基于GIS和地统计学的甘肃省白龙江流域土壤氮素空间变异分析

目的]分析甘肃省白龙江流域土壤氮素(全氮、硝态氮和铵态氮)空间变异规律,为土壤氮素管理与流域综合生态系统调控提供科学依据。方法]采集0—20cm土壤氮素样点,室内试验得到样本土壤氮素含量,利用ArcGIS 10.2和地统计学方法等探讨研究区内土壤氮素的空间异质性和分布格局。结果]土壤全氮、硝态氮和铵态氮都属于中等强度变异,变异系数范围在35%~90%之间;土壤氮素半方差模型的块基比在25%~75%之间,具中等强度的空间相关性,空间变异受到结构性因素和随机性因素共同影响;土壤全氮、硝态氮和铵态氮的最佳拟合模型均为高斯模型。总体上,土壤全氮和硝态氮含量主要由西北向东南逐渐降低;铵态氮含量整体分布表现为西北低,东南高的趋势。结论]土壤全氮和硝态氮在不同土地利用类型和海拔高度间呈极显著或显著差异;土壤铵态氮在不同土地利用类型和海拔高度间差异不明显。

Spatial Variability of Soil Nitrogen in Bailongjiang Watershed in Gansu Province Based on Geostatistics and GIS

Objective] The objective of this study is to analyze the spatial variability of soil nitrogen(total nitrogen, nitrate nitrogen and ammonium nitrogen) in Bailongjiang watershed in Gansu Province, and provide scientific basis for the management of soil nitrogen and the regulation of integrated ecosystem.Methods] Soil samples were collected at a depth of 0-20 cm, and were tested in laboratory. Geostatistical methods combined with ArcGIS 10.2 were applied to analyze the spatial variability and distribution pattern of soil nitrogen.Results] The variation coefficient of total nitrogen, nitrate nitrogen and ammonium nitrogen were moderate, with the value ranged from 35% to 90%. The rations of nugget to sill of total nitrogen, nitrate nitrogen and ammonium nitrogen were ranged from 50.13% to 63.19%, the spatial variability was affected by structural and random factors, and the best fitting theoretical semivariogram models of soil nitrogen were Gaussian models. As a whole, the spatial distribution of total nitrogen and nitrate nitrogen were higher in northwest but lower in southeast, and the soil ammonium nitrogen in the northwest area was lower than that in southeast.Conclusion] The content of total nitrogen and nitrate nitrogen varied remarkably in different land use types and altitudes, while there was no significant correlation between ammonium nitrogen and different land use types and altitudes.