Category: Percy Hebert

Blog Post 6: Data Collection

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I sampled 5 replicates during my initial round of field sampling.  I didn’t have much trouble implementing my sampling procedure.  I did lots of prep in the office before going out to site which made the field work efficient.  The only difficult thing was travel in between sites.  There was still snow on the ground so I used skis for most of the travel.  Some sites did not have enough snow for ski travel (the more south facing slopes) so I was taking off and putting on skis during sampling.  The partial snow cover added an additional slipping/falling hazard while sampling on some of the steeper sites.

While sampling I noticed that the different tree species seem to be growing in clusters.  For instance, if my sampling site is in predominately birch stand, that may not reflect the stand characteristics 200m away.  Additional sampling will help to get a more accurate measurement of the composition of the forest.  I plan on sampling another 5 replicates soon and the snow is gone now so sampling should be easier.

Blog Post #2: Sources of Scientific Information

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I examined The article, Population structure and habitat use of gelada baboon (Theropithecus gelada) in Wof-Washa Forest (Gosh-Meda Area), Central Ethiopia to determine which category of scientific information it fits into.  The article appears to be written by two experts in the field.  As one is employed by the Department of Biology at Debre Markos University and the other is employed at the Department of Zoological Sciences at the Addis Ababa University.  However, neither of their credentials are noted so it does not meet this criterion. The article makes use of in-text citations as well it has a bibliography. The article makes no mention of a referee reviewing the paper before the publication or of a peer review process. The article does have a results sections which are usually associated with an academic, peer-reviewed paper. Because this paper did not document the authors credentials, a referee, or the peer-review process I would classify this paper as non-academic material.

https://www.the-scientist.com/news-opinion/canine-virus–parasites-kill-24-endangered-lions-in-india-64974

Blog Post 5: Design Reflections

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Field Research Project

Posted on May 17, 2019 by caudia

Location: Courtenay Estuary/ K’Omosks Estuary

Date and time of site visit: April 21, 14:20

Collected by:  Cathy Audia

Before traveling to the estuary I check the tide schedule to avoid the problem of arriving and finding the study site submerged in water. Luckily this initial step, allowed me to collect the data with no other problems arising. While collecting the data, I was surprised to find the quadrants were not an accurate representation of the distribution of the subject. As the estuary is so vast I felt I needed to expand the number of quadrants recorded to allow for a larger service area to be represented.  This modification should allow for a more accurate representation of the subjects cover, resulting in more precise findings of the field study.

Blog Post 7: Theoretical Perspectives

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My hypothesis is that increasing distance from a site of forest disturbance, such as a pathway, is correlated with lower tree and shrub species diversity, lower tree and shrub density, larger tree size, a higher ratio of trees to shrubs, and a higher ratio of evergreen to deciduous tree species. This is based on noticing that more deciduous species at higher densities appeared to exist at the edge space of paths than further into the forest.

My research project is focused on examining the changes in species composition, richness across an environmental gradient as a function of distance from a path. There are likely many mechanisms at play here such as the impact of continual human disturbance (clearing of the path and adjacent areas) each time a tree comes down or growth becomes too thick along a path; the presence of additional space, light, and runoff adjacent to the path that likely encourages and discourages the establishment and growth of certain species; the path as a conduit for the dispersal of seeds via wind, humans, and other animals; of course, the cultural requirements of individual plants play a role; as does the known dynamics in Coastal Western Hemlock forests.

Key Words: Edge Environments, CWH Zone, Species Richness, Forest Dynamics, Disturbance Gradient

Blog Post 5: Design Reflections

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Here is a description of my sampling method:

A simple, random and distance based sampling technique was used, incorporating plots along a transect and transects along a path.

Each transect consists of three plots, one immediately adjacent to the pathway, another 10 m away from the path, and another 20 m away from the path. Each location for a transect was selected by entering the range of the number of metres of the trail length, from 0 to 3100 metres, for the trail along which data was to be collected. The first 5 numbers were selected, representing the number of metres from the beginning of the trail at which a transect would be located.

Each proceeding transect alternated from being on the left for the first to the right for the second, etc. The second plot was found by moving in the exact same direction, 10m away from the first plot centre, further into the forest. The third plot was found by moving in the exact same direction, 10m away from the second plot centre, further into the forest.

Upon finding the location along the trail, plot centre was found by moving into the forest 3m to the left (3m is the plot radius ) so that the plot is touching but not overlapping with the path edge. Each 3m plot encompasses 28.27 square meters and was selected based on silviculture survey practices. At each centre a stake was driven into the ground and a plot cord with a mark 3m away from the stake, marked the edge. If the mark touched the bark, a tree or shrub was included in the count.

The first plot represented the site with the most disturbance, the second plot represented the site with an intermediate level of disturbance, and the third plot represented a site with the least disturbance.

