格氏栲天然林土壤养分空间异质性

采用地统计学与GIS技术相结合方法对格氏栲天然林土壤养分和pH值空间异质性进行了研究,结果表明:pH值为弱变异,土壤养分为中等变异,变异强度为有效磷＞速效钾＞水解性氮＞全氮＞全钾＞全磷＞pH值.半方差最优模型拟合分析表明,pH值、全钾、有效磷符合指数模型,全氮符合高斯模型,全磷、水解性氮符合球状模型,速效钾符合线状模型；全钾、速效钾、pH、全氮、全磷、水解性氮和有效磷的有效变程依次为1806、549、267、130、120、182 m和117m；从空间结构特征看,pH值、全氮、全磷、水解性氮、有效磷表现出强烈的空间自相关,其空间异质性主要受结构性因素影响；全钾具有中等强度的空间自相关,其空间异质性是随机性因素和结构性因素共同作用的结果；速效钾具有微弱的空间自相关,其空间异质性主要受随机性因素影响.土壤养分空间分布特征:全氮、全磷由南向北递增；全钾含量呈环状分布,向南北分别呈递增趋势；pH值由东北到西南递增,呈条带状分布；水解性氮从东北向西南递减；有效磷从东南到西北逐渐递增；速效钾分布较均匀,在西北和东南角各有一个高值区,从西南到东北表现为先增加后减少的规律.其结果为区域尺度上土壤养分的空间内插、制图和取样设计提供参考,也为土壤可持续利用、格氏栲天然林的恢复与重建提供科学依据.

The spatial heterogeneity of soil nutrients in a mid-subtropical Castanopsis kawakamii natural forest

The spatial heterogeneity of soil nutrients and soil pH in Castanopsis kawakamii natural forest of Sanming City, Fujian Province was studied by the method of Geostatistics coupled with Geographical Information System (GIS) technique. The experimental results showed that pH had a weak variation, and the soil nutrients exhibited medium spatial variability. The variation intensity of soil nutrients and soil pH ranked from high to low as follows: available phosphorous ( 43.54% ), available potassium ( 32.84% ), hydrolyzable nitrogen ( 31.03% ), total nitrogen ( 29.41% ), total potassium ( 25.25% ), total phosphorous ( 22.14% ), pH ( 3.39% ). In terms of different soil layers, the value of pH and total potassium raised with increase in soil depth, while total nitrogen, total phosphorous, hydrolyzable nitrogen, available phosphorous, available potassium reduced with increasing soil depth. Analysis of variance showed that soil nutrients and soil pH reached an extremely significant levels. Parameters of theoretical variogram models for soil nutrients and soil pH showed that pH, total potassium and available phosphorous fitted exponential model, total nitrogen fitted Gaussian model, total phosphorous and hydrolyzable nitrogen can be best described by spherical model and available potassium was well fitted by linear model. The effective ranges of total potassium and available potassium were 1806 m and 549 m, respectively, while the values for pH, total nitrogen, total phosphorous, hydrolyzable nitrogen and available phosphorous were 267 m, 130 m, 120 m, 182 m, and 117 m ,respectively. In terms of spatial structure, pH, total nitrogen, total phosphorous, hydrolyzable nitrogen and available phosphorous showed high spatial autocorrelation, which was greatly affected by soil structural factors, such as stand structure, topography, microhabitat of forest gap and soil aggregate structure. Total potassium indicated moderate spatial autocorrelation, which was resulted from both soil structural factors and random factors. Available potassium indicated weak spatial autocorrelation. The spatial heterogeneity of available potassium was primarily affected by random factors, such as site preparation, change of land use , the rapid development of the ecotourism, the planning and construction of scenic areas. The spatial distributions of soil nutrients had different characteristics. Total nitrogen and total phosphorous were increased from south to north. The total potassium emerged circle distribution with low in the central area and high in the marginal area. Soil pH showed a decreasing trend from southwest to northeast, presenting a band distribution. Hydrolyzable nitrogen decreased from northeast to southwest. Available phosphorous increased gradually from southeast to northwest. From southwest to northeast, available potassium content increased firstly and then decreased with two high value areas at the corner of northwest and southeast. The results may provide reference for improving the sampling design and for spatial interpolation and map of soil nutrients at a regional scale. It also may give a scientific foundation for sustainable use of soil and the recovery and reconstruction of C. kawakamii natural forest.