Urban Forest Diversity
Species diversity is the vast array of tree species growing in an area, each having different characteristics, value, and purpose in an ecosystem. A number of tree species are native to Edmond’s region of North America. Others were introduced and became adapted to the environmental conditions. Tree species that are easy to care for or attractive in appearance quickly grow in popularity. This popularity and the resulting public familiarity with the species leads to very frequent planting of that tree species.
Inadequate Species Diversity Effects
Embracing well-adapted tree species with positive characteristics can be good, but sometimes there can be too much of a good thing. Species that make up more than 10% of the whole urban forest composition exceed the appropriate ratio of species diversity. It is recommended by urban forestry professionals that no individual species make up more than 10% of the entire urban forest composition.
Pest & Disease Epidemics
Inadequate species diversity of an urban forest population can increase its susceptibility to pest and disease epidemics. An example of this is the over-planting of American elm as street trees, which were decimated by Dutch elm disease in the 20th century. Due to the mass planting of a single species, the disease spread very quickly and was difficult to control. In addition, gaps left in the landscape by the trees that died produced quite a hole in the continuity of urban tree canopy.
Poor species diversity can also lead to other problems. For example, certain tree species’ susceptibility to breakage could cause large-scale problems during storm events, again decimating a large portion of urban tree canopy.
Planting Diverse Trees
By planting under-used, yet adapted species that are appropriate for a site, citizens can enhance a healthy and unique urban forest. To find a unique tree species, see Species for Edmond.