Ecological Techniques Quadrats, Transects and Measuring Abiotic Factors

Candidates should have: “studied an ecosystem in the field and be familiar with the uses, roles and limitations of frame quadrats and line transects, and with the measurement of abiotic factors, including pH, light and temperature.”

Quadrats Why do we use quadrats? What determines the size of a quadrat?

Quadrats Key points: Must be placed randomly (throwing a quadrat is not random!) Take many samples Recording results: Number of species present in quadrat Number of organisms of an individual species Percentage coverage by a species Number of quadrats in which species is present Conclusions: Estimate population sizes (per unit area) The effect of a particular factor (Abiotic/Biotic) on population

Quadrats Point quadrats: provide a more objective sampling method. Normally 10 sliding pins in a quadrat The number of pins that touch the particular organisms is counted. Percentage cover of a species= number of hitsx 100 number of hits + misses

Transects 1)Line transects: Used to show the pattern/distribution of organisms along a line through a habitat. String or tape Record every organism touching the line (continuous) Or record the organism touching the line at regular intervals. (interupted) Environmental features along line should be recorded. More than one line should be taken

Transects 1)Line Transects Convenient method of identifying patterns/ distributions  Doesn’t provide information about density of organisms along the transect.

Transects Belt transect Same as a line transect but sampking a strip of a chosen area. Usually using quadrats providing results per unit area revealing density or abundance of different species.

Measuring Abiotic Factors Light Intensity Light meter What data needs to be collecting to get a reliable measure of light intensity at a particular site? Soil pH Mix a sample of soil in distilled water and shake vigourously. Measure pH with pH probe or indicator paper.