Ecosystems

11 Key excerpts on "Ecosystems"

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  eBook - ePub

  Environmental Issues and Challenges

  • Abhik Gupta, Susmita Gupta(Authors)
  • 2023(Publication Date)
  • Routledge India

    (Publisher)

  2 Ecosystems and their structure and functions DOI: 10.4324/9781032619873-2 2.1. Ecosystem: definitions, basic concepts, and brief history of ecosystem, landscape, biome, and the biosphere 2.1.1. Definitions of an ecosystem Living organisms and their non-living environment are always in interaction with one another. In a given area, the non-living (abiotic) components of the environment along with its living (biotic) components form discrete yet interlinked units, which are termed as Ecosystems. The term ecosystem was first proposed by the British ecologist Arthur G. Tansley in 1935. Tansley could visualize that organisms could not be altogether separated from their physical environment because of the influence of the physical factors. Hence, the organisms in a given environment could be seen as forming a system, which he termed as ecosystem. Perhaps the most comprehensive definition of ecosystem was given by Eugene P. Odum (1971) as Any unit that includes all the organisms (i.e., the “community”) in a given area interacting with the physical environment so that a flow of energy leads to clearly defined trophic structure, biotic diversity, and material cycles (i.e., exchange of materials between living and non-living parts) within the system is an ecological system or ecosystem. 1 2.1.2. Basic concepts of ecosystem Ecosystems are the smallest level of organization in nature that incorporates both living and non-living factors. We can conceptualize the ecosystem in a number of ways. For example, an ecosystem is a combination of all the living and non-living elements in a given area. Organisms exist as individuals in nature. A group of individuals belonging to the same species forms a population. Several populations in a given environment comprise a community. Individual organisms, populations, and communities comprise living components only

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  Ecosystems

  • Gordon Dickinson, Kevin Murphy(Authors)
  • 2007(Publication Date)
  • Routledge

    (Publisher)

  1 The nature of Ecosystems

  The biological world is one of great diversity and complexity. A systems approach is useful in helping us to understand the interactions between living organisms and their environment (which includes the biotic environment of other living creatures). The concept of the ecosystem provides a way in which the functioning of the biological world and its interactions with the physical environment can be understood. The ecosystem concept is useful in resource management and as a basis for predictive modelling. This chapter covers:

  • Complexity of the biological world and its physical environment
  • Development of the ecosystem concept
  • System theory, ecology and Ecosystems
  • Abiotic and biotic environment of Ecosystems

  How this book approaches the complexity of the biological world and its environment

  How can we make sense of the complex and constantly changing interactions between the living world, with its myriad species and individuals, and the multifaceted and dynamic environment which life inhabits? In this book we examine this basic question, starting from the idea of the ecosystem as the basic unit of living organisms in the environment. Understanding how Ecosystems operate, and how they support the existence of groups of organisms, is not just a question of scientific interest. At a gathering pace since the 1940s, there has been increasing concern about harmful effects caused by human actions on the planet’s life support system. Although concerns were, at first, confined to a small group of scientists and environmental activists, it is now a global issue at the top of the international political agenda. Exactly what has occurred and what may happen in the future is not clear. However, most informed people agree that at best the consequences may be uncomfortable for humankind, and at worst may be catastrophic.

  The ecosystem concept is fundamental to examination of human impacts on life on Earth. It provides a way of looking at the functional interactions between life and environment which helps us to understand the behaviour of ecological systems, and predict their response to human or natural environmental changes.

