A transect is a line across a habitat along which samples are taken systematically. Transects are used to study how the distribution of species changes along an environmental gradient, for example from low to high tide on a rocky shore, from a hedge into a field, or from open ground into a wood.
- Line transect: a tape is laid out and the species touching the line at regular intervals (e.g. every 1 m) are recorded. Quick, but shows only presence, not abundance.
- Belt transect: quadrats are placed at regular intervals along the tape, either touching (a continuous belt) or spaced out (an interrupted belt), and the abundance of each species is measured in each quadrat. Gives more information but takes longer.At every sampling point the relevant abiotic factors (light intensity, soil moisture, pH, height above low tide) are measured too, so that changes in species can be linked to changes in conditions.Results are often shown as a kite diagram, in which the width of each band shows the abundance of a species at each distance along the transect.Worked example: a belt transect from a hedge into a field records ivy cover of 60%, 30%, 5% and 0% at 0, 2, 4 and 6 m, while light intensity rises at each point. This suggests a negative correlation between ivy cover and light intensity, which can then be tested statistically.Several transects should be run parallel to each other to check that the pattern is repeatable.
- Line transect: a tape is laid out and the species touching the line at regular intervals (e.g. every 1 m) are recorded. Quick, but shows only presence, not abundance.
- Belt transect: quadrats are placed at regular intervals along the tape, either touching (a continuous belt) or spaced out (an interrupted belt), and the abundance of each species is measured in each quadrat. Gives more information but takes longer.At every sampling point the relevant abiotic factors (light intensity, soil moisture, pH, height above low tide) are measured too, so that changes in species can be linked to changes in conditions.Results are often shown as a kite diagram, in which the width of each band shows the abundance of a species at each distance along the transect.Worked example: a belt transect from a hedge into a field records ivy cover of 60%, 30%, 5% and 0% at 0, 2, 4 and 6 m, while light intensity rises at each point. This suggests a negative correlation between ivy cover and light intensity, which can then be tested statistically.Several transects should be run parallel to each other to check that the pattern is repeatable.