摘要：Soil is the most important organic carbon pool of the terrestrial ecosystem. However, studies on the long-term dynamic changes in organic carbon after land use change have rarely been reported. This study investigated the spatial distribution and dynamic changes in soil organic carbon (SOC) density in grasslands converted from farmlands from 2003 to 2016. In 2003, three plots were established in restored grasslands of the Taowan watershed, Henan, China: a control plot (P1) where planted crabgrass (Digitaria sanguinalis (L.) Scop.) naturally grew, a crabgrass plot where plant litter was removed (P0), and a crabgrass plot with twice the litter amount (P2). The SOC densities at 5-cm intervals from the surface to 30 cm depth were measured at the end of February each year. In 2003, the three plots did not show significant differences in SOC density. In 2016, the SOC densities of P1, P0 and P2 were 5303 ± 438 g m~(-2), 4685 ± 335 g m~(-2), and 4341 ± 347 g m~(-2), respectively, showing significant differences among groups (P<0.05). The SOC densities in P1 and P0 increased annually, whereas that in P2 first decreased then increased. Plant species and litter mass primarily affected the SOC density in the 0-20-cm layer. During the farmland-grassland restoration process, the SOC density reached a new balance after 12 years. The annual SOC sequestration rate was 277 g m~(-2). This study may provide a basis for the assessment of "carbon sink" functions of restored grasslands.
关键词：Grassland Converted from Farmland;Soil Organic Carbon Density (SOC Density);Restored Grassland;Dynamic Change;Spatial Distribution
