm土壤水分含量呈显著的二次函数关系(r~2=0.872,P<0.05).在较低含水量时Q_(10)值随着水分含量的上升而增大,当土壤水分含量较高时转而减小.以往大多数研究认为Q_(10)值与土壤水分含量呈正相关关系,这可能是土壤水分跨度不足造成的,极端的水分条件对Q_(10)值具有重要影响.

Effect of temperature and moisture on temperature sensitivity of soil respiration of Leymus chinensis steppe

Soil respiration rates were measured with static opaque chamber-chromatographic technique in an experimental plot of IMGERS (Inner Mongolia Grassland Ecosystem Research Station). The effect of soil temperature and moisture on temperature sensi-tivity of soil respiration was studied. Soil respiration increased exponentially with soil temperature at 5 cm depth (r~2=0.338～0.858, P<0.001～0.08). The temperature sensitivity of soil respiration (Q_<10>) has been widely used in estimating soil respiration rate. A small change in Q_<10> could cause a significant variation in the modeled soil respiration flux. Therefore, accurately quantifying Q_<10> and its variability is crucial for estimating ecosystem carbon budget. Our research showed that the Q_<10> values ranged from 1.15 to 2,25 with an average of 1.72. The Q_<10> value was negatively correlated with soil temperature at 5 cm depth, however, it related to soil moisture (0～10 cm) with a significant quadratic function (r~2=0.872, P<0.05). In contrast to other reports that Q_<10> value was positively corre-lated with soil moisture, our result showed that this positive correlation existed only when soil moisture was relatively low and Q_<10> decreased when soil moisture nearly reached the field moisture capacity. Extreme soil water conditions will significantly affect the estimate of Q_<10>.