The impact of the plains afforestation program and alternative land use scenarios on ecosystem services in an urbanizing watershed

Ecological restoration programs, which mainly affect land use distribution, may eventually alter the supply of ecosystem services (ESs). Although some positive results have been achieved, the sustainability and long-term effects of ecological restoration program on ecosystem service still remain uncertain. To compare the ES outcomes of ecological restoration programs, the design of alternative land use scenarios is critical for ecological management. This paper presents a case study aiming to explore how the implementation of the Plains Afforestation Program (PAP) and alternative land use scenarios affect the provision of a set of ecosystem services in an urbanizing watershed. We selected 7 ESs, including three water-related services and four ecosystem services (food production (FP), carbon storage (CS), habitat quality (HQ), and air pollution removal(APR)). And the comprehensive ecosystem service (CES) index was adopted to reflect the total provision of multiple ESs. The trade-offs among various ESs through correlation analysis were further conducted. Finally, four alternative scenarios were designed to provide insights into the future design and implementation of ecological restoration programs. The results indicated that the PAP implementation enhanced regulating services (SC, WP, CS, and APR) and supporting services (HQ) and reduced provisioning services (WY and FP). Converting cropland to forestland could not simultaneously lead to an enhancement in all ecosystem services. Our results also showed synergies between supporting (HQ) and regulating services (CS, WP, and APR). It is worth noting that soil conservation showed trade-offs between supporting (HQ) and regulating services (CS, WP). The region with a large proportion of woodland improved habitat quality, water purification and carbon storage, but it failed to enhance soil conservation effectively because of its steeper slopes. After the implementation of PAP, no transition occurred in the relationships among the ecosystem services, whereas the trade-offs between water yield and other supporting services and regulating services have been weakened. After the land use scenarios were analyzed, the RB-400 scenario with the highest CES value of all the scenarios can be considered the optimal option because it showed the largest increase in water purification (34%) and habitat quality (3%). Moreover, water purification and habitat quality account for greater proportions of weight in our research area. This scenario provided policy implications for the land-use planning.