Plant Ecology MSCBOT-602 2022 PDF

MSCBOT-602 M. Sc. III Semester PLANT ECOLOGY PLANT DEVELOPMENT DEPARTMENT OF BOTANY SCHOOL OF SCIENCES UTTARAKHAND OPEN UNIVERSITY PLANT ECOLOGY MSCBOT-602...

MSCBOT-602 M. Sc. III Semester PLANT ECOLOGY PLANT DEVELOPMENT DEPARTMENT OF BOTANY SCHOOL OF SCIENCES UTTARAKHAND OPEN UNIVERSITY PLANT ECOLOGY MSCBOT-602 MSCBOT-602 PLANT ECOLOGY DEPARTMENT OF BOTANY SCHOOL OF SCIENCES UTTARAKHAND OPEN UNIVERSITY Phone No. 05946-261122, 261123 Toll free No. 18001804025 Fax No. 05946-264232, E. mail [email protected] htpp://uou.ac.in UTTARAKHAND OPEN UNIVERSITY PLANT ECOLOGY MSCBOT-602 Expert Committee Prof. J.C. Ghildiyal Prof. G.S. Rajwar Retired Principal Principal Govt. PG College, Karnprayag Government PG College, Augustmuni Prof. Lalit M. Tewari Dr. Hemant Kandpal Department of Botany School of Health Science DSB Campus, Kumaun University, Nainital Uttarakhand Open University, Haldwani Dr. Pooja Juyal Department of Botany, School of Sciences Uttarakhand Open University, Haldwani Board of Studies Prof. P.D. Pant Prof. S.S. Bargali Director, School of Sciences HOD, Department of Botany Uttarakhand Open University, Haldwani DSB Campus, Kumaun University, Nainital Prof. Amrita Nigam Dr. S.S. Samant School of Sciences Retd. Director IGNOU, New Delhi Himalayan Forest Research Institute (H.P) Dr. S.N. Ojha Dr. Pooja Juyal Assistant Professor Assistant Professor (AC) Department of Botany Department of Botany Uttarakhand Open University, Haldwani Uttarakhand Open University, Haldwani Dr. Kirtika Padalia Dr. Prabha Dhondiyal Assistant Professor (AC) Assistant Professor (AC) Department of Botany Department of Botany Uttarakhand Open University, Haldwani Uttarakhand Open University, Haldwani Dr. Pushpesh Joshi Assistant Professor (AC) Department of Botany Uttarakhand Open University, Haldwani Programme Co-ordinator Dr. S.N. Ojha Assistant Professor Department of Botany, School of Sciences, Uttarakhand Open University, Haldwani, Nainital UTTARAKHAND OPEN UNIVERSITY PLANT ECOLOGY MSCBOT-602 Unit Written By: Unit No. 1. Dr. Pooja Juyal 1, 2, 7 & 8 Assistant Professor (AC) Department of Botany Uttarakhand Open University, Haldwani 2. Dr. Prabha Dhondiyal 5&6 Assistant Professor (AC) Department of Botany Uttarakhand Open University, Haldwani 3. Dr. Kirtika Padalia 3, 4, 9 & 10 Assistant Professor (AC) Department of Botany Uttarakhand Open University, Haldwani Chief Course Editor Dr. Kirtika Padalia Assistant Professor (AC) Department of Botany Uttarakhand Open University, Haldwani Co- Editors Dr. S.N. Ojha Dr. Pooja Juyal Assistant Professor Assistant Professor (AC) Department of Botany Department of Botany School of Sciences School of Sciences Uttarakhand Open University, Haldwani Uttarakhand Open University, Haldwani Dr. Prabha Dhondiyal Dr. Pushpesh Joshi Assistant Professor (AC) Assistant Professor (AC) Department of Botany Department of Botany School of Sciences School of Sciences Uttarakhand Open University, Haldwani Uttarakhand Open University, Haldwani Title : Plant Ecology ISBN No. : Copyright : Uttarakhand Open University Edition : 2022 Published By: Uttarakhand Open University, Haldwani, Nainital-263139 UTTARAKHAND OPEN UNIVERSITY PLANT ECOLOGY MSCBOT-602 CONTENTS BLOCK-1- ECOSYSTEM ECOLOGY PAGE NO. Unit-1 Ecology: Introduction, types and importance, the earth environment 1-21 Unit-2 Ecological factors 22-54 Unit-3 Ecosystem structure and functioning 55-89 Unit-4 Ecosystem development and ecosystems of the world 90-117 BLOCK-2- POPULATION ECOLOGY PAGE NO. Unit-5 Population, ecological adaptations in species and survival strategies 118-147 Unit-6 Community: structure and development 148-185 BLOCK-3- CONTEMPORARY ENVIRONMENTAL PAGE NO. PROBLEMS AND CONSERVATION Unit-7 Land degradation 186-200 Unit-8 Environmental pollution and human health 201-229 Unit-9 Global environmental problems and conservation strategies 230-267 Unit-10 Management ecosystems for sustainable living 268-293 UTTARAKHAND OPEN UNIVERSITY BLOCK-1-ECOSYSTEM ECOLOGY PLANT ECOLOGY MSCBOT-602 UNIT-1- ECOLOGY: TYPES AND IMPORTANCE, THE EARTH ENVIRONMENT Contents 1.1 Objectives 1.2 Introduction 1.3 Types of ecology 1.4 Importance of ecology 1.5 The earth environment 1.5.1. Biosphere 1.5.2. Atmosphere 1.5.3 Hydrosphere 1.5.4 Lithosphere 1.6 Ecology in India 1.7 Summary 1.8 Glossary 1.9 Self-assessment questions 1.10 References 1.11 Suggested readings 1.12 Terminal questions UTTARAKHAND OPEN UNIVERSITY Page 1 PLANT ECOLOGY MSCBOT-602 1.1 OBJECTIVES After reading this unit student will be able to-  Know about ecology and its types  Learn about the importance of ecology  Understand the earth environment, i.e., about Biosphere, Lithosphere, Hydrosphere and Atmosphere.  Know about the ecology of India 1.2 INTRODUCTION Ecology is defined as the branch of science that studies the relationships between organism, their habitat and all the living and non-living factors involved in those habitats. The scientist Reiter was the first person to use the word ‘Ecology’. The term ecology was coined by combining two Greek words, oikos meaning ‘house’ or ‘dwelling place’ and logos meaning ‘the study of’ to denote such relationships between the organisms and with their environment. Although, there is uncertainty about the original coining of the term, however many biologists grant credit to the German zoologist Ernst Haeckel, who used the term as ‘oekologie’ in 1866 to refer the inter-relationships of living organisms and their environment. Many scientists defined the ecology in different ways such as: Allee et al. (1949) considered ecology as “the science of interrelation between living organisms and their environment, including both the physical and biotic environments and emphasizing inter-species as well as intra-species relations”. Eugene Odum (1963) is, known as the father of modern ecology. According to him ecology is the structure and function of ecosystems. Lewis and Taylor (1967) have defined ecology as “the study of the way in which individual organisms, populations of some species and communities of populations respond to these changes”. Smith (1977) prefers to consider ecology as “a multidisciplinary science which deals with the organisms and its place to live and which focuses on the ecosystem”. In simple terms ecology is the branch of biology that deals with scientific study of the interactions among organisms and their environment. The environment is made up of both living organisms (biotic) and physical (abiotic) components. Organisms and their environments are closely linked and dependent on one another. Any changes in the environment have an impact on living organisms, and vice versa. The main aim of ecology is to understand the distribution of biotic and abiotic factors of living thing in the environment. Ecology is a vast and encyclopedic biological subject. It is studied at various levels, such as- the main levels of study in ecology are the Biosphere, ecosystem, community, population, and organism. It refers to any form of biodiversity. The study of ecology is closely related to UTTARAKHAND OPEN UNIVERSITY Page 2 PLANT ECOLOGY MSCBOT-602 the fields of physiology, genetics, evolution, and behavior. An example of ecology is studying the food chain in a wetlands region. The interaction of organisms with their environment leads to the formation of group of organisms called ecological hierarchy or ecological levels of organization. It means the ranking of the ecological members. Every species existing in the universe makes the ecology. The basic unit of an ecological system is an individual organism. The different hierarchies of ecological systems are presented below: Hierarchy of Ecology The levels of ecological study offer different insights into how organisms interact with each other and the environment. The study of ecology is divided into two major subdivisions: (i) Autecology, (ii) Synecology 1. Autecology: It deals with the ecology of individual species and its population including the effect of other organisms and environmental conditions on every stage of life cycle. In other words, it is a study of inter-relationship between individual species or its population and its environment. 2. Synecology: The branch of ecology that studies about the relationship of various groups of organisms to their common environment. It deals with the plant communities their composition, behavior and relation to the environment. Autecology helps to understand the relationships between a particular organisms and environment and synecology helps to understand the relationships between communities and environment. For example, if the study is to be carried out about the study of any tree with the environment than it is known to be autecology. If we study effect of forest on environment then it is said to be synecology. In the words of Herreid II (1977) “the two types of study, autecology and synecology, inter- relate, the synecologist painting with a broad brush the outline of the picture and autecologist stroking in the finer details”. UTTARAKHAND OPEN UNIVERSITY Page 3 PLANT ECOLOGY MSCBOT-602 1.3 TYPES OF ECOLOGY Ecological studies are either organism-based or habitat-based and are conducted at different levels. Autecology and synecology are two main branches of ecology. Besides these major ecological subdivisions, different branches were created to explain different specific and detailed aspects of ecology. There are specialized branches of ecology as follows: 1. Organism level: Organism-level ecology is concerned with the adaptations that allow individuals to live in particular habitats. These adaptations can be morphological, physiological, and behavioural. (i). Autecology: Autecology, also called species ecology, the study of the interactions of an individual organism or a single species with the living and non living factors of its environment. (ii). Population Ecology: It is the study of the processes that affect the distribution and abundance of animal and plant population. (iii). Community Ecology: Community ecology, study of the organization and functioning of communities, which are assemblages of interacting populations of the species living within a particular area or habitat. 