喀斯特峰丛洼地小流域表层土壤养分的空间异质性

为研究喀斯特峰丛洼地小流域土壤化学性质的空间变异性,基于规则网格取样(80m×80m),测定了典型喀斯特峰丛洼地木连喀斯特小流域163个表层(0cm~20cm)土壤样点基本养分全氮TN(total nitrogen)、全磷TP(total phosphorus)、全钾TK(total potassium)、有效氮AN(available nitrogen)、速效磷AP(available phosphorus)、速效钾AK(available potassium)、有机质SOM(soil organic matter)含量和pH值,并利用经典统计学和地统计方法进行了空间变异特征分析。结果表明:研究区土壤这8种指标数值的差异及变异系数均较大,各项土壤养分指标的变异程度依次为TK >AP >AN >TN >SOM >AK >TP >pH。不同养分指标具有不同的空间结构和最佳拟合模型,除TK和pH呈现强烈空间自相关、变程较短、空间依赖性较强外,其余6种指标(TN、TP、AN、AP、AK、SOM)均呈中等空间自相关,变程较长,空间连续性较好。Kriging等值线图直观、清晰的反映了研究区土壤养分空间格局。TN、AN、SOM的Kriging等值线图相似并且它们的空间分布趋势与pH正好相反,TP和AP的Kriging等值线图相似,TK和AK的Kriging等值线图相似。除pH外,木连喀斯特小流域养分空间格局可概括为:东边高,西边低,南边高,北边低,洼地高,坡地低。人为干扰和自然条件(地形、地貌、植被、裸岩率、坡度、坡向)是土壤养分空间异质性的主要影响因素。

Spatial Heterogeneity of Surface Soil Nutrients in a Small Catchment in Karst Peak-cluster Depression Area

In order to explore the distribution pattern of the main soil chemical properties in a small catchment in Karst peak-cluster depression area, the spatial heterogeneity of soil nutrients (TN, TP, TK, AN, AP, AK, SOM, pH) in surface soil (0cm~20cm) were studied by the methods of classical statistics and geostatistics. The total 163GPS- referenced soil samples were collected with grid sampling plots (80m × 80m) in Huanjiang Observation and Research Station of Karst Ecosystem in a small catchment in Karst peak-cluster depression area. The results showed that the differences of the contents of the eight soil nutrient components were large; the variance coefficients of all the eight soil nutrient components were large with the order of TK (total potassium) > AP (available phosphorus) >AN (available nitrogen) > TN (total nitrogen) > SOM (soil organic matter) > AK (available potassium) > TP (total phosphorus) > pH. The spatial patterns and the fittest models of the eight soil nutrient components were quite different from each other. All soil nutrient components had medium spatial autocorrelation with long range and well spatial continuum except TK and pH which had strong spatial autocorrelation with short ranges. The Kriging contour maps indicated that, the distribution pattern of TN, AN, SOM and pH were similar, but pH showed an opposite trend in space with others. In addition, similar patterns were also recognized between TP and AP, and between TK and AK. As a whole, expect pH, all the soil nutrient contents were higher in south and east,lower in north and west, higher in depression, lower in slope. The results indicated that human disturbance and nature condition (the topography, the landform, the slope, the exposure, the bare rock rate, the vegetation, etc.) were the most important factors to affect the spatial patterns of soil nutrients in small catchment in Karst peak-cluster depression region.