Multifunctionality of urban forest landscapes and their trade-offs and synergies.

The assessment of the multifunctionality of urban forest landscapes is crucial for decision-making regar-ding landscaple allocation, optimization, and planning. Due to the high fragmentation and heterogeneity, it is a great challenge to scientifically evaluate the multifunctionality of urban forests and trade-offs/synergies. With Changchun City as the study area, we used plot surveys and remote sensing data to construct a model for estimating urban forest ecological functions. A multifunctional evaluation framework was proposed, which comprehensively considered both the quality and quantity of functions to quantitatively characterize the spatial patterns of multifunctionality and their trade-offs/synergies. The results showed that the annual carbon sequestration of urban forests in Changchun's built-up areas reached 36.78 t, with an average cooling effect of 0.96 ℃, an annual removal of PM_2.5 reaching 527.52 t, and a recreational capacity of 50.08 people·m^-2. Compared to the downtown, the suburban forests were stronger in carbon sequestration, air purification, and recreational functions, displaying a spatial distribution pattern that was lower in the interior and higher along the periphery. There was a significant trade-off between recreational functions and carbon sequestration and cooling functions, while carbon sequestration showed strong synergies with air purification and cooling functions. As urbanization varied, the trade-offs/synergies among functions displayed spatial heterogeneity, with carbon sequestration and cooling functions showing synergies in the city center and weak trade-offs in the suburbs. The multifunctionality of urban forest landscapes in Changchun performed optimally when the threshold was 25%, with high-value areas concentrated in the city's outer ring, exhibiting a stronger west and weaker east pattern. The multifunctionality generally increased from the 1^st ring road (1.61) to the 5^th ring road (2.01). Our results provide a scientific foundation for the planning and management of urban forest landscapes in Changchun, contribute to the optimization of urban forest multifunctionality, and promote sustainable urban development.