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From observations gathered from the Alfred Howe Greenway, Port Moody, BC, in Blog Post 1 and Blog Post 3, when walking along from the south end of the trail (elevation: 118 m) to the north end of the trail (elevation: 50m), there appeared to be a change in pine tree density.
A stratified random sampling strategy was used to measure pine tree density along three points of an elevation gradient using the nearest individual method to select each sampling unit. Along each elevation category (A. 120-110 m, B. 90-80 m, C. 60-50 m) five sampling units were selected by generating a random compass bearing and number of paces using an app. From the randomly generated location, the distance from the nearest pine tree to its neighbour was measured.
Although using the nearest individual method to select the sampling unit was more efficient than formulating a coordinate grid overlaying a map of the area in order to select a specific sample quadrant, a few difficulties were encountered in implementing and interpreting data collected using the nearest individual method, stratified random sampling strategy. When interpreting the results of this particular sampling strategy, the pine tree density of a particular elevation category is measured as the average distance from one pine tree to the next, which would (1) record the upper limit of the pine tree density for that particular area, as there would be a disregard for spaces where there is a significant lack of pine trees. This would particularly effect data in areas where it was observed that pine trees were found in “patches” rather than having a more uniform distribution. Furthermore, when implementing the sampling strategy, due to the steep elevation gradient, (2) difficulties were encountered to generate a random bearing that would generate a sampling location within the desired elevation category. If the same technique is used for a future data collection, perhaps the range for the number of paces should be decreased.
The data collected (although having a sample size of less than 10 measurements for each elevation category) represented a linear decrease in the average pine tree density along the elevation gradient. Although this result supports an initial hypothesis of pine tree density decreasing along the elevation gradient, the difficulties encountered (mentioned above) in interpreting the data brings the accuracy of the result to question (ex. perhaps there might be an exponential decline).
It would be favourable to continue to build future research of the Alfred Howe Greenway around pine tree data collection, as they seem to be found along the entire trail, in contrast to other plant species that only appear at one point of the trail or are seasonal. Perhaps a modified approach of a point-centered quarter method will be used for measuring pine tree species density in order to attain more accurate pine tree density measurements. By using the point-centered method, the distance of each pine tree (with the average interpreted as the pine tree density for a particular elevation category) would be recorded as a measurement of the nearest individual from each quarter to the centre point of the quadrant. As a result, recordings of solely the upper density limits will be avoided.
For the second portion of this blog post I commented on kmcara’s Blog Post 3: Ongoing Observations .
EDIT: From researching for archives about the Alfred Howe Greenway on the Port Moody, BC, Government website, it was found that the north point of the trail encompasses an area formerly used as a landfill site from the 1950’s to 1982, in addition to being used for green waste up until 2002. (City of Port Moody, 2018; Payne, 2015)
This offers a clear explanation for the significantly contrasting abundance of pine trees (and overall species diversity) between the north point (formerly a landfill) and south point (historically forested area) of the trail.
As a result of this newly found information I will perhaps shift my area of study to observe any current impact the former landfill has on the surrounding ecosystem.
