A forest is a complex ecosystem which is predominantly composed of trees, shrubs and is usually a closed canopy. Forests are storehouses of a large variety of life forms such as plants, mammals, birds, insects and reptiles etc. Also the forests have abundant microorganisms and fungi, which do the important work of decomposing dead organic matter thereby enriching the soil. Nearly 4billion hectares of forest cover the earth’s surface, roughly 30 percent of its total land area.

The forest ecosystem has two components- the non-living (abiotic) and the living (biotic) component.Climate, soil type are part of the non-living component and the living component includes plants, animals and other life forms. Plants include the trees, shrubs, climbers, grassesand herbs in the forest. Depending on the physical, geographical, climatic and ecological factors,there are different types of forest like evergreen forest (mainly composed of evergreen treespecies i.

e. species having leaves all throughout the year) and deciduous forest (mainly composed of deciduous tree species i. e. species having leaf-fall during particular months of the year).Each forest type forms a habitat for a specific community of animals that are adapted to live in it. The term forest implies ‘natural vegetation’ of the area, existing from thousands of years and supporting a variety of biodiversity, forming a complex ecosystem.

Plantation is different from natural forest as these planted species are often of same type and doesn’t support a variety of natural biodiversity. Forests provide various natural services and products. Many forest products are used in day-today life. Besides these, forests play important role in maintaining ecological balance & contributes to economy also.Ecological Role of Forest: • Forests provide an environment for many species of plants and animals thus protects and sustains the diversity of nature.

• Plants provide habitat to different types of organisms. Birds build their nests on the branches of trees, animals and birds live in the hollows, insects and other organisms live in various parts of the plant. • Forests act as hydrologic flow modulators • Plants provide a protective canopy that lessens the impact of raindrops on the soil, thereby reducing soil erosion. Roots help to hold the soil in place.They provide shade which prevents the soil to become too dry.

Thus increases the soil moisture holding capacity. • Forests help in maintaining microclimate of the area. • Plants clean the air, cool it on hot days, conserve heat at night, and act as excellent sound absorbers. Transpiration from the forests affects the relative humidity and precipitation in a place.

Forests clean the environment by muffling noises, buffering strong winds and stopping dust and gases. • The layer of leaves that fall around the tree prevents runoff and allows the water to percolate into the soil.Thus helping in ground water recharge. • Dead plants decompose to form humus, organic matter that holds the water and provides nutrients to the soil. • Through the process of photosynthesis, forests renew the oxygen supply in the atmosphere by absorbing atmospheric CO2 and moderating the greenhouse effect.

As per the report published by Ministry of Environment and Forests during August 2009, the annual CO2 removal by India’s forest and tree cover is enough to neutralize 11. 25 % of India’s total GHG emissions (CO2 equivalent) at 1994 levels.This is equivalent to offsetting 100% emissions from all energy in residential and transport sectors; or 40% of total emissions from the agriculture sector. Clearly, India’s forest and tree cover is serving as a major mode of carbon mitigation for India and the world.

• Forest cover of an area plays an important role in amount of precipitation received by the area. Thus play an important role in maintaining water cycle of the area. • Some species of trees have the ability to return nitrogen to the soil through root decomposition or fallen leaves.Such trees are planted to increase the nitrogen content of the soil.

• Forests absorb suspended particles in air thereby reducing pollution. • Forests also helps in the process of soil formation by causing weathering of rock • They play vital role in maintaining healthy watershed. Rivers originate in a forest area and carry the organic matter from forest to the downstream thus supporting a variety of fishes and aquatic animals. The richness of forest in upstream decides the biological value of the river ecosystem supported by it.

It provides forest food which has great medicinal value and used by local people in respective season. In performing all these functions, forest stabilizes the climate, maintains the ecological /environmental balance of the area and shape the landscape of the area. Contribution to economy:• It provides valuable items like timber, paper, fuel wood, bamboo, cane, food, fibers, essential oils. • Forest plants provide hundreds of medicinal plants, spices, poisons, insecticides, soap substitutes like ritha and shikakai, tendu leaves used in bidi wrapping. Forests also provide fodder for cattle and other grazing animals.

