Comparing Sampling Strategies

In our recent virtual forest tutorial, we employed three different sampling strategies for studying biodiversity: Random Sampling, Systemic Sampling, and Haphazard Sampling. Each of these methods has its unique advantages and challenges, and their effectiveness can vary depending on the specific circumstances and objectives of the study.

Sampling Times

In terms of time efficiency, the Haphazard Sampling method proved to be the fastest, with an estimated total sampling time of 12 hours and 27 minutes. This was closely followed by the Systemic Sampling method, which took an estimated 12 hours and 36 minutes. The Random Sampling method was the most time-consuming, with an estimated total sampling time of 12 hours and 42 minutes.

Species Abundance and Accuracy

The true densities for the four species across the three sampling strategies are as follows:

Random Sampling

Red Maple: 412.0 stems/ha
Witch Hazel: 158.3 stems/ha
Sweet Birch: 8.3 stems/ha
American Basswood: 8.3 stems/ha

-Percent error calculations:
Red Maple: |(408.3 – 412.0) / 412.0| * 100 = 0.9%
Witch Hazel: |(142.4 – 158.3) / 158.3| * 100 = 10.1%
Sweet Birch: |(1.2 – 8.3) / 8.3| * 100 = 85.5%
American Basswood: |(1.2 – 8.3) / 8.3| * 100 = 85.5%

Systematic Sampling
Red Maple: 412.0 stems/ha
Witch Hazel: 88.0 stems/ha
Sweet Birch: 4.0 stems/ha
American Basswood: 4.0 stems/ha

-Percent error calculations:
Red Maple: |(403.7 – 412.0) / 412.0| * 100 = 2.0%
Witch Hazel: |(74.5 – 88.0) / 88.0| * 100 = 15.3%
Sweet Birch: |(0.4 – 4.0) / 4.0| * 100 = 90.0%
American Basswood: |(0.4 – 4.0) / 4.0| * 100 = 90.0%

Haphazard Sampling
Red Maple: 412.5 stems/ha
Witch Hazel: 158.3 stems/ha
Sweet Birch: 4.2 stems/ha
American Basswood: 4.2 stems/ha

-percent error calculations:
Red Maple: |(403.7 – 412.5) / 412.5| * 100 = 2.1%
Witch Hazel: |(35.5 – 158.3) / 158.3| * 100 = 77.6%
Sweet Birch: |(0.2 – 4.2) / 4.2| * 100 = 95.2%
American Basswood: |(0.2 – 4.2) / 4.2| * 100 = 95.2%

From these calculations, we can see that the accuracy of the sampling strategies does change with species abundance. The percentage error is much higher for the rarer species (Sweet Birch and American Basswood) compared to the more common species (Red Maple and Witch Hazel). This suggests that these sampling strategies may be less accurate when estimating the density of rarer species.

Comparing the three strategies, the random sampling method appears to be the most accurate for all four species, as it has the lowest percentage errors. The systematic sampling method is slightly less accurate for the Red Maple and Witch Hazel, and significantly less accurate for the Sweet Birch and American Basswood. The haphazard sampling method is the least accurate for all four species, with particularly high percentage errors for the rarer species.

Comparing Sampling Strategies

When comparing the three sampling strategies, it’s clear that each method has its strengths and weaknesses. The Random Sampling method, while the most time-consuming, provided a good balance between density, frequency, and dominance for both common and rare species. The Systemic Sampling method was slightly faster and showed similar results, but with slightly higher relative densities for the common species and slightly lower relative densities for the rare species. The Haphazard Sampling method was the fastest, but it also had the lowest relative densities for the rare species.

In terms of area versus distance-sampling methods, the area-based methods (Random and Systemic Sampling) were more time-consuming but provided more accurate results for both common and rare species. The distance-based method (Haphazard Sampling) was faster but less accurate, especially for the rare species.

Relative Efficiencies

The relative efficiencies of the three methods can be evaluated based on the time taken and the accuracy of the results. While the Haphazard Sampling method was the fastest, it had lower accuracy for the rare species. On the other hand, the Random and Systemic Sampling methods, while more time-consuming, provided more accurate results for both common and rare species. Therefore, if time is a critical factor, the Haphazard Sampling method may be the most efficient. However, if accuracy is more important, especially for rare species, the Random or Systemic Sampling methods would be more efficient.

In conclusion, the choice of sampling strategy in a biodiversity study depends on the specific objectives of the study and the constraints under which the study is conducted. While some methods may be faster, others may provide more accurate results. Therefore, it’s essential to carefully consider the advantages and disadvantages of each method before deciding on the most appropriate sampling strategy.