Stop paving space around roots of big trees with concrete or tar. Let the trees breathe
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Trees need appropriate amounts of loose, moist, well aerated, and uncompacted soil in order to mature in the urban environment. These conditions enable the tree’s roots to obtain nutrients, oxygen, and water – all essential for healthy tree growth. Trees need enough soil volume to thrive and reach maturity.
Thousands of old, big trees are falling down in bangalore, Kolkata, and other cities and suburbs in India, over small stints of rainfall or storm . One of the major reasons is, paving the areas around roots of these trees with concrete, tar etc. Also, buildings built by the side of the roads have deep bases built with bricks and concrete. So there are no space for the trees roots to grow and breathe. Requesting policy makers of our country to leave enough space and soil around trees roots and trunks, for the roots to be able to breathe and grow.
“Trees in urban areas are frequently observed either failing in the face of hostile growing conditions, or surviving and causing damage to pavement”
If soil alone is depended on as a structural material and required for the load-bearing of buildings, vehicles, and pedestrians; it will be compacted to the point that air and water are excluded and a totally insufficient space for root growth will be available.
Trees planted in unsuitable urban tree pits are usually surrounded by compacted soil which often leads to the roots seeking out the space between the compacted soil and the paved surface above, where air and water are present. This then causes pavement heaving. If tree roots can’t grow into surrounding soil, they continue to grow until they have filled the space that’s available.
When a tree’s need for nutrients, water, and air can no longer be met, the health of the tree suffers and the tree begins to decline and eventually die.
So, how much uncompacted soil do trees need to be healthy and reach maturity? Various methods of determining required soil volume may be used to calculate the approximate below ground space that a tree should need for healthy root growth like
* Mature Canopy method
* Mature Trunk Caliper Method
and many more.
As a general rule:
32ft for canopy development may be allowed for large trees
20ft for canopy development may be allowed for medium trees
10ft for screens, shelter belts, or park group plantings
Allow a minimum of 8ft in any instance
Minimum recommended soil volumes are:
Small Tree: 5-15 cubic meters
Medium Tree: 20-40 cubic meters
Large Tree: 50+ cubic meters
So how do we maximize uncompacted soil volume available for root growth without jeopardizing a stable base for sidewalks and roads? Soil support cells (refer https://www.greenblue.com/na/type/soil-cells/assemble underground form a structural matrix filled with uncompacted soil to accommodate healthy root growth, while also providing a load-bearing structure for paved surfaces. They are the proven method for street trees, successfully implemented on thousands of projects around the world.
By understanding the soil conditions that urban trees need to reach maturity, landscape architects and related professionals can take the required steps in specifying the systems and best practice procedures that will ensure the success of our urban tree canopies.
Would like to draw attention of our policy makers, citizens and government, to come forward, and make sure the green cover of our cities can be maintained and grown further.
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