Abdul Sahim Ansari 1


Forest is an area set a side for the pt-Auction of timber and other forest produce, or maintained under woody vegetation for certain Indirect benefits which it provides.

Forest constitute some of the most complex natural ecosystems of the world. Environment may be analyzed into a number of factors, such as Soil, Moisture, Wind, Temperature etc. The psycho physiological influence of trees in the form of purified air, clean water, rests and recreation, scenic enjoyment reduced noise level and spiritual replenishment are being fully appreciated. The major parts of healthy environment are FOREST.

The influence of forest on their environment forms part of a vast and complex relationship between environment and forest vegetation Environment generally refers to the sum total of various components of universe that affect life on this earth such as soil, water, and climate etc. Man in generally interferes the environment by destroying vegetation through over-exploitation and mismanagement. Forest improves the environment in many ways such as:

Relative humidity of air is increased. increase fertility of surface soil.

These add large quantities of organic matter in soil by which water and nutrient holding capacity of soil is increased. Domestic animals as well.

In the past, consideration of forests, influence on climate was focused at the microclimate or local level. More recently, increasing attention has been directed at the potential, impact of forests on global conditions.


The forest environment or site consists of the physical environment surrounding the aerial portions of the tree (climatic factors) and that surrounding the subterranean portion (edaphic factor) and the third one is biotic factor. External influences, particularly fire, grazing and browzing animals and humans, affect markedly the nature of sites and their capacity to support tree growth.

As the forest becomes established and develops, the site itself is greatly changed. Forest cover moderates the extreme diurnal temperature regime of open sites resulting in more uniform conditions. Wind velocity is slowed in the vicinity of tree crowns and becomes negligible within the forest.

Trees crowns intercept sunlight and alter the quantity and quality of radiation reaching forest floor compared with that reaching open sites. On the forest floor, accumulating layers of leaves, twigs and other litter attract a characteristic grouping of plants and animals that live on decaying organic matter and on each other.

1.1. Biotic Environment

Ablotic Environment

The physical environment controls the organisms, and organisms also influences and control the abiotic environment in many ways.


2.1. Influence on Air Temperature

Forest vegetation reduces mean annual temperature five feet, above ground from 0.8 to 1.8FO depending upon character of forest and locality, particularly elevation.

The effect of a forest in reducing temperature Is much greater at 5 feet above ground than in the tree crowns.

The following table shows the extent to which species influences the effect of vegetation on air temperature.

Concurrent conclusion of various investigation on the effect of forests on air temperature are:

(a) Forest lower the daily mean temperature in spring and summer and raise it slightly in autumn and winter.

(b) Forest lower the daily maximum of air temperature and raise the daily minimum.

(c) Forest diminish the daily range of air temp. 2.2. Influence on Precipitation

Air of forest is cooler and moister, than a-r in the open. Forest increases the precipitation of any 3rea. As air cools in rising, precipitation increases with increase in elevation. The effect of forest vegetation on precipitation relates to its effect on:

(i) Local precipitation

2.2 Influence on Local Precipitation

The influence of forests on local precipitation at low elevation is negligible but their influence increases rapidly with increase in elevation particularly in mountainous regions.

The forested mountains increase precipitation with increase in elevation to a much greater degree than denuded mountains. Effect of forest on precipitation varies with the species, coniferous trees having a greater influence than broadleaved species (Weber,1903).

2.3 Influence on General Precipitation

The influence of forest on general precipitation is far greater than their local effect. Forest cover profoundly influences evaporation of water from the land. 2.3. Influence on Air Currents.

A forest break or moderate the force of air currents they serve to protect lands lying to their lee against cold and dry winds and against winds of high velocity. three parallel lines of trees planted at 3x2m intervals.

2.4. Influence on Atmospheric Humidity

The effect of forest vegetation .n the relative humidity of the air appears to vary considerably in different localities, more particularly with differences in elevation. 2.5. Influence on Evaporation

Vegetation and particularly forests, in checking the velocity of wind at and near the soil surface, in slightly raising relative humidity of the air in shading the soil, In lowering temperature and in covering the mineral soil with a mantle of leaves and other litter, retards rapid loss of moisture from mineral soil. Loss of moisture through evaporation from surface soil in the open on a windy day may be five times as great as loss of moisture from forest soil of similar character under protection of forest cover. Evaporation from snow surface in the open may be four times as rapid as from similar surface protected by a forest cover.

2.5 Influence on Transpiration Loss

A large part of the water absorbed by vegetation is taken from the soil, enters the transpiration current and is returned to the air through the leaves. Forests often lower the water level in the soil and that the lay6r of forest soil below the surface are usually dryer during the growing season.


