There are many reasons to preserve during construction, including legal requirements, aesthetics, property value and ecological benefits. However, in order for a tree to be considered “preserved” it must survive construction and thrive for many years afterward. In order for trees to be preserved, there are five steps that should be followed:
1. Planning Phase
The planning phase takes before any site disturbance. Trees and the overall site are assessed so that construction and preservation decisions can be made. Accomplishments during this phase include:
Site survey showing all relevant features:
Tree Resource Evaluation
2. Project Design
During this phase, initial construction documents are developed, and a tree preservation plan is developed to consider trees based on construction plans. Specific steps during this phase include:
Tree preservation plan components include:
During this phase, the trees and site are prepared for actual construction activities. Accomplishments during this phase include:
The construction phase is where actual site disturbance and building construction occur. The construction phase is where physical tree impacts are most likely to happen. Accomplishments during this phase include:
-Root collar covered by fill soil
This phase includes the time period after building construction and most site disturbance is complete. Steps to this phase include:
As can be seen, there are many steps to preserving trees during construction. However, the effort is worth it to preserve trees that bring significant benefits to a property. In order for trees to be properly preserved, an arborist must be brought in to a project in the project planning phase. If trees aren’t considered until later phases of construction, it will likely be too late to properly protect them and allow trees to survive and thrive.
Today I had the opportunity to evaluate a honeylocust (Gleditsia triacanthos) for a client that was concerned about the health and safety of the tree. The client was concerned about the tree because it seemed to have decay in its stem and was in close proximity to a driveway and parking lot.
To evaluate the tree, I performed an ANSI A300 Level 3 Advanced Risk Assessment. This assessment included a ground-level inspection of the tree's crown, base and trunk plus surrounding site conditions. Resistance-recording drilling was performed to analyze trunk decay. Such an assessment details tree characteristics and then compares the likelihood of tree failure to the likelihood of damage from failure to assess overall risk.
TREE AND SITE CHARACTERISTICS
The tree measured approximately thirty inches in diameter at a height of 4.5 feet, which is the standard height for measuring tree size.
The tree had a wound in the trunk at a height of six feet on the east side where an old stem was removed. The wound measures approximately sixteen inches by sixteen inches. There is an old pruning wound at twelve feet. There is little to no callus wood around the wounds. Callus is a type of wood that forms in response to wounds in an effort by the tree to seal off the wound. A lack of callus indicates stress in the tree. A fruiting body had been previously removed at a height of three feet on the north side of the tree, which could possibly indicate internal decay.
The tree is approximately 35-40 feet in height. The crown is somewhat one-sided to the east. The tree's leaves appeared green and healthy overall, with only a small amount of dead limbs present in the crown. A small number of leaves have damage from leaf chewing insects, but this damage does not appear severe enough to significantly affect tree health.
The tree is somewhat mature. This means that the energy cost to the tree to maintain itself is beginning to exceed the energy input the tree receives from photosynthesis. This will lead to the tree becoming less able to resist the spread of decay in the future.
I utilized a tool called an IML Resistograph to test for the presence of decay in four locations around the circumference of the trunk at a height of approximately 4.5 feet. The Resistograph uses a small drill bit to penetrate the tree stem and determine the amount of sound versus decayed wood present in a tree. The amount of sound wood is compared to stem diameter to estimate the amount of strength the tree has lost as a result of the presence of decay. The Resistograph showed very little sound wood present where I tested.
The table below shows an accepted manner within arboriculture for evaluating tree risk qualitatively. The likelihood of tree failure and impact are compared to the potential consequences of failure to determine overall tree risk.
Tree risk assessment matrix. Source: www.isa-arbor.com
If the honeylocust were to fail, the main potential targets would include the entry drive, power lines and the parking lot. This accounts for the failure of the entire tree or portions of the tree, such as individual branches. Potential damage would include property damage and injury to persons under the tree. The most likely failure route is to the east or north, which means damage would occur to power lines and potentially the entry drive. Therefore, I rate the potential consequences of tree failure as SIGNIFICANT.
I rated the tree as LIKELY to fail and impact a target, given the tree's overall condition, combined with its presence near several targets as described above.
As can be seen in the table, a combination of LIKELY failure and impact and SIGNIFICANT consequence of failure equates to a HIGH overall tree risk.
I recommended the tree be removed. There are no remedial actions other than removal that would reasonably reduce the amount of decay present in the tree, which is the main concern. Therefore, the high risk present in the tree cannot be reasonably reduced without removal.
People often ask me what the difference is between a consulting arborist and an arborist/sales rep from a tree care firm. Why am I a consultant and somebody from XYZ tree company is not? While there are many similarities (we are both arborists), there are a few differences.
As a consulting arborist, when I visit a property I am not there to sell the client something. What I am selling has already been sold - generally my time and my opinion. The time involved in visiting a property, writing a report, developing a plan, testifying as a witness, etc. are what a you pay a consultant for. In paying for their time, you are also paying a consultant for their expert opinion on a given topic related to trees. A final product such as a report or tree management plan is also generally provided.
