基于GIS的土壤全氮空间分布估算——以江西省兴国县为例

运用GIS的空间分析技术和DEM,在区域范围内,可以表征基于母岩和地形因子的土壤-景观模型。本次研究根据兴国县151个样点数据,分析TN和地形因子的相关关系,建立回归模型,进行估算。结果表明:表层土壤中TN含量平均值为1.06g/kg,千枚岩发育的土壤中TN的平均含量最高,为1.35g/kg ;砂页岩发育的土壤中TN的平均含量最低,为0.88g/kg 。空间分布上:TN含量在0.5g/kg~1.0g/kg的面积最大,为1580km²,TN含量在2.0g/kg以上的面积最小,为127km²。地形变量中坡向对TN含量影响最大,TN含量和母岩、海拔、坡向存在着正相关关系,坡度和TN含量的相关关系不明显。利用回归分析模型和DEM(30m×30m),估算TN的空间分布,R²为0.637。

Spatial estimation of soil total nitrogen using GIS: a case study in Xingguo county, Jiangxi Province

Spatial distributions of total nitrogen(TN) in soils are difficult to estimate because of their inherent spatial variabilities and lack of sufficient sample data.Soil-landscape model,based on parent material and topographic factors,was generated through applying GIS spatial analysis technique and a digital elevation model (DEM) in large areas.Based on 151 sample data, spatial distribution characteristic of TN was studied.Correlations between TN and topographic factors were analyzed and a regression model was established to predict TN content through linear regression analysis.The results for surface soils (0~20cm) showed that the average content of TN was 1.06g/kg in topsoil,with TN content between 0.5g/kg and 1.0 g/kg occupying the largest area (1580km²,49.3% of the total area) and that over 2.0g/kg the smallest(127km²,3.9% of the total area)in spatial distribution. Also,soils derived from sandstone and shale had the lowest average TN content (0.88 g/kg soil),soils developed on phyllite showed the highest average TN content (1.35 g/kg soil).Aspect among topographic variables had an important effect on TN content.The correlations of TN content with parent rocks,elevation and aspect were positively significant (P<0.05),slope exposure had the highest correlation with TN content (r=0.62).The correlation of TN content with slope was insignificant (r=-0.03).In the soils of the whole study area,the step regression analysis of the TN content, topographic factors and parent rocks showed that elevation,slope exposure and parent rocks were the best factors for predicting the TN content in topsoil (P<0.05).The multiple linear regression model is: TN=0.095+0.005×parent rocks+0.001×elevation+0.115×slope exposure classification n=113 R²= 0.637 The spatial distribution of TN content could be predicted by using a multiple linear regression model and DEM ( with a 30m×30m grid).