20 JUL 2026 (MON) 17:05 - 17:35

Understanding urban forests in social-ecological systems based on multi-source data

Mr. GUO Yasong    

( Supervisor: Prof Wendy Y Chen )

Abstract:

Urban forests are widely recognized as vital natural and cultural resources that can support sustainable urban development and enhance residents' well-being. They possess spatial observability, ecological functions, and social significance, serving as a key interface element for understanding social-ecological systems (SES). The unique practical value of urban forests in addressing urban challenges has led to their widespread adoption as a "green prescription" in global urban governance. However, issues such as prioritizing quantity over quality, homogeneous afforestation, and north-south development imbalances have hindered global efforts to increase urban forests. Therefore, it is urgent to clarify the dynamic patterns of urban forests from multiple scales and dimensions, addressing the shortcomings in current practices and research. 

This thesis takes urban forests as its research starting point, conducting four interrelated empirical studies based on multi-source data to explore the dynamic changes in the quantity and quality of urban forests under the influence of different SES subsystem factors from a multi-scale perspective. First, a tree growth quality monitoring framework encompassing chlorophyll, lignin/cellulose, and canopy water content is constructed. Based on this, the dynamics of urban forest quality in heterogeneous urban habitats over a five-year timescale are described, revealing the overall decline in roadside tree quality and the heterogeneous recovery characteristics of trees under the influence of super typhoons. Second, the study compared the growth performance and spatial patterns of native and exotic tree species in urban forests, demonstrating that different species coexist in urban habitats through differentiated spatial occupancy. Third, a new relative water index was developed to monitor canopy water content in urban forests, revealing a widespread water deficit in subtropical dry season and differentiated water drivers between tree-dominated and shrub/grass-dominated forest patches. The former is primarily influenced by wind speed, while the latter is mainly regulated by topsoil water content. Fourth, the study analyzed the dynamics and influencing factors of the quantity and quality of urban forests in capital cities worldwide, revealing that northern capital cities have higher quantities and quality of urban forests, primarily composed of high-quality retained urban forests, while southern capital cities have newly established urban forests of relatively lower quality. 

Given the rapid development of urban forests globally, it is necessary to consider the heterogeneity of urban habitats, implement rational species allocation, conduct long-term, large-scale quantity and quality monitoring, effectively coordinate water resources, and formulate differentiated development strategies based on different social development and natural environments. This thesis proposes management recommendations for urban forests that are both ecologically sound and socially feasible, providing a scientific basis for multi-scale sustainable governance.