Biogeography

Answer : A biome includes all plants, animals and soils of all those areas of the world where all the biota have minimum common characteristics and all the areas of biome are characterized by more or less uniform environmental conditions. The biome or biotic region is in fact a large natural ecosystem.

Following major biotic regions can be identified on the basis of vegetational type and structure, climatic type, pedogenic regime and soil-moisture regimes:

1. Tropical Evergreen Rainforest Biome
2. Monsoon Deciduous Forest Biome
3. Savanna Biome
4. Mediterranean Biome
5. Temperate Grassland Biome
6. The Boreal Forest Biome
7. Tundra Biome
8. Marine Biome

Ecological Aspects of the Monsoon Region:There are three major areas of tropical deciduous forest (Monsoon) biome, viz.

(i)The Neotropics, mainly West Indies

(ii)Indo Malaysian Zone and

(iii)E-Africa & Northern Australia Climate

The monsoon biotic region is characterized by two distinct seasons viz. moist season and dry season. Average temperature of warm dry summer season ranges between 270C and 320 C. On an average the mean annual rainfall is around 1500 mm but there are wide variation in temporal and spatial distribution of rainfall. Temporally more than 80% of mean annual rainfall is received within 3 wet months of summer. So, there is a long dry season. This seasonal regime of annual monsoonal rainfall gives deciduous character to the vegetation characterized by a distinct shedding season.

Pedogenic Regime: Despite the dry season, a substantial soil-moisture availability exists during rainy season. Humus does not accumulate much, leaching of bases and silica is the dominant soil forming process. Common soil types are ultisols, oxisols and alfisols.

Plant Community: The number of plant species is less in the monsoon biome than the rain forest biome. Since the density of plants is also lower in this biome than the rain forest biome so there is comparatively less competition among the plants for getting sunlight. The height of most of the trees ranges between 12 m and 30 m.

There are four strata or layers in the vertical structure of the tropical deciduous forests. The uppermost and the second strata consist of trees, the third stratum is formed by shrubs whereas the last and fourth stratum or ground stratum represents herbaceous plants.

Most of the trees are deciduous but the shrubs of the third stratum are evergreen. The trees are characterized by thick girth of stems, thick rough and coarse bark and large hydromorphic leaves or small, hard xeromorphic leaves. The large hydromorphic leaves enable the trees to trap more and more rainfall during wet seasons but these large leaves are shed in dry periods to conserve moisture whereas small and hard xeromorphic leaves enable the trees to withstand dry weather.

Though there are numerous climbers mainly Lianas and Epiphytes but their numbers are far less in the tropical deciduous forest biome than the tropical evergreen rain forest biome.

Sal and teak trees of Indian deciduous forest form forest canopy but its shape is not like umbrella as in the case with rainforest. Bamboo is another important member of these forests. Besides there are numerous trees, climbers, shrubs and grasses which have spatial variations from one region to the other.

Monsoon forests are excessively exploited for a variety of seasons—it gives hardwood timber which fetches good returns and population pressure is also very high.

Fauna: Fauna of any region is largely affected by the composition and structure of vegetation. It is a significant ecological principle that more is the development of stratification of the vertical structure of the vegetation community and greater the number of plant species, the more will be the number of animal species. This ecological principle holds good in the case of tropical evergreen rainforest. But there are lesser number of animal species in the monsoon biome than the rainforest biome because of comparatively less developed vertical strata and hence less diversification of animal species.

The seasonal character of vegetation, full development of leaves during rainy months, shedding of leaves in dry season etc., has affected and determined the seasonal behaviour of animal communities particularly breeding and migrating behaviours. For example, birds in east Africa breed twice during the two different seasons.

The animals of this biome range from very small animals (mirco-organisms) to very large-bodied animals like elephants, horses, hippopotamus, rhinos, lions, forest bufalo together with a large population of birds of several species. This biome represents the largest number of domesticated mammals because of the development of agriculture. This biome also carries the largest number of human population of the world.

The forests and wild life of this biome have been adversely affected by both natural and anthropogenic factors. This has caused several environmental problems in this region.

