User: | Open Learning Faculty Member:
Shannon Myles
February 1st, 2020
I used the distance-based sampling methods to measure tree species abundance in the tutorial. Table 1 below illustrates the data gathered.
Table 1 Comparison of three distance-based sampling methods used to calculate the abundance of tree species in the Snyder-Middleswarth Natural Area.
| Tree Species | Actual | Systematic | % error | Random | % error | Haphazard | % error |
| Eastern Hemlock | 469.9 | 277.3 | 40.99 | 441.8 | 5.98 | 485.0 | 3.21 |
| Sweet Birch | 117.5 | 109.6 | 6.72 | 144.1 | 22.64 | 121.2 | 3.15 |
| Yellow Birch | 108.9 | 70.9 | 34.89 | 105.6 | 3.03 | 83.9 | 22.96 |
| Chestnut Oak | 87.5 | 38.7 | 55.77 | 115.2 | 31.66 | 93.3 | 6.63 |
| Red Maple | 118.9 | 90.3 | 24.05 | 86.4 | 27.33 | 74.6 | 37.26 |
| Striped Maple | 17.5 | 45.1 | 157.71 | 28.8 | 64.57 | 18.7 | 6.86 |
| White Pine | 8.4 | 12.9 | 53.57 | 0.0 | 100 | 18.7 | 122.62 |
| Estimated time to sample | 4h 18min 53.39 | 4h 40min 36.46 | 4h 38min 28.96 | ||||
Table 1 shows that the estimated times to perform the studies were somewhat similar, but that the fastest method to sample 24 plots was the systematic approach by approximately 20 minutes.
The comparison of measurements of abundance showed that the most precise technique for the most abundant species of tree (Eastern Hemlock) was the haphazard technique. With a % error of only 3.21, it surpasses the random sampling method in accuracy by less than 3%. Both the random and haphazard techniques were far more accurate than the systematic method, which led to a terrible % error of 40.99%. As for the second most abundant species of tree in the area (Red Maple), the best sampling method was systematic, with a % error of 24.05.
For the rarest species of tree (White Pine), the most accurate sampling method was found to be the systematic approach. With a relatively high 53.57% error, it is far more accurate than the two other methods, who have both surpassed 100% error. The abundance of the second least abundant tree (Striped Maple) was very accurately measured by the haphazard method. It scored a 6.86% error, comparatively to 64.57% and 157.71% for random and systematic.
Generally speaking, the accuracy of all three methods seemed to have diminished as species abundance became lower. Except for a few odd data points, the majority of % error was inversely proportional to the actual species abundance, no matter the sampling strategy.
Finally, the average % error of the haphazard method (28.96%) was lower than for random and systematic methods (36.46% and 53.39%). Therefore, I conclude that the distance-based haphazard method is the most accurate for sampling abundance in a forest.
