For the purpose of a virtual forest tutorial community sampling exercise, the Mohn Mill community was selected as the designated site. Spanning across 154 hectares, the Mohn Mill area is situated at coordinates 41°4’N, 77°8’W. It is positioned on the border of Pennsylvania’s Bald Eagle and Tiadaghton State Forests, intersecting Union, Lycoming, and Clinton counties.
In terms of time spent on sampling, the systematic technique proved to be the most efficient, requiring 12 hours and 4 minutes. In comparison, the random sampling technique took 12 hours and 51 minutes, while haphazard sampling took 12 hours and 29 minutes. For each sampling technique, a total of 24 quadrats were sampled.
During the systematic sampling process, an area of 2400 square meters was sampled, resulting in the collection of specimens from 9 different species, totaling 200 specimens.
| SYSTEMATIC | ||
| Quadrats | (x, y) | Species |
| 1 | (0,10) | Red maple, White oak, Witch hazel |
| 2 | (10, 20) | Chestnut oak |
| 3 | (20, 30) | Red maple, Black cherry, Chestnut oak |
| 4 | (30, 40) | Chestnut oak |
| 5 | (40, 50) | Red maple, Red/black oak, White oak, Witch hazel |
| 6 | (50, 60) | Red maple |
| 7 | (60, 70) | Red maple |
| 8 | (70, 80) | Red/ black oak, white oak |
| 9 | (80, 90) | Red maple, Red/ black oak, Eastern Hemlock |
| 10 | (90, 100) | Red maple, Eastern Hemlock, Chestnut oak, White oak |
| 11 | (100, 110) | Red maple, Chestnut oak, White oak |
| 12 | (110, 120) | Witch Hazel, Red/ black oak, Chestnut oak |
| 13 | (120, 130) | Red maple, Chestnut oak, Witch hazel |
| 14 | (130, 140) | Red maple |
| 15 | (140, 150) | Red maple, Chestnut oak, White oak, Downy juneberry |
| 16 | (150, 160) | Red maple, Downy juneberry, Witch hazel |
| 17 | (160, 170) | Red maple, Chestnut oak, Witch hazel |
| 18 | (170, 180) | Red maple, White oak, Witch hazel |
| 19 | (180, 190) | Red maple, White oak, Red/black oak |
| 20 | (190, 200) | Red maple, Red/ black oak, Witch hazel |
| 21 | (200, 210) | Red maple, Chestnut oak |
| 22 | (210, 220) | Red maple, Witch Hazel |
For random sampling process, an area of 2400 square meters was sampled, resulting in the collection of specimens from 11 different species, totaling 182 specimens.
| RANDOM | ||
| Quadrats | (x, y) | Species |
| 1 | (230, 110) | Witch Hazel, Red maple, Black cherry |
| 2 | (120, 20) | Red maple, American Basswood, White oak |
| 3 | (30, 170) | Red maple, Chestnut oak |
| 4 | (0, 70) | Red maple, White oak |
| 5 | (200, 180) | Red maple, White oak |
| 6 | (10, 30) | Witch hazel, White oak |
| 7 | (120, 0) | Red maple, Red/black oak, Chestnut oak |
| 8 | (20, 220) | Red maple |
| 9 | (10, 150) | Red maple |
| 10 | (240, 10) | Red maple, White oak |
| 11 | (170, 230) | Red maple, Witch Hazel, Red/ black oak |
| 12 | (100, 50) | Red maple |
| 13 | (290, 90) | Red maple |
| 14 | (130, 230) | Red maple |
| 15 | (30, 150) | Red maple |
| 16 | (30, 0) | White ash, Red maple, Chestnut oak, Witch Hazel |
| 17 | (280, 0) | Red maple, White oak, Red/ black oak |
| 18 | (100, 40) | Witch Hazel, Black tupelo |
| 19 | (20, 50) | Red maple, Chestnut oak, Witch Hazel |
| 20 | (110, 150) | Red maple, Witch Hazel, Red/ black oak, Chestnut oak, Eastern hemlock |
| 21 | (90, 230) | Red maple, White oak |
| 22 | (260, 40) | Red maple, White oak |
| 23 | (230, 100) | Red maple, White oak, Chestnut oak |
| 24 | (150, 140) | Red maple, Chestnut oak, Red/ black tupelo |
For haphazard sampling process, an area of 2400 square meters was sampled, resulting in the collection of specimens from 11 different species, totalling 182 specimens.
