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.
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