As of January 2015 the tree code has changed for the city of Portland. It will affect trees on both public and private property. The rules are stricter but hopefully easier to understand, and there are penalties if the rules aren’t followed. The ultimate goal is to preserve our trees which affect air-quality, shade and stormwater in addition to just being beautiful. I haven’t done much investigating myself, but the city has a number of ways you can get more information. Call their hotline at 503-823-TREE or click on one of these links: Portland Trees or Portland Tree article.