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Puri, Priya Neena Kaur

University of British Columbia

Arbutus menziesii (arbutus) is an ecologically and culturally important tree species that has been declining throughout the Pacific Northwest for over 50 years. Arbutus faces a complex decline and potentially cumulative set of interacting abiotic and biotic factors which appear to compromise growth. For example, climate change, urban and conifer encroachment, and fire suppression may predispose arbutus to stress incited by drought to exacerbate the incidence and severity of disease. In addition, at least 20 pathogens are known to infect arbutus, many of which take advantage of host stress, but disease resistance remains poorly understood under a changing climate. Past studies have yet to pinpoint a causal agent of arbutus decline; therefore, I sought to address this issue by evaluating arbutus as a host and identifying arbutus provenances potentially displaying high survival, health, and performance. Specifically, I tested the effect of provenance geographic origin and climate on the variation of arbutus phenotypes measured in two British Columbia provenance trials (Holt Creek and Texada Island) using linear and generalized linear mixed-effects models. My objectives were to (1) determine if there are locally-adapted and/or maladapted provenances, (2) determine the effect of provenance (latitude, longitude, elevation) and climate (MAT, MAP, MSP, TD, SHM, FFP) on survival, dieback, blight incidence, and height, and (3) identify candidate provenances displaying high relative survival and adaptive traits of health and performance for assisted gene flow throughout the natural range of arbutus. For both trials, latitude, elevation, MAT, MAP, MSP, and SHM consistently influenced survival, dieback, blight incidence, and height, implying that latitude, temperature, precipitation, and their interactions influence fitness in arbutus. Provenances from BC and CA were least well-adapted to the Holt Creek trial site. BC provenances performed better on Texada Island, but provenances from WA and OR generally outperformed those from BC. These results coincide with latitudinal shifts in climate and fitness for several species of temperate trees, and they emphasize the importance of climate- and disease resistance-based seed source selection for mitigating arbutus decline throughout the Pacific Northwest.

Text

2024-04-11

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/87763

Forestry

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/