2. Based on Habitat or Ecosm or Ecosystem level: (A) Terrestrial Ecosystems (i). Forest ecology: Forest ecology is the scientific study of the interrelated patterns, processes, flora, fauna and ecosystems in forests. (ii). Grassland ecology: Grassland ecology is the study of all aspects of the ecology of grasslands, which are regions dominated by grass species but containing other non-woody plants and, in the case of Savannahs, some trees as well. (iii). Desert ecology: Desert ecology is the study of interactions between both biotic and abiotic components of desert environment. (iv). Wetland or marsh ecology: A wetland is a low-lying land area that is saturated with water, either permanently or seasonally, and contains hydric soils and aquatic vegetation. Marshes, swamps and bogs are typical wetlands. (B) Aquatic Ecosystems (i). Marine ecology: It is the scientific study of living things in the ocean and how they interact with their environment. (ii). Lagoon ecology: Lagoon is defined as a shallow body of water separated from the ocean or from larger bodies of water by a reef or other barrier. An inlet off of the Pacific Ocean that is separated from the ocean by a coral reef is an example of a lagoon. (iii). Estuarine ecology: is a semi-enclosed coastal body of water which has a free connection with the open sea, thus strongly affected by tidal action, and within which sea water is mixed with fresh water from land drainage. Coastal bays, tidal marshes, river mouths, water bodies behind barrier beaches etc ate the examples of estuaries. UTTARAKHAND OPEN UNIVERSITY Page 4 PLANT ECOLOGY MSCBOT-602 (iv). Fresh water ecology or Limnology: Limnology is the study of inland waters, both lotic waters (running water bodies), such as rivers, streams and lentic waters (standing water bodies), like lake, ponds etc. 3. Applied Ecology: Applied ecology is an integrated treatment of the ecological, social, and biotechnological aspects of natural resource conservation and management. It includes the following: (i). Agricultural ecology: Agricultural ecology is the study of agricultural ecosystems and their components as they function within themselves and in the context of the landscapes that contain them. (ii). Phytosociology: The branch of plant ecology concerned with the composition, distribution, characteristics, and interrelationships of plant species in plant communities. (iii). Paleoecology: The study of the relationships between organism and their environment, and the way organisms functioned in physical and biological interaction, within the geologic past. (iv). Conservation ecology: It deals with the application of ecological principles for proper management of resources leading to high and sustained yield of useful biological material for human welfares. (v). Cytoecology: It deals with the cytological details in a species in relation to population in different environmental conditions. (vi). Ecological energetic and production ecology: These deal with the mechanisms and quantities of energy conversion and flow through organisms, production processes, the rate of increase of organic weight over space and time through both green plants and animals. (vii). System ecology: It deals within the structure and function of ecosystem by means of applied mathematics, mathematical models, and computer programs. It concentrates on input and output analysis and has stimulated the development of applied ecology-the application of ecological principles to the management of natural resources, agricultural production, and problems of environmental pollution. (viii). Landscape ecology: It is the science that studies and improves the relationship between ecological processes in the environment and specific ecosystems. This occurs at various landscape scales, spatial development patterns, and within organizational update and policy levels. (ix). Radiation ecology: It is concerned with the effects of radioactive materials on living systems. There are two important facets of radiation ecology: (i) effects of radiation on individual, populations, communities and ecosystems, and (ii) the fate of radioactive substances released into the environment. (x). Ecophysiology: It is the study of how the environment, both physical and biological, interacts with the physiology of an organism. It includes the effects of climate and nutrients on physiological processes in both plants and animals, and has a particular focus on how physiological processes scale with organism size. UTTARAKHAND OPEN UNIVERSITY Page 5 PLANT ECOLOGY MSCBOT-602 (xi). Gene ecology: Genetic ecology is the study of the stability and expression of varying genetic material within abiotic mediums. This field of study focuses on interaction, exchange, and expression of genetic material that may not be shared by species had they not been in the same environment. 1.4 IMPORTANCE OF ECOLOGY The study of ecological principles provides a background for understanding the fundamental relationships of the natural community and also the sciences dealing with particular environment such as soil, ocean, forest and inland waters. Many practical applications of this subject are found in forestry, agriculture, horticulture, fisheries, biology etc. The science of plant ecology deals with the scientific study of relationships of plants and their environment and describes the home life plants. It brings out the physiological relationships between plant and their environmental conditions. Science ecological principles are the basis of practice in agriculture and forestry. Ecological is crucial for human well being and prosperity. It provides new knowledge of the interdependence between organisms with their natural environment that is essential for food production, ensuring resources like land and water, and sustaining biodiversity in a changing climate. Ecology is the basis of nature conservation. The following reasons explain the importance of ecology. 1. Helps in conservation of environment: The study of ecology allows us to understand the negative impact of human behaviour on the environment. By first identifying the primary means by which the problems we experience in our environment begin, we can help guide conservation efforts. By following this identification process, we show where our efforts will have the greatest impact. Environmental conservation means protecting the planet, conserving its natural resources and improving the quality of life for all living things. 2. Proper Resource allocation: Resource allocation is the process of planning, managing, and allocating resources within ecological knowledge. We can know the resources necessary for the survival of various organisms. Ecology provides the basis for developing good conservation policies. Especially when those to whom natural resources are entrusted possess ecological knowledge in areas such as forestry, wildlife, agriculture, land management and fisheries. 3. Enhances energy conservation: Conserving energy means reducing energy use by adapting human behavior and habits. All living things require energy for growth and development. Lack of ecological understanding leads to overexploitation of energy resources such as food, light and radiation, resulting in their depletion. Proper knowledge of ecological requirements prevents unnecessary waste of energy resources and saves energy for future purposes. 4. Eco-Friendliness: The term most commonly refers to products that contribute to green living, or practices that help conserve resources such as energy and prevent air, water, and noise pollution. Ecology promotes harmonious life within the species and the adoption of a lifestyle that protects the ecology of life. 5. Aids in disease and pest: Pests and diseases are a natural part of ecosystems. Many diseases are spread by vectors. Ecological research provides the world with new ways UTTARAKHAND OPEN UNIVERSITY Page 6 PLANT ECOLOGY MSCBOT-602 to understand how vectors and pests behave, and provides people with the knowledge and techniques to deal with pests and diseases. 1.5 THE EARTH ENVIRONMENT The word ‘environment’ is derived from an old French word “Environ” means ‘encircle’. The environment is the physical, chemical and biological component that affects the life of an organism. The environment is the sum of all biotic (living) and abiotic (non-living) factors that surround and affect an organism. Biotic factors include the availability of food organisms and the presence of biological specificity, predators, parasites and competitors. Abiotic factors include amount of sunlight, ambient temperature, pH of the water soil in which an organism lives. Any external force, substance, or condition that surrounds and affects in any way the life of an organism becomes a factor of its environment. These factors are called environmental factors. An environmental factor that, by its decrease, increase, presence or absence, limits the growth, metabolic processes, or dispersal of organisms. The environmental requirements of different organisms are individual and vary according to needs and age. Life activities of organisms are affected by the maximum or minimum amount of environmental components such as water, light, nutrients, space, temperature, and humidity. German Scientist Justus Von Leibig formulated ‘the law of the minimum’, which states that if any plant is deficient in any of its essential nutrients, the plant will grow poorly, even if all other essential nutrients are abundant. However, not only too little of something is a limiting factor, but also too much may limit the growth and distribution of an organism. The concept of the effect of maximum as well as minimum has been incorporated into the law of tolerance by American Zoologist victor Ernest Shelford (1931). According to the Law of Tolerance states that the success of an organism is based on a complex set of conditions, and that each organism has certain minimum, maximum, optimal factors or combinations of factors that determine its success. The life containing and life supporting environment of the world is restricted to a very irregular layer (5 to 20 km thick) around the globe. This thin veil of life on Earth is called the biosphere. The Earth is made up of four spheres: the biosphere, atmosphere, hydrosphere, and lithosphere. 