Abstract:

Paddy soil is one of the major agricultural soils in China. The content of organic carbon in paddy soil varies with the change of global climate, and therefore, it is significant to clarify the distribution of organic carbon in paddy soil of Chinese major agricultural lands and its influence factors. In this research, the distribution of organic carbon in paddy soil of different administrative divisions were investigated based on a national multipurpose geochemical survey (1:250000) soil database. Besides, the influence of soil pH, annual average air temperature, annual average precipitation, cultivating methods etc. on the content of organic carbon in paddy soil were discussed.  Principal components analysis and stepwise multiple regression models were also used to detail these researches.  The results indicate that the content of organic carbon in the paddy soil of Heilongjiang Songnen plain is the highest (15.1 g/kg) and those of Guangdong Pearl River Delta and Hainan Island are less.  The organic carbon in soil can be hardly affected by soil pH, however, content of organic carbon can be phenomenally influenced by soil pH in a negative way when the soil pH ranges from 7.5 to 8.5.  In some high latitude areas like Heilongjiang province and Jilin province, organic carbon in soil is significantly influenced by air temperature. The content of organic carbon in paddy soil reduces 2.51g/kg with the annual average air temperature increase of 0.1 ℃ according to a linear regression model. Cultivating and land managements can influence the content of organic carbon in soil slightly. Among several major influence factors, like annual average precipitation, annual average air temperature and soil pH, the influence of annual average air temperature is the most important.

Key words: paddy soil, soil organic carbon, climate change, principal component analysis