COS 69-3 - Ecosystem Resilience to Thermal Extremes: Urbanization Impacts

Abstract: Because of the complex interplay of urbanization and climate, the patterns of urban ecosystems are highly dynamic. Accurately understanding and simulating the responses of urban ecosystems to their surrounding environments, especially the intensified thermal extremes, is challenging. The objectives of this study are to quantify the resilience of selected ecosystem processes to major extreme thermal perturbations (ETPs, e.g., heat waves) across representative US cities, and to improve the simulated urban ecosystem resilience in the land component of the US Department of Energy’s Energy Exascale Earth System Model (E3SM), called the E3SM Land Model (ELM). To achieve these research goals, we performed advanced statistical analyses, including the machine-learning methods, for the 2001-2019 period to determine significant urban and rural differences in resilience, thresholds, and underlying mechanisms. Based on these observational response patterns, we further optimized relevant parameters to enhance the ELM capability in representing the respective resilience of urban and rural ecosystems to ETPs. We found that heat waves predominantly induced positive resistances and recoveries for most cities and seasons. The urban vegetation responded more positively than rural vegetation in winter but more negatively in the other seasons. North-south and east-west patterns in the urban-rural differences were explainable by interactions between the adaptation of urban vegetation to a warmer environment, background temperature, and urban heat island intensity. More detailed differences between urban and rural pixels were mainly explainable by impervious area fractions and land cover types. Initial ELM calibrations against these observed resilience metrics/relationships demonstrated the necessity of developing unique set of model parameters for the same plant functional types within the urban and rural areas. These findings provide the foundation for future studies on urban-rural differences in vegetation resilience responding to ETPs and potentially useful information for urban ecosystem management.