Everything about Ecosystem Ecology totally explained
Ecosystematic ecology is the integrated study of
biotic and
abiotic components of
ecosystems and their interactions within an ecosystem framework. This
science examines how ecosystems work and relates this to their components such as
chemicals,
bedrock,
soil,
plants, and
animals, see Figure 1.
Ecosystem ecology examines physical and also biological structures and examines how these ecosystem characteristics interact with each other. Ultimately, this helps us understand how to maintain high quality water and economically viable commodity production in this and many other ecosystems. A major focus of ecosystem ecology is on functional processes, ecological mechanisms that maintain the structure and services produced by ecosystems. These include
primary productivity (production of
biomass),
decomposition, and
trophic interactions.
Studies of ecosystem function have greatly improved human understanding of sustainable production of
forage,
fiber,
fuel, and provision of
water. Functional processes are mediated by regional-to-local level
climate,
disturbance, and management thus ecosystem ecology provides a powerful framework for identifying ecological mechanisms that interact with global environmental problems, especially
global warming and degradation of surface water. This article will describe the context of ecosystem ecology and provide an overview of the mechanisms that maintain ecosystem structure and function.
Ecosystems and scale
Ecosystems are difficult entities to define theoretically or to delineate in space For example, consider the
forest in Figure 1. When standing on the
stream bank, one can easily see two ecosystems, an aquatic one where
fish,
insects, and
algae interact, and the other a terrestrial one with
trees, another community of insects, and perhaps
herbivores and
predators such as
deer and
coyote.
Although these
communities appear distinct they interact intimately. Insects may be aquatic for certain parts of their life-cycle and emerge to become herbivores of the vegetation and prey for many predators. Riparian trees utilize stream water for growth and their leaf litter is an important flux of energy and nutrients to a rich community of benthic invertebrates. The distinction becomes even less clear when streams flood and deposit nutrient rich sediment on flood planes and scour other areas clean of biota and soil.
This example demonstrates several important aspects of ecosystems:
- Ecosystem boundaries are often nebulous and may fluctuate in time
- Organism within ecosystems are dependent on ecosystem level biological and physical processes and
- adjacent ecosystems closely interact and often are interdependent for maintenance of community structure and functional processes that maintain productivity and biodiversity.
These characteristics also introduce practical problems into natural resource management. Who will manage which ecosystem? Will timber cutting in the forest degrade recreational fishing in the stream? These questions are difficult for land managers to address while the boundary between ecosystems remains unclear even though decisions in one ecosystem will affect the other. We need better understanding of the interactions and interdependencies of these ecosystems and the processes that maintain them before we can begin to address these questions.
Ecosystem ecology is an inherently interdisciplinary field of study. An individual ecosystem is composed of
populations of
organisms, interacting within communities, and contributing to the cycling of
nutrients and the flow of
energy. The ecosystem is the principle unit of study in ecosystem ecology.
Population, community, and physiological ecology provide many of the underlying biological mechanisms influencing ecosystems and the processes they maintain. Cycling of energy and matter at the ecosystem level are often examined in ecosystem ecology but, as a whole this science is defined more by subject matter than by scale. Ecosystem ecology approaches organisms and abiotic pools of energy and nutrients as an integrated system which distinguishes it from associated sciences such as
biogeochemistry.
Biogeochemistry and
hydrology focus on several fundamental ecosystem processes such as biologically mediated chemical cycling of nutrients and physical-biological cycling of water. Ecosystem ecology forms the mechanistic basis for regional or global processes encompassed by landscape-to-regional hydrology, global biogeochemistry, and earth system science. Although most of Clements ecosystem definitions have been greatly revised by contemporary ecologists, the idea that physiological processes are fundamental to ecosystem structure and function remains central to ecology.
Later work by
Eugene Odum and
Howard T. Odum quantified flows of energy and matter at the ecosystem level, thus documenting the general ideas proposed by Clements and his contemporary
Charles Elton, the intellectual father of the “
food web” concept, see Figure 3.
In this model, energy flows through the whole system were dependent on biotic and abiotic interactions of each individual component (
species, inorganic pools of nutrients, etc). Later work demonstrated that these interactions and flows applied to nutrient cycles, changed over the course of
succession, and held powerful controls over ecosystem productivity. Transfers of energy and nutrients are innate to ecological systems regardless of whether they're aquatic or terrestrial. Thus, ecosystem ecology has emerged from important biological studies of plants, animals,
terrestrial,
aquatic, and
marine ecosystems.
Ecosystem services
Ecosystem services are ecologically mediated functional processes essential to sustaining healthy
human societies. Water provision and filtration, production of
biomass in
forestry,
agriculture, and
fisheries, and removal of
greenhouse gases such as
carbon dioxide (CO2) from the
atmosphere are examples of ecosystem services essential to
public health and economic opportunity. Nutrient cycling is a process fundamental to agricultural and forest production.
