江苏省土壤有机质含量时空变异特征及驱动力研究

土壤有机质(SOM)含量是估算土壤碳储量、评价土壤肥力的重要指标，研究SOM时空演变对评估区域土壤固碳潜力，实现土壤可持续利用具有重要意义。以江苏省为例，利用全国第二次土壤普查资料和2006年采样数据，基于地统计学方法和GIS技术，对比研究了1980 - 2006年全省范围内表层(0 ~ 20 cm)SOM含量的时空变异特征及其驱动因子。结果表明：1980年和2006年江苏省SOM平均含量分别为16.55 ± 8.50 g kg^-1和18.31 ± 8.32 g kg^-1，变异系数分别为51.36%和45.44%。两个时期SOM的变异函数均符合指数模型，块金系数由51.85%增加为56.52%，变程由71.55 km减少至37.83 km，SOM含量的空间自相关性减弱，自相关距离减小。1980-2006年，SOM含量空间分布呈现出北增南减，沿江平原增，宁镇丘陵减，滨海平原基本持平的空间格局，增加幅度由北向南逐渐减小。SOM含量的初始值影响其空间格局的演变，总体上呈现初始SOM含量的高值降低、低值增加的趋势。肥料的大量使用在提高粮食产量的同时也增加了作物残茬和根系的生物量；秸秆还田的大力推行，使得大量的有机物质进入土壤，促进了SOM的累积。不同的土地利用变化对SOM含量变化的作用不同，土地利用方式转变成水田、旱地和林地促进了SOM的增加，而转变成荒地后导致SOM含量下降。

Temporal and spatial variability of soil organic matter and its driving force in Jiangsu Province, China

Soil organic matter (SOM) is a key index in estimating soil fertility and soil C sequestration. Consequently, the study on temporal and spatial variability of SOM is of great significance to assessing regional soil C sequestration potential and realizing sustainable utilization of soil resources. For this research, Jiangsu Province, East China was selected as a subject for case study and comparative study was done of the data of the Second National Soil Survey and the data collected in 2006, using the geostatistic and GIS technologies, to explore temporal and spatial variability of SOM in the surface soil layer (0 ~ 20cm) of the province during the period (1980 - 2006), and its driving forces, as well. Results show that the mean SOM content increased from 16.55 ± 8.50 g kg-1 in 1980 to 18.31 ± 8.32 g kg-1 in 2006, and its coefficient of variation decreased from 51.36% to 45.44%. The variograms of SOM of the years both fitted the exponential model, with nugget coefficient rosing from 51.85% to 56.52%, suggesting that the effect of stochastic variability of SOM content intensified and spatial autocorrelation weakened. The codomain decreased from 71.55 km to 37.83 km, indicating decreasing spatial autocorrelation distance. A general trend was observed that soils high in initial SOM content decreased in the content and vice versa, and the increment reduced in margin from north to south of the province. The application of large volumes of chemical fertilizers improved crop production, and increased soil biomass from crop leftover and roots. The extrapolation of straw incorporation brought large volumes of organic matter into the soil, contributing to accumulation of SOM. Changes in land use brought about changes in SOM. Reclamation of land into paddy fields, upland fields, and forests increased SOM content and vice versa.