Soil Organic Carbon Stocks of Citrus Orchards in Yongchun County, Fujian Province, China

Studies related to the quantitation and distribution of soil organic carbon (C) under different land use types can help to fill the knowledge gaps regarding estimation of the amount of C stored in soils at a global scale. Orchards are an important land use type in southern China; the total area (1.15 × 107 ha) of orchards in China comprises approximately 20.5% of the area of all orchards worldwide. We assessed soil organic C stocks (SOCS) in citrus orchards in Yongchun County (consisting of 22 towns), Fujian Province, China in 1982 and 2010. The southeastern part of the county, an area featuring extensive citrus farming with a gently sloping landscape and low rates of water erosion, had the highest SOCS. In contrast, the lowest SCOS was observed in the northern part of the county, where steep hills with severe erosion problems are common and citrus orchards are sparsely distributed. From 1982 to 2010, the mean SOCS in citrus orchards increased from 22.1 to 41.7 Mg ha−1, which indicated that current management practices such as fertilization, irrigation, and cultivation enhanced soil C stocks. Further in-depth studies on the effects of these practices on C sequestration would be worthwhile and surveys of SOCS throughout Fujian Province are needed, to support efforts to mitigate global C emission.