Blog 5 – Design Reflections

On February 5, 20223, I began data collection at Glenbrooke Ravine to study distribution of sword ferns (Polystichum munitum). Based on my initial observations of the park I predict sword ferns prefer to grow in shaded areas. My study will determine if sword ferns are more abundant on the south bank with the north facing aspect.

Given that a mature sword fern can have a radius of up to approximately 2 metres, I chose to use a round sample unit with a 2 metre diameter. To achieve this, I calculated the circumference and cut a piece of PVC piping to 6.28 metre in length and used a coupling to attach the two ends. For the sampling design I created a transect line through the valley and then collected 5 samples from each aspect. To ensure randomness I used a random number generator to select the transect location and sample location. I placed limits on the number generator to ensure the samples were spaced far enough apart that it would ensure independence.

Throughout this process I have struggled to choose a working hypothesis that I felt I could reasonably measure in the field due to the amount of anthropogenic disturbance, both past and ongoing, that influence the plant community (e.g. water way culverted, logging, dumping, adjacent residential development and neighborhoods, ornamental gardens, invasive species removal, and native vegetation planting). Understanding there are several abiotic and biotic factors that are influencing sword fern distribution in the park, I chose to consider only solar radiation. To eliminate confounding variables (e.g. slope angle, remediation activities, trail maintenance) I decided to limit the study area. I selected an area approximately of 100 metres in length in the north half of the park which does not appear to be impacted by current restoration efforts. As well, the slopes on either side of the ravine appeared similar and the ravine is most closely orientated east to west. Lastly, I chose to eliminate the valley bottom from the study area. This area of the park has been subject to the redirecting of the waterway and has a large gravel trail which is actively used and maintained and therefore would not provide valuable data to the objective of this study.

When I set out to conduct the sampling, I experienced three notable challenges. The first were the park users, I had several people stopping to ask what I was doing which took up more time than I would have liked. The second was access: to access the south slope I had to cross the small but muddy and slippery waterway; the slopes were steep, uneven, and on the north slope a large population of Himalayan blackberry further added to the pain and made it difficult to place my sample unit on the ground. Although I experienced some challenges in the field, I will continue with this same sample strategy as I don’t believe they negatively impacted the ability to collect accurate data.