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Lab 5: Effects of disturbance on understory plant species in Pacific Spirit Park Updated: June 18, 2022 Background History of Pacific Spirit Park Pacific Spirit Regional Park has a long history. The park is located on the ancestral and unceded territory of the xʷməθkʷəy̓əm (Musqueam) nation, who occupied the land for thousands of years. In the late 19 th century, the area was claimed as British Columbia crown lands and xʷməθkʷəy̓əm members were relocated to a small area south of the park. After the area was logged in 1911, it was set aside as part of the University Endowment lands. Finally, in 1988, the park was officially created. Disturbances in Pacific Spirit Park As an urban park, Pacific Spirit Park is bordered by residential areas and roads. These areas can be subject to “edge effects”, in which conditions at and near the boundary of habitats differ from the interior. For example, light levels, pollution, trampling (from humans and dogs), and wind exposure are highest at edges. These are relatively stressful conditions that can affect the types of species we see (for example, invasive species are more likely to be present in edge habitat) and may even impact biodiversity overall. Edge effects are most pronounced in areas of high disturbance. Just west of Pacific Spirit Park in Wesbrook Village, several large condos have been or are currently being developed, which is expected to significantly increase disturbances like pollution and trampling at the forest edge. Though edge effects are typically strongest at the boundary with a highly disturbed area, trails can also create edge effects, albeit on a smaller scale and typically only affecting very sensitive species. Questions We’ll be addressing three main questions in Pacific Spirit Park. With increasing distance from the edge of the forest, how does… (1) biodiversity and overall plant cover change? (2) relative abundance of invasive species change? (3) percent cover of different species change? Methods Field work On June 15 and 17, Biology 230 students visited Douglas Fir trail in Pacific Spirit Park, an area adjacent to recent condo developments in Wesbrook Village (see map on next page). At 9 randomly identified points along the trail, transects were placed 15 metres west of Douglas fir trail and 13 metres east (Fig. 1). This created a gradient of distance from the edge of the forest, with 15m west (-15 m) being closest to the edge and 13 m east (+13 m) furthest from the edge. At every other metre along these transects, a 1 m 2 quadrat was placed, within which understory plants were identified and measured for percent cover. Students also noted any evidence of disturbance (natural or otherwise).

Figure 1. Map and sampling design of the Pacific Spirit Park understory plant survey (June 2022). Fifteen 1 x 1 m quadrats were placed at 2-metre intervals along nine west-facing transects 15 m off-trail (-15 m) and east-facing transects 13 m off-trail (+13 m) to create a gradient of distance from the forest edge. One transect is shown above. Data were analyzed in Excel. For each transect location (-15 m, -13 m, etc.), mean percent cover of each species was calculated (i.e., averaged across all 9 transects). These data were also summed to give a total estimate of plant cover per transect location. Next, proportional abundance of each species (relative to mean total abundance) was calculated for each transect location. These data were used to calculate a Shannon diversity index at each transect location. Finally, proportion of invasive species was calculated by summing the abundances of the invasive species, then dividing by total abundance of all plants for each transect location. Results At every transect, evidence of disturbance was observed. The most common type of disturbance was fallen logs and branches, but garbage, trampling, and dog feces were also frequently observed. Some groups noted stronger evidence of disturbances on the west side of the trail.

Shannon diversity was significantly positively related to transect location, such that increasing distance from the forest edge corresponded to increasing biodiversity (Fig. 2A). Summed plant cover also varied significantly with transect location, though this relationship was found to be quadratic, such that cover was highest when furthest from the trail in both directions (Fig. 2B). Of the two invasive species that were detected in our survey (English holly and wall lettuce), their summed proportion was unrelated to transect location (Fig. 3). A total of 18 species were observed during the survey, but only 9 species were sufficiently abundant to consider their variation in cover with transect location (Fig. 4). Of these, only one species (trailing blackberry) was significantly related to transect distance, such that its cover was highest when furthest from the trail in both directions (Fig. 4E). Though other patterns were not found to be significant, there were some interesting trends (Fig. 4A-D, F-I). Figure 2. Shannon diversity index (A) and summed plant cover (B) are significantly related to transect location. Points indicate means, averaged across 9 transects. R 2 describes variation explained by the best-fit model for the data, either linear (A) or quadratic (B). Transect locations represent increasing distance from the forest edge, such that -15 m is closest to the edge, +13 m is furthest away from the edge, and 0 m is the trail (see Fig. 1). Data were collected in Pacific Spirit Park on Douglas fir trail in June 2022. Figure 3. Proportion of invasive species (English holly and wall lettuce) showed no relation with transect location. Points indicate means, averaged across 9 transects. Transect locations represent increasing distance from the forest edge, such that -15 m is closest to the edge, +13 m is furthest away from the edge, and 0 m is the trail (see Fig. 1). Data were collected in Pacific Spirit Park on Douglas fir trail in June 2022. 2.0

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Figure 4. Percent (%) cover of nine species with transect location: spiny wood fern (A), sword fern (B), red huckleberry (C), salmonberry (D), trailing blackberry (E), English holly (F), salal (G), starflower (H), and wall lettuce (I). Species occurring in fewer than 10 transect locations not shown. The R 2 for trailing blackberry (E) describes variation explained by the best-fit quadratic model to the data. Invasive species (English holly and wall lettuce) are shown in orange. Points indicate means, averaged across 9 transects. Transect locations represent increasing distance from the forest edge, such that -15 m is closest to the edge, +13 m is furthest away from the edge, and 0 m is the trail (see Fig. 1). Data were collected in Pacific Spirit Park on Douglas fir trail in June 2022. Species silhouette images were drawn by Rachel Wilson, with the exception of English holly (sourced from Phylopic). Assignment [15 marks + 0.5 bonus marks] Using the background information, methodology, and results, answer the following questions. Your answers should take up no more than one page (single spaced, 10 pt font, 1 inch margins), but definitely don’t feel obligated to fill that space (longer isn’t always better!). 1. At the beginning of this lab, we outlined some research questions. Based solely on the background information and methodology (i.e., not the results), specifically outline your hypotheses for the following two questions. In other words, what would you have expected to find as we move further away from the forest edge? [4 marks] a. Biodiversity and overall plant cover b. Relative abundance of invasive species 2. Based on the written results and Figures 2-3, evaluate the evidence for each of your hypotheses in question 1. Were there any unexpected results, or did they tend to fit with your expectations? What might be driving the patterns you see? Explain with detail. [6 marks] 0 0 0

a. Biodiversity and overall plant cover b. Relative abundance of invasive species 3. Choose one of the plant species shown in Figure 4 and research its life history traits to determine whether it can be considered r-selected or K-selected (think of some of the traits we’ve discussed in class to get an idea of what to look for). [5 marks] You can use the “Ecological Indicator” information on UBC’s E-Flora website: http://ibis.geog.ubc.ca/biodiversity/eflora/E-FloraTreesofBritishColumbia.html Or try the Fire Effects Information System: https://www.feis-crs.org/feis/ a. Is your chosen species broadly r-selected or K-selected? Justify your answer based on two of its traits. b. Would you have expected the abundance of this species to be positively or negatively related to distance from the forest edge (transect location)? Do the results in Fig. 4 match your expectations? 4. Optional bonus question: choose one of the plant species in Figure 4 and briefly indicate one way in which it is important to local first nations (such as xʷməθkʷəy̓əm). Its importance can be medicinal, used in food, cultural, spiritual, etc. Please keep your response respectful and consult reliable sources (e.g., gardening blogs are not a reliable resource). [0.5 bonus marks]

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