Ecosystems and Processes

What is an Ecosystem?

An ecosystem is a community of living organisms and includes a variety of other elements in the environment they inhabit. The living and nonliving components of an ecosystem are all connected through various ecological processes such as the flow of energy and the exchange of chemical products. In nature, the boundaries of ecosystems are not strictly defined. In fact, the biosphere can be thought of as one big ecosystem in which everything is connected in some way or another. However, some ecosystem boundaries are easily identified, such as the edge of a desert or the coast of the sea.

For example, a rainforest is an ecosystem made up of living things such as animals, plants, fungi, micro-organisms, and insects. At the same time, these living things are also in constant interaction with the nonliving elements found in the ecosystem, such as sunlight, air, nutrients in the soil, and even the temperature.

What makes up an Ecosystem?

The ecosystem is the basic unit of the scientific study of nature. It has two main types of components:

The biotope (abiotic): the physical environment with all its physical and chemical characteristics. This includes temperature, climate, humidity, sunlight, pH levels, gases such as oxygen and carbon dioxide, and the nutrients found in the soil.

The biocenosis (biotic): all living organisms that belong to, and interact with the local environment. Animals, plants, insects, fungi, micro-organisms, are in interconnected and interdependent relationships with each other.

Scientists study these interconnected and overlapping interactions and processes between the biotic, living and abiotic, and unliving, parts of an ecosystem. This way they can determine what each part contributes to the whole picture. Moreover, they can also predict what happens when an ecosystem loses one of its components.

What are the Ecological Processes?

There are four essential ecological processes in ecosystems, namely the water cycle, biogeochemical (or nutrient) cycling, the flow of energy, and succession. Together, these processes produce organic matter, facilitate the transfer of nutrients, shape the soil and its contents, and allow organisms to reproduce.

Water Cycle

Water is indispensable to life on Earth. Each of its three states — solid, liquid, and gas — is directly involved in many of the processes that make our planet habitable. Without question, one such process essential to the survival of many species is the Water Cycle.

The Water Cycle is the continuous movement of water on our planet, in bodies of water, on the Earth, and in the atmosphere. The Water Cycle has no starting point as all its complex processes are constantly in motion and interact with each other.

Liquid water from all bodies of water evaporates into water vapour and rises into the atmosphere. Water in its gaseous form then clumps together, cools, and condenses to form clouds. Eventually, the water vapour in clouds precipitates and falls back to Earth in rain or snow. The cycle is repeated and liquid water again drops to the Earth where it collects into rivers, lakes, seas, and oceans, where it will again evaporate.

Ecosystems and processes are closely entwined with communities of living organisms.

Biogeochemical or Nutrient Cycling

Nutrient circulation is one of the major functions of an ecosystem. In this cycle, biogeochemical elements such as carbon, hydrogen, oxygen, nitrogen, and phosphorus move from living to nonliving and back again in a circular manner. With respect to matter, the Earth is a closed system, which means that none of these elements is lost or destroyed. In an ecosystem, nutrients are then perpetually processed between their biotic and abiotic states. This allows nutrients found in food, the ground, and other organic matter to be indefinitely recycled over and over again.

The elements carbon, nitrogen, and phosphorus are incorporated into living organisms in a multitude of ways. Plants obtain these from the air, water and soil around them. Animals obtain these from consuming other living organisms such as plants and other animals. These chemicals are then transformed and processed within the organism. Sooner or later, either through excretion or decomposition, these nutrients return to the abiotic environment in an inorganic state to be used again once by living organisms.

Energy Flow and Transformation

Each living organism can be classified on a trophic level, a step in the food chain. Plants are primary producers, herbivores are primary consumers, and carnivores are secondary consumers. Furthermore, carnivores that eat other carnivores are considered tertiary or even quaternary consumers.

