What do freaky eaters and trees have in common? They both can withstand very unhealthy conditions and still survive. As a consulting arborist, many of my clients do not manage their trees properly yet the trees survive and the clients often see no reason for changing their behavior. I recently was drawn in by the the cable series "Freaky Eaters" (on Netflix) that documents one person that drank 80 Cokes a day on average and yet another that ate only french fries. What shocked me is that on the exterior these people looked relatively healthy despite their unusual eating habits. Trees often are the same, despite horrible soil conditions or construction damage, they tend to survive. My first point is that there is a difference between surviving and optimal health. Most of us do not live perfect life styles but we understand that when we take care of ourselves it positively impacts our longevity. The same applies to trees. When considering trees we should consider their optimal longevity, not their survival in any given day or year. The second point is that when we go beyond the surface that "healthy" tree may not be as healthy as you think. Like the Coke drinker that had early onset diabetes at the age of 20 after doing a blood test, often trees will be masking decay, disease and or stress that is not readily apparent without tests or to the untrained eye. I equate many street tree installations as "freaky eater" diets for trees by planting them in 4x8 boxes with poor soil, limited water, and cramped rooting conditions. It may initially cost more to eat well, but it will positively impact health and longevity and lower costs over the long run. Don't take your trees health for granted, with proper management that tree could survive much longer and healthier.
Urban streams throughout the country suffer from the effects of development. With every storm, stormwater runoff rushes off of rooftops and pavement, and is piped to the nearest creek through storm sewers. Runoff carries pollution from the streets and landscape, and seriously erodes stream banks and causes flooding. In the Tualatin Basin in Oregon, parking lots cover 5,000 acres and are a significant source of runoff.
What if Mother Nature designed a parking lot? When rain falls on a forest, there is no surface runoff. Trees and shrubs intercept rain and enable it to evaporate before it hits the ground. Rich, organic soil formed by falling leaves acts like a sponge and absorbs rain. Tree roots penetrate clay soils and allow water to infiltrate into the groundwater system. A parking lot that acted like a forest would produce no runoff.
Tualatin Riverkeepers secured funding from an EPA grant through Oregon Department of Environmental Quality (DEQ) to use trees in two parking lots to manage stormwater. Usually parking lots are built on heavily compacted soils, a harsh environment for trees, but new technologies are changing that. At Tualatin Hills Park & Recreation District's (THPRD) Sunset Swim Center and Portland Community College (PCC) Sylvania Campus, contractors constructed linear tree wells using engineered “structural soil” that supports the weight of pavement and vehicles, but allows tree roots to grow and water to infiltrate. Structural soil is a mix of large gravel, soil and other beneficial amendments. Using the structural soil allowed the addition of the trees to the parking lot without losing any parking spaces.
The Sunset Swim Center tree wells were installed in a new pervious concrete parking that allows rain water to pass through the pavement and infiltrate into the ground. More than 650,000 gallons of rain falls on this parking lot in a typical year. None of that rain will become polluting, erosive stormwater runoff.
The PCC project is on a smaller scale and has some significant differences and additional partnerships. The tree wells at PCC will capture runoff from the adjacent pervious parking lot. Volunteers coordinated by our nonprofit partner Depave, removed 400 square feet of asphalt for the linear tree wells. Native evergreen trees will be planted by students this fall. Evergreens will do a better job of intercepting rain in the winter. Water quality monitoring of stormwater running through the tree wells will be performed by Portland Bureau of Environmental Services. Additional monitoring and surveying on the site will be performed by PCC students as part of their science and engineering curriculum.
Educational tours and seminars for planners, engineers, arborists, landscape architects, and other professionals will begin at these sites in November.
Funding partners for this project include EPA/DEQ, J. Frank Schmidt Foundation, Norcross Wildlife Foundation, PCC Bond Measure, and THPRD Bond Measure.
Design and construction partners on the parking lot project include:
• Green Girl Land Development Solutions
• 3J Consulting - Civil Engineers
• Alder Geotechnical
• D&T Excavation, Inc.
• Todd Prager & Associates – Consulting Arborist
• Evolution Paving Resources
For more info about this project and our other demonstration on the PCC Sylvania Campus, go to http://www.parkingforest.org.
"This Project has been funded wholly or in part by the United States Environmental Protection Agency under a federal grant issued under Section 319(h) of the Clean Water Act. The contents of this document do not necessarily reflect the views and policies of the Environmental Protection Agency, nor does mention of trade names or commercial products constitute endorsement or recommendation for use."
By Brian Wegener, Tualatin Riverkeepers
In the Massachusetts Grove, Mollie Freilicher has asked "What are your best practices for planting around walkways and pavement?" Please consider sharing any info by commenting here. Remember you can easily attach any literature or documents to your comment.
Urban trees and green infrastructure have new competition. The concept of complete streets is to provide access and travel for all users, including pedestrians, bicyclist, motorist and public transport users of all ages and abilities. This movement has become very strong over the last few years. In my small town of Decatur, GA several streets have already been redesigned with complete streets in mind (see photo below). Yesterday I attended a bicycle rally at the capitol in Atlanta, GA where people chanted "complete streets" over and over again. The problem is that trees are rarely considered as part of the complete street despite many studies that outline the benefits of trees as a source to slow traffic and off set excessive storm water via green infrastructure. After placing the recreational pathway, sidewalk, cars, parking, and bike lanes, there is little room for trees. Are complete streets and trees incompatible? Decent overstory trees need the space to grow. Solutions might include bulb outs in place of a parking places and bridging roots under the sidewalks. All the same, it is important to design complete streets with trees in mind, otherwise we will end up with highways of imperviousness that provide no vertical element to slow traffic and provide little shade.
Our Village Council recently approved a sidewalk replacement project for spring 2012. The contractor was asked to include root barriers in the bid. The information I have found on root barriers is at best conflicting.
In your experience, what root pruning / barrier techniques have had the most positive outcomes? Can you provide any specifications for your methods &/or materials used?
As a Tree City USA, we always try to keep an eye out for best practices to preserve our mature street trees.
Thank you in advance for your assistance.
Municipalities often wonder how big their street trees will become and if they will create damage to surrounding infrastructure, however New Orleans seems to have different ethic, let them grow! As a result they have one of the most amazing urban forest in the country. We know the the issues surrounding an uneven sidewalk, but have we considered the advantages? Perhaps with an expectation of uneveness, there would be more awareness and less accidents. Humans did not evolve walking on flat surfaces. Anyway, below is a picture of street tree that has exceeded all expectations, one example of thousands in New Orleans.
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