In this article we will discuss about:- 1. Introduction to the Forests of India 2. Classification of Forests 3. Direct Benefits 4. Indirect Benefits 5. Impact of Climatic Factors 6. Site Quality 7. Bioclimate and Microclimate 8. Stand Types 9. Restocking.
Introduction to Forests of India:
Forest is a complex ecosystem consisting mainly of trees that have formed a buffer for the earth to protect life forms (plants, animals, insects, microorganisms, etc.). The FAO has defined forest as land with tree crown cover (or equivalent stocking level) of more than 10 per cent and area of more than 0.5 hectare with more than 5 m height trees. In general, forest is a land set aside for the production of timber and other forest products.
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The history of Indian forests is closely linked with political history. The Epics Ramayana and Mahabharata give an attractive description of forests. The Dandakaranya, the Khandavban and the Nandanvan come from them. Ancient Hindu culture is said to have evolved in Aranyas. Literatures are not, however, scientific treatises. Nevertheless, they give a glimpse into the dim and distant past. They are an indication of the level of significance the forests had in the cultural life of people.
The earliest indication of forestry administration in India is found in 300 BC. It was during the reign of Chandragupta Maurya. A Superintendent of Forests looked after forests and wildlife. Later, Ashoka the Great continued the process and much importance was given for planting trees along roadsides and camping sites. Ashoka is said to have set up the first sanctuary to protect the forests and all life in it.
The Mughal policy on forests was one of indifference. Neither did they seem to pay much attention to the forests nor did they have any religious scruples to destroy them. The Mughal rulers were avid hunters and spent a great deal of time in the forests. The Mughals looked upon the forests as game reserves. They were interested in trees for gardening. They also showed interest in plantations on either side of avenues.
They therefore, displayed an aesthetic and utilitarian approach to plants. They lacked any comprehensive understanding of forests and lacked definitive approach for their preservation, propagation, protection and improvement. The forests were reclaimed for agriculture and the State supported this through incentives. Parts of the farmer community were pushed back into the forests due to the Mughal invasion. They took up shifting cultivation and damaged the forests.
Heavy destruction of forests also occurred in the later part of the 18th and early part of the 19th century. Europeans carried away much of the produce. In the early years of British Raj, large indents were made on the timber wealth of the country. The teak forests along the coast of Malabar were over-exploited.
The timber was supplied to meet the requirement of the British Navy. But it was during the British rule that the first practical move towards conservation in modern times took place. In the post-independence period, the task of consolidation of forests, unification of forest laws and extension of scientific management on a reasonably uniform basis was the most important task of forest administration.
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Rapid development and progress saw large forest tracts fragmented by roads, canals and townships. There was an increase in the exploitation of forest wealth. It was only in the 1970s that the importance of conservation of forests was realized and the preservation of India’s remaining forests and wildlife was given a front seat.
Classification of Forests:
Forests can be broadly classified into many types, some of which are the taiga type (consisting of pines, spruce, etc.), the mixed temperate forests with both coniferous and deciduous trees, the temperate forests, the sub-tropical forests, the tropical forests and the equatorial rainforests. It can be also be classified in different ways and to different degrees of specificity.
One such way is in terms of the “biome” in which they exist, combined with leaf longevity of the dominant species (whether they are evergreen or deciduous). Another distinction is whether the forests composed predominantly of broadleaf trees, coniferous (needle-leaved) trees, or mixed. Accordingly world’s forest can be grouped into 26 major types, which reflect climatic zones as well as the principal types of trees.
These 26 major types can be reclassified into 6 broader categories:
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(1) Temperate needle leaf forest
(2) Temperate broadleaf and mixed forest
(3) Tropical moist forest
(4) Tropical dry forests
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(5) Sparse trees and parkland forests, and
(6) Forest plantations/ planted forest.
In the tropical and subtropical region, forests are further subdivided into plantations and natural forests. Natural forests are forests composed of indigenous trees, regenerates naturally and not deliberately planted. Plantations are forest stands established by planting or/and seeding in the process of afforestation or reforestation or for some profit oriented purpose. In India, there are about 16 major types of forests from the tropical type to the dry type.
Vegetation Types of India:
1. Tropical Wet Evergreen Forest – Dense tall forests, entirely evergreen or nearly so.
2. Tropical Semi Evergreen Forest – Dominants include deciduous species but evergreens are predominant.
3. Tropical Moist Deciduous Forest – Dominants mainly deciduous but sub-dominants and lower story largely evergreen, top canopy even and dense but 25 m high.
