放牧对赖草草地土壤呼吸日、季动态的影响

Effect of Grazing on Diurnal and Seasonal Dynamics of Soil Respiration Rate of Leymus secalinus Communities

土壤呼吸是土壤碳向大气排放的关键过程,受土地利用变化的强烈影响。利用LI-840a静态箱法,对放牧利用下赖草(Leymus secalinus)草地土壤呼吸速率日、季动态进行为期2年(2012–2013)的观测,并分析其与大气、土壤温度和土壤含水量的相关性,旨在为合理利用赖草草地提供依据。结果表明,赖草草地土壤呼吸日、季动态均呈单峰型变化,一天中的最高值出现在午间13点,凌晨4点最低,在生长季初的5–6月和生长季末的9月较低,在生长旺盛期7–8月较高。放牧降低了土壤呼吸速率,但并不改变土壤呼吸速率的变化趋势。土壤呼吸速率日变化与大气温度呈显著相关(P<0.05),季节变化主要受0–10 cm土壤温度的调控。围封和放牧草地土壤呼吸速率可以分别用下列方程拟合:Rs=1.040 8e0.086Ts(R2=0.91,P<0.01);Rs=1.016e0.075 2Ts(R2=0.95,P<0.01)。经综合分析得出如下结论:温度是影响赖草草地土壤呼吸速率的主要因素,放牧通过改变土壤表层温度而降低土壤呼吸速率。

Soil respiration, as a key process in soil CO2 emission, is strongly affected by land-use change. To explore the factors affecting carbon cyclic processes of Leymus secalinus communities under grazing, we measured diurnal and seasonal dynamics of soil respiration by the closed static chamber technique（LI-840a） during 2012 and 2013 to provide some basis for the rational use of L. secalinus communities. Furthermore, we analysed the correlation of soil respiration and air temperature, soil temperature, and soil moisture content. Diurnal and seasonal dynamics of soil respiration rate showed a unimodal distribution, with the peak value occurring at about 13：00 and the lowest at 4：00; the peak soil respiration rate appeared in July and August and the lowest in May, June and September. During the growing season, grazing could reduce the soil respiration rate, but the trend in rate did not significantly change. Diurnal dynamics of soil respiration rate was significantly correlated with air temperature. Seasonal dynamics of soil respiration rate was mainly regulated by the temperature of the 0- to 10-cm soil layer. We found an exponential model that could simulate the relationship between soil respiration rate and surface-layer temperature. Using the model, the caculated Rs were 1.040 8e0.086Ts（fencing plots） and 1.016e0.075 2Ts（grazing plots）. Temperature was the main factor affecting the soil respiration rate of L. secalinus communities, and grazing could decrease the soil respiration rate by changing the surface layer temperature.