1980—2010年北京市农用地碳储量对土地利用变化的响应

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

分析北京市农用地碳储量对土地利用变化的响应,对快速城市化和工业化区域及全国农用地低碳利用调控具有重要意义。利用1980年第二次土壤普查数据与2010年测土配方施肥项目成果土壤数据核算北京市农用地表层土壤碳储量,利用生物量遥感信息(NDVI)模型反演林地、草地植被碳储量,对北京市土地利用变化造成的农用地碳储量变化进行研究,结果表明:1)1980—2010年,北京市农用地碳储量由75.29 Tg-C增至81.13Tg-C,增加5.83 Tg-C,其中,土壤碳储量减少7.51 Tg-C,植被碳储量增加13.34 Tg-C;2)30年间,北京市农用地面积减少14.11×10~4hm^2,其中,耕地流失最为显著,主要去向为建设用地和林地,林地面积略有增加;3)北京市用地类型保持不变的农用地土壤碳储量减少297.63×10~4t,植被碳储量增加1095.21×10~4t,共计增加797.58×10~4t,其中,用地类型保持不变的耕地、林地碳储量增加,草地碳储量减少;4)30年间,土地利用类型转化使北京市农用地土壤碳储量减少75.71×10~4t,植被碳储量增加212.49×10~4t,共计增加136.78×10~4t,其他用地类型转为林地使碳储量增加,有利于碳汇的形成,林地转出为其他用地类型均会造成一定碳排放;5)平原造林、退耕还林等工程有利于增加北京市农用地固碳量。未来北京市可通过控制农用地面积减少量,优化农用地内部结构,降低用地类型间的转换频率以提高农用地碳储量。研究可为其他区域及全国在快速城市化工业化过程中提升农用地碳储量提供一定参考。

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 beneficial to the carbon sequestration of in agricultural land in Beijing. In the future, we could improve the carbon fixation capacity of in agricultural land in Beijing by controlling the reduction of farmland area, optimizing the internal in agricultural land structure, and reducing the frequency of conversion between land use types. The results of this study could provide a reference for other regions and countries to improve the carbon storage of in agricultural land during rapid urbanization and industrialization.