Abstract: The spatial distributions of soil total nitrogen (STN) and available nitrogen (AN) contents are important factors influencing vegetation productivity. A total of 182 soil samples were collected from the upper and lower layers of 91 sampling points in the eastern part of the Xiong’an New Area. The distributions of STN content, AN content, soil total nitrogen density (STND), and available nitrogen density (AND) were predicted with four methods, i.e., kriging combined with land-use (KLU), ordinary kriging, inverse distance weighting (IDW), and radial basis function (RBF). The predictive accuracy of these methods was evaluated by the root mean square error (RMSE), mean absolute error (MAE), and correlation coefficient (R). Furthermore, the spatial distribution patterns of STN and AN contents and the regional reserves were assessed. The results showed that the vertical distribution of STN, AN content and density decreased with increasing soil depth. From a horizontal perspective, there were significant differences for STN and AN content and density among different land-use types (P<0.05). The KLU was the optimal interpolation method for predicting the spatial distribution of STN, AN content and density. In the upper layer of soil, the R values of KLU were 0.574 (STN), 0.426 (AN), 0.555 (STND) and 0.407 (AND), respectively, which were 0.350, 0.390, 0.304 and 0.310 higher than that of the other three interpolation methods on average. The RMSE of KLU was 0.2255 (STN), 21.5902 (AN), 0.0901 (STND), and 8.5365 (AND), respectively, with an average reduction of 0.0481, 3.7874, 0.0166, and 1.4236 compared with the other three interpolation methods; while the MAE of KLU was the best. KLU showed advantages also in the deeper soil layer.

Key words: Xiong’an New Area, soil total nitrogen, available nitrogen, land-use type, spatial distribution