1.5.1 Biosphere The global life-containing and life-sustaining environment is limited to a very thin and irregular veil or film around the world. This thin veil of living material of earth is called the ecosphere and biosphere. The word biosphere came from Greek “bios” that refers to “life” and “sphaira” that refers to “sphere”. The biosphere is defined as a region on, above, and below the earth’s surface where life exist. The Austrian Geologist Eduard Suess (1831-1914) first used the term biosphere in 1875 to describe the space on earth that contains life. According to Hutchinson (1970), the biosphere is that part of earth in which life exist. Biosphere is the entire inhabited part of the earth and its atmosphere including the living UTTARAKHAND OPEN UNIVERSITY Page 7 PLANT ECOLOGY MSCBOT-602 components. It extends from a few kilometers into the atmosphere to the deep-sea vents of the Ocean. Biosphere provides the necessary environmental conditions for survival. It is the zone of the earth where land, water, air and other biotic and abiotic elements interact with each other to support life. The entire global environment is basically made of abiotic (non-living) and biotic (living) components. These components together constitute the biosphere. The abiotic global environment is composed of the atmosphere (air), the lithosphere (earth) and the hydrosphere (water), and the biotic component is made of various forms of life inhabiting in the abiotic environment. The biosphere is one of the four layers that surround the earth along with the lithosphere (rocks), is the outer surface of earth composed of solid and rock, the atmosphere is the surrounding gaseous envelope, and the hydrosphere refers to earth’s liquid water including oceans, lake and rivers. Biosphere can be divided into many major categories of land called Biomes. A biome is a large region of earth that has a certain climate and certain types of living things. There are five major types of biomes: grassland forest, deserts, forests, and tundra, through some of these biomes can be further divided into more specific categories, such as Savanna, freshwater, marine, taiga, tropical rainforest and temperate. Biomes are subdivided into small units which are called as zones. For example a forest biome can be divided into canopy zone and ground zone. The animals and plants of each biome have traits that help them to survive in their particular biome. Land-based biomes are called terrestrial biomes. Water-based biomes are called aquatic biomes. Temperatures, precipitation amounts and prevalent organisms characterize the biomes of the World. Biosphere is made of different types of ecosystem. Living organism requires inorganic metabolites like water, minerals, and oxygen, nitrogen and carbon dioxide etc, for building and maintenance of lives. Living organisms obtain all such inorganic substances from the abiotic counter-parts of the biosphere. The biosphere acts as a life support system for the planet, helping to regulate the composition of the atmosphere, maintaining soil health and regulating the hydrological (water) cycle. Besides the biosphere, the three other main components of the earth are described below. 1.5.2 Atmosphere The earth is enveloped by a gaseous layer called atmosphere. The atmosphere is the layer of gases which surrounds the earth from all sides and is attached to the earth’s surface by the gravitational force of the earth. Gravity prevents gases that make up the atmosphere from escaping to space. Atmosphere is composed of 78% gas, 21% oxygen gas, 0.9% argon, and trace amounts of water vapour, carbondioxide, methane, ozone, and sulfur dioxide. Atmosphere has four main layers. We start measuring these from sea level and move towards space. The first layer is the troposphere, then the stratosphere, and mesosphere and thermosphere. Above the thermosphere the atmosphere merges with outer space in the layer known as the exosphere. Each of these layers holds different properties. e.g., differences in UTTARAKHAND OPEN UNIVERSITY Page 8 PLANT ECOLOGY MSCBOT-602 temperature density, composition of gases etc. The composition of the atmosphere is almost uniform up to about 80 km altitude. The higher the level, the lighter the gas. The atmosphere is denser closer to the Earth and thinner further away. Atmospheric pressure is closer to the Earth than farther from it. The atmosphere has an ozone layer at an altitude of about 32 to 48 km. This layer acts as a barrier that prevents the sun's ultraviolet rays from reaching the earth, which are deadly to living organisms. Among the various components of atmospheric gases, oxygen, nitrogen, and carbon dioxide are essential for the normal functioning of living organisms, as they act as metabolites of living organisms. Fig.1.1: Biosphere and its components Structure of Atmosphere: The atmosphere is divided into five concentric layers which can be distinguished on the basis of temperature. These layers are as follows: (i). Troposphere: The lowest layer of atmosphere in which man and other living organisms live is called troposphere, (“Tropos” means change) This represents the linear portion of the atmosphere that extends upto 20 km above the earth’s surface. It is thin in the polar regions i.e. about 10 km from earth surface. It contains more than 90 percent of gases in the atmosphere. The important events, such as cloud formation, lightning, thundering, thunder storm formation etc, all take place in troposphere. Troposphere is characterized by weather change and steady decrease in temperature with increasing amplitude and it may decrease upto-60oc in the upper layers. The average temperature near the soil surface is about 150c. The upper layers of troposphere which gradually merges with the next zone or stratosphere is called tropopause. The troposphere provides oxygen that humans can breathe, keeps earth at a livable temperature, and allows for weather to occur, making it a very important part of the atmosphere. (ii). Stratosphere: The second layer of air mass extending about 30 km above tropopause is called Stratosphere (it is also called ozonosphere).The uppermost layer of stratosphere is called stratopause. In this zone the temperature shows an UTTARAKHAND OPEN UNIVERSITY Page 9 PLANT ECOLOGY MSCBOT-602 increase in temperature from a minimum of about -60oC to maximum of 5 oC. The increase in temperature is due to ozone formation under the influence of UV (ultraviolet) rays of solar radiation. Ozone is formed from oxygen by a photochemical reaction in which solar energy (symbolized as hv) splits the oxygen molecule to form atomic oxygen which then combines with oxygen molecule to form ozone. O2 ______________ 2O (atomic oxygen) O2 + O ______O3 (Ozone) The above reactions are reversible. Ozone content of stratosphere is constant which means that ozone is being produced from oxygen as fast as it is broken down to molecular oxygen. The highest concentration of ozone (90%) in stratosphere approximately 20-25 km above, around the earth surface is known as ozonosphere. It is important because it absorbs ultraviolet radiation of the Sun and prevents from reaching the earth surface where it would be dangerous to living organism. Fig. 1.2: Layers of atmosphere (Source: http://www.indiagk.net/2016/07/earths-atmosphere-layers.html) (iii). Mesosphere: The third layer of atmosphere next to stratopause is called mesosphere. It is about 40 km in height. The mesosphere is characterized by low atmospheric pressure and low temperature. The temperature begins to drop from stratopause, goes a decreasing with the increase in the height and reaches a minimum of about -95oC at a level same 80 to 90 km above the earth surface. The upper limit of the mesosphere is called mesopause. (iv). Thermosphere: Next to mesosphere is thermosphere, which extends upto 500 km above the earth surface is completely cloudless and free of water vapor. Thermosphere is characterized by steady temperature increase with the height from mesopause. The thermosphere includes the regions in which ultraviolet radiations UTTARAKHAND OPEN UNIVERSITY Page 10 PLANT ECOLOGY MSCBOT-602 and cosmic rays cause ionization of molecules like oxygen and nitric oxide. This region is called ionosphere. In ionosphere, molecules of gases are so widely spaced that high frequency audible sound is not carried by the atmosphere. (v). Exosphere: The region of atmosphere above the thermosphere is called exosphere or outer space which lacks except those of hydrogen and helium. This extends upto 32190 km from the earth. Exosphere has a very high temperature due to solar radiation. The earth is magnetic, field become more important than gravity in distribution of atomic particles in the exosphere. Importance of Atmosphere 1. The atmosphere and Sound: Sound is a form of energy that travels in waves. Sound waves cannot travel through empty space, but they can travel through gases. Gases in the atmosphere provide a source for sound to travel through, and it also allows birds, insects, and airplanes to fly through. 2. The atmosphere and living things: The gases in the atmosphere, namely oxygen and carbondioxide, allow organisms on earth to live. Plants need carbondioxide for photosynthesis. Through photosynthesis plants are able to use carbondioxide to create sugar for food. The reaction for photosynthesis is: 6CO2 + 6H2O + solar energy → C6H12O6 (sugar) + 6O2 Animlas undergo a process that allows them to use oxygen in order to convert sugar into usable energy. Plants also undergo this process in order to consume some sugars they produce. The reaction for respiration is: C6H12O6 (sugar) + 6O2→6CO2 + 6H2O + usable energy 3. The atmosphere and Earth’s temperature: The atmosphere keeps the temperature of the earth constant so that it is suitable to support life. The water vapour and carbondioxide present in the lower layers of the atmosphere absorb the heat radiated by the earth’s surface, and as such they keep the atmosphere warm even during night. Gases in the atmosphere keep out some of the Sun’s scorching heat during the day. 4. The atmosphere and earth’s water: The atmosphere serves an important purpose as a medium for the movement of water. The atmosphere contains a lot of water vapour and acts as an important reservoir for water. It plays significant role in the water cycle. It facilitates the formation of clouds which remains suspended until they are heavy enough to pour down on the earth as rain or snow. 5. The atmosphere and the Sun’s rays: The atmosphere acts like a blanket or a glasshouse for the earth. The earth’s atmosphere acts as an insulating layer that protects the earth’s surface from the intense light and heat of the sun. It protects us from UV and other short wavelength light that would otherwise do a lot of damage to the DNA of living organisms. The presence of ozone layer does this by reflecting the UV rays of the Sun. Gases reflect or absorb the strongest rays of sunlight and receives UTTARAKHAND OPEN UNIVERSITY Page 11 PLANT ECOLOGY MSCBOT-602 the radiation of the Sun but does not allow the insolation to escape into space. As such it keeps the earth warm. 1.5.3 Hydrosphere All the water bodies on the earth’ surface namely lakes, rivers, ponds, ocean, sea together with ice and snow; are collectively called the hydrosphere. The word hydrosphere comes from the Greek word hydro which means ‘water’ and ‘sphere’ stands for a ‘round’, ball-like, spherical shape. The hydrosphere is the biosphere’s aquatic component and it covers about 73% area of the earth’s surface. About 97 percent of the total water of the globe is found in the ocean and the rest 3 percent consists of the water of the ponds, lakes, rivers and the water obtained from snow and ice. Water is the major inorganic nutrient needed by all living organisms; hence, water is essential to all life. First life originated in