However, like most ecosystem processes, nutrient cycling isn't an ecosystem characteristic which can be “dialed” to the most desirable level. Maximizing production in degraded systems is an overly simplistic solution to the complex problems of hunger and economic security. For instance, intensive
fertilizer use in the midwestern United States has resulted in degraded fisheries in the
Gulf of Mexico. Regrettably, a “
green revolution” of intensive chemical fertilization has been recommended for agriculture in
developed and
developing countries. These short-sighted strategies risk alteration of ecosystem processes that may be difficult to restore, especially when applied at broad scales without adequate assessment of impacts. Ecosystem processes may take many years to recover from significant disturbance. An appreciation of the importance of ecosystem function in maintenance of productivity, whether in agriculture or forestry, is needed in conjunction with plans for restoration of essential processes. Improved knowledge of ecosystem function will help to achieve long-term sustainability and stability in the poorest parts of the world.
How do ecosystems work?
Biomass productivity is one of the most apparent and economically important ecosystem functions. Biomass accumulation begins at the cellular level via photosynthesis. Photosynthesis requires water and consequently, global patters of annual biomass production are correlated with annual precipitation. Amounts of productivity are also dependent on the overall capacity of plants to capture sunlight which is directly correlated with plant leaf area and leaf N content.
Net primary productivity (NPP) is the primary measure of biomass accumulation within an ecosystem. Net primary productivity can be calculated by a simple formula where total amount of productivity is adjusted for total productivity losses through maintenance of biological processes:
» NPP = GPP – Rplant
Globally, rates of decomposition are mediated by litter quality and climate. Ecosystems dominated by plants with low-lignin concentration often have rapid rates of decomposition and nutrient cycling (Chapin et al. 1982). Simple carbon (C) containing compounds are preferentially metabolized by
decomposer microorganisms which results in rapid initial rates of decomposition, see Figure 5A, models that depend on constant rates of decay; so called “k” values, see Figure 5B.
However, these models don't reflect simultaneous linear and non-linear decay processes which likely occur during decomposition. For instance,
proteins,
sugars and
lipids decompose exponentially, but lignin decays at a more linear rate
A simple alternative model presented in Figure 5C shows significantly more rapid decomposition that the standard model of figure 4B. Better understanding of decomposition models is an important research area of ecosystem ecology because this process is closely tied to nutrient supply and the overall capacity of ecosystems to sequester CO2 from the atmosphere.
Trophic dynamics
Trophic dynamics refers to process of energy and
nutrient transfer between organisms. Trophic dynamics is an important part of the structure and function of ecosystems. Figure 3 shows energy transferred for an ecosystem at Silver Springs, Florida. Energy gained by primary producers (plants, P) is consumed by herbivores (H), which are consumed by carnivores (C), which are themselves consumed by “top- carnivores”(TC).
One of the most obvious patterns in Figure 3 is that as one moves up to higher trophic levels (for example from plants to top-carnivores) the total amount of energy decreases. Plants exert a “bottom-up” control on the energy structure of ecosystems by determining the total amount of energy that enters the system.
However, predators can also influence the structure of lower trophic levels from the top-down. So called top-down effects can dramatically shift dominant species in terrestrial and marine systems The interplay and relative strength of top-down vs. bottom-up controls on ecosystem structure and function is an important area of research in the greater field of ecology.
Trophic dynamics can strongly influence rates of decomposition and nutrient cycling in time and in space. For example, herbivory can increase litter decomposition and nutrient cycling via direct changes in litter quality and altered dominant vegetation. Insect herbivory has been shown to increase rates of decomposition and nutrient turnover due to changes in litter quality and increased
frass inputs showed that C rich honeydew produced during aphid outbreak can result in increased N immobilization by soil microbes thus slowing down nutrient cycling and potentially limiting biomass production. North atlantic marine ecosystems have been greatly altered by overfishing of cod. Cod stocks crashed in the 1990’s which resulted in increases in their prey such as shrimp and snow crab Human intervention in ecosystems has resulted in dramatic changes to ecosystem structure and function. These changes are occurring rapidly and have unknown consequences for economic security and human well-being.
Applications: Why does this science matter?
The biosphere has been greatly altered by the demands of human societies. Ecosystem ecology plays an important role in understanding and adapting to the most pressing current environmental problems. Restoration ecology and ecosystem management are closely associated with ecosystem ecology. Restoring highly degraded resources depends on integration of functional mechanisms of ecosystems.
This situation is striking considering that these areas are close to each other, the majority of inhabitants are of Mayan descent, and the topography and overall resources are similar. This is a case of two groups of people managing resources in fundamentally different ways. Ecosystem ecology provides the basic science needed to avoid degradation and to restore ecosystem processes that provide for basic human needs.
Further Information
Get more info on 'Ecosystem Ecology'.
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