Distribution Pattern of Soil Organic Carbon and Its Regional Humification Constant in the Coastal Monsoon Region of Eastern China
Authors: Liu Shutian , Xie Xiansheng , Wang Xiaochuan , Feng Xinxin , Hou Xianda , Wang Shuojin , Lin Keyu , Huang Mei , Jia Shugang , Hou Yanlin , Dou Sen 
Published: May 2021

Abstract
Soils are an important pool for storing organic carbon. Soil organic carbon (SOC) content is generally considered as an important indicator to evaluate farmland soil quality. The loss of SOC causes soil degradation and reduces the sustainability of farmland. In order to reveal the distribution pattern of SOC in the coastal monsoon area of eastern China, and to clarify the macro dominant factors of SOC accumulation caused by temperature and precipitation, this paper analyzed the distribution pattern of SOC in the coastal monsoon area of eastern China by using the SOC data collected from the national soil testing and formula fertilization data set, and discussed the effects of temperature and precipitation on SOC content. According to the provincial administrative divisions, the distribution of SOC in the coastal monsoon areas of eastern China from Heilongjiang Province to Hainan Province was calculated. According to the annual average temperature < 10.18℃, 10.18 ℃ ~ 20.95℃, > 20.95℃, annual average precipitation 0 ~ 400 mm, 400 ~ 800 mm, > 800 mm, the study area was divided into different regions, and the effects of annual average temperature and annual average precipitation on SOC content were studied. In the region with annual average temperature less than 10.18℃, the temperature had a negative correlation with the accumulation of organic carbon, and the ratio of precipitation and temperature had a positive correlation with the accumulation of SOC; In the region of 10.18℃~20.95℃, the annual average temperature and annual average precipitation had a significant positive correlation, and the ratio of precipitation and temperature had a positive correlation with the accumulation of SOC; In the region > 20.95℃, the temperature had a negative correlation with the accumulation of organic carbon, and the ratio of precipitation and temperature was not related to the accumulation of SOC. In the range of 0 ~ 400 mm of annual average precipitation, the temperature had a positive correlation with the accumulation of SOC, and the ratio of precipitation and temperature had a negative correlation with the accumulation of SOC; In the range of 400 ~ 800 mm of annual average precipitation, the temperature had a negative correlation with the accumulation of SOC, and the ratio of precipitation and temperature had a positive correlation with the accumulation of SOC; In the region > 800 mm of annual average precipitation, the temperature had a positive correlation with the accumulation of organic carbon before the annual average temperature of 20.95℃, and after the annual average temperature of 20.95℃, the temperature had a negative correlation with the accumulation of organic carbon, and the ratio of precipitation and temperature had no significant effect on the accumulation of SOC. On the macro scale, the annual average temperature and precipitation had significant effects on the distribution pattern of SOC in the coastal monsoon area of eastern China. According to the influence of annual average temperature and annual average precipitation on SOC accumulation, a comprehensive model based on the annual average temperature and annual average precipitation on SOC accumulation is established. Through regression verification of the model, the correlation coefficient, r = 0.9998**, the cubic curve equation could better simulated the relationship between the predicted value and the real value of SOC, r = 0.7048**,the model can reflect the cumulative effect of annual average temperature and annual average precipitation on SOC accumulation Combined with the impact.