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Belt Transect Method


Systematic sampling. a belt transect uses a quadrat to sample a strip or belt of vegetation along the transect line. We can reduce the number of sample points by leaving a pace between quadrats, e.g. by sampling every 2 m. This is called an INTERRUPTED BELT TRANSECT. in this exercise we are sampling along an environmental gradient, the change from light to shade as we go from grassland to forest, and exploring how that affects the type and number of plants growing at ground level.

The importance of light to ground cover plants.

In order to carry out this exercise we will use a rope line and 1m2 quadrats to carry out an interrupted belt transect across the boundary between forest and grassland. We will measure light levels and percentage cover for different types of ground cover vegetation at 2m intervals along a 40m transect line which crosses the vegetation boundary at right angles.

  1. Use a tape measure or marked rope to establish a line across the boundary which extends at least 15m into each area. Number from the forest (0m) to the grassland (40m)

  2. Measure the light readings using your phone app. at 1m intervals along the quadrat. You must do this as quickly as possible to get an accurate light gradient especially if there are passing clouds.

  3. Lay the quadrat down at the 0-1 m mark, the 2-3 m mark etc. along the transect and record the variety and % cover of each type of vegetation inside the quadrat.

  4. Classify the vegetation as follows; Grasses, ferns, herbaceous, tree seedlings. We are looking at ground cover so ignore any vegetation over 2m tall. If your quadrat encounters a mature tree, move it the least possible distance in any direction to be able to lay it flat and complete the sample there.

  5. For each type of vegetation estimate the % of the 1 m2 of ground within the quadrat covered by those plants. E.g. Grasses 90%; ferns – 20%; Herbs 5%; Tree seedlings 0% Total 115% . Don’t worry if the total is over 100% as this simply reflects that there may be more than one layer of vegetation present.

  6. At each quadrat position record the % of the sky overhead obscured by leaves,

  7. Plot your results for light levels and % cover as a line graph, and your results for vegetation % cover as kite diagrams.

  8. What are your conclusions from the data about the effect of light on ground cover vegetation?

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