We just finished hosting the monthly call between researchers working in US Forest Service Research & Development Urban Research. As you can see from the link, these people spend a lot of time answering questions related to people + trees in cities. Sometimes when people think of the US Forest Service, they think of large forested lands in the south and west. And the US Forest Service is certainly there on those lands, but they also work on urban sustainability issues, primarily related to people, trees, and ecological processes.
They provide assessments of trees and forests nationally, and in your state. They also provide tools that can be used to help you assess the quality and quantity of tree cover in your city, and the network of stewardship agencies and organizations that care for trees there.
Closer to home (for me), they participate in the Baltimore Ecosystem Study, a long-term ecological research project of the National Science Foundation that seeks to understand human settlements as ecological systems (now that most of the people on earth live in cities for the first time in human history, this is important!).
I look forward to ongoing interactions with US Forest Service researchers as they identify sustainable solutions for people + trees in cities.