考量生态系统服务供需关系的流域城市生态空间优化研究——以青弋江流域泾县段为例

快速城市化阶段,流域城市对生态系统服务的需求与日俱增,生态系统服务供需失衡加剧,厘清及优化流域城市生态系统服务的供需关系对于流域生态保护与经济发展的协同具有重要意义。以长江下游最大支流——青弋江所贯穿的安徽省泾县为例,运用生态系统服务空间定量评估方法,测算固碳释氧、水文调蓄、土壤保持、生境支持、粮食生产、休闲游憩6种关键生态系统服务的供需水平;通过四象限法,判定供需关系并辨明平衡、赤字、盈余3类区域;以供需平衡为目标,基于“保护平衡区与赤字区,开发盈余区”的策略设定用地情景,利用CA-Markov模型获取供需约束的生态空间布局。结果表明：1)生态系统服务供给的分布以高质量生态要素为基底,呈南高北低态势,需求分布与人类活动集中区较吻合,在县域中部和南部突出;2)研究区供需关系整体匹配,平衡区占比最大,盈余区其次,赤字区最小;3)供需约束情景在非生态空间向生态空间转入上表现较好,能增加林地、水域、草地3类重要生态资源的存量,且在形态上可维护大型生态斑块的完整性并引导城镇空间走向紧凑;4)依据供需关系设定的生态保护空间与生态保护红线在平衡区较一致,但在盈余区与赤字区,后者出现“开天窗”式的管控缺口,使青弋江破碎,而前者未有该现象。

Ecological Space Optimization in River BasinCity Based on Ecosystem Service Supply andDemand: A Case Study of Jing Country Section ofQingyi River Basin

In the rapid urbanization phase, the demand for ecosystemservice in river basin cities has been increasing, exacerbating the imbalancebetween ecosystem service supply and demand. Clarifying and optimizingthe ecosystem service supply-demand relationship in river basin cities isof great significance for achieving synergies between regional ecologicalconservation and economic development. Taking Jing County, traversedby Qingyi River, the largest tributary of the lower Yangtze River, as anexample, this study applied an ecosystem service spatial quantitativeassessment method to measure six key ecosystem services supply-demandlevels: carbon sequestration and oxygen release, rainwater retention, soilconservation, biodiversity, food production, and recreational activities. Byusing the quadrant model, the ecosystem service supply-demand relationshipwas determined, and the region was classified into three categories: balance,deficit, and surplus. With the goal of supply-demand balance, land-usescenario was set based on the strategy of "conserving balanced and deficitareas while developing surplus areas". The CA-Markov model was employedto obtain the ecological spatial layout under supply-demand constraint. Theresults indicate: 1) The distribution of ecosystem service supply relies onhigh-quality ecological elements and shows a trend of being higher in thesouth and lower in the north. The distribution of ecosystem service demandaligns relatively well with areas of human activity, particularly in the centraland southern parts of the county. 2) The overall ecosystem service supplydemandrelationship is relatively balanced, with the largest proportion inthe balanced category, followed by the surplus category, and a smallerproportion in the deficit category. 3) The supply-demand constraint scenariodemonstrates a favorable transition from non-ecological to ecologicalspace, allowing for an expansion of important ecological resources such asforests, water bodies, and grasslands. It also maintains the integrity of largeecological patches and guides urban areas towards compactness. 4) Thedesignated ecological conservation space and ecological conservation redline based on the supply-demand relationship align well in the balancedarea. However, in the surplus and deficit areas, the latter exhibits a controlgap known as the "skylight" phenomenon, leading to fragmentation inQingyi River, which has not been observed in the former.