For the sample strategies, I used area based sampling techniques. The sampling time was actually very close to the same for all three strategies, with systematic being the fastest at 12 hours, 37 minutes, random being second at 12 hours, 39 minutes, and finally haphazard at 13 hours, 1 minute. The percentage error for the two most common species found systematic and random to be the most accurate. But looking just at eastern hemlock, the most common species, Random was the most accurate, then systematic, and finally haphazard. The percentage errors found in the two rare species varied more so, with systematic actually being the least accurate overall. However, looking at just the most rare species, white pine, Random was the least accurate, as there were no white pine found in those sample plots, systematic was next, and haphazard was the most accurate. The accuracy generally decreased as species abundance decreased, which is logical, as some sampling strategies found none of the rare trees, making their percentage of error 100%, which is more likely to happen the less frequent a species is. When the species abundance is higher, systematic and random sampling appear to be more accurate, while haphazard just happened to more accurate in rare species. The transect lines being used (systematic) for rare species is the least accurate as the area is large, and following a single bearing is unlikely to capture all that the area encompasses. However, if the area was stratified before sampling, a transect line would be as accurate. So, all the sampling strategies are likely close to the same accuracy, and if done properly, all strategies likely have very similar accuracy.
Category: Post 4: Sampling Strategies
Blog Post 4
Technique: Systematic Sampling of Area
Sampling Time: 12 hours 7 minutes
1 Most Common Species: Eastern Hemlock
Actual Density: 469.9
Data Density: 425.0
Percent Error: 9.5%
2 Most Common Species: Sweet Birch
Actual Density: 117.5
Data Density: 95.8
Percent Error: 18.4 %
1 Rarest Species: white pine
Actual Density: 8.4
Data Density: 0.0
Percent Error: 100 %
2 Rarest Species: Striped Maple
Actual Density: 17.5
Data Density: 37.5
Percent Error: 114 %
Technique: Random Sampling of Area
Sampling Time: 12 hours 13 minutes
1 Most Common Species: Eastern Hemlock
Actual Density: 469.9
Data Density: 369.6
Percent Error: 21%
2 Most Common Species: Sweet Birch
Actual Density: 117.5
Data Density: 82.6
Percent Error: 29%
1 Rarest Species: white pine
Actual Density: 8.4
Data Density: 13.0
Percent Error: 54.7
2 Rarest Species: Striped Maple
Actual Density: 17.5
Data Density: 0.0
Percent Error: 100%
Technique: Haphazard Sampling of Area
Sampling Time: 13hours 37 minutes
1 Most Common Species: Eastern Hemlock
Actual Density: 469.9
Data Density: 430.8
Percent Error: 8.3%
2 Most Common Species: Sweet Birch
Actual Density: 117.5
Data Density: 126.9
Percent Error: 8.0 %
1 Rarest Species: white pine
Actual Density: 8.4
Data Density: 0.0
Percent Error: 100%
2 Rarest Species: Striped Maple
Actual Density: 17.5
Data Density: 34.6
Percent Error: 97.7 %
Conclusion: Systematic sampling was the fastest technique at 12 hours and 7 minutes; however, Random sampling was close behind at 12 hours and 13 minutes. The accuracy was affected by species abidance the more rare species percent error was easily skewed by not finding any of the species such as white pine in a sampling regiment. With more samples the accuracy improved. All of the sampling techniques were similar in that the rare species had very high percent errors. Random sampling had slightly lower overall percent error.
Post 4: Sampling strategies
Haphazard or subjective sampling took the least time while sampling because sample selection didn’t took a lot of time because it was chosen randomly compared to other sampling techniques.
Two most common species were Eastern Hemlock, Sweet Birch and two rarest species were Striped Maple, White Pine. In Systematic sampling techniques percentage error for these four species; Eastern Hemlock, Sweet Birch, Striped Maple and White Pine each were: 1.6%, 5.6%, 100%, 100%. In Random Sampling technique, 20.2%, 11.3%, 18.8%, 50%. In haphazard or subjective sampling, 10.9%, 45.2%, 54.3%, 100%. Generally, the results turned out to be more accurate if the species were abundant. Only in abundant species systematic sampling was accurate than other sampling techniques. However in overall range, random sampling technique was overall most accurate compared to two sampling techniques.