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  Fundamentals of Environmental Studies

  • Mahua Basu, Xavier Savarimuthu, SJ(Authors)
  • 2017(Publication Date)
  • Cambridge University Press

    (Publisher)

  The ecologists were classified into two groups – those who were engaged with quantifying an ecosystem’s input and output relationships (flows of matter and energy; Evans, 1956) and those that were concerned with particular populations (Levin, 1976). ‘ Populations do react to environmental stimulus and so Ecosystems can also be defined by biota and by the environment .’(Chapin et al. , 1997) 115 Ecosystems An ecosystem is the basic functional unit in ecology , as it comprises both organisms and their abiotic environment. Organisms cannot exist without their environment. Ecosystem thus symbolizes the highest level of ecological integration and is based on energy. A forest, a lake, a mangrove, paddy field and even laboratory culture can represent Ecosystems. Thus, an ecosystem is a specific unit of all the organisms inhabiting a specified space that interacts with the physical element of the environment to produce discrete trophic structure, biodiversity and nutrient cycling. The term ecosystem was first proposed by the British ecologist A. G. Tansley. 4.2.2 Basic/Elementary processes in an ecosystem Nutrient cycle comprises the transfer of inorganic substances between living beings and the environment. The plants are able to prepare complex organic materials from simple raw materials. This organic matter is finally released as raw material after their death and is reverted back to the environment. Continual energy inflow is another fundamental requisite of the ecosystem. Solar energy is trapped by the green plants by photosynthesis. Sun is the ultimate source of energy. Herbivores procure their nutrition and energy from the plants. This energy intake passes on to other organisms. In this way the energy gets transferred from one organism to another. This is known as energy flow in ecosystem . 4.3 Components of Ecosystem 4.3.1 Abiotic components The term abiotic refers to non-living substances like air, water, land, elements and compounds.

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  Ecological Processes Handbook

  • Luca Palmeri, Alberto Barausse, Sven Erik Jorgensen(Authors)
  • 2013(Publication Date)
  • CRC Press

    (Publisher)

  An ecosystem is a unit or functional biotic subsystem that sustains life and includes various biotic and abiotic components. Moreover, the scales are not defined a priori; instead, they depend on the objective of the study. Analysis Synthesis FIGURE 1.2 Analytical results are used for the formulation of a synthesis (model) that, in turn, indicates what new analyses are required. 8 Ecological Processes Handbook © 2008 Taylor & Francis Group, LLC Obviously, the simplest description or model we can conceive will have to include the functional elements that are related to the interaction between the ecosystem and its surrounding environment (flows of matter and energy), and the functional elements of feedback (e.g., the internal cycling of nutri-ents). It is unconceivable to even partially describe an ecosystem while ignor-ing the context in which it is inserted and the internal recycling (Figure 1.3). In practice, once the scope of the study has been identified, the researcher tries to assemble pieces of knowledge into an organic description through empirical studies. By means of comparative studies, descriptions of some functional and structural units of diverse Ecosystems are included. In addi-tion, experimental studies enable the manipulation of the entire system in an attempt to grasp relevant properties. Finally, a model or computer simula-tion proclaims the synthesis. All these steps are needed in order to obtain an adequate holistic description of the ecosystem structure. 1.5 Complexity and Self-Organization Given these definitions, it is now useful to seek criteria that allow us to determine the manner and extent to which two Ecosystems* are different, in short, classification criteria. Two fundamental ecosystem qualities that * Or the same ecosystem at different stages of development.

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  Ecotoxicology

  A Comprehensive Treatment

  • Michael C. Newman, William H. Clements(Authors)
  • 2007(Publication Date)
  • CRC Press

    (Publisher)

  Though the organisms may claim our primary interest, when we are trying to think fundamentally we cannot separate them from their special environment, with which they form one physical system. (Tansley 1935) Thus, one distinguishing feature of ecosystem ecology, which was recognized early in its history, was the necessity of considering integrated physical, chemical, and biological processes. Ecosystem ecologists are not simply recognizing the influences of the physical environment but are considering organisms and the abiotic environment as part of a single system. This holistic perspective is funda-mentally different than how lower levels of organization have been treated in ecology. Likens (1992) defined an ecosystem as a “spatially explicit unit of the earth that includes all of the organisms along with all components of the abiotic environment within its boundaries.” One can see by this broad definition that while the spatial extent of an ecosystem remains somewhat vague, the emphasis is on including organisms and the environment. We will also see that because of the focus on movement of energy and abiotic materials (e.g., C, N, P), ecosystem ecology integrates the fields of chemistry, physics, and biology and is, therefore, necessarily a multidisciplinary science. 613 614 Ecotoxicology: A Comprehensive Treatment 29.1.1 T HE S PATIAL B OUNDARIES OF E COSYSTEMS Because of the loosely defined spatial and temporal boundaries, some ecologists have argued that Ecosystems lack the logical interconnectedness typical of other levels of biological organization (Reiners 1986). Clearly, the spatial boundaries of an ecosystem often extend beyond those of its component populations and communities. These broad spatial and temporal boundaries of ecosys-tems are necessary because they provide ecologists with the flexibility to match questions with appropriate scales.

