Human activities have profoundly impacted the structure and function of forest ecosystems in the northeastern U.S., particularly through urbanization, which not only directly reduces forest area but also indirectly affects forest function by altering the atmospheric environment and air quality due to local urban heating effects, increased emissions of CO₂ and nitrogen oxides, and ozone concentrations. Critical questions are: how do urbanization, climate change, and changes in air quality interact to influence the functioning of forest ecosystems and how will changes in these environmental drivers affect forests of the Northeast in the future. To address these questions, we investigated changes in temperature and air quality along the urban-to-rural gradient and examines their interactive effects on the carbon, nitrogen, and water dynamics of northeastern forest ecosystems. We utilized the percentage of impervious surface area as a metric of urbanization and analyzed the relationships between environmental variables and urbanization along the gradient from across southern New England. These relationships were applied in the development of future climate and air quality scenarios for New England, based on the RCP8.5 climate scenario, an aggressive decarbonization air quality scenario (CES40B), and the New England Landscape Futures (NELF) scenarios. We applied the PnET-CN-daily model under these constructed scenarios to project potential changes in carbon, nitrogen, and water dynamics for the New England region over the period 2020 to 2050 and assess the interactions of climate change and urbanization on the function of northeastern forest ecosystems. Forecasts suggest that New England will continue to function as a carbon sink, however, complexities arise from land-cover changes that affect carbon sequestration, particularly southern New England states. Rapid urbanization will result in carbon loss, especially in soil pools. Furthermore, climate change will accelerate soil decomposition rates, intensifying soil carbon loss. While the role of CO₂ in forest responses is significant, due to nutrient limitations the difference in plant carbon storage between the RCP8.5 scenarios and a constant climate scenario is less than previous studies have anticipated.

¹ Department of Civil and Environmental Engineering, Syracuse University, Syracuse, NY

² School of Management, Wentworth Institute of Technology, Boston, MA

³ Department of Biology, Boston University, Boston, MA

⁴ Department of Earth & Environment, Boston University, Boston, MA

⁵ Harvard Forest, Harvard University, Petersham, MA

* Corresponding Author: limeng@syr.edu