4. Tropical Dry Deciduous Forest – Entirely deciduous or nearly so, top canopy uneven rarely over 25 m high.
5. Tropical Thorn/ Scrub Forest – Deciduous with low thorny trees and xerophytes predominants, top canopy more or less broken, less than 10 m high.
6. Tropical Dry Evergreen Forest – Broad leaved evergreen trees predominates with some deciduous emergent, often dense but usually under 20 m high.
7. Littoral and Swamp Forest – Mainly evergreens of varying density and height but always associated predominantly with wetness.
8. Subtropical Broad-Leaved Hill Forest – Broad-leaved largely evergreen high forests.
9. Subtropical Pine Forest – Pine associated predominant.
10. Subtropical Dry Evergreen Forest – Low xerophytic forest and scrubs.
11. Montane Wet Temperate Forest – Evergreen without coniferous species.
12. Himalayan Wet/ Moist Temperate Forest – Evergreen forests mainly scleriphyllous oak and coniferous species.
13. Himalayan Dry Temperate Forest – Coniferous forests with sparse xerophytic undergrowth.
14. Sub-Alpine Forest – Stunted deciduous or evergreen forests, usually close formation with or without confers.
15. Moist Alpine – Low but often dense scrub of evergreen species.
16. Dry Alpine – Xerophytic scrub in open formation mostly of deciduous in nature.
Benefits of Forests:
Direct Benefits of Forests:
i. They provide a sustainable source of timber (for cabinets, wardrobes, kitchens, desks/tables, chairs, doors, floors, paper, musical instruments, sports goods, boats, agricultural tools), food, fruit, fibre, fuelwood, charcoal, etc.
ii. They also provide NWFPs like essential oil, gum, resin, latex, tannin, dye, beads for jewellery, bio-fuel, bamboo, palm, rattan, etc.
iii. Trees provide organic fertilizer, through the falling of leaves, branches and root segregates.
iv. Leaves provide a high-protein, palatable animal forage and cattle fodder.
v. They have provided medicines for centuries for malaria, heartburn, measles, lung diseases, rheumatism, flu, leprosy.
vi. They serve as national/ international borders.
Indirect Benefits of Forests:
i. They improve living standards for local people.
ii. They create microclimate conditions for life to flourish.
iii. Through shade and by evaporating moisture from their leaves, trees can reduce daytime temperatures by about 5°F and buildings by 20°F.
iv. The roots reduce soil erosion in rainy seasons and replenish the ground with nutrients from the air e.g., nitrogen fixation.
v. They retain groundwater supporting surrounding growth.
vi. Tree roots stabilize river banks, reducing the risk of flooding.
vii. They rebuild worn soils and improve agricultural productivity.
viii. Cooling ground temperatures and sheltering from direct sunlight allows food crops and other growth to return where they otherwise could not grow.
ix. They serve as homes for indigenous wildlife, encourages the return of endangered species. Hence, they sustain eco-system balance and biodiversity.
x. Home for bees, birds, bats, arboreal animals, etc.
xi. Tree and forest can act as natural wind breakers and separate different types of crop farms.
xii. Forest is nature’s gene bank and reservoir of variation and diversity.
It would be impossible for our country to maintain the standard of living it enjoys without the products and services which forests provide. History teaches that the more prosperous nations are those which have productive forests. In every land and in all ages, trees have had an influence on the progress and welfare of man.
His progress form a primitive cave dweller to his present civilized state cannot be told without frequent reference to trees and their products. Trees provided early man with food, medicines, fuel, shelter, protection, shade, tools and other needs. Today, over ten thousand products are reportedly made of and from wood. It is the raw material from which forest industries manufacture countless products for the home, factory and office.
Impact of Climatic Factors on Trees and Forest:
The different climate factors combined together affect the vegetation of a place. These factors influence or modify each other too. This is termed as the bio-climate. Meanwhile, physiography has a profound impact on vegetation, microclimatic types etc. Physiographic factors are as follows – configuration of the ground, altitude or elevation, slope, aspect and exposure.
It is likely that changing temperature and precipitation pattern will produce a strong direct impact on both natural and modified forests. A number of bio-geographical models demonstrate a polarward shift of potential vegetation for the 2 x CO2 climate by 500 km or more for boreal zones.
