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Surveying ecology : 4. Estimating the percentage cover (distribution) of a species from a quadrat

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There are various sections to work through, after 1 they can be read and studied in any order.

INDEX of biology notes on ecological surveying and biodiversity

(4) Surveying Method 3: Estimating the percentage cover (distribution) of a species from a quadrat

Another way to do a survey is to photograph the area or habitat of an organism you are interested in.

This is done on a large scale to survey farmland and monitor the distribution and growth of crops.

Above is a photograph of a section of a stone wall on which two species of lichen are growing.

In order to help estimate the % cover of the orange lichen and grey lichen a 10 x 10 grid (the quadrat) has been drawn over the photograph - making 100 squares (or mini-quadrats).

If a mini-square is filled with half or over half of the species it counts as 1/100 of the area.

If the mini-square is less than half-full a species does not count.

My estimates of the distribution as measured by the % cover (do you agree?)

You can think of the percentage cover as a measure of the distribution or abundance.

Orange lichen: Only 3 squares present (all in top left).

Therefore the orange lichen cover estimate is 3%.

Grey lichen: I found it easier to count the squares where it was absent, which I found to be 17.

Therefore the grey lichen cover estimate is 83%

The estimate of total lichen cover is 3 + 83 = 86%

If you surveyed another part of the stone wall in e.g. different light or moisture conditions, you would find the % cover might be different.

Keywords, phrases and learning objectives for this part on ecological surveying and biodiversity

Using quadrat data analysis in ecology surveying, be able to estimate the percentage cover (distribution) of a species from quadrat measurements.



INDEX of biology notes on ecological surveying


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