Answer : To serve many purposes e.g. timber, firewood, economy, environment, the term and practice of social forestry came into being. Social forestry is seen as an instrument of sustainable development and environmental conservation. Thisis due to its potential of resolving three basic issues of rural poor simultaneously. It has a capacity to provide food security, fuel security and livelihood security with eco-friendly approach to development thus leading to sustainable development. Social forestry has been maintained by the government and significant funds set apart for its progress. Even international agencies are giving generous support for social forestry not only to increase the supply of fuel-wood and fodder, but also to ensure the participation of the rural poor so that the control of these resources would be in the hands of the poor.

The social forestry (SF) is nothing but the trees planted by the community, individuals, government or the individuals outside the conventional forest area. It has many objectives viz. to serve the need of fuel wood and timber, to provide fodder, to provide raw materials, to provide other forest produce and moreover, provide livelihood to rural population and make rural economy diversified and therefore viable.

The social forestry has considerable scope in present scenario as the ill-effects of ongoing practices are coming at the fore. Therefore, the social forestry has been emerged as an engine for change. Though it was conceived as to be the better option in respect of environmental conservation, yet the results have not been the same. The problem is that it has been converted into monopractice i.e. using only few particular species which brings their own adverse impact over the environment.

Answer : The major divisions of soil are-Zonal, Intrazonal and Azonal.

Zonal Soil: These soils reflect climate and vegetation to a large degrees, hence they are formed on well-drained sites on non-extreme parent material.

1. Tundra Soil: Tundra soils are closely influenced by the low temperature. Chemical weather and biological activity in such a cold climate are very limited and water-logging is widespread in summer. This mature soil is known as Arctic soil.
2. Podzol Soil: Russian term meaning ‘ash soil’ that occurs widely in the moist cool climates of mid-latitudes. It is a pooragriculture soil. Huge areas of the coniferous forest regions of the northern Canada and the northern Russia are covered with Podzol.
3. Grey-Brown Podzols: It develops in a temperate climate of moderate rain fall, but it has a greater organic content and is less leached than a true podzol.
4. Chernozem: In Russian language black earth is known as chernozem. It is a fine,fertile soil, black in colour. It covers an extensive area of Russia, Ukraine and Kazakhistan and part of Hungary and Rumania.
5. Prairie Soil: It is a dark-coloured soil in the mid-latitude, sub-humid climatic zone beneath the temperate grassland. These soils occur in eastern Europe and in the U.S.A. from south of Minnesota to Oklahoma.
6. Chestnut-Coloured Soil: These soils are essentially a variety of chernozem. These occur in the steppe areas where about 20 to 25 cm of rainfall is recorded annually. These soils are found in parts of Russia, Rumania, and Hungary are also found in high plain of the U.S.A., Argentina and South African Velds.
7. Red Desert Soil: These are redish- brown soil of the hot deserts. These are mainly ofa sandy texture and contain much salt because of the absence of leaching.
8. Latosol: It is lateritic soil which developed in the hot and humid area. These soils are found in Amazon and Zaire basins, Central America, the coast of Brazil, eastern Madagascar and Indonesia.

Intrazonal Soil: These are:

1. Saline Soil: The pH value of saline alkali soil is around 8.5. Such soils are also known as solontez.
2. Peat Soil: Dark-brown soil material consisting of slightly decomposed fibrous vegetable matter. Peat is a very important source of fuel in some northern countries. e.g. Russia and Ireland.
3. Calcareous Soil: Soils containing calcium carbonate are known as calcareous soil. Rendzine, red and brown mediterranean soil and the brown calcareous soil are some of the examples of this group.

Azonal Soil: These are

1. Mountain Soil: These soils develop on stony unstable surfaces as scree slope or on glacial moraines. These are also known as scree soils.
2. Alluvial Soil: A mixture of sand, silt and clay, consisting of well- mixed rock waste transported and deposited in level beds by running water. The Indo - Gangetic plain, the plains of Hwang - Ho and Yangtze- Kiang, the plain of Mississippi and Missouri etc. are examples.
3. Marine Soil:These soil is deposited by sea-wave action. It is found along the coast of Belgium, Netherland, Germany and Denmark areas of former sea floor, known as polders.
4. Glacial Soil: These soils are deposited by the glacial and fluvial-glacial process. The variety of glacial deposits includes tills, outwash sands and gravels. These soils are generally poor in humus content.
5. Wind-Blown Soil: The wind deposits sand sheets, dunes and loess which are the wind-blown soils. The loess deposits of China, borde of Germany, limon of Belgium are examples.
6. Volcanic Soil: The recent volcanic activity deposits lava, ash and pumice, which weathered easily are transported lower down the slopes of volcanoes by rain-wash and torrents.

