What Is a Transect?

A transect is a line across a habitat along which systematic sampling is carried out to study how organisms are distributed in relation to a changing factor (e.g. light, moisture, distance from a path).

💡 Key Concept: Transects are used to investigate how the abundance of organisms changes across an environmental gradient.

When Are Transects Used?

✔ When you’re studying a pattern or change in species across a habitat
✔ E.g. From a footpath into a woodland, or shoreline to inland
✔ To link changes in distribution to abiotic factors (light, moisture, soil pH)

👉 Suggested Image: A diagram of a transect line showing quadrats placed at intervals with plant species measured.

How to Carry Out a Transect Study

1️ Stretch a measuring tape or string in a straight line across the habitat.
2️ Place quadrats at regular intervals along the line (e.g. every 1m).
3️ In each quadrat, record the organisms present and their abundance.
4️ Also record abiotic factors (e.g. light, temperature) if possible.
5️ Use the data to look for patterns in distribution.

Types of Data Collected

✔ Species richness – number of different species
✔ Percentage cover – how much of the quadrat is taken up by a species
✔ Abundance – how many individuals of each species
✔ Environmental conditions – light, soil pH, etc.

💡 This is a systematic sampling method – not random, but evenly spaced.

Example Investigation

Question: How does light intensity affect the distribution of clover from a path into a field?

➡ Use a transect line, place quadrats every 1m, measure % cover of clover and light intensity.
➡ Expect to see more clover further from the path where light conditions or trampling pressure changes.

Making it a reliable experiment

✔ Use the same size quadrat each time
✔ Keep intervals equal along the transect
✔ Record results at the same time of day/year
✔ Use repeats or multiple transects to increase reliability