water. Water is one of the main agents in pedogenesis and is also the medium for several different ecosystems. The chemical formula for water is H2O which indicates that a single molecule of water is made up of two hydrogen atoms and one oxygen atom. Water moves through the hydrosphere in a cycle, known as hydrological cycle. It is critical to the existence of the hydrosphere. It consists of different stages described below. Hydrological Cycle Water as an important ecological factor determines the structure and function of the ecosystem. Water is constantly being cycled between the atmosphere, the ocean and the land. This process occurs in the cycle continuously so it is called the water cycle or hydrological cycle. This cycling is a very important process that helps sustain life on earth. Cycling of all other nutrients is also dependent upon water as it provides there transportation during the various steps. It acts as a solvent medium for their uptake of nutrients by organism. The continuous circulation of water in earth atmosphere system is composed of the following components: Evaporation, transpiration, sublimation, condensation, precipitation, runoff, infiltration and percolation, groundwater flow. The energy for driving the water cycle comes from the sun. Solar heat evaporated water from the ocean which is the great reservoir of water and other bodies of water (such as river, ponds, lakes etc) through the process of evaporation. A lesser amount of water is also evaporated from the surface of land and from plants, a process called as evapotranspiration. The direct conversion from soild (ice and snow) to vapour, is known as sublimation. All this vaporized water forms clouds which moved by winds, may pass over land where they are cooled enough to precipitate the water as rain or snow. Some of the precipitated water soaks into ground, some runs off the surface into stream and goes directly back to the Seas. Then it evaporates into the atmosphere to start cycle all over again. During the process of water cycle, water changes into three states of matter- Solid, liquid and gas. The frozen part of the hydrosphere for e.g., glaciers, icecaps, iceberg etc. has its own name, the Cryosphere. Earth’s climate and climate variability are largely driven by the cycling of water and energy exchanged among the ocean, atmosphere, and land. Components of Hydrosphere  Glaciers: Water that melts off of glaciers. UTTARAKHAND OPEN UNIVERSITY Page 12 PLANT ECOLOGY MSCBOT-602  Oceans: 97 % of the earth’s water is salt water located mainly in the sea.  Ground water: Rainwater that infiltrates rocks and soil into the earth’s surface make up a small portion of the fresh water on earth.  Fresh water: Only a small portion of the earth’s water is freshwater (only about 3%), which is found in a variety different places such as rivers, lakes, underground etc.  Surface Water: Surface sources of freshwater consist of lakes, rivers, and streams. Fig. 1.3: Hydrological Cycle Importance of hydrosphere: Hydrosphere plays an integral role in the survival of all life forms. 1. A substance found in living cells: The hydrosphere is the source of water is a substance found in living cells. In each living cell, there is at least 75% water that promotes the cells normal functioning. The majority of chemical reactions in living organisms involve materials that are dissolved in water. Without water, no cell would survive or be able to carry out its normal functions. The hydrosphere houses the water and serves as a source and reservoir of water to living organisms. 2. Habitat for many Life forms: The hydrosphere is home to a wide variety of plants and animals, for instance, water dissolves many nutrients such as nitrite, nitrate, and ammonium ions, as well as gases such as oxygen and carbondioxide. These compounds play an integral role in the existence of life in water. 3. Atmospheric existence: The hydrosphere contributes significantly to the current state of atmosphere. When the earth was formed, it had only a thin atmosphere. This atmosphere was comparable to mercury’s current atmosphere as it was densely packed with helium and hydrogen. Helium and hydrogen were later evacuated from the atmosphere. As the earth cooled the gases and water vapour were produced, forming the present atmosphere. 4. Control the weather: Water has a high specific heat, which means it absorbs or loses a lot of heat with small temperature changes, as well as a high latent heat, which means it absorbs or releases a lot of heat with evaporation or freezing. These UTTARAKHAND OPEN UNIVERSITY Page 13 PLANT ECOLOGY MSCBOT-602 properties aid in the stabilisation of plant temperatures and the surrounding environment. It plays an important role in regulating temperatures on Earth, ensuring that temperatures remain within a range suitable for life. The properties of latent heat of water are important not only because they moderate the temperature of the biosphere, but also because they play an important role in the hydrological (water) cycle by evaporating water and causing it to precipitate (condensate) as rain and dew. 5. Human requirements: Human benefit from hydrosphere in numerous ways. Besides drinking, water is used for both home and industrial purposes. It can also be used for agriculture, transportation and hydropower to generate electricity. 1.5.4-Lithosphere The solid component of earth is called lithosphere. The term lithosphere is derived from the Greek words ‘lithos’, meaning stone, and ‘sphaira’, meaning ball or globe. It is the terrestrial component of the biosphere. The uppermost part of the lithosphere that chemically reacts to the biosphere, atmosphere and hydrosphere through the soil forming process is called the pedosphere. The soil provides food, shelter, anchorage and concealment from predators to living organisms. Under the lithosphere is the asthenosphere, the weaker, deeper and hotter part of the mantle. It is a solid rock layer where extreme pressure and heat cause the rocks to flow like a liquid. The asthenosphere's rocks are not as dense as those in the lithosphere. Tectonic activity is the most well-known feature associated with the earth's lithosphere. A lithospheric plate, also known as a tectonic plate, is a massive and irregular slab or solid rock that usually includes both the oceanic and continental lithospheres. These tectonic plates vary in size. The majority of tectonic activity occurs at the plates' boundaries, where they may collide, tear apart, or slide against each other. Thermal energy (heat) from the lithosphere's mantle allows for the movement of tectonic plates. Thermal energy makes the lithosphere's rocks more elastic. Tectonic activity in the lithosphere is responsible for some of Earth's most dramatic geologic events, including earthquakes, volcanoes, and deep ocean trenches. The lithosphere can be shaped by tectonic activity: At rift valleys and ocean ridges, where tectonic plates are shifting apart from one another, both oceanic and continental lithospheres are the thinnest. Lithosphere is multilayered and includes following three main layers: 1. Crust: Crust is the outermost layer of the earth about 8 to 40 km above mantle. Its surface is covered with soil supporting rich and varied biotic communities on which humans and animals live and plants grow. Silica (Si) and aluminium (Al) are major constituent minerals. Hence it is often termed as SIAL. 2. Mantle: Mantle lies between the core and crust. It is the second layer of the earth. It extends about 2900 km above the core. This is in a molten state. It is made up of magnesium and silicate rich iron. It is the chief source of magma that finds its way to the surface during volcanic eruptions. 3. Core: Core lies beneath the mantle. The core is the central fluid or vaporized sphere having diameter of about 2500 km from the centre and is possibly composed of nickel-iron. Core is divide into two sub-zones: (a). Solid inner core: It is the centre and the hottest layer of the earth. Thickness of solid inner core is 1,250 km and its temperature is about 5500-7000 degree C. It is composed of nickel and iron, solid due to extreme pressure. UTTARAKHAND OPEN UNIVERSITY Page 14 PLANT ECOLOGY MSCBOT-602 (b). Liquid outer core: Its temperature is about 6100 to 4400 degree C and composed of iron and molten nickel. Outer core spins, creating the earth’s magnetic field that protects from solar wind. Fig.1.4: Lithosphere comprising the crust and lithospheric mantle (Source: https://en.wikipedia.org/wiki/Lithosphere#/media/File:Earth_cutaway_schematic-en.svg) Table 1: Major Elements in the Earth's crust S.No. Element Percent by Volume 1. Oxygen 46.60% 2. Silicon 27.72% 3. Aluminum 8.13% 4. Iron 5.00% 5. Calcium 3.63% 6. Sodium 2.83% 7. Potassium 2.59% 8. Magnesium 2.09% Types of lithosphere: Lithosphere can be mainly divided into oceanic and continental lithosphere. 1. Oceanic lithosphere: The oceanic lithosphere is found in ocean basins and is associated with the oceanic crust. It is denser than the continental lithosphere and is composed primarily of ultramafic mantle and mafic crust (oceanic crust). As a result, the oceanic lithosphere is much younger than the continental lithosphere because new oceanic lithosphere is constantly being produced at mid-ocean ridges and recycled back to the mantle at subduction zones. The oceanic lithosphere thickens and moves away from the mid-ocean ridge as it ages. This thickening is caused by conductive cooling, which converts hot asthenosphere into the Lithospheric mantle and causes the oceanic lithosphere to become increasingly dense with age. 2. Continental lithosphere: The continental lithosphere is connected to the continental crust and has direct contact with the atmosphere. The continents and continental UTTARAKHAND OPEN UNIVERSITY Page 15 PLANT ECOLOGY MSCBOT-602 shelves are formed by layers of sedimentary and igneous rock. This layer is mostly made up of granite rock. Importance of Lithosphere 1. Different types of rocks such as sedimentary, igneous and metamorphic rocks are found in the lithosphere. 2. Lithosphere helps to provide the necessary nutrients required to the plants. It provides grasslands, forests and is a rich source of minerals. The Lithosphere is largely important because it is the area that the biosphere (the living things on earth) inhabits. 3. Lithosphere is the major source of fuels such as petroleum, coal and natural gas. When the biosphere interacts with the lithosphere, organic compounds can become buried in the crust, and dug up as coal, oil and natural gas that we can use for fuels. 4. Tectonic plates shift due to convection currents lower down in the mantle, and this can cause the formation of mountains, earthquakes and volcanoes. Earthquakes and volcanoes help in the growth of new vegetation and life as they give rise to fertile soil and lands. 