Abstract: This paper analyzed the spatial variability characteristics and its influencing factors of soil organic matter (OM) and alkaline nitrogen (AN) by the method of GIS combined with geostatistics based on 441 topsoil sample data collected in central hilly area of Daying County of Sichuan Province. The results showed that the mean value of OM and AN in study areas was 15.22 g/kg and 76.75 mg/kg, respectively, both of them were generally low. As for the spatial pattern, soil OM played a tendency with values higher in north, lower in south and the lowest in central. While, AN showed no obvious distribution trend, the low value zone just located in the center of study areas. The results of  semivariance analysis showed that the value of nugget to sill for soil OM and AN was 83.55 and 51.32, respectively, indicating OM spatial variability was affected by random factors like tillage and fertilization, while AN was affected by random and structural factorslike climate, soil type and topography. The analysis of affecting factors indicated that topography, soil type and cropping system were the important factors affecting the spatial variability of soil OM and AN, while parent material had no significant impact on  OM and AN contents. These results suggested that we should fully consider the influencing factors on the spatial variability of soil OM and AN during the process of land use and fertilization.

Key words: soil organic matter, alkaline nitrogen, spatial variability, influencing factor, hilly areas of central Sichuan

摘要： 选取典型川中丘陵区域——大英县441个表层土壤样点数据，采用地统计学和GIS相结合的方法，对该区土壤有机质(OM)和碱解氮(AN)的空间变异特征及其影响因素进行分析。结果表明，研究区OM和AN的平均值分别为15.22 g/kg、76.75 mg/kg，总体偏低。空间分布上，土壤OM呈现出北高南低、中间最低的分布趋势；而AN无明显分布趋势，低值区集中分布在研究区的中部。从半方差分析结果来看，土壤OM和AN块金值与基台值的比值分别为83.55和51.32，说明OM的空间变异主要受耕作、施肥等随机性因素影响，而AN的空间变异则受随机性因素和气候、土壤类型及地形等结构性因素的影响。影响因素分析表明，地形、土壤类型及种植制度是影响研究区土壤OM和AN含量空间变异性的重要因素，而成土母质对OM和AN含量的影响不显著。在土地利用与施肥过程中，应充分考虑各影响因素对研究区土壤OM和AN空间变异性的影响。

关键词: 土壤有机质, 碱解氮, 空间变异, 影响因素, 川中丘陵区