内蒙古农牧交错区不同土地利用方式下土壤呼吸速率及其温度敏感性变化

2009年8-10月, 采用动态气室法观测了内蒙古农牧交错区多伦县农田、弃耕和围封3种土地利用方式下, 土壤呼吸速率从6:00到18:00的变化规律, 分析了不同深度的土壤温度与土壤含水量对土壤呼吸速率的控制作用。结果表明, 空间尺度上, 不同土地利用方式的土壤呼吸速率由高到低依次为: 农田>弃耕>围封; 时间尺度上, 土壤呼吸速率在6:00-18:00的变化趋势为单峰曲线, 在12:00-15:00达到峰值, 随后降低, 在18:00基本恢复到6:00左右的呼吸水平, 同时, 土壤呼吸速率在9、10月显著降低。利用Van’t Hoff指数模型研究不同深度土壤温度对土壤呼吸速率的影响发现, 10-15 cm深度的土壤温度对土壤呼吸速率的影响最为显著, 其中, 土壤呼吸温度敏感性由高到低分别为: 农田>围封>弃耕。相反, 由于8-10月土壤含水量变化较小, 故土壤含水量与土壤呼吸速率间的相关性不显著, 土壤含水量不能解释该时段土壤呼吸速率的变化。

Variations of soil respiration rate and its temperature sensitivity among different land use types in the agro-pastoral ecotone of Inner Mongolia

Aims Our objectives are to compare soil respiration rate and its temperature sensitivity at different land use types and discuss soil respiration response to soil temperature (T_s) and soil water content at different soil depths. Methods Periodic measurements of soil respiration rates (R_s) were made during August–October 2009 with a LI-8100 portable automated soil CO₂ flux system in three agro-pastoral ecotone land use types: cropland, abandoned cultivated land and grazing enclosure. Soil temperature and soil water content at 0–5, 5–10 and 10–15 cm depths were measured simultaneous adjacent to the soil collar. Important findings R_s is significantly different among the three land use types and greatest in cropland. R_s exhibited a unimodal curve during 6:00–18:00, with a maximum during 12:00–15:00. R_s decreased with T_s, so R_s was significantly higher in August than in September and October. With the Van’t Hoff model, we concluded there is a positive, exponential relationship between measured T_s and R_s. In addition, temperature sensitivity of soil respiration (Q₁₀), which is derived from the Van’t Hoff model, was largest in cropland. In contrast, R_s was negatively related to soil water content in different soil depths at the sites.