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 ECOLOGY : FIELD TRIP TO CORREZE

TRANSECTS

A transect is a series of observations, or measurements, taken at regular intervals along a line.

Our aim is to use a transect to determine the change in a community as we progress from one habitat to another.

In this exercise an interrupted belt transect will be used.

MATERIALS

Tape or string marked in metre intervals, 1m2 quadrat, identification guide or species check list, hygrometer, soil thermometer, light metre, 2 ranging poles marked in 10cm intervals, spirit level, 20cm ruler.
TI-83 Plus calculator, CBL2 unit and probes.

METHOD

1. Lay out the tape or string across the transition zone so that it is straight and taught. Tie it down at both ends. Be careful not to trample the vegetation beside the line.

Note the orientation of the line (north-south, east-west etc.) and the major features along the transect. Use the prepared data table to record your results.
2. Starting at one end, lay your quadrat by the side of the line and identify the species of plant or animal present. Estimate their abundance using the scale given opposite:
 

Scale

Percentage Cover

Abundance Rating

Trace

<1%

Single individual

1

1 - 5%

Rare

2

6 - 25%

Occasional

3

26 - 50%

Frequent

4

51 - 75%

Abundant

5

76 - 100%

Dominant
  Record each species and their abundance in the table. Repeat this every other metre along the transect (see diagram opposite). Add new species to the bottom of the list.

3. Record at the bottom of your table the abiotic factors measured every other metre along the transect: Measure these within are relative short space of time so that variations in the weather do not influence the readings too much.
You may do this using your calculator and CBL2 interface. The data will be stored in the calculator and can be downloaded later. (Link to instructions)
4. Record the height profile of the transect using the ranging poles and the spirit level. Place the first pole at the beginning of the transect and the second pole at 1 metre. Using the spirit level, measure the difference in height of the two poles. See the diagram on the next page.

  Record an increase as a positive value and a decrease as a negative value. Where there is a sudden change in height place the poles at shorter intervals. On soft ground be sure not to push the poles into the soil, they should be gently resting on the ground.

© Paul Billiet 2004