Response of agricultural land carbon storage to land use change in Beijing from 1980 to 2010

As the capital of China, Beijing has experienced rapid urbanization and industrialization during the past three decades. The analysis of variation of its carbon storage in agricultural land and response characteristics to land use change are of great significance for regional and national regulation of low carbon utilization in agricultural land. Using the second soil census data in 1980 and the results of soil testing and fertilization in 2010, the topsoil carbon storage of agricultural land were calculated and the vegetation carbon storage of forest and grassland were obtained from biomass inversion based on remote sensing. The response characteristics of carbon storage in agricultural land to land use change in Beijing from 1980 to 2010 were analyzed by combining the soil and vegetation carbon storage and land use change information. The major results were as follows: 1) the carbon storage in agricultural land of Beijing increased from 75.29 Tg-C in 1980 to 81.13 Tg-C in 2010 by 5.83 Tg-C,the soil organic carbon (SOC) storage of in agricultural land in Beijing decreased by 7.51 Tg-C, whereas the vegetation carbon (VC) storage increased by 13.34 Tg-C; 2) the in agricultural land area in Beijing decreased by 14.11 × 10~4 hm~2 during the past three decades and cropland decreased by 14.62 × 10~4 hm~2. Most of the lost cropland was converted into construction and forest land. The forest land area increased slightly by 1.13 × 10~4 hm~2,whereas the grassland area decreased by 6.29 × 10~4 hm~2; 3) the SOC storage of the maintained land use types of in agricultural land in Beijing decreased by 297.63× 10~4 t, and the loss was overcompensated by increased VC storage of 1095.21 × 10~4 t. The carbon storage of maintained land use types of in agricultural land increased by 97. 58 × 10~4 t. The carbon storage of maintained cropland and forest land increased, whereas the carbon storage of maintained grassland decreased; 4) the land use type conversion resulted in a decrease of in agricultural land SOC storage in Beijing by 75.71 × 10~4 t and increase in VC storage by 212.49 × 10~4 t. The carbon storage increased by 136.78 × 10~4 t through land use type conversion of in agricultural land in Beijing. The conversion of other land use types to forest land resulted in an increase in the carbon storage and the opposite conversions were not conducive to carbon absorption; 5) the implementation of plain afforestation, returning farmland to forests,and other projects would be