5. The lithosphere serves as a source of minerals and elements, such as copper, magnesium, iron, aluminum. 1.6 ECOLOGY IN INDIA In India there occur so much variation in ecological conditions from one place to another due to wide climatic and seasonal fluctuations, the ecological conditions of a given area donot remain static for a long time and the flora and fauna of the Indian sub continent have evolved wide range of adaptations to cope with them. The ancient Sanskrit literature is full of description of plants, vegetation and fauna as related to the environment. References to ecological thoughts, and Charak described the importance of jala means water, vayu means air and gases, Desha means topograpgy and time in regulation of plants life. Theophrastus (300 B.C.) and other Greek philosophers and scientists like Aristotle, Hippocrates (father of medicine), Reaumur gave ecologically oriented descriptions of organisms. Linnaeus (1970) recognized the influence of environmental factors on the distribution of plants. The first comprehensive ecological contribution was made by Winfield Dudgeon (1921) who published an ecological account of the Upper Gangetic Plains employing the concept of seasonal succession therein. He discussed the role of environment in succession of communities. This was, however, elaborated later by Saxton (1922), Misra (1946, 1958, 1959), however, contradicted this view of succession, and concluded that the processes mentioned therein might be better referred to as seasonality of communities rather than true ecological succession. The Indian ecological society was established in 1974 with eminent ecologist, educationist and administrator, Prof. A.S. Atwal as the founder president. It is one of the pioneering organizations of India engaged in advances in ecological sciences and environmental protection. UTTARAKHAND OPEN UNIVERSITY Page 16 PLANT ECOLOGY MSCBOT-602 Ramdeo Mishra (1908-1998) is known as the father of ecology in India. He laid the strong foundation of ecology in India. He helped in shaping ecology as a major discipline for teaching as well as for research in traditional departments in India in many ways. His research laid the foundations for understanding of tropical communities and their succession, environmental responses of plant populations and productivity and nutrient cycling in tropical forest and grassland ecosystems. He formulated the first post graduate course in ecology in India. Due to his efforts government of India established the National committee for environmental planning and coordination (1972). The second school of ecology developed with Prof. R. Misra at Banaras Hindu University, Varanasi and Sagar since 1942. Earlier workers (1942-48) examined the effect of soil factors on the plant distribution, the nature of seasonal changes and succession in the plant communities. From 1948-1955 they revealed the dynamics of vegetation and environmental factors in grassland and forests. From 1966 to 1967 emphasis was given on autoecology and production ecology. Since 1967 onwards much emphasis, is on energy flow and productivity of various ecosystem. Champion and Pant (1931), Phadnis (1925), Jagat Singh (1925), and Griffith and Champion (1947) were made autecological studies on forest trees. In India Prof. F.R. Bharucha student of Braun Blanquet established the first school of ecology at Bombay. He was the director of the Institute of Science from 1954-1959. He was made substantial contribution to grassland and desert ecology. He was the president of Indian Ecological society, vice president of International Botanical Congress and was commissioned by UNESCO to write the report on ecological research. The extensive investigations into the phytosociology of grasslands and mangroves by Bharucha (1941), deserts by Sarup and co- workers and forests by G.S Puri, (1950, 1951, 1960) made turning point in the history of development of ecology in India. Prof. G.S.Puri (1950, 51) made extensive forest ecological investigation and published them in two volumes of the “Indian Forest Ecology” (1950). Troup (1925), Champion (1929, 1935, 1937), Bor (1947, 1948) etc engaged themselves in the study of ecology of forest vegetation. In the next phase (1963-1971) the Banaras Centre concentrated on autecology of medicinal plants and weeds (R.S. Tripathi), grassland productivity (J.S. Singh) and forest litter decomposition and productivity (K.P.Singh). Keeping in view the role of biological productivity in human welfare, launching of IBP (International Council of Scientific Unions) made an important landmark in the development of ecology in India. S.C. Pandeya developed active centre at Rajkot on Systems analysis, production ecology, desert ecology, grazing lands and other areas. At Shillong, P.S. Ramakrishnan started work in 1974 on ecology of shifting cultivation, weed ecology etc. At Nainital, (Kumaun University), J.S. Singh started work in 1976 on Himalayan ecology, particularly on forest degradation, regeneration, biomass pattern, productivity, nutrient cycling etc. From a small beginning, ecology has emerged into a frontline science by the turn of the 20th century. UTTARAKHAND OPEN UNIVERSITY Page 17 PLANT ECOLOGY MSCBOT-602 1.7 SUMMARY Ecology is the branch of science that studies the relationship of human beings to their geographical and social environment. The study of ecology is divided into two subdivisions: (i) Autecology, is the study of inter-relationship between individual species and its environment. (ii) Synecology, is the study of plant communities and its environment. Ecology can be classified into different types as landscape ecology, population ecology, community ecology, freshwater ecology, grassland ecology, ecological energetic and production ecology etc. Ecology seeks to understand life process, adaptation and biodiversity. Environment, on the other hand, aims to identify the internal and external factors that affect population. The biosphere, atmosphere, hydrosphere, and lithosphere are the four spheres that make up the earth environment. The history of ecology in India began with the descriptive accounts of forests by the officers engaged in forests services in first two decades of the century. Prof. Bharucha established the first school of ecology at Bombay. S.C. Pandey, J.S. Singh, G.S. Puri, K.P. Singh, R. Mishra etc are some notable ecologist. 1.8 GLOSSARY Ecology: The science of relationship between living organism and their environment. Environment: The sum total of all biotic and abiotic factors that surround and influence organisms. Atmosphere: The gaseous envelope surrounding a planet. Biosphere: The planet earth along with its living organisms and atmosphere which sustain life, i.e. the earth and atmosphere in which organism live. Hydrosphere: The part of the earth composed of water (ocean, sea, ice cap, lake, river etc.) Lithosphere: It is the outer solid shell of the earth. Troposphere: The lowest region of the atmosphere, extending from the earth’s surface to a height of about 6-10 km. Stratosphere: It is the second major layer of earth’s atmosphere, just above the troposphere, and below the mesosphere. Mesosphere: It is the third layer of the atmosphere, directly above the stratosphere and directly below the thermosphere. Asthenosphere: A layer in the mantle that is relatively weak and viscous; lies below the solid lithosphere. Crust: Outer envelope of the earth surface. Exosphere: Outermost layer of atmosphere lying beyond the ionosphere. Ozone layer: A layer of atmosphere (above 30-50 km from earth surface) which contains ozone produced by UV radiation. Latent heat- Water possesses the highest heat of fusion and heat of evaporation, collectively called latent heat. Specific heat: Specific heat is a measure of heat capacity, or how much heat a material can store when changing temperature. UTTARAKHAND OPEN UNIVERSITY Page 18 PLANT ECOLOGY MSCBOT-602 Transpiration- The process by which the plant body releases water in the form of vapours through its aerial parts is known as transpiration. Evaporation: It occurs when surface water is energized by solar radiation. Sublimation: The movement of water from a solid to a gaseous state without ever entering the liquid state. This allows water from snow or glaciers to enter the atmosphere directly. Condensation: Condensation is the conversion of water vapour in the air to liquid water. Precipitation: Precipitation is the falling of water from the sky in various forms (rain, snow, etc.). Infiltration: The process by which water on the ground surface enters the soil is known as infiltration. Runoff: When there is more water than land can absorb, runoff occurs. The extra liquid runs off the land and into nearby creeks, streams, or ponds. Sedimentary rock: Sedimentary rocks form from previously existing rocks or fragments of once-living organisms. They form as a result of deposits accumulating on the Earth's surface. Metamorphic rock: Metamorphic rocks are rocks that have been altered by intense heat or pressure during their formation. Igneous rock: Igneous rocks form when molten material from deep within the earth, known as magma, cools and solidifies, forming crystals. 1.9 SELF-ASSESSMENT QUESTION 1.9.1 Multiple Choice Questions: 1. Who coined the word ‘ecology’? (a) Strasburger (b) P. Odum (c) Ernst Haeckel (d) Roxburgh 2. Organisms interact with physical environment that comprises of (a) Atmosphere (b) Hydrosphere (c) Lithosphere (d) All of these 3. The crust of the Earth along with the cooler, upper part of a mantle is called the- (a) Mesophere (b) Stratosphere (c) Troposphere (d) Lithosphere 4. Who is considered as the “father of ecology in India”? (a) M.S. Swaminathan (b) S.L. Mehta (c) Ramdev Mishra (d) Agharkar 5. Name the atmospheric layer that is completely cloudless and free of water vapour. (a) Stratosphere (b) Exosphere (c) Troposphere (d) Thermosphere 6. The region of air close to the earth and extending up to 10 km high is called: (a) Atmosphere (b) Exosphere (c) Troposphere (d) Thermosphere 7. Which layer of the atmosphere is also called ozonosphere? (a) Exosphere (b) Troposphere (c) Mesosphere (d) Stratosphere 8. Who published two volumes of the “Indian Forest Ecology” (1950)? (a) F.R. Bharucha (b) Ramdev Mishra UTTARAKHAND OPEN UNIVERSITY Page 19 PLANT ECOLOGY MSCBOT-602 (c) G.S. Puri (d) J.S. Singh 9. Wide variety of living organisms is called: (a) Population (b) Biodiversity (c) Habitat (d) Diversity 10. Shelford’s law of tolerance is named after: (a) Jacob Shelford (b) James Shelford (c) Ernest Shelford (d) None of the above 1.9.1-Answer Key: 1-(c), 2-(d), 3-(d), 4-(c), 5-(d), 6-(c), 7-(d), 8-(c), 9-(b), 10-(c) 1.10 REFERENCES  Shukla R.S. & Chandel P.S. (1972), A Text book of Plant Ecology, S. Chand & company.  