Leaves and twigs of some plants have high fodder value. It is useful fodder source during drought. In addition to this forests are also popular areas for relaxation & recreation and they add to the aesthetic value of the area. Classification of Forests: Forests can be classified in different ways.

The forest type depends upon the abiotic factors such as climate and soil characteristics of a region. Forests in India can be broadly divided into coniferous forests and broadleaved forests.They can also be classified according to the nature of their tree species-evergreen, deciduous, xerophytes or thorn trees, mangroves, etc. They can also be classified according to the most abundant species of trees, such as Sal or Teak forests. In many cases, a forest is named after the first three or four most abundant tree species.

Coniferous forests grow in the Himalayan mountain region, where the temperatures are low. These forests have tall stately trees with needle-like leaves and downward –sloping branches, so that the snow can slip off the branches.Broad-leaved forests are of several types, such as evergreen forests, deciduous forests, thorn forests, and mangrove forests. Broad-leaved trees usually have large leaves of various shapes and are found in middle to lower latitude. Evergreen forests grow in the high rainfall areas of the Western Ghats, North –eastern India and the Andaman and Nicobar Islands.

These forests grow in areas where the monsoon period lasts for several months. Deciduous forests are found in regions with a moderate amount of seasonal rainfall that lasts for only a few months.Most of the forests in which Teak trees grow are of this type. The deciduous trees shed their leaves during the winter and hot summer months. Thorn forests are found in the semi-arid regions of India.

The trees, which are sparsely distributed, are surrounded by open grassy areas. Mangroves forests grow along the coast especially in the river deltas. These plants are uniquely adapted to be able to grow in a mix of saline and freshwater. They grow luxuriantly in muddy areas covered with silt that the rivers have brought down.The mangrove trees have breathing roots that emerge from the mud banks.

Tropical rainforests Tropical rainforests can be characterized in two words: warm and wet. Mean monthly temperatures exceed 18 °C (64 °F) during all months of the year. Average annual rainfall is no less than 168 cm (66 in) and can exceed 1,000 cm (390 in) although it typically lies between 175 cm (69 in) and 200 cm (79 in). This high level of precipitation often results in poor soils due to leaching of soluble nutrients. Tropical rainforests are unique in the high levels of biodiversity they exhibit.Around 40% to 75% of all biotic species are indigenous to the rainforests.

Rainforests are home to half of all the living animal and plant species on the planet. Two-thirds of all flowering plants can be found in rainforests. A single hectare of rainforest may contain 42,000 different species of insect, up to 807 trees of 313 species and 1,500 species of higher plants. Tropical rainforests have been called the "jewels of the Earth" and the "world's largest pharmacy", because over one quarter of natural medicines have been discovered within them.It is likely that there may be many millions of species of plants, insects and microorganisms still undiscovered in tropical rainforests. Tropical rainforests are among the most threatened ecosystems globally due to large-scale fragmentation due to human activity.

Habitat fragmentation caused by geological processes such as volcanism and climate change occurred in the past, and have been identified as important drivers of speciation. However, fast human driven habitat destruction is suspected to be one of the major causes of species extinction.Tropical rain forests have been subjected to heavy logging and agricultural clearance throughout the 20th century, and the area covered by rainforests around the world is rapidly Mediterranean forests Mediterranean forests, woodlands, and scrub biome, as defined by the World Wildlife Fund, are characterized by dry summers and rainy winters. Summers are typically hot in low-lying inland locations but can be cool near some seas, as near San Francisco, which have a sea of cool waters. Winters are typically mild to cool in low-lying locations but can be cold in inland and higher locations.The Mediterranean forests, woodlands, and scrub biome can be found around the world.

More specifically, it occurs in the world's five Mediterranean climate zones, on the west coast of These regions are home to a tremendous diversity of habitats and species. Vegetation types can range from forests to woodlands, savannas, shrublands, and grasslands; "mosaic habitat" landscapes are common, where differing vegetation types are interleaved with one another in complex patterns created by variations in soil, topography, exposure to wind and sun, and fire history.Much of the woody vegetation in Mediterranean-climate regions is sclerophyll, which means 'hard-leaved' in Greek. Sclerophyll vegetation generally has small, dark leaves covered with a waxy outer layer to retain moisture in the dry summer months. All these ecoregions are highly distinctive, collectively harboring 10% of the Earth’s plant species. [2]Phytogeographers consider the Fynbos (South-Africa) as a separate floral kingdom because 68% of the 8,600 vascular plant species crowded into its 90,000 square kilometres (35,000 sq mi) are endemic and highly distinctive at several taxonomic levels).

