In this first blog I want to address some of the most common and generic issues that trees face in an urban environment. Trees in an urban landscape face many problems that are not present in their natural habitat, the forest. These issues will be tackled in greater detail in future blogs.
The roots that inhabit an urban soil lack an adequate amount of oxygen, bacteria, fungi and other organisms that are essential to the health of the tree. Urban soil has been described as “A soil material having a non-agricultural, manmade surface layer more than 50cm thick, that has been produced by mixing, filling, or by contamination of land surfaces in urban and suburban areas” (Bockheim,1974).
On the surface trees often have to compete for water and nutrients with turfgrass. A difficult coexistence that doesn’t occur in the trees natural habitat. This can be partially mitigated by mulching correctly, which will be the subject of the next blog.
Above ground trees tend to grow into unnatural shapes due to excessive light stimulus from lack of competition from other trees. They will have a tendency to grow multiple trunks and very large lateral branches that eventually become too heavy for the wood to support. This is not only a concern for the health of the tree, as large tears along the trunk will become an entry point of decay and compromise the structure of the rest of the tree, but is also a hazard to people and property. To correct this structural and subordination pruning can be done when the tree is young to prevent bad structure from occuring in the first place. In mature trees the hazard can be partially reduced by weight and sail reduction pruning and, as a last resort, an ANSI approved cabling system.