The equilibrium models and some dynamic vegetation models project that this vegetation shift toward newly available areas with favourable climate conditions will eventually result in forest expansion and replacement of up to 50 per cent of current tundra area.
There is, however, a concern that the lagged forest migration (compare the tree species migration rates after the last glacial period of few kilometers per decade or less to projected future climate zones shift rate of 50 km per decade) may lead to massive loss of natural forests with increased deforestation at the southern boundary of the boreal forests and a correspondent large carbon pulse. At the same time, tree species migration rates can be much more rapid.
Meanwhile, increasing concentrations of the atmospheric CO2, aside from modifying the temperature and precipitation pattern, may also increase the production through the “carbon fertilization effect”. Experiments in closed or open-top chambers have demonstrated the very high potential for CO2-induced growth enhancement, increase in stem growth and higher wood production. Regardless of the contradictory effects of variations in CO2 concentration, insolation, nutrients availability, temperature and precipitation, the forest growth rate have been increasing since the middle of the 20th century.
The climate change-induced modifications of frequency and intensity of forest fires, outbreaks of insects and pathogens and extreme events such as high winds, may be more important than the direct impact of higher temperatures and elevated CO2. At the same time, very few forest production models include these effects, which severely limit the reliability of the model results.
Forest fire may be exclusion here. The last two decades demonstrated increasing burned areas in Canada, the western United States and Russia, because of both climatic conditions and other factors such as fuel conditions, ignition sources, land-use change and variations in fire protection. The potential losses of the timber, pulp and paper production, as well as the damage to health and non-timber forest products caused by elevated fire activity, are quite uncertain as much of the fire damage is expected to occur in less-accessible regions.
For many forest types, forest health questions are of great concern with pest and disease outbreaks as major sources of natural disturbance. The effects vary from defoliation and growth loss, to timber damage, to massive forest diebacks. Even without fires or insect damage, the change in frequency of extreme events, such as strong winds, winter storms, droughts, etc. can bring massive loss to commercial forestry.
These effects of climate extremes on commercial forestry are region-specific. This assessment based on climate projections of Regional Climate Model of the Hadley Centre (HadRM3) using 740 ppm CO2 and 575 ppm CO2 scenarios of Special Report on Emissions Scenarios and the BIOME4 vegetation response model gives the conclusion that, under the climate projection for the year 2085, 77 per cent and 68 per cent of the forested grids in India are likely to experience shift in forest types.
Site Quality of Forest Land:
The productivity of forest land is defined in terms of the maximum amount of volume that the land can produce over a given amount of time. Site quality is measured as an index related to this timber productivity. Site quality will vary with species, for instance a best quality site of teak may not be a poor site for Bamboo species.
Of all the indirect measures investigated, the rate of height growth has been the most practical, consistent and useful indicator of site quality with respect to timber production. The standard practice has been to define site index in terms of the total height of the dominants – the largest, full-crowned trees in a stand.
Site index based on height growth is the most widely accepted method for estimating site quality. Height and age measurements from free-growing, uninjured, dominant and codominant trees are used with a family of height-age (site index) curves to estimate total tree height at a specified index age. For most northern species 50 years is the index age. The site index method is accurate and simple to use when – (1) suitable trees are available for measuring site index, and (2) when accurate site index curves are available.
It is very important to understand that the productivity of timberlands varies greatly by site. On one site, very good growth may be observed, while on another site, the same species at the same age may grow very poorly. Site quality can be changed by fertilization, vegetation control, irrigation, or drainage. Only highly intensive treatment can make a poor site into productive site.
Bioclimate and Microclimate of Forests:
Climate is the set of characteristic temperature, humidity, sunshine, wind and other weather conditions that prevail over large areas of space for long periods of time. The smallest scale sub-climate is the microclimate defined as the climate that holds over a distance (in any direction) of less than 328 ft. (100 m). Microclimate refers to a climate that holds over a very small area. Microclimates usually are slight modifications of the main background climate altered by features in the landscape.
A forest creates a microclimate or bioclimate within the canopy of trees which is cooler, wetter and has altered soil chemistry compared to the area outside the forest. The altered climate found within forests can support organisms that cannot survive in the surrounding grassland. Microclimate frequently supports unique ecosystems. Mountain meadows, river valleys, tidal marshes and crop lands have one or several microclimates which help to determine the amount and type of organisms that thrive in these locations.