Agarwal S.K. (2008), Fundamentals of Ecology, APH Publishing Corporation.  Singh H.R. (2005), Environmental Biology, S. Chand & company.  Sahoo A.K. (2001), The Text book of forest ecology, biodiversity and conservation, International Book Distributors.  Singh. J.S, Singh S.P. & Gupta S.R. (2014), Ecology, Environmental Science and Conservation, S. Chand & company  B.P. Pandey (2007), Botany for Degree Students (B.Sc.-III), S. Chand & company  https://www.yourdictionary.com/ecology  www.britishecologicalsociety.org>...  byjus.com>…>Biology Article  www.conserve-energy-future.com>type  www.ukessays.com>essays>hydrosphere  en.m.wikipedia.org>wiki>Hydrosphere  www.vedantu.com>physics.lithosphere  https://chem.libretexts.org/Courses/Honolulu_Community_College/CHEM_100%3A _Chemistry_and_Society/14%3A_Earth/14.01%3A_Spaceship_Earth_Structure_and_ Composition 1.11 SUGGESTED READING  Singh H.R. (2005), Environmental Biology, S. Chand & company.  Sahoo A.K. (2001), The Text book of forest ecology, biodiversity and conservation, International Book Distributors.  Shukla R.S. & Chandel P.S. (1972), A Text book of Plant Ecology, S. Chand & company.  Agarwal S.K. (2008), Fundamentals of Ecology, APH Publishing Corporation.  Singh. J.S, Singh S.P. & Gupta S.R. (2014), Ecology, Environmental Science and Conservation, S. Chand & company UTTARAKHAND OPEN UNIVERSITY Page 20 PLANT ECOLOGY MSCBOT-602  B.P. Pandey (2007), Botany for Degree Students (B.Sc.III), S. Chand & company 1.12 TERMINAL QUESTIONS 1.12.1 Short answer type Questions: 1. Why is the lithosphere important? 2. Why do we need atmosphere? 3. What is a tectonic plate? 4. What do you understand by the term hydrosphere? 5. Write a short note on Oceanic lithosphere? 1.12.2 Long answer type Questions: 1. Define ecology. Discuss about the types of ecology. 2. Describe in detail about the importance of ecology. 3. Define atmosphere and discuss about its structure. 4. Write a short note on: (a) Hydrosphere (b) Lithosphere (c) Biosphere 5. Give a detailed account about Ecology in India. 6. Discuss about the layers of the atmosphere. UTTARAKHAND OPEN UNIVERSITY Page 21 PLANT ECOLOGY MSCBOT-602 UNIT-2- ECOLOGICAL FACTORS Contents 2.1 Objectives 2.2 Introduction 2.3 Abiotic Factors 2.3.1 Climatic factors 2.3.2 Edaphic factors 2.3.3 Physiographic factors 2.4 Biotic factors 2.5 Anthropogenic factors 2.6 Summary 2.7 Glossary 2.8 Self Assessment Question 2.9 References 2.10 Suggested Readings 2.11 Terminal Questions UTTARAKHAND OPEN UNIVERSITY Page 22 PLANT ECOLOGY MSCBOT-602 2.1 OBJECTIVES After reading this unit students will be able:  To understand about the ecological factors  To discuss about abiotic factors- climatic edaphic and physiographic factors  To know about biotic factors  To discuss about anthropogenic factors 2.2 INTRODUCTION An ecosystem is a community of living organisms interacting with each other and their non- living environment. Modern ecology focuses on the basic functional ecological unit, the ecosystem. Ecosystems are composed of organisms interacting with each other and with their environment such that energy is exchanged and system level processes, such as the cycling of elements, emerge. A.G. Tansley (1935) coined the term “ecosystem” as a biological assemblage interacting with its associated physical environment and located in a specific area. The environment includes chemical, physical and biological components. When a component surrounding an organism affects the life of an organism, it becomes a factor. In any ecosystem, a living organism is influenced by a number of factors and forces which are known as eco-factors or ecological factors. These environmental factors which influence the behavior, growth, distribution, abundance, and ultimate survival of organisms are of two basic types: abiotic (non-living) environment which determine the interactions between the population and the biotic (living) environmental factors which include interactions between different populations and instinctive control mechanism that are internal to the population itself. (Clapham, Jr., 1973) All these ecological factors can be divided into the following three groups: 1. Abiotic factors 2. Biotic factors 3. Anthropogenic factors 2.3 ABIOTIC FACTORS The abiotic factors are non-living chemical and physical elements in the environment that aren’t living but which are important to sustain the life of the living. Abiotic factors includes: Climatic, Edaphic, Physiographic etc. The sum total of all these factors constitutes the environment of an organism. Every organism has an ecological minimum and maximum for every factor and the UTTARAKHAND OPEN UNIVERSITY Page 23 PLANT ECOLOGY MSCBOT-602 range between two limits is known as limit or zone of tolerance. To explain the effect of different limiting factors on living organisms, number of laws and principles has been proposed by different Scientists. The law of tolerance, usually called Shelford‟s law of tolerance presented by American Zoologist Victor Ernest Shelford in 1911. The law states that, the abundance or distribution of an organism can be controlled by certain factors (e.g., the climatic, topographic and biological requirements of animals and plants) where levels of these exceed the maximum or minimum limits of tolerance of that organism. For example- For the proper development and growth of plants, all the soil nutrients are equally important, but anything in excess might limit the uptake of the other nutrient, restricting the proper growth. German Biochemist, Justus Liebig in 1840, presented the Law of minimum; it states that the growth of an organism is dependent on the amount of food stuff which is presented to it in minimum quantity. For example- if the soil is deficient in any one nutrient, it will make the other nutrient metabolically inactive and the proper growth of the plants will get restricted. Liebig‟s Law of minimum is also incorporated with the Laws of limiting factors developed by British Physiologist F.F. Blackman (1905). This law of limiting factor states that a biological process is controlled by a number of factors and the deficiency of any of these factors will affect the process on the whole. For example- Photosynthesis by plants. Blackman listed five factors involved controlling the rate of photosynthesis are amount of water, carbondioxide, chlorophyll, intensity of Solar radiation and temperature of the chloroplast. The same principle of limiting factors applies to animal functions also. The abiotic variables or factors which affect the living things are given below: 2.3.1 Climatic Factors Climate is the long term pattern of weather in a particular region. Climate is one of the important natural factors which affect the plant life and responsible for determining the climatic conditions of a region. Its study is known as climatology. The climatic factors are grouped under these categories- 1. Light 2. Temperature 3. Water (Humidity and Precipitation) 4. Wind 5. Fire 1. Light: Light is one of the most important abiotic factors without which life cannot exist. The chief sources of natural light are sunlight, moonlight, starlight, and the light produced by luminescent organisms. The sun is the main source of light. Light is the part of the electromagnetic spectrum that can be seen by the human eye. Electromagnetic spectrum is the term used by scientists to describe the entire range of light that exists. The electromagnetic spectrum is generally divided into seven regions, in order of decreasing wavelength and increasing energy and frequency: radiowaves, microwaves, infrared, visible UTTARAKHAND OPEN UNIVERSITY Page 24 PLANT ECOLOGY MSCBOT-602 light, ultraviolet, x-rays and gamma rays. Each particle of electromagnetic radiation, called a photon, has certain amount of energy. Types of radiation with short wave length have high energy photons, whereas types of radiation with long wave lengths have low energy photons. Scientists break it electromagnetic spectrum into three separate categories or division. The short wave includes cosmic rays, x-rays and ultra violet rays, which have wavelengths shorter than 0.4 to 0.7 mm. This is also known as photosynthetically active radiation (PAR). The medium sized waves are called infrared waves (longer than 0.740 mm). Radiant energy reaching the surface of the earth on a clear day is about 10% ultraviolet, 45% visible light, and 45% infrared. It is a form of kinetic energy from the sun that travels in waves in the form of tiny particles called quanta or photons. Sunlight pass through prism disperse in series of wavelength exhibiting seven different colours- violet, indigo, blue, green, yellow, orange and red (VIBGYOR). All these colours make visible spectrum of light that affect physiological processes of plant. e.g., Photosynthesis. On the basis of wave length, there are three types of ultraviolet radiation. These are:  UV-A radiation (320 to 400 nm)  UV-B radiation (280 to 320 nm)  UV- C radiation (100 to 280 nm) Out of these three radiation types, UV-C is lethal to organisms, and UV-B, is harmful to the organisms. The intensity of light reaching the earth’s surface varies with the angle of incidence, degrees of latitude and altitude, season, time of the day, amount absorbed and dispersed by the atmosphere and a number of climatic and topographical features. Importance of light to plants: Light affect the growth and distribution of plants through its effect upon soil temperature, photosynthesis, transpiration, rate of water absorption etc. Light is essential for the formation and function of chlorophyll. Three properties of this climatic factor that affect plant growth and development are light intensity, light quality and day length or photoperiod. The intensity of light is measured in terms of foot candle is equal to 10.76 Lux and varies according to the latitude and season of the year. An increased light intensity leads to a high rate of photosynthesis and a low light intensity would mean low rate of photosynthesis. At a very high intensity of light, rate of photosynthesis would drop quickly as the light starts to damage the plant. Light quality refers to the colour or wavelength reaching the plant surface. Day length or photoperiod refers to the amount of time that a plant is exposed to sunlight with respect to the night period. Light affects many physiological activities of the plants. Light influences the plants in the following ways: (i). Photosynthesis: Sunlight acts as the ultimate source of energy for plants. Plants are autotrophic organisms, which need light for carrying out the process of photosynthesis. Photosynthesis is the process by which plant converts light energy UTTARAKHAND OPEN UNIVERSITY Page 25 PLANT ECOLOGY MSCBOT-602 