| The water and heat conditions are good in the subtropical area of China, the natural environment is superior, and is rich in natural resources, the subtropical is one of China’s best ecological environments, and plays an important role in environment protection, maintaining the sustainable development of human. Soil P is one of the important soil nutrients, and a indispensable nutrient elements for pants growth, it can participate in various biochemical and physiological process by different ways, can promote the normal metabolism and affect plants growth, affect forest growth and forest productivity enhancement a certain extent. Research on spatial heterogeneity of soil P element is an effective method to research the relationship between soil P and environment factors can help us to understand the soil structure formation and research soil physical and chemical properties and function. On forest community scale, analyzed the characteristics of spatial variability of Choerospondias axillaris deciduous broad-leaved forest soil P content and its relationship with the terrain factors (Elevation, Convexity)、biologic factors (Litter-layer, Species, Numbers)、 soil factors (Moisture Content, pH, Organic C, Total N), it will provide a scientific basis for revealing the regulatory mechanism of subtropical forest soil P spatial distribution, and subtropical forests healthy management.This study located in 1 hm2(100m*100m) fixed sample in the Choerospondias axillaris deciduous broad-leaved forest of Da Shanchong state-owned forest farm of Changsha city, Hunan Province, the fixed sample was divided into 100 sample of 10m* 10m. In the central of each sample collecting litter amount soil samples by the humus layers,0-10cm,10-20cm and 20-30cm soil layer and determinating soil physical and chemical properties, the ligin content of litter biomass and the soil P, soil C and total N content. Based on the method of combination of geo statistics and GIS, the spatial analysis was performed on the basis of semi variance function and Version GS+ 9 software, spatial variability of soil P content and its influencing factors were studied. The results showed that:(1) The sample of Choerospondias axillaris deciduous broad-leaved forest terrain factors、biologic factors and soil factors both follow normal distribution, probability density and frequency distribution are more concentrated, In terrain factors, altitude range between 4.00～51.80 meters, variance coefficient 43.04%, convexity range between -2.48～2.06, variance coefficient 61.42%, both follow moderate degree of variation; In biologic factors, litter-layer range between 2.03 t·hm-2～16.50 t·hm-2, variance coefficient 48.74%, The number and species of plants were in the range between of 1.00～13.00 and 2.00～44.00, variance coefficient were 32.55% and 48.66%, both follow moderate degree of variation; In soil factors, moisture content range between 25.37%～46.27%, variance coefficient 9.17%, soil pH range between 4.02-4.69, variance coefficient 3.43%, both were weak degree variation, Organic C and Total N range between 16.33 ～ 116.81 g·kg-1 and 1.60～3.83g·kg-1,variance coefficient were 35.94% and 17.8%, moderate degree of variation.(2) The sample humus layers,0-10cm,10-20cm,20-30cm soil total P content was in the range of 0.12～0.54g·kg-1, the average values were 0.36,0.26,0.27, 0.23g·kg-1, the variation coefficient were 19.10%,23.95%,28.22%,28.24%; the soil available P content was in the range of 4.88～22.29mg·kg-1, respectively 12.13,2.46, 2.63,1.90 mg·kg-1, the coefficient of variation were 31.36%,35.40%,40.69%, 44.95%; the content of total P and available P have reached the moderate intensity variation, and decreased with the increase of soil depth, the variation degree increased; the variation degree of available P in the same soil layer was higher than total P; theoretical model of soil total P semi variance function accorded with exponential model and spherical model and Gauss model; theoretical model of soil available P semi variance function accorded with exponential model and spherical model; In the middle scale range, the content of soil total P and available P showed moderate intensity spatial autocorrelation, which showed that the spatial heterogeneity was mainly caused by structural factors.(3) The total P content variation of each soil layer was range of 92.800～ 168.900m, available P content variation was range of 79.430～106.200m. The content of soil total P has larger space autocorrelation scale and higher spatial continuity than available P; the divided dimensions of soil total P were between 1.86～1.978 and available P were 1.803～1.869, showed that soil total P and available P both had good fractal characteristics, and the divided dimensions of available P content was lower than total P, has better structural, spatial distribution was more simple, and the spatial pattern of the total P was relatively complex.Using Kinging interpolation method to spatial interpolation the soil P content of 1 hm2 plots, the soil total P and available P content were obvious banded and plaque gradient distribution, and had similar spatial distribution pattern in some samples.(4) There was significantly or extremity significant negatively correlation between soil total P、available P and elevation, there was negatively correlation between soil total P、available P and concave and convex degree, in addition to the 20-30cm soil layer reached significant level, the rest of soil layer didn’t reach significant level. There was significantly negative correlation between soil total P and litter biomass, there was negatively correlation between soil total P and plants species, excepted the 20-30cm soil layer were reached significant level, there was no correlation with planting trees. The soil available P content and litter biomass had significantly negative correlation, and planting trees also there was no correlation. Soil available P and soil moisture content was negatively correlated but not significantly, in addition to the 0-10cm soil layer were reached significant level, the rest of soil layer didn’t reach significant level. The total P, available P content and soil pH was positively correlated, excepted the total P of humus layer、the 0-10cm soil layer and the available P content of 20-30cm soil layer, the other soil layer and soil pH didn’t reach significant level; The total P, available P content and soil organic C、total N were significantly positively correlated. Obviously, the spatial variation characteristics of soil P are influenced by various environmental factors. |
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