Abstract: Soil respiration is the main way that the soil carbon pool releases CO₂ into the atmosphere, and there are obvious differences on the spatial scale. The spatial change of soil respiration increases the uncertainty of soil carbon emission assessment, so studying the spatial heterogeneity of soil respiration is of great significance for the accurate assessment of ecosystem carbon emissions. In this study, we randomly selected 30 plots along the east-west transect of Hulunbuir Grassland. We measured soil respiration of the plots by Li-8100 automatic instrument. The results indicate that along the east-west transect of Hulunbuir, the soil respiration rate is significantly decreased with a decrease in mean annual precipitation. The soil respiration rate under mowing utilization (3.36 μmol·m^-2·s^-1) is significantly higher than that under grazing utilization (1.87 μmol·m^-2·s^-1). Soil organic carbon content and aboveground biomass are the main factors that determine the spatial heterogeneity of soil respiration, and they explain 52% of the variation of soil respiration. Soil organic carbon and vegetation biomass directly affect soil respiration, and soil bulk density and soil moisture indirectly affect soil respiration. Changes in the spatial pattern of precipitation and disturbance of human activities are the main driving factors for the spatial heterogeneity of soil respiration in Hulunbuir grassland.

Key words: Hulunbuir, Soil Respiration, Spatial Heterogeneity, human activities, Precipitation Gradient

摘要： 土壤呼吸作用是土壤碳库向大气释放CO₂的主要途径，其在空间尺度上具有明显差异性，土壤呼吸的空间变化增加了土壤碳排放评估的不确定性，研究土壤呼吸作用空间异质性对于准确评估生态系统碳排放具有重要意义。2020年9月1日—9月6日，本研究沿呼伦贝尔草原东西样带随机选取了30个观测样地，利用土壤呼吸自动观测系统(Li-8100)测定土壤CO₂排放通量，并对其影响因子进行分析。结果表明：沿呼伦贝尔东西样带，随着降水量的减少，土壤呼吸速率显著减小；刈割利用下的土壤呼吸速率(3.36 μmol·m^-2·s^-1)显著大于放牧利用(1.87 μmol·m^-2·s^-1)；土壤有机碳含量和地上生物量是决定土壤呼吸空间异质性的主要因子，二者共同解释土壤呼吸变异的52%；土壤有机碳含量和植被生物量直接影响了土壤呼吸作用，土壤容重和土壤水分间接影响了土壤呼吸作用。降水空间格局变化和人类活动扰动是呼伦贝尔草原土壤呼吸作用空间异质性的主要驱动因素。

关键词: 呼伦贝尔, 土壤呼吸, 空间异质性, 人类活动, 降水梯度