Category: Percy Hebert

Post Seven: Theoretical Perspectives, Cates Park

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There are many ecological processes that relate to my research at Cates Park on the successful growth of Tsuga heterophylla on nurse logs.

  • Anthropogenic microdisturbances caused by timber harvesting is followed by gap phase microsuccessions occurring throughout the park where large, old growth trees have been logged.
  • These microsuccessions likely have founder-controlled communities, as the species that grow on nurse logs have similar environmental tolerances, as I have observed ample species richness.
  • Facilitation is an ecological process that benefits Tsuga heterophylla, as the substrate of the abiotic nurse habitats benefits this conifer’s success.
  • Because I am collecting information on canopy cover, I might be able to analyze asymmetric competition, to determine if larger species that cast more shade exclude smaller flora.

Keywords that summarize this research in Cates Park are

  • microdisturbance and microsuccession
  • nurse log
  • Temperate Rainforest

 

Blog Post 9: Field Research Reflections

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This project, and the course in general, gave me a greater appreciation for ecology as a discipline of science.  I didn’t really have a good idea of what it was about before I started this course.  Once I got into the project I didn’t have any trouble implementing the design and didn’t find any reason to change it too much.  The focus of the project changed slightly due to my observations once out in the field.  The overall theme remained the same but I did narrow my focus.  I would have liked to collect more data: sample more sites, in more locations, to get a better representation of the true forest ecology in my data.  This, I think, is the struggle in science.  Juggling time and cost with efficient and accurate data collection.

I found the project very interesting once I had all my data and began analyzing it in the office.  This is an aspect of ecology that I really like.  I’m a numbers guy so I really like the statistical analyses of the data, looking for patterns and correlations.  To me this is really interesting; quantifying and testing patterns we observe in the field.

Blog Post 3: Ongoing Field Observations

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  1. The organism that I plan to study is the white spruce (Picea glauca).
  2. The gradient that I will be analysing is the amount of space between trees from very crowded to 3m apart. This distance is an average of the distance between tree trunks at ground level. The most crowded location (location 1, annotated in red, Figure 1) is the forest stand at the north end of my study site; the mid-level spacing (location 2) is a cluster of trees near the house (annotated in blue, Figure 1); the location with the furthest distance between trees (location 3) is at the north west corner of the study site (annotated in black, Figure 1). Figure 1.

These trees were all planted by my family about 10 years ago. I am planning to study and compare various patterns within the white spruces. These patterns consist of tree height, new growth/bud abundance, and DBH (diameter at breast height). I plan to use tree height and DBH to calculate biomass, which can be used to determine productivity through a regression model based on the relationship between DBH (cm) and biomass (kg). There are many opportunities for comparison.

3. The most obvious underlying process that may cause observed patterns is the amount of direct sunlight received by an individual. Another might be any limiting of a resource due to a higher density of individuals in the area. It is hypothesized that overcrowding of white spruce (Picea glauca) decreases overall productivity and ability for seasonal growth (budding). If trees have more space between each other, they will be more productive due to more available sunlight and resources. Trees that are subject to crowding will be less productive than those that have ample space to themselves. For example, I predict that location 1, the most crowded, will have higher competition for soil resources, which may restrict growth. In contrast, trees in location 3 may have more room to spread their roots and absorb sufficient resources.

4. One potential response variable is whether the white spruce (sample unit) is crowded or spaced. A potential response variable is the abundance of new buds or tree height. These variables will both be continuous, as they will both be measured on a numeric scale (centimetres or metres for distance between trees and height; number of buds).

Blog Post 8: Tables and Graphs

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I used regression analysis to quantify the correlation between birch distribution over varying aspects across a hillslope.  On the graph I included a logarithmic trendline and the coefficient of determination (R squared) value.  A R^2 value of 0.4198 does not indicate a strong correlation between aspect and birch distribution.

I didn’t have any trouble organizing my data and felt like this was a straightforward exercise.  When I first started this project I expected to see a stronger correlation between aspect and birch distribution but now I think there are other factors that are more influential than aspect alone.  I still think that soil moisture is a very dominant factor and is correlated with aspect, however; drainages, depressional terrain, or other areas where water accumulates will likely create suitable habitat for birch trees regardless of aspect.

That being said, this is a small sample size over a small area.  More samples over a greater area may yield a stronger correlation between aspect and the distribution of birch.

Post 2: Sources of Scientific Information

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The source of ecological information that I have selected is a paper entitled “Effect of local stand structure on leaf area, growth, and growth efficiency following thinning of white spruce.”

(Link:https://www-sciencedirect-com.subzero.lib.uoguelph.ca/search/advanced?docId=10.1016/j.foreco.2016.03.005). It was written by experts in the field. It also includes in-text citations (Tree growth is a function of the amount of foliage, the rate of photosynthesis per unit of foliage, allocation of photosynthate to components and conversion rates to new structural matter (Brix, 1983)) and a bibliography, making it academic material. It is not clear whether the article was reviewed before publication: “Acknowledgements: This research was funded by J.D. Irving, Limited and by a Natural Sciences and Engineering Research Council of Canada Collaborative Research and Development grant to a team led by D.A. MacLean. Kwadwo Omari was funded by a NSERC Industrial Post-graduate Scholarship. We thank the staff at J.D. Irving, Limited for their input and assistance with the project.” I would classify this source as non-peer-reviewed academic material.