Cooling of air temperature due to the effect of trees has been well documented in the past through various studies. A tree can be regarded as a natural “evaporative cooler” using up to 100 gallons of water a day. The release of moisture into the atmosphere through the stomata of leaves is caused due to the evaporation of water at the stomata into the air, thus causing cooling of the air.
Microclimatic effects within a forest cover are explained in terms of morphological characteristics such as branching (bifurcation), growth periodicity (evergreen or deciduous), size, density, texture, orientation of leaves, height of trees, plant coverage, etc. Different forest types have different spatial organizations and so their effects on microclimate.
Generalized microclimatic effects within a forest cover may be described as below:
i. Modification of Energy Transfers – The canopy of a forest cover significantly changes the pattern of incoming and outgoing radiation that is reflected mainly as change in albedo, energy trapped and absorption of short-wave radiation and penetration of light.
ii. Modification of air flow.
iii. Modification of air temperature.
iv. Modification of precipitation.
v. Modification of humidity.
vi. Modification of carbon-dioxide in air.
Stand Types in Forests:
Stand is an aggregation of trees or other growth occupying a specific area and sufficiently uniform in species composition, size, age, arrangement and condition as to be distinguished from the forest or other growth on adjoining areas. The composition of stands is conceived of as being either pure or mixed.
These are defined as:
i. Pure Stand:
A stand in which at least 80 per cent of the trees in the main canopy are of single species.
ii. Mixed Stand:
A stand in which less than 80 per cent of the trees in the canopy are of a single species.
The density of stocking expressed in number of trees, basal area, volume or other criteria, on a per-acre basis is called as stand density.
In addition, stocking is further modified and defined as:
i. Fully Stocked Stands:
Stands in which all the growing space is effectively occupied but which still have ample room for development of the crop trees.
ii. Overstocked Stands:
Stands in which the growing space is so completely utilized that growth has slowed down and many trees, including dominants, are being suppressed.
iii. Understocked Stands:
Stands in which the growing space is not effectively occupied by crop trees.
Stands are usefully described and considered from the stand point of the age classes of which they are composed.
Different stand forms generally available are:
i. Even-Aged Stands:
Stands in which there exists relatively small age differences between individual trees.
ii. Uneven-Aged Stands:
Stands in which there exists relatively large age differences between individual trees. At least 3 age classes are present. A similar meaning is all-aged stand.
iii. Two-Aged Stands:
Stands in which there are two distinct age classes.
Mixed plantation systems seem to be the most appropriate for providing a broader range of options, such as production, protection, biodiversity conservation and restoration. Mixed plantations yield more diverse forest products than mono-specific stands, helping to diminish farmer’s risks in unstable markets.
If planned with consideration for each species’ response to mixed conditions, mixed designs can be more productive than mono-specific systems. In addition, a mixture of species, each with different nutrient requirements and different nutrient cycling properties, may be overall less demanding on site nutrient than monoculture stands.
Mixed plantations can produce more biomass per unit area because competition among individuals is reduced and the site is used integrally. The roots of different species may occupy different soil strata allowing more complete utilization of soil and water resources. More solar energy can be captured because different species have different light requirements and crowns are broadly distributed in the vertical plane.
However, the success of the establishment of mixed forest plantations depends on plantation design and an appropriate definition of the species to be used, taking into consideration ecological and silvicultural aspects.
Restocking of Forests:
Natural regeneration is the process by which forests are restocked by vegetation that develops from seeds/ other mode of propagation originates from the available vegetation. Whereas artificial regeneration is the process of establishing seedlings in the nurseries and planting them in the field for gap filling or planting them in required spacing as plantation.
For the last four decades, forests were restocked and woodlands were created by using transplants grown in nurseries. Natural regeneration was rarely used until the late 1980’s when a combination of factors, including a desire to “do things more naturally”, and a change in the grant structure, lead to its use becoming more popular. Restocking by natural regeneration is often unsatisfactory, frequently for unknown reasons; which demonstrate the need for research to understand the processes occurring.
The main objectives of artificial regeneration are:
1. Supplementing Natural Regeneration:
The natural regeneration is a slow and difficult process and cannot be relied upon. Natural regeneration does not give adequate and uniform stocking over the area. Therefore the failed patches need to be filled upon by artificial methods. The coppice system of working also fails to give adequate natural regeneration and calls for artificial regeneration.
