密云水库上游流域土壤有机碳和全氮密度影响因素研究

为揭示影响密云水库上游流域土壤有机碳(soil organic carbon,SOC)和全氮(total nitrogen,TN)密度的主要因子,采用野外采样、实验室分析和数理统计分析相结合的方法,研究了气候(温度和降水)、地形(海拔和坡度)、土壤理化性质(土壤容重、含水量、pH值和黏粒含量)以及土地利用方式等因素对SOC和TN密度的影响.结果表明,密云水库上游流域森林、草地、农田这3种土地利用类型表层(0～20 cm)SOC密度分别为4.77、6.79和2.90 kg.m-2,TN密度分别为0.41、0.69和0.30kg.m-2,3种土地利用类型之间SOC和TN密度差异显著(P<0.05);土壤含水量、土地利用方式、坡度、土壤pH值和黏粒含量是影响SOC密度的主要因子,土地利用方式、土壤黏粒含量和含水量则是影响TN密度的主要因子;气候、地形、土壤理化性质等区域环境因子共同解释了SOC和TN密度变异性的63.6%和53.4%,而环境因子和土地利用方式对SOC和TN密度变异性的综合解释程度分别为67.6%和57.8%.土地利用对SOC和TN密度变异性的贡献相对于环境因子而言较小,因此,建立高空间分辨率的区域环境因子数据库将是精确估算区域土壤碳氮贮量的关键环节.

Factors Controlling Soil Organic Carbon and Total Nitrogen Densities in the Upstream Watershed of Miyun Reservoir, North China

Effects of climate (temperature and precipitation), topography (elevation and slope), soil properties (soil bulk density, pH, water and clay contents) and land use on soil organic carbon (SOC) and total nitrogen (TN) densities were investigated in the study to identify dominant factors controlling SOC and TN densities in the upstream watershed of Miyun Reservoir of North China by soil sampling, laboratory analysis and statistical analysis. Results showed that SOC and TN densities in the 0-20 cm soil layer were 4.77 kg·m^-2and 0.41 kg·m^-2 in forestland, 6.79 kg·m^-2 and 0.69 kg·m^-2 in grassland, 2.90 kg·m^-2 and 0.30 kg·m^-2 in cropland, respectively. Significant differences in SOC and TN densities were observed among the three land uses. Soil water content, land use, slope, soil pH and clay content were the most significant factors controlling SOC density, while land use, soil clay and water contents were the most significant determinants of TN density. Climate, topography and soil properties jointly explained 63.6% and 53.4% of SOC and TN densities variability, respectively, while environmental factors and land use together explained 67.6% and 57.8% of variations in SOC and TN densities, respectively. Clearly, environmental variables were more important for SOC and TN densities variability than land use in the study area. Therefore, establishing a high-spatial-resolution database of environmental factors is a key to more accurate assessments of SOC and TN stocks on a regional scale.