Answer : Till the time a balance exists between the process of soil formation and soil erosion, there is no problem. When this balance is disturbed, the soil erosion becomes a menace. Indiscriminate felling of trees, careless overgrazing of pasture lands, Unscientific drainage operations and improper land use are some of the important causes which upset this balance. Soil erosion is a major problem in the world.

The two most active agents of soil erosion are wind and running water. Wind erosion is common in arid and semi-arid areas of the world. Light soil are more susceptible to wind erosion than heavier soil. Sands removed by wind spread over adjoining cultivated lands and destroy their fertility.

Water erosion which is more serious and occurs extensively in different parts of the world and takes place mainly in the form of sheet and gully erosion. Sheet erosion takes place on level lands after heavy shower and the soil removal is not easily noticeable. Gully erosion is common on steep slopes. Gullies deepen with rainfall, cut the agricultural lands into small fragments and make them unfit for cultivation. Several factors contribute to soil deterioration. For example, when the forests are cut, the supply of humus to the soil stops, and the capacity of running water to remove its top layer increases. If drainage system is disturbed, water logging or loss of soil moisture takes place, and if it is over used, it loses its fertility.

The agents of soil erosion are running water, wind, snow, animals and human beings. Human beings disturb the soil ecology by deforestation, overgrazing and uncientific methods of cultivation. Deforestation is one of the major causes of soil erosion.

Soil Conservation: Contour bunding, countour terracing, regulated forestry, controlled grazing, selective weeding, cover cropping, mixed farming and crop rotation are some of the remedial measures which are often adopted to reduce soil erosion.

In arid and semi arid areas; efforts should be made to protect cultivable lands from encroachment by sand dunes through developing shelter belts. forest lands not suitable for cultivation should be converted into pastures for grazing. Efforts should be made to stabilise sand dunnes.

Efforts should be made to prevents gully erosion and control their formation. Finger gullies can be eliminated by terracing. In bigger gullies, the erosive velocity of water may be reduced by contructing a series of check dams. Some important and well known measures to conserve soils are as follows:

Scientific crop rotation

Contour ploughing and bunding

Afforestation especially in the upper reaches of river basins.

Construction of barriers against water gullies in wet regions and against wind in desert and semi-desert regions.

Increased use of organic manures.

Replacing flood irrigation by sprinkler and drip irrigation.

Answer : Weathering has been defined as the total of all processes acting at or near the earth's surface to cause physical disruption and chemical decomposition of rocks in situ. In other words, weathering is the process by which rocks are broken down and decomposed by the action of external agencies such as temperature change, rain, wind, plants, bacteria etc.

Rocks are disintegrated and decomposed and ultimately are broken down into smaller pieces due to the operation of different weathering processes, viz. physical weathering, chemical weathering and biochemical weathering. These different weathering processes produce immense volume of rock waste of weathered materials. These weathered material lying over the unweathered rock are called regoliths.

These weathered material are very economically important because they help in the process of soil formation since soil is nothing but the upper weathered layer of the earth's crust. It is a dynamic entity which is always undergoing physical, chemical and biological changes. Weathering contributes both in the formation of soils and physical and chemical changes occurring in the soil.

Soil is made up of substances existing in three states-solid, liquid and gases. The major part of the solid portion of soil is inorganic matter. Weathering of the rocks produces inorganic particles that give a soil the main part of its weight and volume. These fragments range from gravel and sand down to tiny colloidal particles.

• Rain forests are characterized by the most dense forest cover on the earth and they are also the most bio-diverse regions among the forests. Amazon basin is one of the most important regions where maximum development of rain forest biome has taken place.
• Man has also started to damage this biologically rich ecosystem through his rapacious economic activities. A sizeable portion of Amazonian rain forest has already been damaged through mining activity and industrial as well as agricultural expansion.
• The construction of large dams and reservoirs on Amazon and its tributaries at the cost of rich forest cover has upset the ecological balance of the area.
• The powerful elite society and even the local Brazilean government is not paying any attention to the mass movement of the local aborigins against mass felling of trees.
• However, the Amazon rain forest could have been exploited on a sustainable basis maintaining a balance between the requirement and the environmental concerns.
• The high biomass and high biodiversity of the region provides ample scope in this context but long term priorities will have to be kept in mind.