Carbon, Nitrogen Cycles & Ecosystem Dynamics Explained

Carbon Cycle

The main reservoir of carbon is the atmosphere, but water also contains small amounts of CO2. Atmospheric CO2 is fixed by producers through photosynthesis. Consumers and decomposers incorporate carbon through food. Carbon can escape the cycle and remain separated from living beings, such as when fossil fuels are formed.

Nitrogen Cycle

The atmosphere is composed of 78% nitrogen, but this gas is inaccessible to most living things except bacteria. Consumers and decomposers incorporate nitrogen through food. Atmospheric nitrogen can be transformed into nitrates, which can leave the cycle when transported by water to sediment, where they form sedimentary rocks.

Homeostasis in Ecosystems

Homeostasis is the set of self-regulatory mechanisms that maintain the characteristics of the ecosystem despite changes that occur within it.

Feedback Mechanisms

Feedback is a property of many systems where outputs are processed as inputs. In ecosystems, feedback mechanisms help control the system, establishing a dynamic equilibrium.

Ecosystem Changes

Ecosystems are subject to both natural and human-induced changes:

• Natural changes: Climatic variations, meteorite impacts, floods, fires, etc.
• Human-induced changes: Environmental pollution, aquifer depletion, deforestation, etc.

Ecological Succession

Ecological succession is the dynamic process by which some populations are replaced with new ones, creating more complex relationships.

Primary Succession

Primary succession starts on a barren site, such as a newly formed volcanic island or a young mountain. The first occupants of this soil are pioneer species such as mosses, which are eaten by small consumers. The pioneers introduce changes in the environment that promote the installation of plants and shrubs. These changes also allow other species to develop, eventually leading to a climax community.

Secondary Succession

Secondary succession begins when a mature ecosystem suffers severe disturbances such as fire, lightning, or floods. The immature ecosystem loses components. Over time, the species that start the recovery of the disturbed ecosystem are replaced by new ones. Many ecosystems return to a climax community through secondary succession. For example, forests usually recover after a fire.