Spatial Variation of Surface Soil Available Phosphorous and Its Relation with Environmental Factors in the Chaohu Lake Watershed
2. Material and Methods
2.1. Study Area
2.2. Surface Soil Survey
2.2.1. Sampling Sites
2.2.2. Laboratory Analysis
2.3. Spatial Interpolation and Validation
2.4. Analysis Method of Spatial Variation
2.5. Analysis Method of Relation
3. Results and Discussion
3.1. Validation of Interpolation Results
3.2. Spatial Characteristics of Surface Soil Available Phosphorus
3.3. Soil Available Phosphorus under Different Elevation and Slope
3.4. Soil Available Phosphorus under Different Land Use
3.5. Relation between Subwatershed Scale Soil Available Phosphorus and Environmental Factors
- In the prediction of soil available phosphorus in the Chaohu Lake watershed, the Spline Tension method performed the best and then followed by the Spline Regularized method in second, Kriging Ordinary Gaussian method in third and Kriging Ordinary Spherical method the worst.
- The spatial variation of surface soil available phosphorus was high in the Chaohu Lake watershed. The upstream regions around Chaohu Lake, including the west of Chaohu Lake (e.g., southwest of Feixi county, east of Shucheng county and north of Lujiang county) and to the north of Chaohu Lake (e.g., south of Hefei city, south of Feidong county, southwest of Juchao district), had the highest soil available phosphorus content.
- The mean and standard deviation of soil available phosphorus content gradually decreased as the elevation or slope increased. The regions ranging from 0 to 50 meters of elevation were mainly dominated by paddy fields and had the highest soil available phosphorus contents, the regions ranging from 100 to 1480 meters of elevation were mainly dominated by forest land and had the lowest soil available phosphorus contents. The region ranging from 0 to 3 degrees of slope was dominated by cultivated land and had the highest soil available phosphorus content, the regions ranging from 5 to 49.75 degrees of slope were dominated by forest land and had the lowest soil available phosphorus contents. The cultivated land comprised 60.11% of the watershed and of that land 65.63% belonged to the medium to very high SAP level classes, and it played a major role in SAP availability within the watershed and a potential source of phosphorus to Chaohu Lake, resulting in eutrophication. Among the land use types, paddy fields have some of the highest maximum values and variation of coefficients.
- The subwatershed scale soil available phosphorus content and the various environmental factors, including average elevation, slope, precipitation, percentage of cultivated land and percentage of forest land, were significantly correlated, the percentage of construction land, NDVI and soil available phosphorus did not have significant linear relationship. The results after ANOVA and LSD analyses between subwatershed scale soil available phosphorous and five significant environmental factors showed that all the differences were significant (P < 0.05), and E, S, P, PCL1 and PFL had significant effects on subwatershed scale soil available phosphorus. Subwatershed scale soil available phosphorus was decided not only by these environmental factors but also by some other factors such as artificial phosphorus fertilizer application.
- Conflict of InterestThe authors declare no conflict of interest.
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|<O>||Mean of the observed variable|
|<P>||Mean of the model-predicted variable|
|MAD||Mean absolute difference|
|MAPD||Mean absolute percent difference|
|Method||Kriging Ordinary Exponential||Kriging Ordinary Gaussian||Kriging Ordinary Spherical||IDW||Spline Regularized||Spline Tension|
|Pearson correlation coefficient||0.738*||0.835**||0.267||0.738*||0.809**||0.906**|
|Kriging Ordinary Exponential||13.25||20.77||7.52||9.12||68.78|
|Kriging Ordinary Gaussian||13.25||20.04||6.78||8.32||62.80|
|Kriging Ordinary Spherical||13.25||20.81||7.55||12.05||90.92|
|Item||Mean (mg/kg)||Minimum (mg/kg)||Maximum (mg/kg)||Range (mg/kg)||Std. Deviation(mg/kg)||Variation coefficient(%)|
|Level code||Level range(mg/kg)*||Level description||Area percentage(%)||Mean (mg/kg)||Std. Deviation(mg/kg)||Variation coefficient(%)|
|Elevation level code||Elevation range (m)||Area percentage (%)||Minimum (mg/kg)||Maximum (mg/kg)||Mean (mg/kg)||Std. Deviation (mg/kg)||Variation coefficient (%)|
|Slope level code||Slope range (degree)||Area percentage (%)||Minimum (mg/kg)||Maximum (mg/kg)||Mean (mg/kg)||Std. Deviation (mg/kg)||Variation coefficient (%)|
|Land use type code*||Area percentage (%)||Minimum (mg/kg)||Maximum (mg/kg)||Range (mg/kg)||Mean (mg/kg)||Std. Deviation (mg/kg)||Variation coefficient (%)|
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Gao, Y.; Gao, J.; Chen, J. Spatial Variation of Surface Soil Available Phosphorous and Its Relation with Environmental Factors in the Chaohu Lake Watershed. Int. J. Environ. Res. Public Health 2011, 8, 3299-3317. https://doi.org/10.3390/ijerph8083299
Gao Y, Gao J, Chen J. Spatial Variation of Surface Soil Available Phosphorous and Its Relation with Environmental Factors in the Chaohu Lake Watershed. International Journal of Environmental Research and Public Health. 2011; 8(8):3299-3317. https://doi.org/10.3390/ijerph8083299Chicago/Turabian Style
Gao, Yongnian, Junfeng Gao, and Jiongfeng Chen. 2011. "Spatial Variation of Surface Soil Available Phosphorous and Its Relation with Environmental Factors in the Chaohu Lake Watershed" International Journal of Environmental Research and Public Health 8, no. 8: 3299-3317. https://doi.org/10.3390/ijerph8083299