REPORT: Landscape Planning and Ecological Management: Plantation of bare root common trees.
We often take trees and other flora, all around us, for granted maybe because almost all of us have seen trees and captured the word and their image deep inside our sub-consciousness. As we grow up, we learn about the benefits and advantages of trees parrot-fashion. No person or entity teaches us anything about the aesthetics so when we see captivating landscape photographs and images, we take in the beauty without taking in the trees. It is beyond this point that most of us change directions and go off towards modern, fast-process systems, which we then proceed to specialize in. Say once or twice every five years, trees come to our mind but that is in such situations such as hurricane uprooting ancient tree, kids asking us about them etc. In recent years, things have changed to some extent. Like all other subjects, trees too are an ardent and interesting subject, this fact being already known by those few among us who have made careers out of forestry.
In the past fifteen to twenty years, in a development eerily similar to the word “innovation”; another word the present day media and everyone else appears to have been possessed with is the word” sustainability”. Now, sustainability is a word, which by itself means nothing. As we are aware, nature has always carried out a balancing act, throughout. All organisms in nature, are intricately related to each other so that different systems are balanced with each other making each other’s existence possible. This is the way by which different organisms depend on each other so that only co-existence is possible and not sole existence. This is what ecology is all
about i.e. Sustainability is this example of an entity or organism so that ecological designs should ensure that the eco-system is not only value enhanced, but should also be perennial like nature originally meant it to be This is what has been pointed out by Johnson and Hill.(2001). The overall design of the landscape along with soil management should be in harmony with nature. .In case the ecological balance gets a little biased than, the changes introduced will not be sustainable.
Soil requirements of a plantation of bare root common trees.
Let us now focus on the characteristics of the soil required by tree plantations, (the most important factors being soil and water). As there is presumed to be no shortage of water earlier, for landscaping it is generally such that the bed on which the trees are planted are given a gradient. Depending upon the type of soil, the gradient can be slightly more or less but without the gradient the water will have the tendency to accumulate at the ground which is definitely not good for tree sapling. For planting of the trees, the following are the specifications as per the International Society of Arboriculture
“ For trees and shrubs planted in individual holes in areas of good soil that is to remain in place and/or to receive amendment in the top 150-mm (6 in.) layer, excavate the hole to the depth of the root ball and to widths shown on the drawing. Slope the sides of the excavation at a 45 degree angle up and away from the bottom of the excavation.” (Guide for Developing Planting Specifications, International Society of Arboriculture; n.d. )
What does soil consist of? Lavelle and Spain (2001) defines soil as “an unconsolidated‚ stable‚ three-dimensional assemblage of organic‚ mineral and organic-mineral materials with a characteristic biota and located at the earth’s surface” Soil contains the following in varying proportions and/or intensities
– Soil constituents
There are four main constituents of soilAir, Water, Minerals and SOM (Soil Organic Matter). SOM is in general found in soil in very small quantities in proportion to the others. But even then, any change in this small quantity is enough to bring radical changes in soil fertility. The other factors as evident also influence soil properties by being in varying quantities at different places.
In soil ecology, Soil is expected to do and carries out the following functions. (a) Serves as a mechanical prop (b) stores water (c) allows passage of air and (d) provides food for the plant. Hence, for a particular plant or tree, the best soil is the one which allows the optimum use of the above.
The maximum organic matter is found in the region (layer A) which gives the layer a slightly darker appearance in comparison with the rest of the layers. This layer plays a very large role in fertility enhancement and reduction of the soil
– Soil Formation and Texture
Soil formation is a process, which takes place over time. Weathered debris finds itself in a layer over which final soil gets deposited and then a layer of fallen leaves and biological waste, gets distributed. Finally over the compost, wind and other agents of change builds a top soil layer. This is hidden away from sunlight over another layer of fallen leaves and debris. The same is shown in the picture above for easy comprehension.(Sectional view of the layers of soil). Here A, which is the topsoil layer is vital as it plays a very important role for the young plant. Most of the SOM concentration is in the layer A. It should be noted that the boundaries shown in the sketch are very discernible. All soils will not show such marked difference as far as boundary demarcation is concerned. However, the layers will be more or less as per the order shown.
Diameter and approximate size of four soil particles.
