植烟前后土壤有效锰含量的空间变异特征

Spatial variability characteristics of soil available manganese content before tobacco planting and after tobacco harvest

采用地统计学和地理信息系统(GIS)相结合的方法,对植烟前后土壤有效锰含量的空间变异规律进行研究.结果表明,植烟后土壤有效锰平均含量比植烟前有所降低,从60.10 mg.kg-1下降至49.82 mg.kg-1,差异达到了显著水平;植烟前后土壤有效锰含量的分维数分别为1.929和1.853,变程分别为42.3和89.1 m,最优模型分别是指数模型和球状模型,块金系数由6.13%增至41.20%;植烟前区域土壤有效锰含量在0°,45°,90°和135°方向表现为各向异性,烟草收获后在4个方向表现为各向同性;烟草种植后,土壤有效锰含量在低值和高值范围变化最为显著,低值(小于47.61 mg.kg-1)所占面积由8.7%增加到38.9%,高值(大于60.01 mg.kg-1)由45.8%降低为17.1%.

A geostatistics method, with geographic information System （GIS）, was applied to study the spatial variability of soil available Mn before tobacco planting and after tobacco harvest in Guizhou Province. The results showed that average content of Mn after tobacco harvest was reduced, from 60.10 to 49.82 mg · kg^-1, and the difference reached significant level. The results of geostatistics showed that soil available Mn before tobacco planting was exponential model, and the nugget/sill ratios was 6.13% , whereas Mn after tobacco harvest was best represented through spherical model and the nugget/sill ratios was 41.20%. The range of Mn before tobacco planting and after tobacco harvest were 42.3 m and 82.1 m, respectively, and he fractal dimension （D） of which were 1. 929 and 1. 853, re- spectively. The anisotropic analysis indicated that Mn before tobacco planting was anisotropic in 0°, 45°,90° and 135 ° direction, after tobacco harvest, and Mn nearly had isotropism. The content of Mn after tobacco harvest had relatively high variation in the range of low value （ 〈 47.61 mg · kg^-1） and high value （ 〉60.01 mg · kg^-1 ）. The proportion of the area in the range of low value was increased, from 8.7% to 38.9% , and in the range of high value was reduced, from 45.8% to 17.1% after to- bacco harvest.