耕种对沙地土壤全磷空间变异性的影响

Influence of cultivation on spatial variability of soil total phosphorus in sandy land.

利用经典统计学和地统计学相结合的方法,以科尔沁沙地东南缘的丘间低地为例,分析了农业耕种对沙地土壤全磷空间变异性的影响.结果表明,草地开垦8年后的耕地同未开垦的草地相比,表层和亚表层土壤全磷量均有明显增加(P<0.05);两层土壤全磷贮量增加7.64%,约增加25.71kg/hm2.耕地同草地相比,土壤全磷空间结构和格局存在明显差异.耕地表层表现为一种随机上下波动的空间分布格局,而草地表现为相对均一的空间分布格局.亚表层耕地同草地相比,基台值、结构方差和变程明显偏大,结构异质性和空间依赖性较强,而随机性较弱的空间分布格局.分数维进一步说明耕地与草地土壤全磷空间变异性的差异.克立格制图直观地反映2种土地利用方式下土壤全磷的空间结构特征.为此,认为耕种易导致沙地土壤退化,退耕还草有利于维持脆弱沙地生态系统的稳定性.

The influence of cultivation on spatial variability of soil total phosphorus (STP) in sandy land was studied, utilizing the low land of southeastern Keerqin Sandy Lands, and the combined technique of classical statistics and geostatistics. STP amounts of surface and subsurface all increased obviously (P<0.05) after the grassland was brought under cultivation for 8 years compared with the grassland not cultivated; the stored amounts of STP of both layers increased 7.64% and 25.71 kg/hm2; and the spatial structure and pattern of STP were different obviously. The spatial distribution of STP of surface layer of grassland was uniform pattern while that of cultivated land was stochastic and fluctuant pattern. Compared with grassland, the sill value, structure variance and change range of subsurface cultivated land were larger obviously with stronger structure heterogeneity and spatial dependence. The spatial distribution pattern of weaker randomness and fractional dimension further explained the difference of spatial variability of STP between cultivated land and grassland. Kriging maps also directly the spatial structure character of STP under two kinds of land utilization pattern. It was considered that cultivation could easily lead to the degradation of sandy soil, and the conversion of cultivated land to grassland was favorable to maintain the ecosystem stability of frazil sandy land.