Soil mainly consists of four primary ingredients which are minerals, sand, silt and clay. The different proportion of each, which may be present in the soil, is called the Soil Texture. Soil Texture’s importance in ecology and horticulture lies in the fact that different textures suit different plants and hence texture is an important concept in planning of trees, arboriculture and horticulture projects. As shown in the table above, particles of size 2mm or less are only considered while discussing and/or designing texture for a particular cultivation. But, from where do we get this soil texture and can it be changed as per our convenience? The answer is negative. Soil texture is a result of weathering of different types of rocks throughout the centuries. Different types of rocks, different conditions of weathering, the contours of the area under consideration etc. result in different textures. For instance, sandstone weathering produces sand but if located in water logged areas, then the texture can be silt-sand mixture. Soil texture also plays a very important role in the water absorption capacity of the soil. Soil can have voids and crystals in which case, porosity of the water increases. However, some plants/trees require a longer retention period of water as these plants need more water. How mixtures of the four constituents of the soil give rise to soil having more commonly used names is shown below.
This figure shows how different textural characters of soil come about at different proportions of sand, silt and clay.
Water is such an important characteristic of management of soil ecology that we will again briefly touch it here.The concept of porosity is very important and has to be understood if one is to understand the role of water in soil ecology. For the seedling to become a sapling and then on and on growing into a mighty tree, the presence of water is necessary and its percolation is necessary too. Without water, the organic stickiness, which works as a sort of adhesive paste will be absent. Now, subsoil compaction now comes into the picture. On planting, the roots of the tree will go downward following the percolating water and say because of over compaction, if the water makes its way much too slowly, two things can happen here. As the percolation rater will minimize, water may accumulate and the roots if immersed in water for long periods may suffer damage and disease.
Again, the roots of the plant may not appear to grow straight down as due to the unnecessary compaction of the soil, the roots may contort, thicken and even corkscrew. Finally, (this may sound very simple but a lot of wannabe farmers) make this mistake.
Why trees should not be watered at the trunk? Watering at the truck is fine at the young stage.
When the tree has grown enough to open its boughs, water provided at the trunk of the tree serves no purpose It is the root ends which require sustenance and watering should be done along the perimeter of an circle upto which the root ends can be estimated to have gone upto..
The Crucial Water-Plant Water Relationship is expressed in the above figure in simple terms. To Here, the percentage water content is plotted against the fineness of the soil texture.
The Plant-water relationship, as shown in the image, shows us that say at first the field is flooded with water and saturates all the soil’s need for water. Any excess water is now run-off. We will first define a few terms such as Field Capacity (FC) which is the amount of water after loss due to gravity i.e. the water which is absorbed by the earth and contributes to ground water. The balance water is either held by capillary action at the microspores or held by the forces of surface tension. The water which remains in the soil after the capillary and surface tension water is water unavailable to the plant as the soil holds the water too firmly to give it up. Therefore, from the saturation point to the point, upto the point where all water in the soil, which is extractable and usable by the plant, is marked by a boundary called ‘the wilting co-efficient line’, as shown in the figure.
Now, Soil compaction is defined as an increase in the density of unsaturated soil. The top layer of agricultural soil experiences cycles of loosening and compaction during the year. This is due to tillage and traffic as well as weather conditions and inherent soil processes triggered by soil conditions.
Chemical and Biological properties:
The soil pH value indicates the acidic or basic nature of the soil. Generally the colloids will have
negative charges but they will be neutralized by the positive ions in the image below which are mostly of Hydrogen.
The Biological properties of soil ecology is also very well designed by nature in the sense that earth worms here act as the skilled engineers. They eat the soil burrow down and again come back, shed whatever they have eaten in the process thoroughly aerating the soil
An earth worm burrow not only aerates but also makes passages for water.
We have covered most of the topics which need mention for tree planning. The job may be strenuous and exhausting but then giving life, always is.
– Ehlers, W. Goss, M. J. CAB (2003) Water Dynamics in Plant Production; CABI Publishing
– Johnson, Hill & Melnick (2001) ; Ecology and Design, The Island Press, Washington, USA
– Lavelle, P. Spain, Alister V. (2001) Soil Ecology ; Kluwer Academic Publishers, NJ, USA
– Rees, R. M. Ball, B. Watson, C. (2001) Sustainable Management of Soil Organic Matter; CABI Publications, Cambridge USA
– Robinson, Nick Wu, Jia-Hua (2004) Planting Design Handbook, Ashgate Publications GBR
– Schjonning, P. Elmholt, S. Christensen, B. T.(2003);Managing Soil Quality : Challenges in Modern Agriculture, CABI Publications USA