UNIT 7 TYPES OF ECOSYSTEMS : TERRESTRIAL ECOSYSTEYS Structure Introduction Objectives Biomes of, the World Forests Types of Forests Importance of Forests Deforestation and its Causes Consequences of Deforestation Social Forestry and Forest Conservation Grasslands Typespf Grasslands Economic Importance Dcserts Desertification Indian Deserts Summary Terminal Questions Answers In the previous units you have studied what our ecosystem is and what constitutes this system. As you know the world itself is very vast, and it represepts a big 'ecosystem called biosphere . In an ecosystem there is continuous .functional * inferaction between the living organisms and the non-living materials.' The interrelations between organisms and environment on the land constitute "Terrestrial Ecology". However, due to variation in the topographic features of valleys, mountains and slopes, certain differences are bound to.occur. These differences arrs reflected in both the material and biotic diversities. Altitudinal and latitudinal variations cause shiftsand differences in the climatic patterns. Due to varied climate the plant and animal life existing in different terrestrial areas diversify which result in differentiation of biomes as segments within the large biosphere. In the present unit we shall discuss various types of biomes. Besides, you will learn about the importance of the forests, consequences of deforestation, chipko movement, importance of grasslands and the phenomenon of desertification. Objectives After reading this unit you will be able to : explain the concept of biome and identify various biomes of the world, differentiate between the major types of terrestrial ecosystems such as grassland, forests and deserts, a relate the importance of forests to human welfare. a identify the causes and consequences of deforestation, describe the concept of social forestry and chipko movement, describe the distribution and classification of Indian grasslands, economic and ecological~importanceof grasslands, ecological features of Indian deserts and understand the process of desertification, 0 understand and explain the concept of wasteland and methods of their rehabilitation. 7.2 BIOMES OF THE WORLD 1 As you know, the land mass constitutes Tth of our planet. A large var~etyot plants and animal communities have developed in relationi to climatic and edaphic variations. Types of Ecosystems : As one attempts at combining plant and animal distribution into one system the 1 Termstrid &?systems classifications given earlier were found to be inadequate because plant and animal distributions do not coincide. Another approach was to accept plant formations as the biotic units and to associate animals with plants. This approach is fairly workable because animal life depends on plants. These broad integrated natural biotic units are called biomes. Thus a biome is a large community unit characterised by the kinds of plants and animals present. Each biome consists of a distinctive composition of plant and animal species, the climax communities in each are of uniform life form of vegetation such as grasses or coniferous trees. It also includes stages in the development of the community towards its final form, which may be dominated by other life forms. On a local and regional scale, jommunities are considered as gradients in which the combination of species varies as the individual species respond to environmental gradients. On a larger scale one can consider the terrestrial and even some aquatic ecosystems as gradients of communities and environments on a world scale. Such . gradients of ecosystem are ecolines. Apart from gradual changes in vegetation other ecosystem also changes significantly. As one goes from highly mesic and warm temperatures to xeric situations or cold temperatures, productivity, species diversity, and the amount of biomass decreases. There is a corresponding decline in the complexity and organisation of ecosystems, in the size of plants, growth form and in the number of strata in the vegetation. The following three major biomes,recognised by ecologists as forests, grasslands a'nd deserts occur as belts around the world (Fig. 7.1). Mesophyt~cforest Oak-Hickoryforest Oak woodland Fig. 7.1 r Three major types of biomes, i.e.,fmfft, grasshd-Bnd desert. Ecasystem : Functioning and Types 7.3 FORESTS Now let us see as to what a forest is. The word forest is derived from the Latin word 'foris' meaning outside, the reference being to village boundary fence and must have included all uncultivated and uninhabitated land. Today a forest is any land managed for the diverse purpose of forestry whether covered with trees, shrubs, climbers etc. or not. The forest biomes include a complex assemblage of different kinds of biotic communities. Optimum conditions of temperature and ground moisture responsible for the growth of trees contribute greatly to the establishment of forest communities. The nature of soil, climate and local topography determine the distribution of trees and their abundance or sparseness in the forest vegetation. Forests may be evergreen or deciduous. They are distinguished on the basis of leaf into broad-leafed or needle- leafed coniferous forests in the case of temperate areas. Characteristics of different types of forests arc described below. 