农田沙漠化演变中土壤性状特征及其空间变异性分析

SPATIAL HETEROGENEITY OF SOIL PROPERTIES IN THE DESERTIFICATION PROCESS OF RAINFED FARMLAND IN HORQIN SANDY LAND

应用经典统计分析和地统计学的方法 ,研究了科尔沁沙地旱作农田 30 0m× 90m尺度下 0～10cm土层土壤理化性状的沙漠化演变及其空间变异性特征。结果表明 ,表层土壤的粗粒化、持水性能和孔隙分布的恶化、以及土壤养分的贫瘠化演变表征了农田沙漠化的发生和发展。在农田沙漠化演变中 ,土壤性状的变异增大 ,变异系数在 5 .9%～ 5 0 .7% ,其空间分布在研究的尺度上有明显的规律性 ,存在明显的空间异质性和格局。变异函数很好地反映了沙漠化演变的趋势、程度和尺度。在研究区域 ,沙漠化发生发展的尺度在南北两个方向从农田边缘到农田中部约 10 0m处。土壤性状之间及其各因子的空间异质性有密切的关系。沙漠化对土壤有机碳和氮磷养分影响显著 。

This study was carried out to examine the changes of soil physical and chemical properties and their spatial heterogeneity on the rainfed farmland of Horqin Sandy Land in the desertification process using methods of classical statistics and geostatistics. Sixty soil samples of 0～10 cm layer were taken on the 300 m×90 m scale. The data were analyzed geostatistically to determine the degree and nature of spatial heterogeneity. The results showed that soil particle size distribution develop towards being coarse, soil water holding capacity and porosity distribution deteriorated, and soil organic C and N, P nutrients depleted in the desertification process. The variability of soil parameters increased and the coefficient of variation ranged from 5.9% (bulk density) to 50.7% (organic carbon). Geostatistical analysis revealed that there are clearly regular changes in the pattern of distribution and high degree of spatial variability in soil properties in the desertification of the farmland. Semivariograms and its model well reflected the degree and spatial scale of the development of desertification. In the studied area, the strip of land, where desertification developed inside the edges of the farmland along the longitudinal direction was about 100 m wide. There were close relationships between soil properties and between semivariograms of soil properties, except for pH. Desertification had very significant effect on soil organic carbon and nutrients, whereas, its effect on soil pH was relatively small.