And now for an internet finding, as I have never put foot in Porto Alegre (or anywhere in Brazil). Here is a rather local street, that has wonderful trees (Tipuana tipu, or rosewood) and an interesting space, with a regular paving for cars and sidewalks with irregular stone slabs which seem nice, at least seen from Google Street View’s car.
According to the blog poavive, these trees have been planted and maintained by the neighbors, and the street is now a listed space, with legal protection.
What surprises me, seen from Spain, is that planting and taking care of the trees is assumed by the neighbors. In many countries this is clearly a municipal affair. Looking at google maps I can see there are other streets in Porto Alegre which also have fine trees, as Marqués de Pombal (a little less dense, in fact), but I do not know if it is also due to the neighbors. Even here in Madrid, far from being a tropical city, we have some streets with good trees, albeit less exuberant. I reckon also that sometimes the relevant role of the neighbors is preventing the trees from being logged; after reading the post on the amics arbres- arbres amics blog, it seems this was also the case in Porto Alegre.