Blog Post 4: Sampling Strategies
The three sampling strategies I used in the virtual forest were, Distance-systematic, Distance-random, and Distance-haphazard. The results from the three strategies were similar in that species percentages remained in order, and no strategy sampled any White Pine.
Of the three strategies I used, Distance-systematic had the fastest estimated sampling time at 4hrs 16min, followed by Distance-random at 4hrs 30min. The slowest estimated sampling time belonged to the Distance-haphazard strategy, at 4 hrs 49min.
Species:
Eastern Hemlock(EH), Yellow Birch(YB),Striped Maple(SM), White Pine(WP)
%Error/Strategy:
Systematic: EH:15.06%, YB: 97.33%, SM: 17.14%, WP: 100%
Random: EH: 0.17%, YB 1.56%, SM: 56.01%, WP: 100%
Haphazard: EH: 1.92%, YB: 35.45%, SM: 5.14%, WP: 100%
As can be seen, the accuracy varied between species abundance in the different sampling strategies. As per my virtual forest survey, it can be assumed that species does not affect accuracy. The only consistent % error was with White Pine, which was not sampled in any of the three strategies I used, and therefore had a % error of 100%.
The least accurate of the strategies was Distance-systematic, while the other two were fairly similar in their accuracy.
Blog Post 4: Sampling Strategies
Hello!
For the Virtual Forest tutorial, I used “Area” rather than “distance” and performed systematic, random, and haphazard sampling. The sampling technique with the fastest estimate sampling time was systematic at 12 hours, 5 minutes. following not too far behind was random sampling at 12 hours and 46 minutes and haphazard at 12 hours and 30 minutes. The percent error for the density of the 2 most common and the rarest species are as follows:
most common: Eastern Hemlock. Haphazard: 31.24% Systematic: 25.03% Random: 16.15%
Sweet Birch: Haphazard: 17.02% systematic: 53.87% random: 32.60%
rarest: White Pine. Haphazard: 1.20% systematic: 48.81% random: 50.00%
Striped Pine. Haphazard: 42.86% Systematic: 4.57% random: 76.00%
The accuracy did not seem to change with species abundance as there is no consistent trend between the standard errors for the common species and the rare species. as well, one sampling strategy does not appear to be more accurate than the others.
Post 4: Sampling Strategies
For the virtual sampling exercise, I sampled from the Snyder-Middleswarth Natural Area. I utilized random, systematic, and haphazard sampling strategies. Of these, the systematic was the most time efficient clocking in at 4hrs and 5 minutes, though the haphazard was a close second at 4 hrs 27 minutes compared to the random strategy which took 12 hours and 34 minutes.
Post 4. Sampling Strategies
Systematic sampling had the fastest estimated sampling time (12 hours, 37 minutes). Table 1 below summarizes the percent error and estimated total sampling time for each sampling method (systematic, random, haphazard), two most abundant (Eastern Hemlock and Sweet Birch) and two most rare (Striped Maple and White Pine) tree species.
Percent error was higher for the two most rare tree species (Table 1). Random and systematic sampling methods had similar accuracies, and both provided more accurate results than the haphazard sampling method (Table 1).
Table 1. Frequency of the two most rare and most abundant tree species in the field sampling tutorial.
