北京灵山草地土壤CO_2源汇和排放通量与温度湿度昼夜变化的关系

The diurnal variations of soil CO_2 source, sink and flux in grassland of Lingshan Mts., Beijing and their relationships with temperature and soil moisture

大气中温室气体含量不断升高是造成目前全球变暖的主要原因,而土壤CO2是大气CO2的重要来源之一。研究表明温度、湿度是土壤CO2最主要的气候影响因素,通过对植物夏季雨后次日对土壤CO2排放过程中的源(不同深度土壤CO2体积分数)、汇(大气CO2体积分数)和中间CO2气体交换通量(土壤CO2排放通量)、气温、土温以及表土湿度进行同步连续的昼夜观察,研究日和小时变化尺度上温度和土壤湿度对CO2地气交换的影响。结果表明土壤CO2排放通量、大气CO2和土壤CO2体积分数的昼夜变化特征不一致,只有土壤CO2排放通量与气温变化存在明显的正相关关系,在日变化尺度上随表土湿度增加而增加;表土湿度在日变化尺度和小时变化尺度上与草丛空气CO2体积分数正相关;土壤CO2体积分数则在日变化尺度上当表土湿度较小时与表土湿度正相关。气温主要影响土壤CO2向大气的扩散和对流过程,而不是昼夜尺度上影响土壤CO2体积分数变化的主要环境因素。

The continuous increase of trace gases in atmosphere results in global warming. The soil CO_2 is believed to be one of ma- jor sources of atmosphere CO_2. The former studies have demonstrated that temperature and soil moisture are major climatic factors affecting soil CO_2. In this paper, the influences of temperature and soil moisture on the CO_2 exchange between atmosphere and soil are analyzed on diurnal and hourly scales by observing diurnal variations of the CO_2 source (soil CO_2 concentrations at different depths), the CO2 sink (atmospheric CO_2 concentration), the soil CO_2 emission flux, air and soil temperatures, and soil moisture. It is found that the diurnal variations of the soil CO_2 emission flux, CO2concentrations in atmosphere and soil air are different. The soil CO_2 emission flux increases with the soil moisture increasing on the diurnalscale and is positively correlated to the air temperature. The air CO_2concentration in tussock is positively correlated to the soil moisture on the diurnaland hourly scales. The CO_2concentra- tion in soil air is positively correlated to the soil moisture on the diurnal scale when the soil moisture is lower. The air temperature mainly influences the diffusion and convection processes of soil CO_2 and is not a major factor changing the soil CO_2 concentration on the diurnal scale.