Quadrat
Aquadratis a frame used inecology,geography,andbiologyto isolate a standard unit of area for study of the distribution of an item over a large area. Quadrats typically occupy an area of 0.25m2and are traditionally square, but modern quadrats can be rectangular, circular, or irregular.[1][2]A quadrat is suitable for sampling or observingplants,slow-moving animals, and some aquatic organisms.
A photo-quadrat is a photographic record of the area framed by a quadrat. It may use a physical frame to indicate the area, or may rely on fixed camera distance and lensfield of viewto automatically cover the specified area of substrate.[3]Parallel laser pointers mounted on the camera can also be used as scale indicators. The photo is taken perpendicular to the surface, or as close as possible to perpendicular for uneven surfaces.
History
[edit]The systematic use of quadrats was developed by the pioneering plant ecologists R. Pound andF. E. Clementsbetween 1898[4]and 1900.[5]The method was then swiftly applied for many purposes inecology,such as the study ofplant succession.[6]Botanists and ecologists such asArthur Tansleysoon took up and modified the method.[7][8]
The ecologistJ. E. Weaverapplied the use of quadrats to the teaching of ecology in 1918.[9]
Method
[edit]A quadrat can be used by researchers to methodically count organisms within a smaller, representative area in order to extrapolate to a largerhabitatwhen comprehensive sampling is impossible or not practical. The quadrat's size corresponds to the size of the organism being sampled and the overall sampling area. To avoidselection bias,researchers will randomly distribute quadrats throughout the sampling area.[10]
For long-term studies, the same quadrats can be revisited after their initial sampling. Methods of precisely relocating the area of study vary widely in accuracy and include measurement from nearby permanent markers, use oftotal stationtheodolites,consumer-gradeGPS,anddifferential GPS.[11]
See also
[edit]References
[edit]- ^Krebs, C.J. (1999).Ecological Methodology.Addison-Wesley.
- ^Wheater, C. Philip; et al. (2011).Practical Field Ecology: Project Guide.John Wiley and Sons.
- ^Littler, M. M.; Littler, D. S. (1985). "Nondestructive sampling".Handbook of Phycological Methods.Vol. 4. Ecological Field Methods: Macroalgae.Cambridge, UK:Cambridge University Press.pp. 161–175.ISBN9780521249157.
- ^Pound, R.;Clements, F. E.(June 1898). "A method of determining the abundance of secondary species".Minnesota Botanical Studies.2:19–24.
- ^Pound, R.;Clements, F. E.(1900).Phytogeography of Nebraska(Second ed.). Lincoln, Neb. Published by the Seminar. pp.61–63.
- ^Clements, F. E.(1916).Plant Succession.The Seminar, Lincoln, Nebraska. pp. 423–437.
- ^Oliver, F. W.;Tansley, A. G.(December 1904)."Methods of surveying vegetation on a large scale".New Phytologist.3(9–10): 228–237.doi:10.1111/j.1469-8137.1904.tb05867.x.
- ^Tansley, A. G.(1911).Types of British vegetation.Cambridge University Press.
- ^Weaver, J. E. (November 1919). "The Quadrat Method in Teaching Ecology".The Plant World.21(11): 267–283.JSTOR43477708.
- ^"Questions about Quadrats".Science and Plants for Schools.Retrieved20 June2018.
- ^Dodd, M. (2011)."Where are my quadrats? Positional accuracy in fieldwork".Methods in Ecology and Evolution.2(6): 576–584.doi:10.1111/j.2041-210X.2011.00118.x.