In terms of species densities, this is equivalent to about 40% of the plant species of the United States and Canada combined, found within an area the size of the state of Maine. The Fynbos and Southwest Australia shrublands have flora that are significantly more diverse than the other ecoregions, although any Mediterranean shrubland is still rich in species and endemics relative to other non-forest ecoregions. These forests are found to the south of the temperate regions around the coasts of the Mediterranean, California, Chile and Western Australia.The growing season is short and almost all trees are evergreen, but mixed hardwood and softwood.

Temperate forests Temperate deciduous forests or temperate broad-leaf forests are dominated by trees that lose their leaves each year. They are found in areas where warm, moist summers alternate with mild winters. The three major areas of this forest type occur in the northern hemisphere: eastern North America, eastern Asia, and Europe. Smaller areas occur in Australasia and southern South America. Examples of typical trees include oak, maple, beech, and elm.The diversity of tree species is higher in regions where the winter is milder, and also in mountainous regions that provide an array of soil types and microclimates.

One of the world's great protected examples of this forest type is found in Great Smoky Mountains National Park. The principal factor operating in these forests is the seasonal appearance and disappearance of the canopy. Shade from the canopy limits the growth of many kinds of plants; many species that are typical of these forests time their growth and flowering to the short period just before the canopy opens. Hence they are known as spring ephemerals.Examples include trilliums and bloodroot.

Most are insect-pollinated. The seeds themselves are often transported by ants, a mode of dispersal known as myrmecochory. There are a smaller number of species able to grow under the canopy, and even that a few grow during the period when leaves are being lost. Many of the plants have leaf adaptions to cope with low light levels, and the need to exploit moving light flecks on the forest floor. A few understory plants, such as Indian pipe and Corallorhiza orchids, have adapted to the shade by parasitism. The trees similarly are controlled by shade.

Most tree seedlings require small gaps produced by falling trees in order to regenerate. A few require larger gaps such as those produced by windstorms. Gradients of soil moisture, soil depth, elevation and aspect control the distribution of many trees, shrubs and herbaceous species. Some require unusual conditions such as steep slopes, infertile soil, and drought to escape competition from the more common tree species.

Found in such places as eastern North America, northeastern Asia, and western and eastern Europe, temperate forests are a mix of deciduous and coniferous evergreen trees.Usually, the broad-leaved hardwood trees shed leaves annually. There are well-defined seasons with a distinct winter and sufficient rainfall. Coniferous forests coniferous forest is a terrestrial biome found in temperate regions of the world with warm summers and cool winters and adequate rainfall to sustain a forest. In most temperate coniferous forests, evergreen conifers predominate, while some are a mix of conifers and broadleaf evergreen trees and/or broadleaf deciduous trees.

Temperate evergreen forests are common in the coastal areas of regions that have mild winters and heavy rainfall, or inland in drier climates or mountain areas. Coniferous forests can be found in the United States, Canada, Europe, and Asia. Many species of tree inhabit these forests including cedar, cypress, Douglas fir, fir, juniper, kauri, pine, podocarpus, spruce, redwood and yew. The understory also contains a wide variety of herbaceous and shrub species. Structurally, these forests are rather simple, generally consisting of two layers: an overstory and understory. Some forests may support an intermediate layer of shrubs.

Pine forests support a herbaceous understory that is generally dominated by grasses and herbaceous perennials, and are often subject to ecologically important wildfires. Temperate rain forests occur only in seven regions around the world: the Pacific temperate rain forests of the Pacific Northwest, the Valdivian temperate rain forests of southwestern South America, the rain forests of New Zealand and Tasmania, northwest Europe (small pockets in Ireland, Scotland, Wales, Iceland and a somewhat larger area in Norway), southern Japan, and the eastern Black Sea-Caspian Sea region of Turkey and Georgia to northern Iran.The moist conditions of temperate rain forests generally support an understory of mosses, ferns and some shrubs. Temperate rain forests can be temperate coniferous forests or temperate broadleaf and mixed forests.