into chemical energy (in the presence of chlorophyll) which is subsequently used for the preparation of carbohydrate from carbondioxide and water. The various wavelengths in Sunlight are not all used equally in photosynthesis. Instead, photosynthetic organisms contain light absorbing molecules called pigments that absorb only specific wavelengths of visible light, while reflecting others. The set of wavelengths absorbed by a pigment is its absorption spectrum. The best wavelengths of visible light for photosynthesis fall within the blue range (450-500 nm), and red range (600-700 nm). Therefore the best light sources for photosynthesis should ideally emit light in the blue and red ranges. Green (500-570 nm) light is least effective. Plants look green, it is because the chlorophyll molecules in the plant absorb blue and red light and reflect other colours, resulting in the green colour we see. The rate of photosynthesis is greater in intermittent light than in the continuous light. (ii). Respiration: The method by which cells get chemical energy by the consumption of oxygen and the liberating of carbondioxide is called respiration. The process of respiration in plants involves using the sugar produced during photosynthesis plus oxygen to produce energy for plant growth. The process of respiration is represented as follows: Enzymes C6h12O6 + 6O2 6CO2 + 6H2O + 32 ATP (energy) Respiration takes place in all type of living cells and generally called cellular respiration. Cellular respiration is a process that takes place inside the cells where energy is released by the breakdown of glucose molecules. Cellular respiration can occur both aerobically (using oxygen), or anaerobically (without oxygen). Plants respire all the time, whether it is dark or light. There is no direct effect of light on the respiration. Indirect effect is very important because in the presence of light the respiratory substrates are synthesized. Light at which both photosynthesis and respiration become equal is called as light compensation point. This means that the carbondioxide released from respiration is equivalent to that which is taken up during photosynthesis. The compensation point is reached as light intensity increases. If the light intensity is increased beyond the compensation point, the rate of photosynthesis increases proportionally until the point of light saturation is reached, beyond which the rate of photosynthesis is no longer affected by light intensity. Effect on transpiration and opening and closing of stomata: Transpiration is the biological process by which water is lost in the form of water vapour process from UTTARAKHAND OPEN UNIVERSITY Page 26 PLANT ECOLOGY MSCBOT-602 aerial parts, such as stems, flowers and leaves in plants. In the absence of transpiration, excess water will get accumulated in the plant cells, and the cells will eventually burst. The stomata open during the day and close in the dark. Presence of light is directly proportional to the rate of transpiration. Light affects opening and closing of stomata, influences the permeability of plasma membrane and has heating effect. All these in turn affect transpiration which in turn affects absorption of water. (iii) Growth and flowering of plants: The day length, the quality and intensity (photoperiodicity) of light are the most important factors which affect growth and flowering of plants. Based on photoperiodic responses plants can be classified into three groups: (a) Short-day plants: The short day plants in general develop flowers when the days are less than 12 hours long. Example- Saccharum officinarum (Sugarcane), Glycine max (Soybean), Xanthium strumarium (Cocklebur). Day length is critical and varies from species to species. (b) Long-day plants: The long day plants develop flower when the days are longer than 12 hours. Example - Daucus carota (Carrot), Lactuca sativa (lettuce), Spinacea oleracea (Spinach). (c) Day neutral plants: Day neutral plants are those whose flowering are not affected by day length, but rather is controlled by age, number of nodes, previous cold treatment etc. for e.g., tomatoes (Lycopersicon lycopersicum) are “day neutral” and do not flower based on the length of the day or night. Instead, tomato plants simply flower after they have reached a certain developmental age. Other examples are- Helianthus annuus (Sunflower), Cucumis sativus (Cucumber), Gossypium hirsutum (Cotton). Plants which grow in bright Sunlight are called heliophytes and those growing in the shades are called Sciophytes. There are some heliophytes which can grow in shade are known as facultative sciophytes and those heliophytes which fail to grow in shade said to be obligate sciophytes. Similarly facultative heliophytes are those sciophytes which may grow in light and obligate heliophytes are those sciophytes which fail to grow in bright Sunlight. The shade plants maintain a high rate of photosynthesis in low light intensities, while the heliophytes are adversely affected by shade. Movement: Sunlight affects the movement in plants. The effect of Sunlight on the plant movement is called heliotropism or phototropism. The movement of plant parts UTTARAKHAND OPEN UNIVERSITY Page 27 PLANT ECOLOGY MSCBOT-602 towards the light source is known as positive phototropism. For example the growth of plant stem in the upward direction in response to sunlight, whereas the movement of plant parts away from light is known as negative phototropism. For example roots are negatively phototropic as they grow downwards into the soil. Germination: Most plants need light to grow and keep them healthy, but not all plants need light to germinate. Some seeds germinate best in absolute darkness, and others perform well with continuous sunlight. Experts from Thompson and Morgan report that light in the red wavelength range promotes germination, while blue light impedes it. This is because the red light affects a plant pigment, phytochrome, (regulate the germination of seeds (photoblasty), synthesis of chlorophyll, elongation of seedlings, size, shape and number and movement of leaves and the timing of flowering in adult plants) that is within the seeds. But if the plants are below a thick canopy of leaves, blue light may be needed as well. However, in Typha species yellow light has been found to promote germination of seeds and also counters the inhibitory effect of blue light. Effect of light on animals: Light affects the various phase of animal life such as growth, development, reproduction and diapause (resting phase), migration, locomotion, metabolism etc. Some major effects of light on animals are described below: (i) Effect on metabolism: The metabolic rate of different animals is largely affected by light intensity. The increased intensity of light results in an increase in enzyme activity, general metabolic rate and solubility of minerals and salts in the protoplasm. The cave-dwelling animals are not affected much by light. Solubility of gases decreases at high light intensity. (ii) Effect on pigmentation: Formation of pigments depends on light. It is found that higher the intensity of light, higher will be pigmentation. For example the darkly pigmented skins of human inhabitants of the tropical region have higher concentration of melanin in their skin. Cave animals and many inhabitants of deep sea, where light has no ecological significance, have vestigial eyes or are blind. (iii) Effect on development: Light in some cases accelerates the development, and in some other cases, it retards. For example, Salmon larvae undergo normal development in sufficient light whereas, Mytilus larvae grows larger in darkness. (iv) Effect on reproduction: In many animals and birds, the breeding activities are induced by light through its inoculating action over the gonads. The gonads of birds are found to become active during summer (increased illumination) and to regress during winter (shorter periods of illumination). UTTARAKHAND OPEN UNIVERSITY Page 28 PLANT ECOLOGY MSCBOT-602 (v) Effect on animal movement: In certain lower animals, the speed of locomotion is regulated by light. The phenomenon is known as photokinesis. They are of two types: (a) Phototaxis: Oriented locomotory movements towards and away from a source of light is called as Phototaxis. When an animal moves towards the light source, it is called positively photoactic. Euglena, Ranatra are the examples of positively photoactic animals. When an animal moves away from the light source, it is known as negatively photoactic. Earthworms, planarians, cope-podes, slugs, siphonophores are negatively photoactic animals. (b) Phototropism: Phototropism occurs when only a part of organism shows responsive movement to light stimulus. It is seen in sessile animals. 2. Temperature: Temperature is one of the most important ecological factors. The moisture and temperature, acting together, determine in large measure the climate of a region and the distribution of plant and animal life (Smith, 1977). Development and rate of plant growth is dependent upon the temperature surrounding the plant and each species has a specific temperature range represented by a maximum, minimum and optimum. In organisms all metabolic processes necessary for life start at a certain minimum temperature. The temperature at which physiological processes are at their maximum efficiency is called optimum temperature. Minimum temperature is that below which all metabolic processes necessary for life cannot initiate and proceed with lowest motion. The maximum temperature is the temperature above which no biological activity can be observed. The minimum, optimum and maximum temperatures are called cardinal temperature varies from species to species, and in the same individual from part to part. For example, some hot-spring algae can live in water as warm as 73°C under favorable conditions and some arctic algae can complete their life cycles in places where the temperature barely rise 0oC. Non-pathogenic bacteria inhabiting hot springs can actively grow at temperatures greater than 90 oC (Bott and Brock, 1969). Organisms which can tolerate a very large fluctuation in temperature for growths are called eurythermal plants include jasmine, roses, conifers, daisy, Ashoka tree etc. The organisms who can tolerate only a small variation in temperature are known as Stenothermal organisms. Stenothermal plants include Eucalyptus, Bougainvillea, Plumeria etc. On the basis of temperature tolerance, fungi have also been classified into the following three kinds: thermotolerant, thermophilic and mesophilic fungi (R. Emerson, 1968). Thermophilic fungi require optimum temperature 450C for growth. Temperature influences most plant processes, including transpiration, respiration, etc. UTTARAKHAND OPEN UNIVERSITY Page 29 PLANT