I am using the three sample strategies from the Virtual Forest Tutorial. I looked at three different sample strategies: area random, area systematic, and area haphazard. Data from the Snyder-Middleswarth Natural Area, which was Area: 250m by 300m = 75,000 sq. m or 7.50 ha and Quadrat: 10m by 10m = 100 sq. m, was gathered using all sampling methodologies.
22 Quartets were sampled by this technique. 2200 sq m area was sampled. 6 species were sampled.
Total time to sample: 11 hours, 40 minutes
Eastern hemlock and sweet birch were the 2 most common species. Red maple and striped maple were the rarest species.
The percentage error of the different strategies for the two most common and two rarest species: Using area haphazard sampling, Eastern hemlock and sweet birch had a density of 26.6% and 0.7% respectively.
Some sample calculations for percentage of error –
Haphazard –
For most common species
Eastern Hamlock
(469.9 – 590.9)/590.9 x 100 = 20.48%
sweet birch-
(117.5-218.2)/218.2 x 100 = 46.42%
Least Common Species:
Red Maple-
(17.5-31.8)/31.8 x 100 = 45%
In conclusion, the choice of sampling strategy matters, and the accuracy did vary with species abundance. Although useful, Area Haphazard might not be the most accurate for all species.