1985—2015年陕西黄土台塬表层土壤有机碳空间分布

中尺度范围土壤有机碳的长期动态变化状态对大气温室气体的浓度、当地环境的生态效应至关重要。论文研究了陕西黄土台塬近30 a表层（0~20 cm）土壤有机碳密度的空间分布特征,并探讨了气候、地形、土壤类型、土地利用与土壤有机碳密度和储量的关系。结果表明：1）近30 a黄土台塬土壤有机碳密度和储量呈增加趋势,且增加幅度愈来愈明显,其中,1985—2000年有机碳密度和储量的增量分别为0.20 kg/m²和1.46×10⁶ t,2000—2015年分别为0.75 kg/m²和10.87×10⁶ t。2）1985—2015年有机碳密度随气温和降水量的增加而增加,随高程和坡度的增加呈现先增加后减少的趋势,在高程679~779 m、坡度10°~20°范围达到最大值。3）大多数土壤类型有机碳密度和储量随时间延长呈增长趋势,其中,黑垆土有机碳密度增加最大（1.59 kg/m²）,黄绵土储量增量最多（5.64×10⁶ t）;不同土地利用类型有机碳密度和储量随时间延长也呈增加趋势,林草地有机碳密度增加量明显大于耕地。4）研究区表层土壤有机碳密度与气温、土壤类型、土地利用类型在P<0.001水平上相关性显著,与降水在P<0.05水平上显著相关。

Spatial Distribution of Organic Carbon in Topsoil of the Loess Tableland in Shaanxi Province during 1985-2015

The long-term dynamic of soil organic carbon in the mesoscale range is critical to the concentration of atmospheric greenhouse gases and the ecological effects of the local environment. Taking twelve soil types and seven types of land use in the Loess Tableland in Shaanxi Province as the research object, this paper studied the spatial distribution characteristics of soil organic carbon density (0-20 cm) in the past three decades. The relationships between soil temperature, topographic factor, soil type, land use type and soil organic carbon density and storage are discussed. The results show: 1) In the past three decades, the soil organic carbon density and storage in the Loess Tableland have increased, and the increase rates were bigger and bigger. The increments of soil organic carbon density and storage were 0.14 kg/m² and 2.04×10⁶ t during 1985-2000, and the increments were 0.80 kg/m² and 10.10×10⁶ t during 2000-2015. 2) From 1985 to 2015, with the increases of temperature and precipitation, the soil organic carbon density showed an increasing trend. With the increases of elevation and slope, the organic carbon density increased first and then decreased, reaching the maximum in the ranges of 679-779 m and 10°-20°. 3) The organic carbon density and storages in most soil types increased with time, among which the soil organic carbon density of the black loam increased the most (1.59 kg/m²) and the storage capacity of the yellow soil increased the most (5.64×10⁶ t). The organic carbon density and storage in different land use types increased with time. The organic carbon density in forest grassland is obvious higher than that in cultivated land. 4) Surface soil organic carbon density is significantly correlated with temperature, soil type and land use type with P <0.001, and significantly correlate with precipitation with P <0.05. Regardless of which factor is the controlling factor, both soil type and land use type are significantly related to the organic carbon density of the topsoil (P <0.001), indicating that these two factors are the dominant factors affecting the organic carbon density.