| HAPHAZARD | ||
| Quadrats | (x, y) | Species |
| 1 | (7, 234) | Red maple, Witch Hazel, Chestnut oak, Red/black oak |
| 2 | (23, 200) | Red maple, Eastern Hemlock |
| 3 | (9, 227) | Red maple, Eastern Hemlock |
| 4 | (29, 237) | Red maple, Red/black oak, Witch Hazel |
| 5 | (32, 233) | Red maple, Witch Hazel |
| 6 | (246, 230) | Black tupelo, White pine, red maple, Witch Hazel |
| 7 | (289, 231) | Red maple, Chestnut oak, White oak |
| 8 | (253, 239) | Red maple, Eastern hemlock, Witch hazel |
| 9 | (278, 197) | Red maple, Downy June berry, Witch Hazel |
| 10 | (273, 229) | Red maple, Witch hazel |
| 11 | (7, 21) | Red maple, Chestnut oak, Red/black oak |
| 12 | (8, 31) | Red maple, Witch Hazel |
| 13 | (32, 17) | Red maple, Witch Hazel |
| 14 | (15, 37) | Red maple, Witch Hazel |
| 15 | (21, 33) | Red maple, Black cherry, Chestnut oak |
| 16 | (270,39) | Red maple, Witch hazel, White pine |
| 17 | (255,11) | Red maple, Witch hazel, White oak, Chestnut oak, Red/black oaks |
| 18 | (265, 21) | Red maple, Witch hazel, White oak |
| 19 | (289,6) | Red maple, Witch hazel |
| 20 | (272, 10) | Red maple, Chestnut oak, Red/black oak |
| 21 | (143, 125) | Red maple, Chestnut oak |
| 22 | (146, 125) | Red maple, White oak |
| 23 | (149, 137) | Red maple, Chestnut oak, White oak, Eastern Hemlock, Red/black oak |
| 24 | (134, 129) | Red maple, Chestnut oak, Downy Juneberry, Witch Hazel |
Upon comparing the densities of various species between actual and estimated values, it was observed that a majority of species exhibited higher actual densities than estimated densities. This includes:
- Red maple: actual 402.7 & estimated: 379.2
- Witch hazel: actual 142.4 & estimated 104.2
- Black tupelo: actual 35.5 & estimated 4.2
- White pine actual 12.8 & estimates 0.0
- Striped maple: actual 13.6 & estimates 0.0
- Hawthorn: actual 4.5 & estimated 0.0
- Sweet birch: actual 1.2 & estimated 0.0
- American basswood: actual 1.5 & estimated 0.0
- Yellow birch: actual 0.8 & estimated 0.0
- White ash: actual 0.8 & estimated 0.0
Out of all the species examined, only six displayed lower actual densities compared to their estimated densities.
- White oak: actual: 74.5; estimated: 75.0
- Chestnut oak: actual: 82.9 & estimated 133.3
- Red/ black oaks: 46.7 & estimated 50.0
- Eastern hemlock: actual 45.6 & estimated 66.7
- Down Juneberry: actual 9.9 & estimated 12.5
- Black cherry: actual 1.5 & estimated 8.3
The dominant species in terms of overall frequency was Red maple, accounting for 91.0% of the occurrences. It was followed by Witch hazel (36.0% frequency), White oak (35.0% frequency), Chestnut oak (28.0% frequency), and Red/black oaks (24.0% frequency). On the other hand, the rarest species, found at a frequency of only 1.0%, included Black cherry, Sweet birch, American basswood, Yellow birch, and White ash.
Sample Calculations for percentage error: only calculated the percentage error for Red maple (the most common species) and White ash (one of the least common species).
Systematic Sampling:
Most common species (highest frequency): Red maple
- Systematic Sampling: (403.7 – 379.2)/379.2*100 = 6.460%
- Random Sampling: (403.7 – 416.7)/416.7*100 = -3.120%
- Haphazard: (403.7 – 433.3)/433.3 *100 = -6.831%
Rarest species (lowest frequency): I chose White Ash
- Systematic Sampling: (0.8-0)/0.0*100= 0.0
- Random Sampling: (0.8-8.3)/8.3*100= -90%
- Haphazard: (0.8-8.3)/25.0*100=-30%
Based on my analysis, systematic sampling proves to be the most precise sampling strategy for common species. However, when dealing with the rarest species, the percentage error varied depending on the sampling technique employed. Notably, both random sampling and haphazard sampling yielded negative percentage errors. To further illustrate this, I specifically computed the percentage error for Yellow birch and found that it followed the same pattern, exhibiting a 0.0% percentage error in systematic sampling.
I believe that utilizing more than 24 sample points would have yielded superior results, given the greater number of values along the x-axis compared to the limited sample points used in the systematic sampling technique. Despite my haphazard sampling approach being evenly distributed between areas of high and low aggregation, it is essential to acknowledge the potential errors and limitations that may arise. One such consideration is the aspect of randomness. Even when striving for an equitable distribution of samples, there remains a possibility of unintended clustering or selection bias
I am always surprised at how close the sampling times are. I wouldn’t include all the graphs or all the data but summarize it as it is hard to sort through in the blog posts.