The natural regeneration has always been a problem in Sal bearing moist deciduous forests in Uttar Pradesh, fir and spruce forests in Himachal Pradesh, tropical moist deciduous and evergreen forests in many States and dry deciduous forests containing teak in Madhya Pradesh, Maharashtra, Andhra Pradesh, etc.
2. Replacing Natural Regeneration:
Due to increase in the biotic pressure, the natural regeneration in several areas is poor, slow and uncertain. In such areas, various operations e.g., shrub cutting, weeding, soil working, trenching, etc. increase the cost of natural regeneration but fail to give the desired result. Therefore, it is necessary to regenerate the forest with the help of artificial regeneration which must be done on a large scale where the labour supply is easily available.
Artificial regeneration of fir-spruce forests in Himachal Pradesh, sal forests in Uttar Pradesh, West Bengal and Assam, teak forests in Madhya Pradesh, Maharashtra and Kerala, etc., are some of the examples, where the forests have been regenerated successfully. The artificial regeneration needs to be resorted where the forest fires often obliterate natural regeneration.
3. Reforestation of Degraded Forest Area:
Degradation of forest areas have occurred due to large scale firewood and poles requirement of poor villagers. They are not in a position to purchase firewood or any other fuel for running their hearth. The only easy way for them is to collect fuel wood from the nearby forests. A lot of damage is being done to our forests on account of this factor.
The density of the forest is continuously going down especially in dry deciduous and thorn forests where the pressure of grazing, browsing, lopping, illicit removal and fire are heavy. There is no possibility of reclamation through natural regeneration. Such areas should be reforested by means of artificial regeneration.
4. Increasing Proportion of Valuable Species:
Many forests such as wet evergreen, moist deciduous and also the dry deciduous forests have more percentage of less valuable species. The more valuable species, on account of many factors, are unable to regenerate naturally. Such areas need to be enriched by intensively planting valuable species including exotics too. The value of the forests can be increased by introducing sal, teak, Dipterocarpus, rosewood, etc.
5. Afforestation of Wastelands:
Wastelands have hardly any vegetation due to poor and unstable soil, lack of moisture, swampiness, etc. These areas can be afforested by selection of suitable species and proper technology of plantation development.
6. Introduction of Exotics to Increase Production:
The artificial regeneration can be taken up for introduction of valuable exotics. Some of the exotics which have been selected for plantations are- eucalypts, poplars, acacias, Prosopis, tropical pines, etc.
7. To Increase Production:
Trees occupy land for many years. The land should be used in such a manner so as to give maximum economic returns during a given period of time. There will be a great loss due to low productivity of the area. The total growing stock in India is only 32 cubic m per ha. The present production level is 0.5 cubic m per ha per annum which is not sufficient to meet our growing demands. This can be solved by artificial regeneration of valuable and fast growing species in large scale.
8. To Promote Farm Forestry and Agroforestry:
Growing trees simultaneously with the agricultural crop is always beneficial to trees as well as to the agricultural crop. If the land is not suited to good agriculture, only tree crop can be grown separately or alternately. The various farm forestry and agroforestry models viz., intercropping, alley cropping, etc., will certainly minimize the biotic pressure on the forests.
9. Environmental Conservation:
Planting more and more trees will immensely help in ameliorating climate, conserving soil and water, retaining and developing water courses, controlling drought and floods and protection of fauna.
Artificial regeneration also has certain demerits:
(i) Reduction in Species Richness and Diversity:
The natural regeneration has the tendency to produce mixed crops which are rich in diversity whereas, the plantations are completely devoid of diversity. In a plantation, the canopy density is high and other species find it hard to come up except in failed patches. Due to lack of diversity, the population of wild animals, birds etc., are less as compared to their number in mixed stocking or natural forests.
(ii) Reduction in Soil Productivity:
The plantations are raised after removing the existing vegetation. As soon as the existing vegetation is removed, the soil gets exposed, site conditions are drastically changed and the net result is reduction in soil productivity. Loss in productivity has been observed for many species but no such reduction was found in acacia species. Hence, natural eco-system is the best for soil protection and climate amelioration.
(iii) Large Damage by Pests and Diseases:
The outbreak of pests and diseases in the epidemic form may destroy the whole plantation. The various silvicultural practices e.g., thinning, pruning, etc., may also invite various pests and diseases in the plantation area. The fungus attacks are transmitted mainly through roots rapidly in plantations whereas, their occurrence in natural forest is only sporadic.