ENEMIES OF CITY TREES Trees in cities lead a hard life. The air is charged with smoke, soot and noxious gases. These clog the leaf doorways, thus interfering with the tree's life processes. Paved streets and side walks prevent the proper ventilation and watering of the soil. The roots need to breathe as well as the leaves. Leaks in sewer pipes and gas mains often suffocate a tree through its roots.
Regrading and filling in change the ground level, and trees are left with roots exposed or buried deeper than before. Either is a distinct damage, which lowers the tree's vitality, and in extreme cases kills it outright. The soil of towns is often "made," containing refuse, such as tin cans, glass bottles, ashes and cinders —anything but good soil. Roots obliged to batten on such pas turage can hardly be expected to keep the top growing well.
Excavations for buildings and for the laying of sewer pipes, water and gas mains generally ignore the trees whose roots lie in the way. Whatever interferes is cut out without thought of the rights of the community in the trees that give beauty and shade to its streets.
Horses gnaw the bark and kill by girdling unguarded trees used as hitching posts in front of stores. This may be seen in small towns where no public sentiment in defense of street trees has been aroused. Bruising and scraping of the bark by contact with loaded wagons and other heavy vehicles produce the disabled, ugly trees one sees along streets and in congested market places.