| Soil acidification,as an important aspect of soil degradation,greatly affects the food security of the people in the world.The factors affecting soil p H are extremely complex.Defining its source and identifying and analyzing soil p H impact factors can provide theoretical guidance for controlling soil acidification and improving cultivated land quality.In this study,the object to be evaluated based on the rule model is divided into different discriminant subsets,and then each discriminant subset is unbiased.The results of the model constructed by Cubist method include the contribution degree of each impact factor to the model.Then,the contribution of each impact factor and the different rules of the model are used to identify the main causes of the current situation of the object to be evaluated,and then the dominant influence factors of soil acidification are analyzed.Based on the soil data of Guangdong Province in 1980 s,2010 and 2015,the spatial and temporal variability of soil p H values in different farming areas were analyzed.And the soil p H value of 54632 sampling points in Guangdong Province in 2015 was research object.The 67 impact factors may affect the soil p H value were selected by using the idea of data mining and big data analysis and reading related literature,and then constructed the Cubist models to determine the natural and anthropogenic sources of soil p H.The main research conclusions include:(1)The spatial distribution pattern of soil p H in Guangdong Province changed significantly in different periods.The whole province arable soil p H decreased by 0.3 from 1980 s to 2010,showing acidification trend.During 2010 and 2015,Soil p H has risen by 0.09,but the unbalanced situation has been enhanced,that is acid-base differentiation trend is more obvious.From the perspective of various regions,from 1980 s to 2010,the soils in all regions showed acidification trend;from 2010 to 2015,the average soil p H value in the Pearl River Delta region increased by 0.27,while the soil p H values in the east and west wings decreased by 0.05 and 0.15,respectively.The p H change in the mountainous soil is not obvious.(2)The main factors affecting the overall distribution of soil p H values in Guangdong Province are crop category,rice planting area,the proportion of transportation land and construction land.The proportion of transportation and construction land was positively correlated with soil p H,while the rice planting area was negatively correlated with soil p H.(3)From different regions,the factors affecting the overall distribution of soil p H in the Pearl River Delta region are mainly rice planting area.The area of traffic land,rice planting area and construction land are the main factors affecting the p H value of local soil in the Pearl River Delta region;The factors affecting the overall distribution of soil p H in the East Wing area are mainly the proportion of traffic land.The main factors affecting the local distribution of soil p H in the East Wing area are the proportion of traffic land and the distance from the 5th basin;affecting the overall p H value of the soil in the East Wing The distribution factor is mainly the planting area of melon crops.The main factor affecting the local distribution of soil p H value in the west wing area is the distance from the 5th basin.The factors affecting the overall distribution of soil p H in mountainous areas are mainly the proportion of traffic land,affecting mountain areas.The main factor for the local distribution of soil p H is the contribution rate of the secondary industry.The research results can provide theoretical guidance for different areas to control soil acidification and improve the quality of cultivated land. |
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