PRESERVING EXISTING TREES THROUGH CONSTRUCTION
Successful tree preservation during site development
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In general, most trees require the soil to be somewhat porous to allow for a gas exchange between the air and the tree's roots. This exchange is crucial to their health, just as it is for us to be able to breath properly. Most tree roots grow within 12" of the surface of the ground, so vehicle traffic, regular mowing and extensive foot traffic all can cause soil compaction and can have a dramatic affect on the health and appearance of trees over time.
Better stewardship of our trees during site development and construction
The first strategy in any site development should be to preserve as many trees as possible and include them in the site design and arrangement while fulfilling as much of the client site criteria. In a heavily wooded site, not all trees can remain; it just wouldn't be economically feasible in most conventional commercial developments to build without the densities necessary for a return on investment. However, in a well thought out site layout a good landscape architectural planning team can maintain a good mix of site building and vehicle parking criteria, while preserving trees, the existing site assets.
Here are some proven methods of tree preservation that work well in conjunction with site development;
Maintain the same slope and elevation of the natural ground under any remaining existing trees, and do not add soils to the area under the canopy or at the trunk base.
Create a fencing perimeter during construction to stop use of these areas and protect trees from soil compaction or scaring from heavy equipment while construction is under way. An adequate fencing distance can be measured by calculating the perimeter of the 'root protection zone'. The root protection zone equals 1 foot radius outward from the trunk for every inch of trunk diameter, measured 4 feet from the ground. This will give an accurate location for establishing a fencing perimeter around any existing site trees.
Where it is feasible, bore utilities instead of trenching to minimized impact on existing tree root structures where utilities cross trees path.
Where it is possible, try to maintain under story plantings which protects existing trees roots from hot drying sun and wind. If sod or another ground cover is proposed as the finished planting, wait until all construction is complete, before removing any existing under story shrubs or groundcovers under existing trees. Since most new plantings are installed near the completion of building and paving construction, the roots exposure time will be minimal. This technique will minimize the shock to the tree and soften the affect of any site changes.
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