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  Ecology & Environ Mgmt

  • Roger Park(Author)
  • 2019(Publication Date)
  • Routledge

    (Publisher)

  Table 3.18 ) related to both the structure and function of the organic world is integrated within the ecosystem approach. Colinvaux has suggested that 'the ecosystem concept is one of the most powerful ideas of ecology, a concept which allows us to examine the workings of the natural world in an objective and understanding way' (Colinvaux, 1976); whilst Caldwell concludes that 'no more promising means for relating the biological and social science contributions to an understanding of human life in its environmental context has yet been found' (Caldwell, 1966). Because it offers such a unifying framework within which to consider both biotic and abiotic aspects of environmental management, Ripley and Buechner (1967) refer to the ecosystem as a point of synthesis of the 'human-society-plus-environment complex'.

  Table 3.18 MAIN PROPERTIES OF THE STRUCTURE AND FUNCTION OF Ecosystems

  ECOSYSTEM STRUCTURE:
  (a)	composition of the biological community (such as species numbers, biomass and life history)
  (b)	quantity and distribution of abiotic materials (such as nutrients and water)
  (c)	range or gradient of conditions of existence (such as temperature or light)
  ECOSYSTEM FUNCTION:
  (a)	range of energy flow through the system (ECO-ENERGETICS).
  (b)	rate of nutrient cycling (ECO-CYCLING).
  (c)	regulation by physical environment and by organisms (ECO-REGULATION)

  Source: Odum (1968)

  Fundamental ecological unit

  The ecosystem also appears to be a more meaningful unit on which to base strategies of environmental management than the community, whose virtues have been pointed out by Moss and Morgan (1967). Evans (1956) argues that the ecosystem is the basic unit of ecology for four main reasons. The ecosystem involves the movement and accumulation of matter and energy through the medium of living things and their activities; and the system is characterized by a large number of regulatory mechanisms which limit the numbers of organisms present, influence their physiology and behaviour and control the qualities and rates of movement of matter and energy. The concept of Ecosystems applies at all levels from individual plants to the entire biosphere; and Ecosystems are, by definition, open systems rather than closed ones.

  Systems analysis and modelling

  A further value of Ecosystems is that techniques of systems analysis can be readily applied (Chorley and Kennedy, 1971). In particular mathematical modelling of system behaviour and response can be valuable in characterizing system changes in response to either internal or external stresses, and in predicting the likely ecosystem changes associated with human manipulation or exploitation. Halfon (1976) has demonstrated that modelling techniques can give valuable results, but he also warns that much study now needs to be devoted to objective methods of modelling, and in particular to solving operational problems of systems identification and optimal solutions for systems aggregation procedures. Modelling can be valuable in predicting the impacts of management strategies. For example Botkin, Janck and Wallis (1972) have outlined a dynamic computer model of forest growth in which future changes in the state of a forest can be predicted on the basis of the present state of the system plus random future changes. The model has been calibrated for the Hubbard Brook ecosystem, and it simulates the end process of competition between species and between individuals, of secondary succession (see Chapter 4

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  The SAGE Handbook of Geographical Knowledge

  • John A Agnew, David N Livingstone, John A Agnew, David N Livingstone, SAGE Publications Ltd(Authors)
  • 2011(Publication Date)
  • SAGE Publications Ltd

    (Publisher)

