喀斯特峰丛洼地区坡地不同土地利用方式下土壤水分的时空变异特征

基于典型喀斯特峰丛洼地坡面土地利用方式试验火烧、刈割、刈割除根、封育、种植桂牧1号、种植玉米(面积分别为20m×70m)控制性试验建设,通过网格法(5 m×5 m)采样,用经典统计学和地统计学方法,分析了6种土地利用方式下(火烧、刈割、刈割除根、封育、种植桂牧1号、种植玉米)表层土壤水分在不同季节的空间变异特征。结果表明:喀斯特峰丛洼地土壤含水量均很高,雨季显著大于旱季,雨季为火烧封育、刈割除根玉米、桂牧1号刈割,旱季为刈割、火烧、刈割除根桂牧1号、封育玉米,均呈中等至强度变异,且含水量越低变异越大;不同土地利用方式土壤水分的自相关函数均呈由正向负方向发展的相同趋势,但拐点不同,且旱季大于雨季,不同土地利用方式旱季、雨季土壤水分的最佳拟合模型不同,但均呈中等或强烈的空间相关性,变程为6.8—213 m,且旱季大于雨季;同一土地利用方式旱季、雨季表层土壤水空间格局相似,不同土地利用方式空间格局则不同,因此在该区域进行植被恢复和生态重建时应采取不同的水资源利用策略。

Spatiotemporal variation of soil moisture under different land use types in a typical karst hill region

In this study, spatiotemporal variation of soil moisture was investigated on six manipulated land use types, i.e., burning, cutting, cutting plus root removal, enclosure, maize field, and sward of Guimu No. 1.Each land use type covered an area of 20 m×70 m on a typical slope in depression between karst hills. Soil moisture was measured with 5 m × 5 m sampling grid and was analyzed through classical statistics and geostatistical methods. Soil moisture was high in depression between karst hills, and was significantly higher in rainy season than in dry season. In rainy season, soil moisture changed in the order of burning > enclosure and cutting plus root removal > maize field and sward of Guimu No. 1 > cutting, while in dry season, soil moisture changed in the order of cutting, burning, cutting plus root removal > sward of Guimu No. 1andexclosure > maize field. Soil moisture varied moderately or strongly, and the variation was larger when the soil moisture was lower. All autocorrelation coefficients of soil moisture under different land use types tended to change from positive to negative direction but with different inflection points and the values were larger in dry season than in rainy season. The best fitted models of soil moisture differed under different land use types, but all showed moderate or strong spatial correlation. The spatial variation rangedfrom 6.8 to 213 m and was larger in dry season than in rainy season. The spatial pattern of surface soil moisture under the same land use type in rainy season was similar to that in dry season, while spatial pattern of surface soil moisture varied among different land use types. Therefore, diverse strategies in the utilization of water resources should be adopted during ecological restoration and vegetation reconstruction in depressions between karst hills.