An Agent-Based Modelling Framework for Whitebark Pine Restoration in the South Cascades, Washington

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2016-01-05
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Abstract
The iconic and endangered whitebark pine is in decline in the South Cascades, Washington, facing numerous threats most prominently white pine blister rust, but also mountain pine beetle, and increased competition from subalpine species and climate change, the combined effects of which are threatening its obligate mutualism with Clark’s nutcrackers, its primary seed disperser. The long-term conservation of whitebark pine is thus inextricably linked with the maintenance of this mutualism, a relationship which is dependent on the response of nutcrackers to changing landscape conditions and selection of alternative life- history strategies. An agent-based modeling (ABM) approach is uniquely poised to address the efficacy of alternative restoration strategies for whitebark pine, due to its ability to incorporate the individual adaptive behaviours of nutcrackers and their responses to future restoration landscapes in a bottom-up hierarchical habitat selection process, ultimately leading to their choice of a resident or emigrant life-history strategy. This thesis addresses the development of this framework for whitebark pine restoration through innovative research. Through simulations, I found that nutcrackers integrate short- and long-term energetic requirements while foraging and perform second-order habitat selection (emigration) through a bottom-up, hierarchical process. I also determined that proximate causes of nutcracker emigration include: landscape composition (total available energy at the home range scale, or cone production), population influences, and landscape configuration, with their level of influence ranked in that order. Synthesizing these findings, I established possible future energetic scenarios defined by declines in existing WBP and energetic gains from restoration initiatives and simulated the responses of nutcrackers. I found that by adopting a conservative restoration initiative that involves planting whitebark pine seedlings at a density of 440 seedlings/ha and 5% of existing WBP land cover (approximately 2,621 ha), that managers can chart a future that maximizes the probability of maintaining the mutualism and returning whitebark pine abundance levels to their current state, while accounting for uncertainties. My ABM is portable and future evaluation of restoration initiatives in this and other regions would benefit from utilization of my established framework.
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Citation
McLane, A. (2016). An Agent-Based Modelling Framework for Whitebark Pine Restoration in the South Cascades, Washington (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/24807