  Tansley introduced ecosystem as follows: The Ecosystem I have already given my reasons for rejecting the terms ‘complex organism’ and ‘biotic community.’ Clements’ earlier term ‘biome’ for the whole com-plex of organisms inhabiting a given region is unobjectionable and for some purposes conven-ient. But the more fundamental conception is, at it seems to me, the whole system (in the sense of physics), including not only the organism-complex, but also the whole complex of physical factors forming what we call the environment of the biome – the habitat factors in the widest sense. Though the organisms may claim our primary interest, when we are trying to think fundamen-tally we cannot separate them from their special environment, with which they form one physical system. It is the systems so formed which, from the point of view of the ecologist, are the basic units of nature on the face of the earth. Our natural human prejudices force us to consider the organ-isms (in the sense of the biologist) as the most important parts of these systems, but certainly the inorganic ‘factors’ are also parts – there could be no systems without them, and there is constant interchange of the most various kinds within each system, no only between the organisms but between the organic and inorganic. These ecosys-tems , as we may call them, are of the most various kinds and sizes. They form one category of the multitudinous physical systems of the universe, which range from the universe as a whole down to the atom. Tansley 1935 (italics original). As a historical context of importance, eco-system combined eco- and -system at a time when system was beginning to be part of the lexicon of the emergence of physics as the king of the sciences. Botkin (1990) noted that the turn toward systems was part of a larger adoption of a mechanistic view of nature that had moved to replace an organis-mic view over the preceding two centuries.

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  Handbook of Environmental Economics

  Environmental Degradation and Institutional Responses

  • Karl-Goran Maler, Jeffrey R. Vincent(Authors)
  • 2003(Publication Date)
  • North Holland

    (Publisher)

  Chapter 2

  Ecosystem Dynamics

  Simon A. Levin; Stephen W. Pacala    Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544-1003, USA

  Abstract

  From Ecosystems we derive food and fiber, fuel and pharmaceuticals. Ecosystems mediate local and regional climates, stabilize soils, purify water, and in general provide a nearly endless list of services essential to life as we know it. To understand how to manage these services it is essential to understand how ecological communities are organized and how to measure the biological diversity they contain. Ecological communities are comprised of many species, which are in turn made up of large numbers of individuals, each with their own separate ecological and evolutionary agendas. Not all species are equal as regards their role in maintaining the functioning of Ecosystems or their resiliency in the face of stress. This chapter explains how Ecosystems evolve and function as complex adaptive systems. It examines ecological systems at scales from the small to the large, from the individual to the collective to the community, from the leaf to the plant to the biosphere (including the global carbon cycle). It reviews theoretical and empirical models of ecosystem dynamics, which are highly nonlinear and contain the potential for qualitative and irreversible shifts. It considers applications to forests, fisheries, grasslands, and freshwater lakes.

  Keywords Ecosystems communities biodiversity global carbon evolution

  JEL classification: Q22 Q23 Q25

  1 Introduction

  Ecosystems are the meeting grounds on which species interact, the integrated networks of biotic and abiotic elements through which materials and information flow, and that support our continued existence on the planet. From Ecosystems we derive food and fiber, fuel and pharmaceuticals. Ecosystems mediate local and regional climates, stabilize soils, purify water and in general provide a nearly endless list of services essential to life as we know it [Daily (1997)

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  Environmental Science and Technology

  A Sustainable Approach to Green Science and Technology, Second Edition

  • Stanley E. Manahan(Author)
  • 2006(Publication Date)
  • CRC Press

    (Publisher)

