不同尺度下森林土壤特性空间变异与取样策略

采用网格法采样，对天然更新的次生阔叶林群落林分尺度（40m×40m）和植物个体尺度（2m×2m）的0～20cm土壤分别取样80个和64个，测定pH、有机质、全N、水解N、有效P、速效K等6个指标．结合传统统计与地统计方法，分析在2种尺度下不同土壤性质空间变异特征与样本容量．研究结果表明，各土壤性质的变异系数、极差和半变异函数的基台值均随尺度的放大而增加；不同土壤性质变异性从大到小顺序依次为：有效P〉速效K〉有机质〉全N〉水解N〉pH，说明在相同的精度要求和置信水平下，土壤性质的变异越大，其合理的取样数应相应增加；半变异函数结构说明，除有效P和pH外，多数土壤空间变异主要受随机性因素影响，且无明显基台效应．最后，在对比分析2种尺度下土壤的空间变异特征和样本容量的基础上，探讨优化森林土壤的取样策略．

Spatial Variability and Sampling Strategy of Forest Soil in Different Scales

At stand scale （40 m×40 m） and individual plant scale （2 m×2 m）, 80 and 64 samples were taken respectively using the grid sampling method from the surface soil （0-20 cm） in a secondary broadleaved forest under natural regeneration. Soil pH, organic matter, total nitrogen, hydrolysable nitrogen, available phosphorus and available potassium were analyzed for every sample. Based on traditional statistics and geostatistics, the characteristics of spatial heterogeneity and sampling number of different soil properties were examined. The resuhs showed that the coefficient of variation, range, nugget of semivariogram of every soil property increased with the extended scale. The magnitude of soil heterogeneity was in the order of available phosphorus 〉 available potassium〉 organic matter 〉 hydrolysable nitrogen 〉pH, which indicated that the reasonable sampling number increased with the increasing soil variation at the same precision and confidence level. Meantime, structure of semivariogram indicated that most of the properties were affected by chance factors and without obvious sill effect except for available phosphorus and pH. On the basis of comparing required sample numbers and characteristics of spatial heterogeneity in two scales, the optimizing sampling strategy of forest soil was discussed.