JOIN USRecent news reports about trees which fell down in Bangalore and posed a threat to life and property is a serious issue. This happens because the tree’s root system is denied water and air, leading to its malnutrition. Eventually this affects the strength of the tree to remain upright for long.
Once a Garden City, Bangalore is gradually losing its green glory owing to various developmental activities. Yet, it is not too late to save the existing tree cover around us. How then do we go about this exercise? In this context some suggestions by a tree lover about how to ensure the health of the subterranean root systems are worth considering.
Trees are synonymous with their green canopies which are visible, but their root system which is invisible, “anchors” the tree to mother earth. It is therefore necessary to comprehend the characteristics of the root system in order to conserve the invaluable life of these trees in and around our homes and cities.
Trees have a strong root system which is almost two thirds of their aerial structure which comprises the trunk and canopy. The root system has a main large and strong root, the downward continuation of the trunk, called the tap root that grows deeper into the soil.
It produces many branches called the secondary roots, which grow in an inclined and horizontal manner deeper into the soil. The secondary roots further produce smaller branches known as tertiary roots, which grow in a similar manner. These tertiary roots produce further branches or tiny root hairs which originally absorb a major part of water and nutrients. The spread of the root system below the soil extends almost to the circumference of the tree canopy above.
Soil water and soil air are very important for a healthy root system, but they are not fully available to the trees growing in cities because of asphalted roads and concreted pavements which do not allow percolation of water and exchange of gases into the soil.
This makes the root system fragile and weak, unable to withstand and hold the tree, even from a light wind or rain. As a result, trees tend to wither and fall. The water poured around the stem, around the root ‘flare’ (the joint of the trunk and root system) may not reach the root hairs. At least two thirds of the canopy “drip space” should be left around the trunk, on the surface of the soil, to enable percolation of water, aeration of soil and humus formation.
How does one attempt to conserve trees in a concrete jungle? In a concreted or asphalted surface of soil, vertical poly vinyl chloride or mud or iron pipes of 2-4 feet in length and 4-6 inches in diameter can be inserted into the soil after drilling out the soil, around the stem, in the canopy “drip” area of a tree. These tubes should be porous in their peripheral walls.
After installation, these tubes are filled with large-sized gravel or broken bricks of 3-4 inches width or even raw coir fibre, which allow percolation of water and enable gas exchange into the soil. Around 8-10 such pipes can be inserted in different directions, in two concentric circles of four each, with a gap of 6-8 feet between each pipe around the trunk.
The upper edge or the rim of these tubes shall be closed by welding a sieve plate (porous plate) of plastic or iron in order to make the surface of these tubes even with the surface of the surrounding cemented area. During monsoons, the rain water collected around the tree on a concreted surface flows into these tubes and enters the soil where the roots are abundant. During dry season, water can be manually poured into these pipes to enrich the soil water around the roots. This can be done on an experimental basis.
Avoid asphaltation
Another method to save the existing trees is to avoid complete asphalting or concreting the soil below the tree canopies. Instead, the canopy “drip area” under a tree can be paved with slabs of cement or stone, leaving a gap of an inch or two between the slabs. To increase the aesthetic value, the common Cyanodon grass, (garike hullu in Kannada), can be grown between the slabs.
This also enables percolation of water and gas exchange. In fact, shrubs are more suitable in areas with less soil and narrow roads. Even when they are uprooted there will be less damage and will also be easier to grow and maintain them.
When every individual attempts to save water, grow plants and conserve the health, wealth and the beauty of nature many more ideas will evolve and our surroundings will remain young forever.