Forestry practices are thought to be the major cause of degraded salmonid habitat and declining steelhead populations in the Oktwanch River on Vancouver Island. Large woody debris installations and channel modifications were completed in Reach 1 of the Oktwanch River and adjacent side channels in 2001 to provide spawning and rearing habitat for multiple salmonid species and prevent further degradation, but were ultimately unsuccessful. This study investigated if watershed-scale restoration, rather than reach-scale, is necessary to restore this habitat for steelhead in the Oktwanch River indefinitely. This was achieved through an assessment of fish habitat in Reach 1 of the Oktwanch River and adjacent side channels and spatial analysis of the Oktwanch watershed using Landsat historical aerial imagery and i-Tree Canopy. The findings from this study suggest watershed-scale changes to forestry practices are required to restore steelhead populations in the Oktwanch River., forestry practices, watershed-scale restoration, reach-scale, woody debris installations, channel modifications
In agricultural landscapes, hedgerows provide critical habitat for songbirds. Himalayan Blackberry (Rubus armeniacus; HBB) is a widespread invasive species in the Pacific Northwest that has been linked to lower breeding songbird diversity. My study explored two possible explanatory mechanisms: educed structural complexity and lower arthropod abundance as a food source. I conducted avian point counts in 51 hedgerow segments at two locations in the Lower Mainland of British Columbia. In these segments, I quantified vegetation structure using a Foliage Height Diversity (FHD) metric derived from LiDAR data. I sampled arthropod abundance on the foliage of woody understory vegetation. I used multiple regression to identify best fit generalized linear models. Songbird diversity decreased with HBB % cover and increased with FHD. However, arthropod abundance was unrelated to bird metrics, and similar between HBB and other native shrubs. This suggests that hedgerows should be managed to control HBB and maximize vegetation structure., songbird diversity, agricultural landscapes, Himalayan Blackberry, hedgerows, arthropods, LiDAR
Old field is a unnatural habitat that usually occurs as a result of agricultural land abandonment and is the product of early-stage natural succession on a previously managed field. In an agricultural setting with monoculture crops, old fields provide more vegetative complexity through ground cover diversity and shrubs and hedgerows. In Delta, British Columbia, several old-field sites are managed for wildlife and provide nesting habitat for songbirds over the summer, as well as foraging habitat for overwintering raptors during fall and winter months. I surveyed two old-field sites near Boundary Bay, and two field sites at the Vancouver Landfill to compare the influence of old-field vegetation on different bird communities and improve understanding on species using the landfill. I conducted fixed-radius point counts for songbirds, and standing counts for raptors. Comparing replicate field types (n=2) I found that overall diversity of songbirds was higher in old field, and also associated with structural features like shrubs and trees, while abundances of Savannah Sparrows (Passerculus sandwichensis) decreased with proximity to shrubs and trees. My results support the conclusion that installing structural vegetation features at the landfill would maximize breeding songbird diversity. I also found the landfill to support higher diversity of wintering raptor species, but old field supported consistently higher abundances. This suggests that the landfill is currently functioning as lower quality wintering habitat, and that different management techniques should be considered.
Large woody debris removal has been ongoing in the Fraser River Delta since the late 1800’s. I investigated how offshore winds and the absence of large wood may have contributed to the recession of the Sturgeon Bank Marsh. I suggest large wood increases marshland resilience and promotes new marsh establishment by attenuating wave energy, decreasing sediment mobilization, deterring herbivory, and promoting the establishment of vegetated islands from which the marsh can expand. I analyzed historical wind data for patterns in offshore wind duration and installed several pieces of large wood onto the tidal flats of the Sturgeon Bank. I developed a technique for anchoring wood in the intertidal and give my recommendations for further development. Finally, I conclude the recession of the Sturgeon Bank Marsh was the result of multiple interacting stressors and coin the term keystone structural element to describe the function of large wood within a foreshore marsh., large woody debris, keystone structural element, marsh recession, ecological restoration, wave sheltering, coastal marsh
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Reed canarygrass (Phalaris arundinacea) is an invasive grass common in wetlands and riparian areas throughout the Pacific Northwest. It is highly adaptable and resistant to many control methods, but is vulnerable to shading. We sought to control reed canarygrass by establishing desirable native shrubs to overtop and shade it. Plots were rototilled, mulched, live-staked, and monitored for 2-6 growing seasons. We tested 1) effective planting densities by live-staking hardhack (Spiraea douglasii) at 50, 30, and 15 cm spacing, 2) relative species performance by planting hardhack, red-osier dogwood (Cornus sericea), and thimbleberry (Rubus parviflorus), all at 30 cm densities, and 3) alternative site preparation methods by using cardboard mulch or excavating the top 20 cm of topsoil. Higher planting density significantly reduced reed canarygrass cover and biomass. Both hardhack and red-osier dogwood successfully suppressed reed canarygrass, though thimbleberry did not. No significant differences between site preparation methods were observed., reed canarygrass, Phalaris arundinacea, invasive species management, live staking, planting density, Spiraea douglasii