Sampling
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This document discusses two methods for estimating population size: the Lincoln Index and the quadrat method. The Lincoln Index involves capturing, marking, and recapturing a sample of individuals to estimate the total population size using a calculation. The quadrat method involves randomly placing quadrats (sample areas) throughout a total area and counting individuals within each quadrat. The mean number of individuals per quadrat is then extrapolated to the total area to estimate the overall population size.
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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