ECOLOGY MSCBOT-602 (a). Temperature and cell: The minimum and maximum temperatures have lethal effects on the cells and their components. In the extremely low temperature, cell proteins may be frozen to ice. On the other hand; heat coagulates proteins (Lewis and Taylor, 1967). Few organisms survive temperatures above 45°C because of protein denaturation at high temperature. Certain organisms can exist at higher temperature due to heat stable proteins where as some organisms can exist at slightly lower temperatures using antifreezes such as glycerol, salts. (b). Temperature and metabolism: Usually the various metabolic activities of plants, animals and microbes are regulated by different kinds of enzymes and enzymes in turn are influenced by temperature, consequently increase in temperature, upto a certain limit, brings about increased enzymatic activity, resulting in an increased rate of metabolism. However, the metabolic rate may decrease when there is higher increase in temperature. (c). Temperature and reproduction: Flowering in plants is affected by temperature through thermoperiodism (the sum of the responses especially of a plant appropriately fluctuating temperatures). Temperature is an important factor, in the phenology of plants. Phenlogy is the study of periodical phenomena of plants, as the time of flowering in relation to climate; colour changing and leaf fall in the autumn, etc. (d). Temperature and sex ratio: In some animals the environmental temperature determines the sex ratio. For example, the sex ratio in the copepod Macrocyclops albidus is determined by temperature. As the temperature rises there is a significant increase in number of males. In Daphina, under normal condition parthenogenetic eggs are produced, which develop into female. But when the temperature is raised, they give rise to sexual eggs, which after fertilization may develop either into females or males. (e). Temperature and Parasitic infection: Certain diseases develop on plants due to unfavourable temperature i.e., high temperature together with wind and high humidity causes dissemination and development of bacterial diseases. (f). Temperature and growth: Plant growth and development is dependent on the temperature around the plant. Each species has a specific temperature range. Both very high and very low temperatures can have a negative effect on plant growth. There are two main forms of extreme temperature stress on plants - cold and heat. During high temperature, membrane stability decreases due to excessive fluidity of lipids in the membrane. There is a disruption of the membrane and cell compartment, leading to problems with function. Low temperatures can cause cold injuries such as dehydration, chilling injury, and freezing injury. In desiccation, tissues are dehydrated and injured due to rapid transpiration and slow absorption during winter. Chilling injury can occur at a range of temperatures that are low but not freezing for that species. Chilling has negative effects on cellular function, growth, and colouration. It can also lead to tissue death. Freezing injury occurs when the temperature is below UTTARAKHAND OPEN UNIVERSITY Page 30 PLANT ECOLOGY MSCBOT-602 the freezing point of water, resulting in protoplast shrinkage, destruction of chlorophyll, and ice formation in intercellular spaces, resulting in cellular water movement toward ice. (g). Temperature and colouration: In warm humid climates many animals like birds, insects and mammals bear darker pigmentation than the races of some species found in cool and dry climates. The phenomenon is known as Gioger rule. (h). Temperature and respiration: Usually, the rate of respiration becomes doubles as per the Vant Hoff‟s law with increase in temperature by 100 C in case of Poikilothermic animals. According to Smith (1974), optimum temperature for photosynthesis is lower than that for respiration. (i). Temperature and transpiration in plants: Transpiration is the process of loss of water from the aerial surface of plants. Higher temperature increases the capacity of air to hold more moisture in vapour form, which results in difference between vapour pressure defects, hence the rate of transpiration increases. Besides increasing the rate of transpiration if temperature rises above maximum limits, the plant becomes inactive, and may develop choruses. (j). Classification of organisms according to temperature tolerance: On the basis of the response of plants to temperature of environment, the entire vegetation can be divided into four classes as: (i). Megatherms: Plants which require more or less constant high temperature throughout the year. e.g., tropical rain forests and desert vegetation. (ii). Mesotherms: Plants of habitat which is neither very cold nor very hot. These plants cannot endura extreme high or low temperature. e.g., tropical deciduous forests and aquatic plants. (iii). Microtherms: These plants require low temperature for their growth. These plants cannot endure high temperature. All high altitude plants of the tropical and subtropical regions included in this group. (iv). Hekistotherms: Plants growing in regions with very low temperature. They tolerate long and extremely cold winter months. e.g., alpine vegetation. 3. Water: Water is the basis of life for all living beings on the earth. Water makes up a large proportion of the bodies of animals and plants e.g., cytoplasm holds 70-80 percent of water. Water is a compound composed of two atoms of hydrogen and one atom of oxygen. It is the most abundant compound found in all organisms. Water constantly moves around the earth and changes between solid (snow, sleet, hail and ice), liquid (rain, water droplets) and gas (water vapour). The water cycle, also known as the hydrological cycle is manage by Sun’s energy. This solar energy drives the cycle by evaporating water from the lakes, rivers, oceans and even the soil. Other water moves from plants to the atmosphere through the process of transpiration. The water vapour forms clouds in the air by condensation and precipitates back to earth in the form of rain and snow. In plant, UTTARAKHAND OPEN UNIVERSITY Page 31 PLANT ECOLOGY MSCBOT-602 absorption of nutrients, the rate and magnitude of photosynthesis, respiration, growth and other metabolic processes are influenced by the amount of water available. Water plays diverse roles in plants. As it evaporates from the leaf tissue during transpiration, gives cooling to the leaves. It is also a chief component in photosynthesis and respiration. Water act as a solvent for carbohydrates and minerals moving through the plants. In the atmosphere, water is present in the form of water vapours. This is called atmospheric humidity. Humidity is greatly influenced by intensity of solar radiation, wind, water, status of soil, temperature, altitude etc. Evaporation of water from earth surface and transpiration from plants are the main cause of atmospheric humidity. Most of the plants cannot make use of atmospheric humidity, however, several mosses, lichens, filmy ferns and epiphytic orchids can absorb moisture directly from the air. Clouds and fog are the visible forms of humidity. Humidity is measured using a psychrometer and hygrometer and is measured as a percentage. Humidity is described in three different terms: (a). Relative humidity: Relative humidity is the ratio of the actual amount of water vapours in the atmosphere to the amount that can be held in the air at a particular temperature and pressure. (b). Specific humidity: It refers to the “amount of water vapours present per unit weight of air”. (c). Absolute humidity: It refers to the “amount of water vapours present per unit volume of air”. Effects of humidity on organisms: It influences the rate of transpiration in plants. Higher the humidity, lesser is the rate of transpiration. Low relative humidity increases water loss through transpiration and affects plant growth. It also influences the rate of sweat in humans. So, at high humidity sweating is more. It is an important source of water for epiphytes like lichens, mosses. It plays an important role in the germination of spores of fungi. Precipitation: Precipitation is the release of water from clouds that falls to the ground as rain, snow, sleet, or hail. Precipitation occurs when a portion of the atmospheric becomes saturated with water vapor (reaching 100% relative humidity), so that the water condenses and ‘precipitates’ or falls. Precipitation depends upon temperature, wind, season and pressure. Precipitation has a significant impact on productivity and species richness of community or perennials and in determines the vegetation of particular region. Precipitation can affect germination, seedling growth and survival, and phenology (the study of recurrent phenomena), thereby altering annual productivity and species richness in many arid and semi-arid ecosystems. Plant productivity is influenced not only by quantity of precipitation, but also by temporal patterns of precipitation at a given site. The seasonal precipitation has a stronger UTTARAKHAND OPEN UNIVERSITY Page 32 PLANT ECOLOGY MSCBOT-602 influence on productivity than total precipitation in arid and semiarid ecosystems, since water is the most limiting resource. The main types of precipitation include rain, snow, hail, plus a few less common occurrences such as ice pellets, diamond dust and freezing rain. Thus, mist and fog are not precipitation but suspensions, because the water vapour does not condense sufficiently to precipitate. Rainfall is the most common form of precipitation. Moderate and continuous rains are beneficial instead of heavy rains because in the heavy rains a large amount of water is lost from the surface of soil as runoff and the soil is eroded. The distinction between equatorial forests zones, desert zones near the tropics and temperate forest zones is based upon rainfall. In India the tropical evergreen forest is found with 100 inch rainfall tropical moist deciduous forest are monsoon forest of Western Ghats, Chota Nagpur correspond to a rainfall of 60 to 68 inches, the tropical dry deciduous forest of Sal and Teak occur in regions with only 40-50 inch rainfall. The regions of negligible rainfall consist of deserts. In terrestrial habitats precipitation is the only source of water for growth of most plants. 4. Wind: Air is the invisible mixture of gases present in the troposphere. Air in motion is called wind. Wind is the movement of air, caused the uneven heating of the earth by the Sun and the earth’s own rotation. Wind traveling at different speeds, different altitudes, and over water or land can cause different types of patterns and storms. They are a giant, spiraling tropical storm. Hurricane- originated over warm oceans and derives energy from the latent heat o