Nutrient Cycling in an Ecosystem
Recycling is an excellent stewardship activity since it can reduce the depletion of Earth’s natural resources, as well as the number of landfills needed for storing our waste. However, in the natural world, recycling is not an optional event. Every living thing is made up of a variety of elements (e.g., carbon, hydrogen, and nitrogen) that are essential for existence. The total amount of these elements on planet Earth has not changed over millions of years. For example, the amount of water (hydrogen and oxygen elements combined) present today is the same amount that existed when dinosaurs roamed the Earth. If these elements were not recycled, life would cease to exist since nature would rapidly exhaust its supply of these nutrients.
Like all nutrients, water molecules inside the bodies of dinosaurs, or located elsewhere in the prehistoric landscape, have moved in a circular pattern over millions of years. Those molecules currently exist somewhere in the Biosphere. Possibly one of these molecules exists inside you.
The water cycle illustrates how molecules of water move in a circular pattern. They enter the atmosphere after evaporation from the surface land or water or from transpiration that moves water through plants into the air. In addition to passing through plants at times, some water molecules pass through other life forms. Thus, the water currently in the Biosphere, is the same amount that was present when dinosaurs roamed the Earth.
Technically, we call the circular movement of elements biogeochemical cycles since these chemicals, over a period of time, move through the living and nonliving environment. The term “nutrient cycle” is really a generalized designation for the different biogeochemical cycles of many elements. It could, for example, be the water cycle, the oxygen cycle, the carbon cycle, the phosphorus cycle or the nitrogen cycle. When inorganic elements pass through living organisms, they often become bound up as complex organic substances (e.g., organic molecules called carbohydrates contain the inorganic elements carbon, hydrogen and oxygen). When organisms die in both terrestrial and aquatic ecosystems, their bodies represent a reservoir of inorganic elements (nutrients). Nature needs to separate the elements from their bound up state so that they can be recycled. All dead organic matter (dead bodies of all living things, as well as animal feces and shed body parts like snake skin) is called detritus. Some elements are removed from detritus by the leaching action of water. However, most removal occurs from the action of organisms called detritivores (pronounced di try’ ti vores) and decomposers.
Detritivores digest the organic matter internally after ingesting it. They speed up decay by shredding the dead matter, and as a result increasing the surface area for attack by the decomposers - bacteria and fungi (e.g., mushrooms). Both bacteria and fungi have the capacity to release enzymes that break apart the organic molecules, thereby releasing the inorganic elements into the environment (e.g., soil or water). This process is called decomposition. Some of these elements are then taken inside the bacteria or fungus to provide them with nutrients, as well as energy; those that are not taken in can be absorbed by plants and are eventually passed to herbivores and carnivores in the food chain. Nutrient cycling within an ecosystem is not a perfect process because some nutrients may be lost from the ecosystem due to soil erosion.
Detritivores and decomposers play a vital ecological role in assuring the survival of producers such as plants, and thus all life, by recycling nutrients back to them. Furthermore, detritivores and decomposers are nature’s garbage collectors - insuring that an ecosystem will not suffocate under a mass of dead matter.
Some books erroneously list organisms such as termites and earthworms as decomposers. They loosely use the term detritivore and decomposer synonymously. This is a mistake. While detritivores increase the surface area for decomposition, they are not true decomposers, since they do not convert dead tissue into inorganic elements.
The rate of decomposition is affected by a variety of abiotic (nonliving) factors. For example, decomposition is reduced by low temperature, poor aeration of the soil, a lack of moisture and acidic conditions.
A gardener who composts lawn matter and food remains works to overcome these limitations in order to accelerate decomposition. By creating the proper environment for detritivores and decomposers, the outcome will be nutrient rich matter that will stimulate the growth of plant life. Composting is an excellent stewardship activity, in which students can observe the decomposition process conducted by detritivores and decomposers.
Technically, we call the circular movement of elements biogeochemical cycles since these chemicals, over a period of time, move through the living and nonliving environment. The term “nutrient cycle” is really a generalized designation for the different biogeochemical cycles of many elements. It could, for example, be the water cycle, the oxygen cycle, the carbon cycle, the phosphorus cycle or the nitrogen cycle. When inorganic elements pass through living organisms, they often become bound up as complex organic substances (e.g., organic molecules called carbohydrates contain the inorganic elements carbon, hydrogen and oxygen). When organisms die in both terrestrial and aquatic ecosystems, their bodies represent a reservoir of inorganic elements (nutrients). Nature needs to separate the elements from their bound up state so that they can be recycled. All dead organic matter (dead bodies of all living things, as well as animal feces and shed body parts like snake skin) is called detritus. Some elements are removed from detritus by the leaching action of water. However, most removal occurs from the action of organisms called detritivores (pronounced di try’ ti vores) and decomposers.
Detritivores digest the organic matter internally after ingesting it. They speed up decay by shredding the dead matter, and as a result increasing the surface area for attack by the decomposers - bacteria and fungi (e.g., mushrooms). Both bacteria and fungi have the capacity to release enzymes that break apart the organic molecules, thereby releasing the inorganic elements into the environment (e.g., soil or water). This process is called decomposition. Some of these elements are then taken inside the bacteria or fungus to provide them with nutrients, as well as energy; those that are not taken in can be absorbed by plants and are eventually passed to herbivores and carnivores in the food chain. Nutrient cycling within an ecosystem is not a perfect process because some nutrients may be lost from the ecosystem due to soil erosion.
Detritivores and decomposers play a vital ecological role in assuring the survival of producers such as plants, and thus all life, by recycling nutrients back to them. Furthermore, detritivores and decomposers are nature’s garbage collectors - insuring that an ecosystem will not suffocate under a mass of dead matter.
Some books erroneously list organisms such as termites and earthworms as decomposers. They loosely use the term detritivore and decomposer synonymously. This is a mistake. While detritivores increase the surface area for decomposition, they are not true decomposers, since they do not convert dead tissue into inorganic elements.
The rate of decomposition is affected by a variety of abiotic (nonliving) factors. For example, decomposition is reduced by low temperature, poor aeration of the soil, a lack of moisture and acidic conditions.
A gardener who composts lawn matter and food remains works to overcome these limitations in order to accelerate decomposition. By creating the proper environment for detritivores and decomposers, the outcome will be nutrient rich matter that will stimulate the growth of plant life. Composting is an excellent stewardship activity, in which students can observe the decomposition process conducted by detritivores and decomposers.
Water Cycle
Credits: Water Cycle, Dinosaurs (Dorling Kindersley)
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