3.1. Influence on Soil

The beneficial influence of forest vegetation on soil is due to its beneficial effect and its power of increasing fertility of the land by adding nutrients.

In general the influence of forest vegetation on soil related to -the producing of a new substratum of soil and the changing of soil structure. Forest vegetation assists in the formation of soil by the accumulation of plant remains by stimulating weathering through the action of acids formed by vegetation, and by the resistance which forest vegetation offers to moving air and water.

3.2. Influence on Soil, Temperature

Forest usually reduce the maximum soil temperature and increase the minimum soil temperature with the depth of the soil

The influence of the forest in reducing the maximum soil temperature results partly from the shade of the crowns and partly from the insulation of the forest floor. The influences of forest vegetation on freezing of soil are of great importance. Soil under a forest usually remains soft when that in the open is frozen to considerable depth.

The distance beyond the edge of the forest's influence on the soil temperature is about the same as the distance of the influence on radiation.

3.3 Influence on Seepage and Water Retention

Forest vegetation, by reducing surface runoff, increase the amount of water that percolates into a soil. The effect of forest in preventing freezing of forest soil of vast importance in increasing the amount of water that percolates into it, particularly during the spring months (Auten, 1933).

Forest cover in increasing the volume of soil in mountainous region over the solid rock foundation, increase seepage. The humus layers, characteristic of every well-managed forest, absorb from two to four times their weight of water. Forest soil, with its overlaying organic layers is in a real sense a vast sponge capable of absorbing much more water per unit area than soil in the open. Therefore water-holding capacity of humus rich soils is highly increased.

3.4. Influence on Wind Erosion

Soil is transported from one place to another either by wind or by water. Forests, by checking the velocity of wind and by reducing surface runoffhave a great influence on the stability of soil. Sands subject to wind erosion should be covered with forest growth or their soil binding plants because permanent, stability can be attained only where sands liable to shift are so covered (Kellogg, 1915).

3.5. Influence on Water Erosion

One of the most important and far-reaching influences of the forest is the protecting of the soil from washing. Forest plays an important role in erosion control owing to the combined effect of:

3.6. Influence on Springs

Part of the water that seeps into soil at higher elevations reappears at the surface lower down in springs. A forest through its influence in increasing seepage and decreasing, surfaces runoff provides a large supply of ground water, particularly in mountainous and hilly region, for the feeding of springs. In level contrives where the general effect of an forest is to drain the soil and lower the ground water, springs seldom cover and the effect of the forest upon them is of minor importance.

3.7. Influence on Floods

Forests, in reducing surface runoff and increasing seepage, extend the time over which precipitation reaches as streams. The most striking influence of forest vegetation on stream flow is shown where heavy


4.1. Influence on Animal life

Plants are probably the most important feature in the environment of terrestrial animals. All animals are dependent directly or indirectly upon plants for food. Forests also provides many animals with shelter from inclement weather, protection from enemies, situation for homes, and materials for nests.

4.1.1.Forests as Source of Food for Animals

Many forest animals feed very largely upon seeds, fruits, buds, leaves, twigs and other parts of forest plants, other feed in forests when food is plentiful there and scarce elsewhere.

4.1.2 Forest as a Source of Shelter and Protection

Forests provide protection for most terrestrial 'game birds. classed as game are more or less dependent upon forest for food and protection.

4.1.3.Forest Influence on Animal Distribution

4.2. Influence on Mankind

4.2.1. Influence on Civilization

Forest have had an important influence on the distribution of mankind over the earth's surface. Three stages in the relation of human progress to forests.

In regions where forests are abundant, logs and lumber are usually so dwelling; but in regions leaving forest or where forests products are scare


5.1. Favorable Influence on Weather

5.2. Carbon Sink

Forest have the potential to contribute to climate change through their influence on the global carbon cycle. Forest are being recognized as playing important roles in global biochemical cycle. Major pools of carbon are the atmosphere, fossils fuels, oceans and terrestrial biota and soils. Forest have the potential to influence global warming in other ways too. Carbon pools In forest

The world's forests contain more than 55% of the global carbon stored in vegetation and more than 45% of that in soil. Most of the carbon Pools in forest vegetation is located in tropical forests (62%), whereas most of the carbon pool in forest soils is located in boreal forests (54%).

To prevent environment it is essentially to prevent carbon emissions by conserving existing carbon pools in forests and establishing plantation on non forested lands.The adoption of forest management options that conserve and sequester carbon would help to prevent forests from becoming a significant net source0f C02 for the atmosphere in the future and thereby help to offset other factors that contribute to accelerate global warming.'

