Theory:

Forest prevents flood:
  • Forest absorbs rainwater and allows it to seep.
  • That helps in maintaining the water table throughout the year.
  • In the absence of the forest, the rain hits on the ground can flood the area.
  • Rainwater will damage the soil causing an erosion. Trees bind the soil and thus prevents soil erosion.
  • Forests thus not only prevent flood but also maintains the flow of water in streams, so that there is a constant supply of water.
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(Ncert book class 7 science - chapter 17)
  
Forest provide habitat to organisms:
  • There are different vegetation that support different organisms to inhabit the forest.
  • Forest thus provides food and shelter to animals, birds, insects, and for humans who inhabit the forests. 
  • A food chain of the forests is depicted below.
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  • Sun is the ultimate source of energy information of the food chain.
  • Green plants harness the energy of the sun to make food (sugars).
  • Energy from producers or autotrophs is passed on from one organism to another. From the producers, the energy goes to primary consumers (herbivores) and then to secondary consumers (carnivores), then, to the tertiary consumers and so on.
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Forest as a dynamic living entity:
  • Forests harbor a large variety of plants and thus provides enough for food for the herbivorous animals. And, these herbivorous were consumed by carnivores.
  • The wide variety of animals helps forests to regenerate and grow.
  • Decomposers maintains the supply of nutrients to the plants in the forest.
  • The forest is thus a dynamic living entity.
  • Thus, the forest is a dynamic living entity as we see interactions between the soil, water, air, plants and the animals that present in the forest.
Forest regenerate on own:
  • Dead parts of the plants and trees, dead animals, and the animal wastes keeps accumulating in the forest floor.
  • Decomposers like fungi and bacteria degrades to simple organic material called humus.
  • The humus makes the soil fertile as it has mineral salts that enrich the soil.
  • The animals, birds, wind and water disperse the seeds in the forest soil.
  • Seeds germinate to form seedling and then grows to form the forest vegetation.
  • This way, the forest regenerates on its own.