“三线”约束下土地利用变化及其对碳储量的影响——以武汉城市圈为例

Land use change and its impact on carbon storage under the constraints of “three lines”: a case study of Wuhan City circle

陆地生态系统碳储量作为全球碳循环研究的基础,与土地利用变化密切相关。生态保护-永久基本农田-城镇开发边界红线(简称“三线”)是国土空间规划的核心,能较好地约束土地利用,进而对碳储量造成影响。以武汉城市圈为例,采用Markov-FLUS耦合模型模拟“三线”约束下的土地利用变化情景,并运用InVEST模型定量研究不同情景下土地利用变化对碳储量的影响。结果表明:(1)2000—2015年武汉城市圈耕地、林地、草地和未利用分别减少了1267.582、112.703、24.896、42.14 km^(2),建设用地和水域分别增加了1092.282 km^(2)和355.039 km^(2)。2035年“三线”约束情景下耕地减少面积小于自然发展情景,林地实现了增长,新增建设用地被引导至城镇开发边界红线内聚集。(2)2000—2015年武汉城市圈总碳储量呈连续递减势态,其中武汉市碳储量减少量最大。“三线”约束情景下碳储量和地均碳密度下降幅度明显变小,武汉市碳储量减少量仅为自然发展情景的44.89%。(3)耕地-建设用地之间的转换是引起碳储量剧烈变化的主要原因,土地利用强度与碳储量呈显著负相关,较低强度带的碳储量最高。因此,“三线”约束下的武汉城市圈土地利用能合理统筹布局生态-农业-城镇等功能空间,减缓碳储量的损失,对区域国土空间优化具有重要意义。

As the basis of global carbon cycle research, terrestrial ecosystem carbon storage is closely related to land use change. Ecological protection red lines, permanently basic farmland protection red lines, urban development boundary lines(referred to as the “three lines”) are the core of the national space planning, which can better restrict land use, and then affect carbon storage. Taking Wuhan City circle as an example, this paper uses the Markov-FLUS composite model to simulate land use pattern of this region under the “three lines” constraints, and uses the InVEST model to study the impact of land use change on carbon storage under different scenarios quantitatively. The results showed that:(1) The area of the cultivated land, forest land, grass land and unused land decreased by 1267.582 km^(2), 112.703 km^(2), 24.896 km^(2) and 42.14 km^(2) in Wuhan City circle from 2000 to 2015, while the construction land and water area increased by 1092.282 km^(2) and 355.039 km^(2). In 2035, under the “three lines” constraint scenario, the reduced area of the cultivated land is less than the natural development scenario, and the area of forest land is increased, and the new construction land is guided to gather within urban development boundary lines.(2) The total carbon storage showed a continuous decline trend in Wuhan City circle from 2000 to 2015, and the carbon storage of Wuhan City decreased the most. Under the “three lines” constraint scenario, the decline of carbon storage and average ground carbon density is observably smaller than the natural development scenario, and the reduction of carbon storage in Wuhan City is only 44.89% of the natural development scenario.(3) The conversion between cultivated land and construction land is the main reason for the drastic changes of carbon storage. There is a significantly negative correlation between land use intensity and carbon storage, and the lower intensity zone has the highest carbon storage. Therefore, under the “three lines” constraints, the land use of Wuhan City circle can reasonably coordinate the layout of ecological-agricultural-urban functional space, and slow down the loss of carbon storage, which is of great significance to the optimization of regional national space.