Much of the energy that transfers through the food chain is lost to the different bodily processes of living organisms. Less energy is available at the herbivore level than the primary producer level. Even less energy is available at the carnivore level than at previous levels. As a general rule, less and less energy is available as it is transferred from organism to organism. It can then be said that the energy transfer through the food chain is highly inefficient.

Ecological Succession

Ecological succession, or simply succession, is the process whereby the composition of an ecological community changes over time. There are two types of succession: primary and secondary. In primary succession, lifeless regions with soil incapable of sustaining life are colonised by living things for the first time. Secondary succession happens when areas previously inhabited by living things is disturbed, then reinhabited after a small-scale disturbance.

Ecological succession is a gradual process that takes place over many years. In essence, both primary and secondary succession shape a given ecosystem by creating an ever-changing mix of species as different disturbances of varying effects alter the landscape.

Primary Succession

First, uninhabitable rock and substrate are weathered down by natural forces to the point that pioneer species like lichens and some plants can take root. The pioneer species would then further break down the mineral-rich lava into the soil on which other species can eventually grow and succeed the pioneer species. The first inhabitants would then decompose and die, further nourishing the new soil.

With each additional stage comes a new set of species living in the area, made more hospitable by their predecessors. These species will eventually also die and be replaced. This process will continue and repeat multiple times during succession. A community can reach a relatively stable point and experience a halt in the changing of composition. However, it is still unclear if succession truly reaches a stable endpoint.

Secondary Succession

Secondary succession occurs when a formerly inhabited area is recolonised after a disturbance that wipes out most if not all of the existing community.

For example, a forest decimated by wildfire. The fire would have killed off the majority of the vegetation and the animals unable to flee. However, the nutrients would return to the soil in the form of ash. This nutrient-rich soil would then be an ideal place for recolonisation.

Climax Community

It was originally believed by early ecologists that succession was a predictable process in which a community would experience the same series of stages. They believed that after a certain amount of time, the succession would reach a stable, unchanging final state known as a climax community. This final state is characterised by an equilibrium of existing species in which no other species can be accommodated.

Recently, however, this idea has been challenged. Instead of following a predetermined, set path, succession appears to follow different roads depending on the circumstances. It is also possible for an ecosystem to experience too many disturbances to reach a state of equilibrium. Climax communities could occur in some cases, but this may be unlikely for most ecological communities.

The Importance of Ecological Processes

Ecological processes, as abundant as they are ubiquitous, maintain many of the environmental conditions that support life on Earth. In this respect, the success and development of ecosystems are wholly reliant on these biological, physical, and chemical processes. Collectively, these processes perform a plethora of functions that benefit all of the planet’s living and nonliving inhabitants.

However, these processes are impacted by both natural and artificial forces happening at varying times and different locations. As custodians of our only home, the Earth, it is of utmost importance for us to realise the effect of human activity on the ecological processes, especially how artificial forces can change, disrupt, and be detrimental to the ecological balance.

Artificial Products

Pesticides, waste products, pollutants, and chemicals used in various industries can have a directly harmful effect on surrounding ecosystems. Waste-water treatment plant discharge, nutrients from fertilisers, and manure can also have a detrimental effect on the water quality of an ecosystem.

Land Use and Conversion

Human manipulation of land can disrupt the natural balance of ecological processes. This can trigger a chain of events felt throughout the whole ecosystem. For example, converting woodlands into urban or agricultural areas influences the types of primary producers, water collection and distribution, and the cycling of nutrients. Additionally, many human activities can exacerbate sediment erosion, impacting the soil on which primary producers grow.

References

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Cite/Link to This Article

  • "Ecosystems and Processes". Geography Revision. Accessed on August 19, 2022. https://geography-revision.co.uk/a-level/physical/ecosystems-and-processes/.

  • "Ecosystems and Processes". Geography Revision, https://geography-revision.co.uk/a-level/physical/ecosystems-and-processes/. Accessed 19 August, 2022.

  • Ecosystems and Processes. Geography Revision. Retrieved from https://geography-revision.co.uk/a-level/physical/ecosystems-and-processes/.