1. Population Sampling

2. Measuring Population Size
• Census (count EVERYTHING?!?!)
• Sampling
– Lincoln Index (capture, tag, recapture)
– Quadrat (count in a small sample area,
apply to entire area)

3. Lincoln Index
population size = (n1 X n2)/n3
where . . .
• n1= number of individuals initially caught, marked and
released
• n2 = total number of individuals caught in the second
sample
• n3 = number of marked individuals in the second sample

4. Quadrat Method
• Random sampling of plant species
usually involves counting numbers
in small, randomly located, squares
within the total area.
• These squares are usually marked
with frames called quadrats.

5. Quadrat Method
• Mark out gridlines
along two edges of
the area
• Use a calculator or
tables to generate
two random
numbers to be used
as coordinates.
Place a quadrat at
the coordinates
Example: 14, 31

6. Quadrat Method
1. Count how
many
individuals
are inside
the quadrat.
2. Repeat steps
2 and 3 as
many times
as possible.

7. Quadrat Method
1. Measure the total
size of the area
occupied by the
population, in
square meters

8. Quadrat Method
1. calculate the mean number of
plants per quadrat. Then calculate
the population size using the
following equation:
Population = (quadrat mean X total area)
quadrat area