[Spatial variability of soil nitrogen and related affecting factors at a county scale in hilly area of Mid-Sichuan Basin].

Spatial distribution characteristics of soil total nitrogen ( TN ) and available nitrogen ( AN ) were analyzed by using geostatistical methods and the effects of the influencing factors were quantified by regression analysis based on 555 soil samples collected in RenShou county. The results showed that the contents of soil TN ranged from 0.34-2.57 g x kg(-1) with a mean value of 1.12 g x kg(-1), which indicated the TN of the study area was at a medium level, and AN ranged from 25.86-184.17 mg x kg(-1) with a mean value of 74.35 mg x kg(-1), which indicated the AN of the study area was low. The values of the nugget to sill ratio were 0.608 and 0.790 respectively, which suggestd TN had moderate spatial dependence, which was determined by the co-effects of structural and random factors, while AN was mainly affected by random factors. The contents of TN and AN in north area were much higher than those of south area and distribution of Patchy. The soil parent materials were able to explain 6.3% and 1.0% of TN and AN spatial variability. Soil types explained 26.5% - 36.1% of TN variability and 27.7% - 28.7% of AN variability. Topographical factors explained 5.5% of TN variability and 6.1% of AN variability, the structural factors of soil types reflected spatial variability of nitrogen in the study area. The randomness factors of land use types explained 37.7% of TN variability and 40.0% of AN variability that were much larger than the other factors, which suggested land use had the higherst independent explaining capacity for nitrogen spatial variability among those influence factors and land use type was the main factor to accurately predict the spatial distribution of soil nitrogen in the hilly area of Middle Sichuan Basin.