Urban tree growth models for two nearby cities show notable differences

Reliable models of urban tree growth over time are useful for selecting appropriate species for available planting sites, anticipating future tree maintenance and removal costs, and quantifying the benefits provided by trees. There is a need to develop growth models for multiple cities within the same climate region to understand the degree of variability for the same species in different cities. In this study, we developed tree growth models for 13 common street tree species in Cincinnati, Ohio, USA, based on field data and planting records. These models relate tree age to diameter at breast height. Then we compared the modeled tree growth curves for Cincinnati to analogous models from nearby Indianapolis, Indiana. To estimate how differences in modeled tree growth translate to differences in ecosystem services, we compared annual ecosystem service estimates from Cincinnati and Indianapolis using the i-Tree Eco model. The comparisons showed varying levels of difference between cities; for example, modeled growth curves for Acer platanoides were nearly identical, while models for Pyrus calleryana differed by > 47% over 35 years of growth. These results advance our understanding of urban tree growth rates by comparing models from two nearby cities, and by underscoring the inherent variability in urban tree growth that will drive attendant differences in the ecosystem services provided by trees.