茂兰喀斯特常绿落叶阔叶林土壤养分空间分布特征

Spatial distribution characteristics of soil nutrients in Maolan karst evergreen and deciduous broad-leaved forest

在茂兰喀斯特森林1.28 hm^(2)固定样地内,按10 m×10 m等距离网格布点取样测定了128个土壤氮磷钾养分数据,采用经典统计学和地统计学方法,对喀斯特森林土壤养分含量及其空间分异规律进行研究.结果表明:(1)研究区土壤养分含量较低,6种土壤养分变异系数从大到小依次为有效磷(89.95%)、全钾(55.04%)、全氮(40.58%)、有效钾(40.15%)、碱解氮(33.02%)、全磷(30.75%),属于高中等程度变异.(2)土壤养分的空间依赖性(Moran′I指数)随着距离的增加逐渐降低,全磷、有效磷、全钾对空间的依赖程度较大,空间结构相似,全氮和碱解氮依赖程度较小.(3)土壤养分有效磷半方差模型为线性模型,全氮、全钾为指数模型,全磷、碱解氮为高斯模型,有效钾为球面模型,决定系数均在0.68以上,可以较好地反映土壤养分的空间结构特征.(4)土壤养分全钾、全氮、有效钾、有效磷的空间分布呈带状,中部、南部含量高,北部含量低.碱解氮、全磷分布呈块状,破碎化程度较高,中部含量高,东西方向含量较低.(5)全氮与碱解氮为显著负相关关系,全磷与碱解氮、全钾与有效磷为显著正相关关系,全磷与海拔、碱解氮与海拔、全磷与坡度、全钾与坡向均呈显著负相关,喀斯特森林土壤养分空间分布受地形因子的影响.

To study the distribution characteristics of soil nutrition in evergreen deciduous forest in the karst region of Guizhou Province,128 soil samples were collected by 10 m×10 m equidistant grid within a 1.28 hm^(2)fixed plot established in Maolan Karst Forest.Soil nutrition,including total nitrogen(TN),alkalytic nitrogen(AN),total phosphorus(TP),available phosphorus(AP),total potassium(TK)and available potassium(AP)were detected.Classical statistics and geostatistical methods were used to evaluate the soil nutrient status of the karst forest.The results showed that(1)soil nutrient contents were relatively low in the study area.The coefficients of variation of the 6 parameters in the descending order were AP(89.95%),TK(55.04%),TN(40.58%),AP(40.15%),AN(33.02%),and TP(30.75%),showing moderate to high variability.(2)The spatial dependence of soil nutrients(Moran’I)decreased with increasing distance.TP,AP and TK were more dependent on space,demonstrating a similar spatial structure,while TN and AN were less dependent.(3)The semivariance model of AP was linear.The semivariance models of TN and TK were exponential.Those of TP and AN were Gaussian models,and that of AP was a spherical model.Their determination coefficients were all above 0.68,implying that these models can reflect the spatial structural characteristics of soil nutrients.(4)The spatial distributions of TK,TN,AK and AP were banded,with high contents in the central and southern areas and low content in the northern area.The distributions of AN and TP were blocky,with high degrees of fragmentation,demonstrating high contents in the middle and low contents in the east-west direction.(5)There was a significant negative correlation between TN and AN.While TP and AN,TK and AP were each significantly positively correlated.Significant negative correlations occurred between TP and elevation,AN and elevation,TP and slope,and TK and slope.Therefore,the spatial distribution of soil nutrients in Maolan Karst Forests was affected by topographic factors.