退耕还林还草工程对生态系统碳储存服务的影响——以黄土高原丘陵沟壑区子长县为例

陆地生态系统碳储量是表征生态系统碳储存服务的重要指标,与土地利用变化之间存在着密切的关系。退耕还林还草工程使区域土地利用格局发生巨大变化,并对生态系统碳储存服务造成了较大的影响。为了能简单快速的评估退耕还林还草工程对陆地生态系统碳储存服务所带来的影响,以位于黄土高原丘陵沟壑区的子长县为例,运用InVEST模型评估了退耕还林还草工程对陆地生态系统碳储量的影响,进一步耦合InVEST模型和FLUS模型,并设置四种不同的退耕还林还草实施情景,预测子长县2037年陆地生态系统碳储量变化和碳汇产生的经济价值。研究发现：（1）子长县退耕还林还草工程实施效果显著,17年间共有31627.98 hm²耕地退耕为林地和草地,境内的林草覆盖率由2000年的53.26%增长至2017年的64.20%;（2）退耕还林还草工程的实施显著提升了子长县陆地生态系统碳储存服务,碳储量由2000年的39.19×10⁶ t增长至2017年42.34×10⁶ t,增加量集中在工程实施主要阶段（2000—2008年）;（3）未来子长县若继续实施退耕还林还草工程,其生态系统碳储存服务会得到进一步提升,且会获得一定的碳汇经济价值。预计到2037年子长县在退耕还林还草工程实施A、B、C、D四种情景下的陆地生态系统碳储量将分别达到：43.78×10⁶ t、44.10×10⁶ t、44.32×10⁶ t和44.54×10⁶ t,并将由此获得碳汇经济价值净收益分别为1627.88万美元、1979.89万美元、2231.39万美元和2471.67万美元。耦合InVEST-FLUS模型,不但能利用InVEST模型简单快速的对陆地生态系统碳储量进行评估,而且还能基于FLUS模型对未来土地利用变化情景下的陆地生态系统碳储量和碳汇经济价值做出测算。

Assessing the effects of the Green for Grain Program on ecosystem carbon storage service by linking the InVEST and FLUS models: A case study of Zichang county in hilly and gully region of Loess Plateau

Terrestrial carbon storage is an important indicator of ecosystem carbon storage services, and it has a close relationship with land use change. The Green for Grain Program (GFGP) has brought about great changes in the pattern of land use in the region and had a major impact on ecosystem carbon storage services. In order to simply and quickly assess the impact of GFGP on terrestrial ecosystem carbon storage services, this paper takes Zichang county, which is located in the hilly and gully region of the Loess Plateau, as an example, and used InVEST model to assess the impact of GFGP on the carbon storage of terrestrial ecosystems. Moreover, by coupling InVEST model and FLUS model, according to the set A, B, C, and D scenarios of GFGP, the change of terrestrial ecosystem carbon storage and the economic value of carbon sinks in Zichang county in 2037 were predicted. The study found that: (1) Remarkable effect of GFGP in Zichang county occurred. From 2000 to 2017, a total of 31627.98 hm² of cultivated land was converted to woodland and grassland. The forest and grass coverage rates in the study area increased from 53.26% in 2000 to 64.20% in 2017. (2) The carbon storage service of the terrestrial ecosystem was significantly improved from 2000 to 2017. The terrestrial carbon storage increased from 39.19×10⁶ t in 2000 to 42.34×10⁶ t in 2017, and its growth was mainly found in the main stage of project implementation from 2000 to 2008. (3) In the future, it is assumed that the GFGP will continue to be implemented in the county, and its ecosystem carbon storage services will be further improved. In addition, certain carbon sink economic value will be obtained. Until 2037, it is expected that the terrestrial carbon reserves under the four scenarios of GFGP in the county will reach 43.78×10⁶ t (GFGP scenario A), 44.10×10⁶ t (GFGP scenario B), 44.32×10⁶ t (GFGP scenario C) and 44.54×10⁶ t (GFGP scenario D), respectively. Thus, the net income from the economic value of carbon sinks was US$ 1627.88 million, US$ 1979.89 million, US$ 2231.39 million and US$ 2471.67 million, respectively. The coupled InVEST-FLUS model can not only use the InVEST model to evaluate land carbon stocks simply and quickly, but also calculate the terrestrial carbon reserves and carbon sink economic value under future land use change scenarios based on the FLUS model.