An ecosystem is a naturally occurring, interrelated group of plant and animal life that works together to live and grow within a community. Thousands of years of co-evolution have resulted in several distinct native plant communities here in southern Wisconsin, including prairies, woodlands, wetlands, and aquatic ecosystems, to name a few. Each has its own groups of interrelating species and requirements. The introduction of exotic invasive species and pests has posed challenges that we are trained and equipped to manage.
Soil Compaction
Our main concern with the general construction process is soil compaction. The addition of concrete and the process involved in installing the concrete pose the most danger. Soil compaction cuts off air and water to the tree roots. The damage caused by soil compaction occurs slowly, sometimes not becoming evident for several years. BEST PRACTICES during construction in or around the root systems of existing trees should involve an absence of machinery within the dripline of the specific tree in question. The root zone should be designated by a barrier such as an orange construction fence with a designation of “No Machinery or Vehicle Traffic Allowed.”
Raising the Existing Grade
Grade changes are often necessary during the construction of a new building. When the grade around an established tree is being raised, consider methods of preventing injury to the tree before the fill is made, rather than attempting to take corrective measures after the damage has been done. While the initial cost may be high, prevention is always cheaper and more effective than attempting to correct the situation after damage has been done.
Remove all vegetation, including underbrush and sod, beneath the branch spread of the tree. Break up the top 3 to 6 inches of soil carefully to disturb the least possible amount of roots. This allows better contact between the fill and soil surface. Apply fertilizer at recommended rates.
Construct an open-joint wall of shell, brick, rock, or masonry in a circle around the tree trunk, with at least 2 feet minimum between the wall and trunk. This wall should be as high as the top of the new grade. This opening is commonly referred to as a tree well.
Construct an aeration system using 4-inch perforated PVC pipe arranged in five to six horizontal lines radiating from the tree well like spokes in a wheel to a point beyond the branch spread. Allow excess moisture to drain away by installing the radial lines so they slope away from the trunk. Connect the outer ends of the radiating system with a circle of perforated PVC pipe.
Cover the exposed soil and PVC system with clear gravel to a depth of 6 to 18 inches, depending on the amount of fill. Place a layer of woven plastic or other porous material over the gravel to prevent soil from filtering into the gravel and stone. Fill with good topsoil to the desired grade. To discourage rodents, fill the tree well with enough coarse gravel to cover the ends of the lines opening into the well. Also, fill the upright bell tile and cover with a screen or grill. To provide vents, place 4- or 6-inch plastic pipe or bell tile upright over the junction of the radial lines with the circle. They should extend to the surface of the planned grade level.
The tree well can be left open, covering the grade with decorative gravel or mulch.
Severing Roots
Although some cutting of roots near construction is inevitable, much of it can be avoided with good planning and cooperation. It is not necessary to route underground utilities in a straight line from the street to the house. Careful route selection can often avoid the root systems of important trees. If this is not possible, reduce damage by tunneling beneath the roots. To reduce trenching for foundations, substitute posts and pillars for footers and walls.
Prairie Restoration
Of Wisconsin’s 2.1 million acres of original native prairie, less than 10,000 acres still exist today. These highly diverse communities are an important part of the ecosystem, and their restoration is crucial. We can assist in the soil preparation, seeding, and maintenance of your prairie restoration.
Many invasive species plague our landscapes and natural ecosystems, especially Buckthorn, Honeysuckle, Multiflora Rose, and Garlic Mustard. We use several methods to control these invasive plants depending on effectiveness, budget, and the scope of your project.
Other Problems
Often, when grade changes are made, the terrain is altered, and there may be a change in how water drains from the land. If too much water drains into a wooded site, trees in that area may eventually die from a lack of oxygen. It may be necessary to build a drainage system to maintain the previous amount of moisture that provided natural growing conditions for the existing trees. If sites are deprived of water, irrigation may be necessary to maintain existing trees.
Watch for equipment damage to limbs and trunks and repair promptly. Chemicals and other products that are often dumped on a construction site can change the soil chemistry, weakening and oftentimes killing trees on the property. To prevent adverse effects on construction site soils:
Spread a heavy plastic tarp where concrete is to be mixed or sheet rock will be cut. These materials raise the pH, causing alkaline soils. Do not clean paintbrushes and tools over tree roots. Dispose of chemical wastes (paint thinner, oil, etc.) properly. Do not drain these wastes on-site.