Abstract:

Land-use change has an important impact on carbon sources and sinks, playing a critical role in the global carbon cycle. To reveal the impact of land use change on carbon balance, this study used Shaanxi Province as the research area and calculated the social indirect carbon emissions and natural direct carbon stocks of the province from 2002 to 2022 using the bookkeeping model and GIS software based on multi-source datasets from resource inventory, soil survey, and energy consumption. Moreover, night light data inversion was applied to illustrate the variations in carbon density and the evolution of spatiotemporal patterns among and within different land classes. The results showed that 1) the distribution of land-use types in Shaanxi Province had obvious features. Forest and cultivated land accounted for 71.7% of the total area of Shaanxi. In 2022, the areas of construction land, forest land, and water area increased by 2.67×10⁵, 1.05×10⁶, and 7.73×10³ hm², whereas the areas of cultivated land, grassland, and unused land decreased by 7.76×10⁵, 3.75×10⁵, and 1.73×10⁵ hm², respectively, compared with those in 2002. 2) During the study period, there was a serious imbalance between land use-related carbon uptake and emissions in the Shaanxi Province. The average annual sink of land use-related carbon was 4.98×10⁶ t, which was related to the expansion of forest area and improvement in carbon sequestration capacity. Nevertheless, the average annual carbon emission was 3.1×10⁷ t and increased by 7 times compared that in 2002, which was related to the energy consumption with high carbon emissions. 3) The carbon sink in the Shaanxi Province decreased from 2002 to 2007, increased after 2007, and exhibited a faster growth rate after 2017. Nevertheless, carbon emissions have been growing at a high speed, but have stabilized after 2017 owing to the impacts of ecological protection and emission reduction policies. 4) The average carbon density of the Shaanxi Province showed a decreasing trend from the Qinling-Daba Mountains in southern Shaanxi to the Guanzhong Plain to the Loess Plateau in northern Shaanxi. Regions with a relatively stable increase in carbon density (>60 t·hm⁻²) were mainly concentrated in the transition zone between Ankang, Shangluo, and Hanzhong. The carbon emission areas were mainly concentrated in the Guanzhong Plain and northwest Shaanxi, and showed an expanding trend in the grid cell space. This study also found that forests dominated the carbon sequestration. At present, carbon emissions in the Shaanxi Province tend to be stable. Improving the carbon sequestration capacity of forests and grasslands is a key issue for the “dual carbon” goal.

Key words: land use change, carbon accounting, carbon density, spatio-temporal evolution, Shaanxi Province

摘要：

土地利用变化对碳源-汇有着重要的影响，在全球碳循环中扮演着重要的角色。为揭示土地利用变化对碳平衡的影响，以陕西省为研究区，基于资源清查、土壤调查、能源消费等多源数据，利用簿记模型和GIS软件核算了该省2002-2022年社会间接碳排放和自然直接碳储量，并引入夜间灯光数据反演，揭示了不同地类及地类内部的碳密度差异与时空格局演变。结果表明：1）陕西省土地利用类型空间特征明显，林地和耕地占全省面积71.7%，2022年与2002年相比建设用地、林地、水域面积分别增加2.67×10⁵、1.05×10⁶、7.73×10³ hm²，耕地、草地、未利用地面积分别减少7.76×10⁵、3.75×10⁵、1.73×10⁵ hm²；2）研究期间陕西省土地利用相关碳吸收与碳排放严重失衡，土地利用相关年均碳汇量为4.98×10⁶ t，与林地面积的扩大及固碳能力的提升有关，年均碳排放量为3.10×10⁷ t，增长了7倍，与高排放能源的消耗有关；3）研究期间陕西省碳汇量在2007年后开始由负增长变为正增长，2017年后增长速度变快，碳排放量则一直处于高速增长，但受生态保护和减排政策等影响2017年后排放趋于稳定；4）研究期间陕西省地均碳密度表现为陕南秦巴山地>关中平原地区>陕北黄土高原，增长较为稳定的碳密度>60 t·hm⁻²的地块主要集中在安康与商洛、汉中交界一带，碳排放区域主要集中在关中平原一带和陕西西北部，并在栅格单元空间上呈现扩张趋势。研究还发现，固碳主要依靠林地碳汇，当前陕西省碳排放趋于稳定，如何提升林草地的固碳能力将成为“双碳”目标实现的关键问题。

关键词: 土地利用变化, 碳核算, 地均碳密度, 时空演变, 陕西省