Camas (Camassia leichtlinii (Baker) S. Watson, C. quamash (Pursh) Greene) functional trait responses to urban pressures in Greater Victoria

Date

2023-08-31

Authors

Rolleman, Erin

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Abstract

Coastal oak meadows are fragmented across an increasingly urbanized landscape in Greater Victoria with implications for great and common camas (qʷɫəɫ/KȽO,EL/Camassia leichtlinii and C. quamash) success. Both camas species are ecologically and culturally important across this region. Research into plant response to urbanization has largely examined how urban pressures shape plant community composition and structure, but how these pressures influence individual plant fitness remains unclear. To improve our understanding, Chapter Two of this thesis examined the response of common camas growth and reproduction to urban pressures in oak meadows across Greater Victoria. An urban-rural gradient was defined across the landscape and environmental conditions and camas growth and reproductive traits were measured. Urbanization was associated with increased trampling and soil compaction, and decreased soil depth, canopy cover, and soil phosphorus and reduced common camas growth and reproduction. Chapter Three examined the capacity of great camas (a slow-growing geophyte) to express phenotypic plasticity in response to three urban pressures (soil compaction, canopy cover, and grazing) within a single growing season in a greenhouse experiment and examined how these pressures affected resource allocation back into the bulbs. Great camas bulbs were divided into a cross-treatment design and growth and storage organ traits were measured. Great camas exhibited a limited capacity to respond to pressures within a single growing season with growth most strongly correlated to pre-season bulb mass. Bulb resources were not affected by urban pressures, but nearly all bulbs lost mass over the season. The shortened growing season and abnormally warm temperatures during the spring growth phase were highlighted as important drivers impacting great camas growth, reproduction, and development. These results can inform local and regional planning to support more successful urban camas populations into the future.

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Keywords

plant functional traits, urban ecology, intraspecific variation, phenotypic plasticity, urbanization, coastal oak meadows, camassia leichtlinii, camassia quamash

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