Spatial Distribution Of Soil Nitrogen In Urban-rural Fringe And Its Influencing Factors

Urban-rural fringe was a special zone where evolution comes from the suburbanization, accompanied by a strong landuse changes from agricultural land to non-agricultural land. To understand the mechanism of soil nitrogen change with landuse conversion was important to predict and manage the regional nitrogen sink in the fringe. Based on the 3S platform, this paper researched the spatial distribution of soil nitrogen (Soil total nitrogen, STN; Dissolved organic nitrogen, DON; Microbial biomass nitrogen, MBN; Nitric nitrogen, NO3--N; Ammonium nitrogen, NH4+-N) and its influencing factors(Different landuse; Vegetation; Soil texture; Building density, BD; Road density, RD) at the urban-rural fringe of the western suburbs of Chengdu. The results are as follows.In the study area, STN average contents of four layers(0-100 cm) were 1.50±0.42,0.91 ±0.22,0.91±0.22 and 0.69±0.21 g/kg respectively, the distribution of the layer 0-20 cm presented northeast and southeast lower the central and western, the type of distribution was massive and banded,20-100 cm was same, massive mainly in southwest of Yongning town. DON average contents of four layers (0-100 cm) were 48.29±26.92,50.12±26.31,55.04± 25.32 and 48.58±26.9 mg/kg, the condition of content of 0-20 cm presented east and west low, north and south high,20-40 cm showed the same, the main distribution of 40-100 cm was massive, low contents mainly concentrated in the northwest Deyuan and the west of Pitong town areas. Average contents of soil MBN at the four layers (0-100 cm) were 14.57± 13.48,7.36±6.47,5.81± 3.68 and 3.24±2.28 mg/kg,0-20 cm showed that the high content was located in the south and north, mainly distribution located Pitong town, Deyuan and Pitong town, high value areas mainly located in the eastern Tashui town, central Wanchun town and the western region of Gongping town, showing the sheet and strip distribution. 20-40 cm mainly presented flakiness distribution. Southwest is high and the east is Low, The distribution of 40-60 cm is similar with 20-40 cm, high in the west and lower in the east is obvious’, and the distribution of 60-100 cm showed flaky distribution, and the values is lower than 0-40 cm. Average contents of soil NO3--N at the four layers (0-100 cm) were 51.2± 23.86,33.48±20.7,28.35±19.19 and 25.49±18.01 mg/kg, the contents showed a trend of reduction,0-20 cm presented massive distribution, high values region were mainly located in Yongning Town, the three layers of 20-100 cm showed a massive distribution also. Soil NH4+-N contents at the four layers were 6.27±3.38,5.77±2.56,5.53±2.54 and 5.56±2.91 mg/kg, four layers were banded and block-based distribution, high value regions located in the Tashui town, Wanchun town and Yongning town.Study combined urban-rural fringe landuse and agricultural economy changes, and the status of urbanization urban land conflicts. This paper researched the main effect under the main factors of urbanization at the urban-rural fringe. Analysis of variance showed that soil nitrogen contents presented an obvious significance under different landuse(P<0.05). Different soil nitrogen showed different diversity at different soil layers. STN and soil NO3--N in 0-20 cm showed a significant different (P<0.05), while soil DON and MBN, at 40-60 cm and 60-100 cm, showed a significant differences, but soil NH4+-N has no significant differences (P>0.05). Soil nitrogen have an obvious significant differences under different vegetation cover at 0-40 cm except soil DON (P>0.05). Soil MBN, at different soil texture and different soil layers, has no significant differences (P>0.05), the remaining soil nitrogen showed a significant difference (P<0.05). Regression analysis showed that between building density and two layers of 0-20 cm and 60-100 cm STN was significantly negatively correlated (P<0.01), while between building density and soil NH4+-N in the first two layers (0-40 cm) showed a significant differences (P<0.05), but between building density and the rest of soil nitrogen in the relevant soil layers were not showing a more significant correlation (P>0.05). Between road density and STN in the 0-40 cm was shown significant correlation (P<0.05), so did soil DON. Between road density and soil MBN only in 0-20 cm was significant difference (P<0.05), while remaining soil nitrogen in the relevant soil layers showed no significant correlation (P>0.05). In summary, the urbanization significant influenced the distribution of soil nitrogen at the urban-rural fringe, with the urban construction and economic development such influence would be advanced and enhanced.