The evening storms of Thursday, June 15, 2023 was quite impactful for many things in our city. Not only on cars and structures, but also had an effect on our local plant life.
See the following article by Dr. Ken Baker of Heidelberg University and The Shade Tree and Beautification Commission from January of 2023 on root depth and the existence of trees in City tree lawns.
Urban Forests, by Dr. Ken Baker, Heidelberg University (retired)
There is little that’s “natural” about a city. Not the houses, store fronts, schools, factories, hospitals, or City Hall itself.
Not the cable, gas, and power lines, the water and sewage conduits, or the storm water sewers. Not the sidewalks and roads, nor the bus, car, and bicycle traffic they carry.
And certainly not the trees lining the city’s streets or shading its suburban lawns. What business have they growing out in the open, away from the dense, light-limiting forests in which they evolved over so many millions of years?
Urban planners sometimes talk about two types of critical infrastructure necessary for a thriving, livable city. Hard (or fixed) infrastructure is its “built” environment, the physical structures that carry people, materials, and information from one place to another.
Soft infrastructure refers to the social and economic institutions that provide the specialized services—from employment opportunities and healthcare to law enforcement, trash removal, and school boards—that maintain quality of life in the city.
The urban forest, a town’s treescape, is neither and both of these.
Trees are not “built” in the sense of the steel, concrete, and fiber elements of a city’s transportation, sanitation, and telecommunication systems, but they are nonetheless built and maintained by human agency. Neither are trees a human institution, although the services they provide residents are manifold and quantifiable.
Several weeks ago, I was one of about 20 attendees at a two-day workshop (the first in a series of four such programs) presented by Urban Foresters Stephanie Miller, Alistair Reynolds, and Colleen Berg of the Ohio Division of Forestry. The “Tree Commission Academy” offers a unique curriculum designed to assist members of city Shade Tree Commissions, professional arborists, city administrators, and elected officials in navigating the complex set of issues involved in managing the State’s many urban forests.
The two packed days addressed a diverse array of topics ranging from the biology of trees and municipal ordinances detailing a municipality’s responsibilities for maintaining its trees, to the basic elements of urban forestry and suggestions for communicating the social and economic importance of a well-managed urban forest to elected officials and the general public.
One point that got my attention: Trees are not native to the urban environment. Virtually all the species planted in and around our towns and cities are forest trees possessing the adaptations one would expect for a life where competition for light is the primary limiting factor.
In a forest setting, trees shed their lower branches as they age and rely on the autumn leaf fall to nourish and protect their roots. But in an urban setting, trees are flooded with light, and it is factors limiting root growth that typically threaten a tree’s health and longevity.
Perhaps contrary to expectations, even the tallest oaks and maples have very shallow root systems, typically penetrating no deeper than the top 18 inches of the soil. However, what roots lose in depth they make up in spread, extending out in all directions two to four times beyond the diameter of the tree’s leafy crown.
Thus, knowledgeable pruning of tree branches and regular mulching around the tree base (mimicking forest conditions) help limit stress leading early mortality. And taking special care when replacing sidewalks or running underground pipelines to avoid cutting roots that firmly anchor a tree in place is of critical importance.
In 2011, the USDA published a report (summarizing the results of a number of previous studies) that suggested the average life expectancy for street trees in large cities varied from 19 to 28 years, and that urban planners in such areas could typically expect to see half of newly planted trees dying in 13-20 years.
Although there’s a lot of variability in the need for tree replacement between small towns and large cities, and between towns with well-considered tree management plans and those with poorly developed plans, even the most thoughtfully designed management programs face significant challenges in implementing their objectives.
The overworking of arborists possessing the knowledge of how to evaluate tree health and the skills for appropriate pruning and timely replacing of diseased or hazardous trees is all too common. In the past, so has been a lack of the political will to adequately fund long-term maintenance of a high quality urban forest throughout the city.
But across Ohio, elected officials, city administrators and the public they serve, are coming to understand that developing and maintaining a vibrant, diverse urban forest entails far more than the simple beautification of a cityscape.
Study after study shows that greened streets contribute to demonstrable increases in residents’ health and sense of community, enhanced real estate values and retail sales in downtown areas, reductions in crime and domestic violence, extended life of street surfaces, cleaner air, lowered household energy expenses, and improved management of storm water runoff.
And it’s worth noting that trees are the only component of a city’s infrastructure that increase in value with age.
For more information on The Shade Tree and Beautification Commission, visit TiffinOhio.gov/ShadeTree