不同放牧制度下短花针茅荒漠草原土壤呼吸动态研究

Dynamics of soil respiration under different grazing systems in a Stipa breviflora desert steppe

采用动态密闭气室法(IRGA),对短花针茅荒漠草原土壤呼吸进行野外定位观测,分析了生长季不同放牧制度土壤呼吸速率的日变化、季节变化及其与环境因子的关系。结果表明,1)不同放牧制度下短花针茅荒漠草原土壤呼吸日、季节动态差异不大,日动态受温度影响呈单峰曲线,季节变化主要受到水分因子的影响;2)与自由放牧土壤呼吸日均速率(0.449 7μmol CO2/m2.s)相比,划区轮牧(0.504 7μmol CO2/m2.s)在干旱月份较大,围栏禁牧(0.529 5μmol CO2/m2.s)除生长季初都显著增大,但纵观整个生长季,不同放牧制度下土壤呼吸均值差异不显著;3)土壤呼吸日均速率与气温的相关性大于与土壤温度的相关性,水温复合模型较单因子模型更好地解释土壤呼吸速率的变化;4)划区轮牧和自由放牧较围栏禁牧增大了土壤呼吸的温度敏感性(水分充足时),降低了土壤水分对土壤呼吸的影响。研究表明,不同的放牧方式对土壤呼吸速率及其环境因子效应影响较小,围栏禁牧较自由放牧改变了土壤呼吸日均速率及水热因子效应。

Using a dynamic enclosed chamber（IRGA）,the effects of grazing systems on diurnal and seasonal variation of soil respiration in Stipa breviflora desert steppe were studied.1） There was no significant difference between grazing systems in diurnal or in seasonal variation.The diurnal variation of soil respiration could be expressed as a single peak curve,and the seasonal variation was mainly affected by soil moisture.2） The daily mean soil respiration rate was significant lower in continuously grazed plots（0.449 7 μmol CO2/m2·s） than that in rotationally grazed（0.504 7 μmol CO2/m2·s,in dry months）,or in non-grazed plots（0.529 5 μmol CO2/m2·s,throughout the growing season,except the first month）,but there was no significant difference among different grazing systems in seasonal mean soil respiration rate.3） Correlation of soil respiration diurnal variation with air temperature was greater than that with soil temperature,and a water-temperature composite model was better than a single-factor model to explain the changes in soil respiration rate.4） Compared with non-grazing,rotational grazing and continuous grazing elevated the temperature sensitivity of soil respiration（adequate moisture）,while reducing the impact of soil moisture on soil respiration.It was concluded that the soil respiration rate and effect of environmental factors were similar between rotational grazing and continuous grazing,and there were differences between continuous grazing and non-grazing in daily mean soil respiration rate and effect of environmental factors in S.breviflora desert steppe.