| Sampling Method | Systematic | Random | Haphazard | ||||||
| Tree Species | Estimated Frequency (%) | True Frequency (%) | % Error | Estimated Frequency (%) | True Frequency (%) | % Error | Estimated Frequency (%) | True Frequency (%) | % Error |
| Eastern Hemlock (1) | 76 | 73 | 4 | 65 | 73 | 11 | 80 | 73 | 10 |
| Sweet Birch (1) | 48 | 43 | 12 | 46 | 43 | 7 | 44 | 43 | 2 |
| Striped Maple (2) | 0 | 6 | 100 | 12 | 6 | 100 | 20 | 6 | 233 |
| White Pine (2) | 4 | 4 | 0 | 4 | 4 | 0 | 8 | 4 | 100 |
| Total Time (hours.minutes) | 12.37 | 13.43 | 13.2 | ||||||
| 1 = Most common tree species | |||||||||
| 2 = Most rare tree species | |||||||||
| Note: % Error calculated as an absolute value | |||||||||
| % E = (Estimated-True/True)*100 | |||||||||
Blog Post #4 – Sampling Strategies
For sampling simulation of Snyder-Middleswarth Site using area-based sampling.
The fastest estimated sampling time was haphazard sampling at 12 hours and 27 minutes, 11 minutes faster than random and 9 minutes faster than systematic sampling.
Eastern Hemlock (common): haphazard – 2.9% ; random – 26.4% ; systematic – 12.3%
Red Maple (common): haphazard – 8.7% ; random – 12.1% ; systematic – 12.5%
Striped Maple (rare): haphazard – 65.7% ; random – 138.3% ; systematic – 8.6%
White Pine (rare); haphazard – 50.0% ; random – 100% ; systematic – 100%
Most accurate sampling strategy for common species (Eastern Hemlock and Red Maple) is haphazard sampling, and the most accurate for rare species (Striped Maple and White Pine) is also haphazard sampling. In this case, haphazard sampling was more accurate compared to random and systematic.
Accuracy, in general, was better with species that are more common, and worse with species that are more rare. The accuracy decreased for rare species as all percentage errors for each of the three sampling techniques increased.
24 sampling points is not a sufficient number of sampling points. With the abundance of each species varying greatly throughout the study area, only having 24 points doesn’t properly represent the number of species. There are a lot of missed species.
Blog Post 4: Sampling Strategies
The virtual forest tutorial utilized three sampling strategies;
(1) Haphazard Sampling,
– Uses samples that are most readily available, usually not random
(2) Systematic Sampling,
– Uses samples from a larger population, random starting point with fixed pattern
and (3) Random Sampling
– Chosen randomly, allows for equal opportunity
The most time efficient sampling from fastest to slowest are Haphazard Sampling, Systematic Sampling and then Random Sampling. Accuracy of the sampling was dependent on what was being examined. For example Systematic Sampling was most accurate when studying the two most common tree species. Whereas Haphazard worked best for the rarest species. Overall the Haphazard Sampling was most effective for this tutorial.
Blog Post 4: Sampling Strategies
For the Sampling Theory Using Virtual Forests tutorial, the Snyder-Middleswarth Natural Area was selected. I used area-based methods for Systematic Sampling, Random Sampling and Haphazard Sampling.
On review of the three methods, the estimated time for Systematic Sampling was 12 hours, 36 minutes. For Random Sampling, the estimated time was 13 hours, 40 minutes and for Haphazard Sampling the estimated time was 12 hours, 22 minutes. Haphazard sampling was estimated to be the most time efficient, followed by Systematic and Random.
For the Systematic Sampling, the percentage error for the two most common species were 17.4% and 38.7% respectively, with the percentage error for the two least common species at 100% and 60% respectively. For the Random Sampling, the percentage error for the two most common species were 20.3% and 16.7% respectively, with the percentage error for the two least common species at 100% and 78% respectively. For the Haphazard Sampling, the percentage error for the two most common species were 3.3% and 4.2% respectively, with the percentage error for the two least common species at 100% and 52.6% respectively. A percentage error of 100% indicated there were no trees of that species identified during the sampling.
The lowest percentage error was consistently the most common species, with the largest percentage error consistently the two least common species. Based on this, it could be assumed that the accuracy increases with an increase in abundance. It could also be assumed that the accuracy decreases with a decrease in abundance. On average, Haphazard Sampling had the lowest percentage error (40%), followed by Random Sampling (53%), then Systematic Sampling (54%).
Overall, the Haphazard Sampling was estimated to be the most time efficient and had the lowest percentage error.
