| Spatial variability characteristics and influential factors of soil total nitrogen (STN) in different hilly areas of the central Fujiang river Valley were analyzed using conventional statistic and geostatistics techniques. Also uncertainly characteristics of STN deficiency or excess in different hilly areas were researched using Probability Kriging interpolation and Sequential Indicator Collaborative simulation methods. The main results of the study were as follows.(1) Conventional statistic characteristics of STN in different landforms were variant, and spatial correlation of STN in every hilly area was to attain medium or extreme level. The distribution of the mean of STN in different hilly areas were mostly skewed to the right, and the distribution of the mean of STN in low and medium landforms were slightly sharp than the normal distribution, while the high landforms were comparatively flat inside. The content of STN in low hilly areas were significantly higher than the content in high hilly areas(F=4.192, P=0.041), and there were extremely significant differences between L3and M3(F=4.835**,P=0.003)The most fitting models were exponential model in low hilly areas, spherical and exponential model in medium hilly areas, and spherical model in high hilly areas. The spatial distribution of STN in low hilly areas presented Group article and ribbon shapes and the content were generally in0.90g kg-1or above. The spatial distribution of STN in medium hilly areas presented ribbon and blocky shapes, and the content were generally between0.75-1.05g kg-1. The spatial distribution of STN in high hilly areas presented ribbon shapes and the content were generally below0.90g kg-1(2) The influential factors of STN in hilly areas were analyzed. TN content of Mudstone slope-deposits and Sandshale slope-eluvium from which soil derived were extremely significant higher than that of Siltstone slope-eluvium(F=5.073, P<0.01) among the four main parent materials, and TN content of Mudstone slope-deposits were significant higher than that of Sandshale slope-eluvium (F=5.073, P=0.043). In low and high hilly landforms, TN content of any couple parent materials were no significant difference, however there was extremely significant difference among three parent materials of medium hilly areas(F=8.306**, P<0.01). There were extremely significant differences among Paddy soil, Fluvo-aquie soil and Purple soil(F=7.867, P<0.01). In low hilly areas, TN content of Paddy soil was significantly different between Purple soil and Fluvo-aquie soil (P<0.05), and In medium hilly areas, there was extremely significant difference among three soil types (F=7.771**P=0.001). However in high hilly areas, there was no significant difference among three parent materials. There was extremely significant positive correlation between TN content and organic matter (OM) content. Among different land use types, TN content of paddy land was significantly higher than that of dry land (P=0.000) and was significantly higher than that of wood land (P=0.047). In low hilly areas, there was significantly difference between paddy land and wood land (P=0.001). and in medium hilly areas, there was extremely significant difference between paddy land and dry land (P=0.001). In high hilly areas, TN content of any couple land use types were no significant difference (P>0.05).(3) The probability maps produced by Probability Kriging showed that the high probability region (probability>0.5) of STN below the threshold value of0.75g kg-1were mainly distributed where the TN content was low, and there was a high risk of TN content deficiency or leaching loss in these regions. Whereas the high probability region (probability>0.5) of STN exceeding the threshold value of1.25g kg-1were mainly distributed where the TN content was high, and there was high risk of TN content exceed in these regions. The probability maps based on100realizations of Sequential Indicator Collaborative simulation showed that the high probability region (probability>0.5) of TN content deficiency or leaching loss were mainly distributed in hilly top, hilly side and steep hill in low and medium hilly areas, and the high probability region (probability>0.5) of TN content exceed were mainly distributed in hilly slope, hilly gully and flat ground in low and medium hilly areas. In high hilly areas, TN content was generally low, and there was a high risk of TN content deficiency or leaching loss, but in the hilly gully, the probability of TN content exceeding the threshold value of1.25g kg-1was high, it maybe because that in the steep regions of high hilly areas, TN content was leaching, and it was accumulated in the gullys and then generated the high exceeding regions.In the gullys and flat grounds of hilly landforms, the risk of TN content exceeding is high, whereas in the hilly tops and steep regions, the risk of TN content deficiency or leaching loss is high. |
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