Abundance (ecology)
Encyclopedia
Abundance is an ecological
concept referring to the relative representation of a species in a particular ecosystem
. It is usually measured as the large number of individuals found per sample. How species abundances are distributed within an ecosystem is referred to as relative species abundance
s.
Abundance is contrasted with, but typically correlates to, incidence
, which is the frequency with which the species occurs at all in a sample. When high abundance is accompanied by low incidence, it is considered locally or sporadically abundant.
A variety of sampling methods are used to measure abundance. For larger animals, these may include spotlight counts, track counts and roadkill
counts, as well as presence at monitoring stations. In many plant communities the abundances of plant species are measured by plant cover
, i.e. the relative area
covered by different plant species in a small plot.
Relative species abundance
is calculated by dividing the number of species from one group by the total number of species from all groups.
to indicate how many organisms there are in a particular habitat when it would not be practical to count them all. Instead, a smaller representative sample of the population is counted instead.
The ACFOR scale is as follows:
This method of sampling is simple and easy to implement, but can be subjective. Species frequency is the number of times a plant species is present in a given number of quadrats of a particular size or at a given number of sample points. Frequency is usually expressed as a percentage and sometimes called a Frequency Index. The concept of frequency refers to the uniformity of a species in its distribution over an area. No counting is involved just a record of species present. Each individual of the species present is recorded, is a more accurate and reliable method of sampling.
Ecology
Ecology is the scientific study of the relations that living organisms have with respect to each other and their natural environment. Variables of interest to ecologists include the composition, distribution, amount , number, and changing states of organisms within and among ecosystems...
concept referring to the relative representation of a species in a particular ecosystem
Ecosystem
An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving , physical components of the environment with which the organisms interact, such as air, soil, water and sunlight....
. It is usually measured as the large number of individuals found per sample. How species abundances are distributed within an ecosystem is referred to as relative species abundance
Relative species abundance
Relative species abundance is a component of biodiversity and refers to how common or rare a species is relative to other species in a defined location or community...
s.
Abundance is contrasted with, but typically correlates to, incidence
Incidence
Incidence may refer to:* Incidence , a measure of the risk of developing some new condition within a specified period of time* Incidence , the binary relations describing how subsets meet...
, which is the frequency with which the species occurs at all in a sample. When high abundance is accompanied by low incidence, it is considered locally or sporadically abundant.
A variety of sampling methods are used to measure abundance. For larger animals, these may include spotlight counts, track counts and roadkill
Roadkill
Roadkill is an animal or animals that have been struck and killed by motor vehicles. In the United States of America, removal and disposal of animals struck by motor vehicles is usually the responsibility of the state's state trooper association or department of transportation.-History:During the...
counts, as well as presence at monitoring stations. In many plant communities the abundances of plant species are measured by plant cover
Plant cover
The abundances of plant species are often measured by plant cover, i.e. the relative area covered by different plant species in a small plot. Plant cover is not biased by the size and distributions of individuals, and is an important and often measured characteristic of the composition of plant...
, i.e. the relative area
covered by different plant species in a small plot.
Relative species abundance
Relative species abundance
Relative species abundance is a component of biodiversity and refers to how common or rare a species is relative to other species in a defined location or community...
is calculated by dividing the number of species from one group by the total number of species from all groups.
ACFOR
ACFOR is an acronym for a simple, somewhat subjective scale used to describe species abundance within a given area. It is normally used within a sampling quadratQuadrat
A quadrat is a square used in ecology and geography to isolate a sample, usually about 1m2 or 0.25m2. The quadrat is suitable for sampling plants, slow-moving animals , and some aquatic organisms.When an ecologist wants to know how many organisms there are in a particular habitat, it would not be...
to indicate how many organisms there are in a particular habitat when it would not be practical to count them all. Instead, a smaller representative sample of the population is counted instead.
The ACFOR scale is as follows:
- A - The species observed is "Abundant" within the given area.
- C - The species observed is "Common" within the given area.
- F - The species observed is "Frequent" within the given area.
- O - The species observed is "Occasional" within the given area
- R - The species observed is "Rare" within the given area.
This method of sampling is simple and easy to implement, but can be subjective. Species frequency is the number of times a plant species is present in a given number of quadrats of a particular size or at a given number of sample points. Frequency is usually expressed as a percentage and sometimes called a Frequency Index. The concept of frequency refers to the uniformity of a species in its distribution over an area. No counting is involved just a record of species present. Each individual of the species present is recorded, is a more accurate and reliable method of sampling.
See also
- Living Planet IndexLiving Planet IndexThe Living Planet Index is an indicator of the state of global biological diversity, based on trends in vertebrate populations of species from around the world....
- Occupancy-abundance relationshipOccupancy-abundance relationshipIn macroecology, the occupancy-abundance relationship is the relationship between the abundance of species and the size of their ranges within a region. This relationship is perhaps one of the most well-documented relationships in macroecology, and applies both intra- and interspecifically . In...
- Range (biology)Range (biology)In biology, the range or distribution of a species is the geographical area within which that species can be found. Within that range, dispersion is variation in local density.The term is often qualified:...
- Species richnessSpecies richnessSpecies richness is the number of different species in a given area. It is represented in equation form as S.Species richness is the fundamental unit in which to assess the homogeneity of an environment. Typically, species richness is used in conservation studies to determine the sensitivity of...
- Plant coverPlant coverThe abundances of plant species are often measured by plant cover, i.e. the relative area covered by different plant species in a small plot. Plant cover is not biased by the size and distributions of individuals, and is an important and often measured characteristic of the composition of plant...
External links
- "Abundance in ecology" (article, with works cited)