Variation Characteristics And Driving Factors Of Soil Organic Carbon And Phosphorus In Hilly Regions Of Subtropical China

Subtropical hilly regions play very important roles in the production of grain crop, economic forest and fruit farming in China. High temperature and rainfall, as well as irrational land use type (LUT) and its management in this area bring about rapid degradation of organic matter, unbalance of nutrient cycling, and deficiency of phosphorus, particularly, available phosphorus in the soils. The amounts of soil organic carbon and phosphorus have become the factors limiting land productivity in hilly regions of subtropical China. Soils were sampled combining with farmer survey in two agro-ecological hilly units from south and north middle subtropical China, respectively. The amounts and variation characteristics of soil organic carbon and phosphorus were investigated. The responses of soil organic carbon and phosphorus contents to different LUTs and fertilization regimes were studied by means of area sampling and long-term experiment, respectively. The driving factors of the variations of soil organic carbon and phosphorus pools were discussed in the paper. The works aimed at providing some theoretical or practical foundation for optimizing soil organic carbon and phosphorus management, improving soil sustainable productivity and preventing ecological environment deterioration in hilly regions of subtropical China. Main results and progressions were summarized as follows:1. There was significant difference in soil organic carbon and phosphorus pools between south area and north area in hilly regions of subtropical China. Compared with north area, soil total organic carbon (TOC) and dissolved organic carbon (DOC) in south area increased by 39.1% and 77.0%, respectively; but soil microbial biomass carbon (MBC) decreased by 74.9%. Ratios of DOC, MBC to TOC were 0.96% and 1.62% in south area, while those were 0.83% and 3.58% in north area, respectively. In general, the natural and anthropologic conditions in south area favored more accumulation of soil organic carbon pool than in north area. As a whole, soil phosphorus was deficient in both south and north areas. The contents of soil total phosphorus were 0.312g/kg for south area and 0.465g/kg for north areas, respectively. There were no significant differences in soil available phosphorus and microbial biomass phosphorus (MBP) between the south and north areas, namely, the contents in both areas were about 9.0mg/kg for soil available phosphorus and about 23.0mg/kg for MBP. Ratios of soil available phosphorus, MBP to total phosphorus were 2.34% and 1.80% in south area, while those were 7.70% and...