Arborists from most tree care firms will generally visit a property free of charge, provide an evaluation and then prescribe a service, if necessary. They provide this service for free because they make money off of the services they sell during their visits. There is nothing wrong with this model; it is just different from what a consultant will do.
Many consulting arborists also have expertise outside of traditional arboriculture. My main outside expertise is in urban planning, municipal government and data visualization/mapping. Such outside experience gives a consultant a more-wide ranging of trees. For instance, my experience in municipal government is useful in interpreting codes and ordinances as they relate to trees. My knowledge of urban planning is useful in understanding the design and functionality of cities, and how trees can be used as a functional element of this design. Consulting arborists also attain credentials that most others do not, such as Registered Consulting Arborist. Some may have other certifications and accreditations, such as LEED AP, CNU-A or AICP. This just goes to show that they have enough experience in an area to have attained certification.
So when do you need a consulting arborist? And who should hire one?
The ASCA website does a great job of explaining this:
So just be aware of the differences. If what you need is advice, unaffected by a future sale, hire a consulting arborist.
One of the most common questions I get from clients and attendees at speaking engagements is this:
What tree should I plant in my yard?
I always wish I could give a straightforward answer and instantly spit out the names of one or two trees that will thrive in their yards for the next 50+ years.
Unfortunately it is not that easy, as there are many factors to consider. Failure to think through your choice could doom your newly planted tree, or at least limit it in living up to its full potential. Here are a few considerations to help determine what will best meet your needs and the growing requirements of the tree.
So many aspects of tree health are determined by the soil in which it grows. It is much easier to select a tree suited to the soil you have than to try to adjust the soil to a certain species. Is it clay? Sand? Loam? Cement? Bricks? This website gives a good overview of how to determine the texture of your soil. However, you may want to consider sending in a sample to a local lab if you want a detailed analysis.
(Not so) high quality soil is often what urban trees are forced to grow in.
2. Tree goals
Do you want shade? Wildlife attraction? Fruit to eat? Home energy savings?
A good question to ask is: what is missing in my yard that could be at least be partially provided by a mature tree? For a good overview of urban tree benefits, check out the website for the Friends of the Urban Forest, here.
3. Growing space
What is important here is the mature size of the tree. Make sure you consider the tree's crown as well as its base. The online tree selectors, below, all give a good idea of mature tree height and spread.
This tree needs more space than it has been given to grow, and will therefore never live up to its full potential.
And remember to look up. You don't want to plant a tall-growing tree under utility lines.
Some trees will require more water than others. Some have leaves that can be a pain in the fall. Roots of some species are more prone to lift sidewalks or enter basement walls. Do you want to grow grass/shrubs/perennials under the tree but future shade will require heavy pruning?
These are just a few factors that can cause maintenance issues years down the line. Make sure you take these and others into consideration.
Online tree selectors
Once you have determined the above information, you can input everything into an online tree selector. A couple of my favorites are below.
When selecting a tree to plant, there are a lot of variables to consider - mature height/spread, soil needs, climate, fruiting, aesthetics, etc. Luckily there are a number of online tree selectors that can do the thinking for you. You simply put in the variables (or as many as you know) and the selector spits out a list of trees suitable for your planting location. Below are 5 of my favorites. These work well for the Upper Midwest, but can be applied to many other parts of the country as well. The University of Florida Selector is my favorite of the bunch, but all will work relatively well.
1. University of Florida - http://lyra.ifas.ufl.edu/NorthernTrees/NorthernTreeSelector.swf
2. Minnesota Department of Transportation - http://dotapp7.dot.state.mn.us/plant/faces/index.jsp
3. Arbor Day Foundation - http://arborday.org/shopping/trees/treewizard/intro.cfm
4. University of Illinois Extension - http://extension.illinois.edu/treeselector/
5. Morton Arboretum - http://www.mortonarb.org/trees-plants/tree-and-plant-advice/tree-selector
This past summer, the Green Building Certification Institute (GBCI) officially launched the Sustainable SItes Initiative (SITES) rating system. GBCI is the organization that certifies LEED projects and accredits LEED professionals. SITES addresses many of the landscape and site issues that are vital to sustainability outside of the physical building.
From the SITES website - "The Sustainable Sites Initiative is a program based on the understanding that land is a crucial component of the built environment and can be planned, designed, developed and maintained to protect and enhance the benefits we derive from healthy functioning landscapes."
We've been hearing about SITES for a few years now. It's development began in 2006, through a collaboration between the Lady Bird Johnson Wildflower Center, United States Botanic Garden and the American Society of Landscape Architects. A 2 year pilot recently certified 46 projects across the country.
Being an arborist and urban forester, I am largely interested in how SITES concerns trees. Broadly, the topics of climate change, biodiversity and resource depletion concern urban trees. Specific credits concern the topics of landscape water use, managing precipitation on site, native plants, urban heat islands and energy use around buildings. These are all marked improvements from any LEED rating system, which only gives minimal attention to the landscape. How effective these credits are at achieving their intended goals will be seen as more SITES projects are registered, but I am hopeful that they will make projects both more environmentally sustainable and marketable.
I look forward to having the opportunity to learn more about SITES and hopefully work on some projects under the new rating system.