Experiments have repeatedly d3monstrated an increased productivity of crops and trees when irrigated with waste water as compared with clear water. The application of waste water at the rate which ensure a balance between nutrient input and plant uptake will promote optimal plant growth while limiting the risks of pollution.


Trees and other green plants produce oxygen and consume carbon dioxide. Major pollution such as water, air and noise pollution can be controlled through forests.

6.1 Air Pollution

According to who, air pollution may be defined as:

A wide range of inorganic gases, organic compounds, inorganic metallic substances and root particles, is discharged into the atmosphere by motor vehicle, factories, power plants, have furnaces and waste incineration plants. Air Pollutants

Following are the major air pollutants:

6.2.Control of Air Pollution through Forests

Plants materials are among the most effective air conditioners in existence. Under present circumstances and grave situation of air pollution it appears that plant as a great source of natural air conditioning is being overlooked.

Forests play an important role in climate amelioration by reducing the intensity of solar radiation, modifying temperature, reducing evaporation from soils and increasing the amount precipitation.

6.3 Plants as air cleaner

Plants Perform an important role in reducing air pollution and thus they act as cleaner.

6.4 Water Pollution

6.4.1 Causes of Water Pollution

Water pollution arises from a variety of sources industry, domestic sewage, agricultural fertilizers and feedlots, construction activities, and forest practices. Toxic chemicals dumped by both industrial units and government agencies are the major source of water pollution. These chemicals are greatest threat to fresh water. - Pesticides

6.4.2. Control of Water Pollution through Forests

Plants reduce pollution in water and can hold top soil in place, thereby reducing the sediments and nutrients as a pollutant to water resources in the following ways:

Erosion control and watershed protection

Plants use in conservation practices reduce water cause soil erosion by intercepting rainfall, holding soil with their roots, and increasing water absorption through addition of organic matter. 'thus plants are more attractive than mechanical water erosion control devices.

In forest, pesticide or insecticides are commonly used to control harmful insects and pests. Salts occur naturally in soils and waters. In humid regions, rain readily leaches salts out of the soil. The salts present is the water are thus the main source of salt accumulation in those soils. Plants. Many fruit trees also absorb salts through their leaves.

6.3 Noise Pollution

Experts refers to noise as "Invisible pollution".

6.3.1 Causes of Noise Pollution

Today traffic is the major source of human communication, which ultimately lead to noise pollution.

6.3.2 Control of Noise Pollution through Forests

Wind Belt
Proper Highway Design

Plants mask unwanted sounds. Wind Belt

Tree species did not differ greatly in their ability to reduce noise levels, provided that deciduous trees are in full leaf. Proper Highway Design

Well design planting in such situation can aid tremendously in sound control. It is concluded that plants play a vital role in noise abetment. They can become more effective in playing their role of noise control if planted in massive form. Thus trees, shrubs and all other vegetation aid in noise pollution reduction if used properly.

The present study deals with the biological and physical influences of forests, as it relates to the weather and other environmental factors.

Summary and conclusion

Forest environment can be conveniently divided into two broad categories, which are biotic environment and abiotic environment.

Biotic environment includes living organisms while abiotic environment is related with those physical and non-living chemical aspects, which exert an influence on linings organisms such as soils, water, atmosphere etc.

The influence of the forest in modifying climate under the trees is matter of common experience. Air humidity is relatively high under tree cover. Wind speed is reduced in forests.

In varying degrees, the forest affects light and solar radiation, air temperature, wind, atmospheric humidity, precipitation, evaporation and transpiration.

Forests modify physical and chemical properties of soil through addition of organic matter, decomposition of leaves and other plant parts, root penetration and activity of other animals inhabiting the forest. The forest is more than a defense against erosion. Forest Influences.

Forest influence upon water production is a controversial subject. Some attribute all the desirable qualities of streams which issue from forest land to climate and geology and they deny any effect of forest itself. Some, on the other hand, are so certain that the forest alone is responsible for good water supplies.

Forests help in reducing floods in the hills as well as in the plains by reducing the volume of surface run-off.

Forests have also sanitary influences upon environment due to the production of oxygen through photosynthesis. Forest plays a major role in reducing various types of pollution such as water, air and noise pollution.

Influences of forest upon biotic conditions include its effect on animal life and mankind. Forests significantly influence the life of many terrestrial animals. Forest acts as source of food and shelter for many animals. The life of man is affected by the presence or absence of forests. All the above mentioned influences also affect human life.


The first thank should go to Miss Fakiha Zaffar for her contribution towards this paper. The author would also like to express his profound thanks and appreciation to Mr. Birendra Kandel, Nepal National Parks Department for his contribution towards my research study.


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