For this exercise I chose to use the area-based method.
Which technique had the fastest estimated sampling time?
The systematic sampling method had the fastest estimated time (12 hours, 37 minutes), as opposed to random (12 hours, 42 minutes) and haphazard (13 hours, 3 minutes).
Compare the percentage error of the different strategies for the two most common and two rarest species.
The two most common species were the Eastern Hemlock and the Sweet Birch (actual frequency of 73% and 43%, respectively), and the two rarest species were the Striped Maple and the White Pine (actual frequency of 6% and 4%, respectively).
% error of density for the different sampling strategies:
Systematic (quadrats along a transect):
Eastern Hemlock: 0.4%
Sweet Birch: 8.1%
Striped Maple: 54.3%
White Pine: 4.8%
Random:
Eastern Hemlock: 62.8%
Sweet Birch: 4.3%
Striped Maple: 138.3%
White Pine: 197.6%
Haphazard:
Eastern Hemlock: 6.4%
Sweet Birch: 4.7%
Striped Maple: 77.1%
White Pine: 90.5%
Was one sampling strategy more accurate than another?
These results show that in general, the systematic sampling method is more accurate than the random and haphazard methods (i.e., it resulted in the smallest overall percent error for density).
Did the accuracy change with species abundance?
Yes, these results show that the accuracy is significantly lower for the rarer species (Striped Maple and White Pine) than for the more common species (Eastern Hemlock and Sweet Birch). One exception to this was with the sampling of Eastern Hemlock using the random strategy, which resulted in a percent error of 62.8%. This high percent error means that the density of Hemlock in the quadrats randomly chosen to sample did not reflect the species’ actual density – it was significantly lower than expected.
The highest percent error for the two species with greater abundance was 62.8% (the second highest being 8.1%), whereas the two rarer species had a percent error that ranged from 4.8% to 197.6%. In conclusion, based on the above data, accuracy diminishes with species’ rarity (the less abundant species are generally less accurately sampled).