Post 1: Observations

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The location that I have chosen to conduct my research in my family property in Metcalfe, Ontario, which is 2.1 hectares and contains several different types of vegetation and conditions. Within the property, there are two still water ponds (originally dug for drainage) (Figures 1 and 2), a small forest stand (plus several more spaced apart) of white spruce (Picea glauca) (Figures 3 and 4). There is also areas of swamp containing various species of coniferous trees and woody plants (Figure 5) in addition to the kept gardens and grass. I first went out to observe on May 27th around 9:00, it was overcast and around 12 degrees Celsius. When I took the following pictures, it was 15:30, sunny and 18 degrees Celsius.

 Figures 1 and 2

Figures 3 and 4

Figure 5

From my initial observations, I noticed some differences between the two ponds. One is in the front yard with some ducks and rabbits, enclosed in a fence (Figure 1). It had lots of tadpoles swimming around but interestingly there were no adult frogs (multiple undetermined species) to be seen. In contrast, the second pond (Figure 2), which is in the backyard and is completely open to the surrounding agricultural fields (Figure 6), had fewer visible tadpoles but at least 10 frogs were counted. What causes this difference in species richness between two similar sized ponds only approximately 200 metres apart?

Figure 6

I also noticed many robins (Erithacus rubecula) all throughout the property. I am considering observing how long they spend feeding on the ground in various areas with different surroundings. What influences that behaviour? I would analyse the surroundings to try and explain any differences in time spent feeding.

Finally, in the stand of white spruces, the trees are very close together, to the point where it is hard to walk between them (Figure 7). There are also some nearby that have been planted further apart. I noticed bright green buds on the tips of the branches. On the crowded trees, only the outer branches had these buds while the spaced trees had them all around them. Is access to direct sunlight the only factor that causes this variation within species or is there something less obvious?

 Figure 7

I have included a rough sketch map of the study site in Figure 8. Each of these potential study subjects are very interesting to me, so I need to evaluate which one I would realistically be able to study for my final project.

Figure 8

Post 8: Tables and Graphs

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I used an ANOVA analysis using excel to plot plot distance from a path (categorical variable) to mean ratio of trees to shrubs (continuous variable), inclusive of standard deviation, and found statistical significance. I was significantly stressed about doing this because I haven’t yet taken a stats class but I found some resources (thank you Percy) and learned quite a bit about statistics that will help me in the classI have to come.

With my hypothesis I am testing for a number of variables and decided to present this relationship because it is statistically significant. However, most of the tests did not disprove the null-hypothessis. I was wondering what I did see during initial observation. I still think there may be a relationship. Many of my p-values were low but not near the 5% threshold, lending themselves to show more of a relationship than not. I am doubtful of the 5% p-value rule and have read academics challenging the 5% threshold. I have much more to learn.

 

Post 5: Design Reflections

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For the initial collection of data I used what I initially thought was a systematic sampling technique because I walked a certain number of paces to get to certain areas of each corner of the field. However, I realised that I was not actually using a systematic sampling technique because the sample taken in the middle of the field was not able to be measured by a certain number of paces equally from each “edge” of the field. This was due to the field not being uniform. Hence, I determined that I used a simple random sampling technique for the initial collection of data. This was not so much a difficulty but more of a misunderstanding on my part for sampling.

My initial hypothesis stated that there would be more dandelions towards the northern and eastern perimeters of the field because I had typically observed less prolonged human activity in those areas in the field whereas the southern and western parts of the field had benches, a playground, and a street hockey area. The data from the replicate in the southwest corner of the field surprised me because it had the greatest number of dandelions in the quadrat I set. However, I did not initially consider whether I would count flattened (versus upright) dandelions in my counts.

I still intend to use the random sampling technique for future data collection although I may consider adding more replicates to get a better idea of the abundance of dandelions in different parts of the field. One thing I may have to consider is that the park is maintained every so often and the dandelions may be mowed down during subsequent samplings.

Post 6: Data Collection: Cates Park

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The first collection of viable field data was collected on Sunday May 19 at Cates Park in North Vancouver. Separating the park between east and west, north (inland) and south (next to shore), I have four areas to collect data to ensure independence and to account for variables (see Image 1). I sampled 20 replicates of 80 that I plan to sample, and noted the presence of absence of common species. Ten replicates were west and close to shore, ten were west and inland. These were nurse logs, and I will repeat this in the two eastern sections of the park as my data collection continues, and with forest plots of the same size as the circumference of the nurse logs in all four defined regions.

I have revised my experimental design and sampling strategies from previously posted attempts, as initial data collected was solely distance-based counts of conifers from the centre of nurse logs, and this seemed an inadequate representation of the species that grow within nurse logs. The difficulties I now face include sampling randomly selected forest plots, as they may contain dense growth and be more inaccessible.

Patterns observed include differences in mosses, lichens and berry species between the regions close to shore and further inland. However, Western Hemlock, or Tsuga heterophylla, has been the most frequent conifer studied within nurse log units, regardless of the distance from shore. These patterns continue to support my hypothesis, however studying forest plots that are not nurse logs will aid in determining how common Tsuga heterophylla are versus other conifers in the region, and will aid to prove or falsify my hypothesis.

Blog Post 7: Theoretical Perspectives

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My hypothesis (paper birch (Betula papyrifera) distribution changes with aspect across a hillslope) touches on habitat preference of Betula papyrifera.  If my data shows that aspect is correlated to the presence of birch, I can then try and infer the environmental conditions that cause this distribution pattern.  One such factor may be soil moisture.  While I’m not able to directly measure soil moisture content, I can infer soil moisture conditions by using proxies such as changes in undergrowth composition.

My study may also relate to successional community development.  The distribution may not be correlated with aspect but may be a more random patchy distribution of tree species that colonized the area during an initial seral stage after a disturbance.  These patterns should become more apparent once I collect additional data.

 

Keywords:  Distribution gradient, community structure, Betula papyrifera