Identifying eco-functional zones on the Chinese Loess Plateau using ecosystem service bundles

Optimizing the function of ecosystem services (ESs) is vital for implementing regional ecological management strategies. In this study, we used multi-source data and integrated modelling methods to assess the spatiotemporal variations in eight typical ESs on the Chinese Loess Plateau from 2000 to 2015, including grain production, raw material provision, water conservation, carbon storage service, soil conservation, oxygen production, recreation, and net primary productivity (NPP) services. Then, we divided the ecosystem service bundles (ESBs) according to relationships among the eight ESs, obtaining four types of eco-functional areas at the county (city or banner or district) level based on the spatial clustering of similarities in different ES types. We also identified and assessed the contributions of influencing factors to these eco-functional areas using principal component analysis (PCA) across spatiotemporal scales. We found that the spatiotemporal variations in different ESs were noticeable, with an overall increase in grain production and soil conservation services, no significant change in carbon storage service, and overall decreases in raw material provision, water conservation, oxygen production, recreation, and NPP services. From 2000 to 2015, the number of significant synergistic ES pairs decreased, while that of significant trade-off pairs increased. To the changes of ESBs in the eco-functional areas, the results indicated that the indirect loss of these ESs from forest and grassland due to urban expansion should be reduced in ecological development area (ESB 2) and multi ecological functional area (ESB 3). Meanwhile, crop planting structures and planting densities should be adjusted to reduce ES trade-offs associated with water conservation service in grain-producing area (ESB 4). Lastly, ESB-based eco-functional zoning can be used to improve ecological restoration management strategies and optimize ecological compensation schemes in ecologically fragile area (ESB 1).