Chapter - 17 Forests : Our Lifeline

• Forest is a system comprising various plants, animals and micro-organisms.
• In a forest, trees form the uppermost layer, followed by shrubs. The herbs form the lowest layer of vegetation.
• The forest floor provides favourable conditions for seeds to germinate and develop into seedlings and saplings. Some grow up into trees. The branchy part of a tree above the stem is known as the crown of the tree. The branches of the tall trees look like a roof over the other plants in the forest. This is called a canopy.
• Trees have crowns of different types and sizes. These had created different horizontal layers in the forest. These are known as understoreys.
• Giant and tall trees constituted the top layer followed by shrubs and tall grasses, and herbs formed the lowest layer.
• Due to different climatic conditions there are variations in the types of trees and other plants. The types of animals also differ from forest to forest.
• The forest floor is dark coloured and is covered with a moist layer of dead and decaying leaves, fruits, seeds, twigs and small herbs.
• There are several organisms and micro-organisms that live in the soil. They feed upon the dead plant and animal tissues and convert them into a dark coloured substance called humus.
• The micro-organisms which convert the dead plants and animals to humus are known as decomposers. These micro-organisms play an important role in the forest.
• All animals depend ultimately on plants for food. Organisms which feed on plants often get eaten by other organisms, and so on. For example, grass is eaten by insects, which in turn, is taken by the frog. The frog is consumed by snakes. This is said to form a food chain: Grass→ insects→ frog→ snake→ eagle. Many food chains can be found in the forest. All food chains are linked. If anyone food chain is disturbed, it affects other food chains. Every part of the forest is dependent on the other parts.
• The presence of humus ensures that the nutrients of the dead plants and animals are released into the soil. From there, these nutrients are again absorbed by the roots of the living plants.
• Plants release oxygen through the process of photosynthesis. The plants help to provide oxygen for animal respiration. They also maintain the balance of oxygen and carbon dioxide in the atmosphere.
• Trees take in water from their roots and release water vapour into the air through evaporation.
• The animals also disperse the seeds of certain plants and help the forest to grow and regenerate. The decaying animal dung also provides nutrients to the seedlings to grow
• By harboring greater variety of plants, the forest provides greater opportunities for food and habitat for the herbivores. Larger number of herbivores means increased availability of food for a variety of carnivores. The wide variety of animals helps the forest to regenerate and grow. Decomposers help in maintaining the supply of nutrients to the growing plants in the forest. Therefore, the forest is a 'dynamic living entity '
• The forest also acts as a natural absorber of rainwater and allows it to seep. It helps maintain the water table throughout the year. Forests not only help in controlling floods but also help maintain the flow of water in the streams so that we get a steady supply of water. On the other hand, if trees are not present, rain hits the ground directly and may flood the area around it. Heavy rain may also damage the soil. Roots of trees normally bind the soil together, but in their absence the soil is washed away or eroded.

REASONS TO PROTECT FORESTS

1. The amount of carbon dioxide in air will increase, resulting in the increase of earth's temperature.
2. In the absence of trees and plants, the animals will not get food and shelter.
3. In the absence of trees, the soil will not hold water, which will cause floods.
4. Deforestation will endanger our life and environment.