  The nature of such a community depends upon the physical and chemical characteristics that influence the life-forms in it and on the physical and chemical characteristics that influence the life-forms in it and on the interactions of the organisms in the community. A biological community is the the interactions of the organisms in the community. A biological community is the biological component of an biological component of an ecosystem, which includes the organisms and their phys-ecosystem, which includes the organisms and their phys-ical environment. The community functions in a manner such that it tends to uti-ical environment. The community functions in a manner such that it tends to uti-lize and convert energy and materials in the most efficient manner that will enable lize and convert energy and materials in the most efficient manner that will enable the organisms in it to reproduce and thrive. Therefore, the exchange of matter and the organisms in it to reproduce and thrive. Therefore, the exchange of matter and energy among the organisms and with their physical environment is a key aspect of energy among the organisms and with their physical environment is a key aspect of an ecosystem. The study of biological communities is called an ecosystem. The study of biological communities is called community ecology community ecology . There are many interactions of organisms in a community. Many of these inter-There are many interactions of organisms in a community. Many of these inter-actions are mutually advantageous. For example, grazing animals derive their food actions are mutually advantageous.

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  The Origin and Nature of Life on Earth

  The Emergence of the Fourth Geosphere

  • Eric Smith, Harold J. Morowitz(Authors)
  • 2025(Publication Date)
  • Cambridge University Press

    (Publisher)

  Thus the ecosystem appears as the bridge between incipient order in geochemistry and the earliest biochemistry. Organisms are a derived level of orga- nization that forms, in diverse ways, within a framework of constraints of biochemical and ecological order that are more conserved than the properties of the individuals that help to instantiate them. Whether we try to understand the nature of metabolic universality, or the widely varying degree of chance and necessity among patterns that together produce the living state, we need a way to refer to Ecosystems as primary entities in their own right and as carriers of patterns fundamental to life. Ecosystems must become “first-class citizens” 1 in biology, in some respects prior to and more fundamental than organisms. 2.2.1 No adequate concept of ecosystem identity in current biology Biology in its descriptive tradition, as part of natural history, was sensitive to relations of many kinds, both in the growth and form of organisms and in their ecological rela- tions. Darwin was a master of noticing and cataloging such relations. However, with the publication of On the Origin of Species, Darwin made a commitment to the individual as the sole sufficient level of selection to account for adaptation. 2 The effects of ecological 1 We borrow the title of this section from a famous expression in computer science – Functions as first-class citizens – coined by Christopher Strachey in the mid-1960s [105]. First-class functions are not merely sequences of steps, but genuine entities, which can be passed as arguments to and from other functions in the same manner as other data types [10]. Languages that support this concept have a fundamentally greater expressive power than those that relegate functions to the status of “second-class citizens” relative to first-class “data” objects.

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  Ecology

  From Ecosystem to Biosphere

  • Christian Leveque(Author)
  • 2003(Publication Date)
  • CRC Press

    (Publisher)

  102 Ecology: constitute an isolated case and this type of system has been observed in different parts of the world. Theoretically, an ecosystem is made up of a set of ecodemes that interact in different ways. The tendency of an ecodeme to approach a state of least entropy is thus counterbalanced by the overall system, which tends on the contrary towards a state of greater entropy. Johnson (1994) ultimately developed a theory that the ecosystem is the result of two opposing but nearly equivalent forces: one tends to increase the energy in the system and defer its transfer (case of ecodemes), while the other tends to accelerate it. Thus, the ecosystem is at the intersection of two opposing tendencies. On the one hand, on the scale of ecological time, which is that of succession, it tends towards a stable state, climax. The dominant tendency is towards homogeneity. On the other hand, on the scale of evolution, which is that of diversification, with an increase in the number of species and the complexity of ways in which energy travels, the tendency is to increase the flow of energy across the system. Change of entropy in a dissipative system is presented in the form of a balance between an energy flow of low entropy coining from external sources and crossing the system, and the production of entropy within the system itself (Nicolis and Prigogine, 1977). These are input-output systems (Patten et al., 1997) in which the anabolic and catabolic processes oppose each other. The former tend to construct an organized structure far from thermodynamic equilibrium, while the latter draw the system towards thermodynamic equilibrium. The subsequent chain reaction summarizes the preceding considerations: — The source of energy of low entropy is solar radiation (high energy photons). — Anabolism (charge phase) is the incorporation of this high quality energy into biochemical structures, which keeps the system far from thermodynamic equilibrium.

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