7.3.1 Types of Forests The forest biomes of the world have been classified into the three major categories: coniferous forest, tropical forest and temperate forest (Fig. 7.3. All these forest biomes are generally arranged on a gradient from north to south or from high to lower altitude. We shall discuss each category in detail. T-.-.,-- -h\,,+v \ ?,.\-,*\\rn\\\\-\-\ - Tropical forest Subtropical forest Temperate Mixed temporate Boreal forest Tundra deciduous forest forest Fig. 7.2 : Types of Forests i) Coniferous forest : Cold regions with high rainfall and strongly seasonal climates with long winters and fairly short summers are characterised by boreal coniferous forest which is transcontinental. For example, adjacent to Tundra regions either at latitude or high altitude is the northern coniferous forest, which stretches across both north America and Eurasia just south of Tundra (i.e. Canada, Sweden, Finland and Siberia). The term taiga is applied to the northern range of coniferous forests. This is characterised by evergreen plant species such as Spruce. (Picea glauca), fir (Abies balsamea ) and pine trees (Pinus resinosalPinus strobus) and by animals such as the lynx, wolf, bear, red fox, porcupine, squirrel, and amphibians like Hyla, Rana, etc. Boreal forest soils are thin podozols and are rather poor both because the weathering of rocks proceeds slowly in cold environments and because the litter derived from conifer needle is broken down very slowly and is not particularly rich in nutrients. These soils are acidic and are mineral deficient. This is due to movement of large amounts of water through the soil, without a significant counter upward movement of evaporation, essential soluble nutrients like calcium, nitrogen and potassium which are leached sometimes beyond the reach of roots. This process leaves no alkaline oriented cations to encounter the organic acids of the accumulating litter. The productivity and community stability of a boreal forest are lower then those of any other biome. ii) Temperate deciduous forest : The temperate forests are characterised by a moderate climate and broad-leafed deciduous trees, which shed their leaves in + fall, are bare over winter and grow new foliage in the spring. These forests are characteristic of north America, Europe, Eastern Asia, Chile, part of Australia and Japan, with a cold winter and an annual rainfall of 75-150 cm. and a 56 temperature of 10-20°C. The precipitation may be fairly uniform throughout year. In Himalayas occur Temperate vegetation including piiies, fir and juniper Types of Ecosystems : trees with an undergrowth of scrubby rhododendrons at elevations of 2743-3658 1 Terrestrial Ecosystems metres. Trees are quite tall about 40-50 m in height and their leaves are thin and broad. The predominant genera of this biome are maple (Acer), beach (Faqus), oak (Quercus), hickory (Carya), basswood (Tilia),chestnut (Castnea), and cotton wood (Populus). In some locations, coniferous vegetation may be quite predominant and that includes white pines (Pinus strobus), and willow (Salix). Soils of temperate forests are podozolic and fairly deep. The an~malsinhabiting the temperate forests are deer, beers, squirrels, gray foxes, bobcats, wild turkey and woodpeckers. Common invertebrates include earthworms, snails, millipedes, coleoptera and orthoptera and vertebrates like amphibians. such as toad. salamander. cricket and frog, reptiles., such as turtle, lizard and snake, mammals such as racoon, opossum. pig, mountain lion, etc. and birds like horned owl, hawks, etc. The range of animal size and adaptations is wide; the larger animals include such as deer and black deer. The dominant carnivores are large including the wolf and mountain lion although smaller carnivores such as fox and skunk are also common. Plants and animals of temperate forest allow a profound seasonality in behaviour, some even hibernate throughout the winter. iii) Temperate evergreen forest :Many parts of the world have a mediterranian type of climate which is characterised by warm, dry summers and cool, moist winters. .These are commonly inhabitated by low evergreen tree$ having broad leaves. In a woouiand, trees are essentially lacking although shrubs may range up