Here is my reflection on the sampling method:

I did not have much trouble with my sampling strategy. This was largely due to experience having conducted silviculture surveys over the past summer. I was nervous before and during the first number of plots as I had my fingers crossed that my predictions weren’t not true and I believe the data verified that. To find distance markers, indicating the placement of transects and distances between plots, I used my cell phone’s GPS technology and this probably introduced inaccuracies in distances as it is not as accurate as using an actual GPS with a low degree of error.

Some of the data collected did not seem to make sense. For instance, the number of large trees was often greater closer to the path. Though, my basic hypothesis is that they would be more plentiful further away from the path. When looking at the trees, the largest ones with a circumference of over 1m were most often found furthest away whereas trees considered ‘large’, more than 2m, may have been more plentiful but had a much smaller circumference. With this adjustment to sampling, adding another ‘class’ of tree size, I was able to reconcile the data on the ground and my hypothesis.

Post 4: Sampling Strategies

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I used the distance-based method for the Sampling Theory Using Virtual Forests Tutorial. Below is a table summarizing the comparison between the actual and estimated densities of the seven tree species in the Snyder-Middleswarth Natural Area as well as the percentage error using each (distance-based) sampling method. Also included in the table is the estimated sampling time for each method.

Based on the results above, the systematic method had the fastest estimated sampling time.

The two most common species are the eastern hemlock and red maple while the two rarest species are the striped maple and white pine. Between the three different strategies, percentage error is generally inversely related to species abundance. This is more prominently seen in the random sampling strategy.

When we only look at the most common and rarest tree species, the haphazard approach is the most accurate. However, when we consider all tree species, the systematic approach is the most accurate with a maximum percentage error of 57.7% versus the 100% error with the haphazard approach for the striped maple.

Overall, the systematic approach is best because of its relatively lower sampling time and for its relatively higher accuracy.

Blog Post 4: Sampling Methods

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In the virtual forest I chose to use Area Based sampling. No sampling method showed much efficiency over the other in terms of time spent.

The most accurate method overall was the random sampling method. For the most common species random sampling was the most accurate. For the least common species random sampling was somewhat accurate, although random sampling failed to return any samples of the least common tress, striped maple. Accuracy was better for the common species of trees due to lower percentage errors.

I would want to sample more areas in a random fashion to lower % error rates.

Tree Species Actual Density Area Systematic % error Area Random % error Area Haphazard % error
Most Common Eastern Hemlock 469.9 320.0 31.9 341.7 27.3 550.0 17.0
2nd Most Common Red Maple 118.9 84 29.4 137.5 15.6 162.5 36.7
2nd Least Common Chestnut Oak 87.5 36.0 58.9 58.3 33.4 41.7 52.3
Least Common Striped Maple 17.5 52.0 197 0 N/A 29.2 66.9
Time to Sample 12h37m 12h47m 12h31m

Blog Post 3: Ongoing Field Observations

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I have selected to study the pattern of trees adjacent to and away from pathways in Stanley Park. Three locations along the environmental gradient include survey plots with a diameter of 3m located adjacent to a pathway, 10m away from the pathway, and 20m away from the pathway.

I observed a more diverse mix of trees immediately adjacent to paths as well as an abundance and rich diversity of herbaceous plants including shrubs, ferns and grasses. Ten meters away from the pathway I observed less deciduous tree species and reduced incidence of shrubs and other understory plants. At 20m away I observed mostly mature evergreen species with a limited understory.

My hypothesis is that increasing distance from a site of forest disturbance, such as a pathway, is correlated with lower tree species diversity, lower tree density, and larger tree size. Based on this hypothesis I would expect to see larger cedar and hemlock trees further from a pathway due to the lack of disturbance. The disturbance of a pathway would allow for new species of plants to establish due to the availability of sun, runoff from pathways, and additional space. Further, the clearing of the edges of pathways would allow for continual colonization of new plants.

The response variable is the number (continuous), type (categorical) and size (categorical due to slotting trees into size brackets) of trees in a plot. The predictor variable is distance from a pathway (categorical due to 3 distance measurements being used).

10m From Trail
Adjacent to Trail
Notes1
Notes2
Notes3
20m From Trail

Post 2: Sources of Scientific Information

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McPherson, Miller, Smith-Lovin, Lynn, and Cook, James M. 2001. Birds of a Feather: Homophily in Social Networks. Annual Review of Sociology 27: 415-444. http://www.leonidzhukov.net/hse/2017/networkscience/papers/McPherson_HomophilyInSocialNetworks.pdf.

The article is an academic, peer-reviewed review because the authors are subject matter experts, academics associated with several universities; the piece is printed in a peer reviewed journal based on information provided on the process for publication for authors in the Annual Review of Sociology’s website (https://www.annualreviews.org/page/authors/author-instructions/submitting/publication-timeline); and, it is a review as opposed to research because there is no methods or results section, the content of the piece does not seek to answer a research question.