[Spatial variability of soil organic carbon sequestration rate and its influencing factors in Fengqiu County, Henan, China.]

Carbon sequestration rate in cropland soil is an important index to evaluate the effect and potential capacity of soil carbon sequestration. Accurate estimation of soil organic carbon sequestration rate is very important for studying cropland soil fertility and environmental effect. In this research, a typical fluvor-aquic soil area, Fengqiu County of Henan Province, located in Yellow Ri-ver basin of Huang-Huai-Hai Plain of China, was chosen as the study area. A total of 70 soil samples were collected according to combined unit grid method of soil utilization with soil type in 2011. The soil organic carbon content, soil mechanical composition, soil bulk density and pH were mea-sured, respectively. The spatial variability of the soil organic carbon sequestration rate of Fengqiu County in recent 30 years was also investigated by using geostatistics method and geography information system (GIS) technique, based on the comparative analysis of soil organic carbon content from samples surveyed in 2011 and the results surveyed by the 2nd state soil survey of China in 1981. In addition, the influencing factors of the soil carbon sequestration rate were quantitatively analyzed by statistical methods, such as significance testing, regression analysis and variance analysis. The results revealed that the soil organic carbon sequestration rate of recent 30 years was about 0.33 t C·hm ^-2 ·a ^-1 with a coefficient variance of 74%, which belonged to a medium variation. The spatial variability characteristics of soil organic carbon sequestration rate was of sheet distribution, which was higher in the west and lower in the east, and decreased from the central region to the south and north. The primary influencing factors of soil organic carbon sequestration rate were structural factors, such as soil type, mechanical composition, soil bulk density and pH, which could explain 59.5% of the spatial variability in the study area. The secondary factors were random factors, such as straw application and fertilizing amount, which could explain 40.5% of the spatial variability.