Seminar: Postdoctoral Speakers

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August 31, 2020 11:30 am - 12:20 pm
Speaker: Dr. Kyle Doherty, MPG Ranch Postdoctoral Researcher, NAU School of Forestry Adjunct

Title: Coarse-filter bee conservation strategies benefit from fine-grained topography data

Abstract
Climate change complicates the task of prioritizing sites for conservation, because conditions that currently support biodiversity may not in the future. One strategy to circumvent this problem is to prioritize sites that are diverse in climate-resilient abiotic conditions, such as geology and topography. Geodiverse areas contain more niche space, are more likely to maintain processes that promote biodiversity in the future, and thus are useful coarse-filter surrogates for site prioritization. Comparatively few studies have scrutinized the relevance of topography to invertebrate pollinators, and the importance of data below 30 m grain-sizes is largely unknown, though could be useful for identifying microrefugia and corridor designation. We surveyed grass, shrub, and woodland sites for bees and plants in the Sapphire Mountains of western Montana, USA to explore if coarse-filter strategies are effective for these groups. We gathered fine-grained elevational data for the region with structure-from-motion photogrammetry, and derived metrics of topodiversity with these data to study the importance of grain-size (0.25 to 250 m) and neighborhood (1 to 500 m) of topodiversity calculation. We found that bee rarity-weighted richness (RWR) was most strongly correlated with 2 m grain topodiversity data, while plant RWR was most strongly correlated with 235 m data. We explored the potential for hierarchical models spanning grain-sizes and neighborhoods, but found that simple linear models of topodiversity performed best at ranking sites by RWR in both groups. The best model for plants performed relatively poorly for the task of bee site prioritization. Modeling RWR with pooled biodiversity data aggregated from both groups slightly improved site rankings for bees and slightly decreased ranking performance in plants. While the costs of fine-grained elevational remote sensing technologies may be high at present, national efforts to gather these data are on the horizon, and may facilitate conservation of bees and other groups at the local scale.


Speaker: Dr. Adrianna Foster, NAU SICCS Postdoctoral Researcher

Title: Simulation of boreal treeline migration in a warming world

Abstract

The North American boreal region is warming at an accelerated rate compared to the rest of the globe, which will impact vegetation, soils, and the disturbance regime. Recent studies using modeling, remote sensing, and field data predict boreal range shifts, with contractions predicted in the southern margins as a result of drought and insect infestation, and expansions predicted in the northern margins as temperatures warm. While the climate suitability ‘envelope’ for boreal tree species may be expanding northward with climate change, it is still unclear how fast migration may actually occur given constraints on seed rain, regeneration, and growth to reproductive age and size. We use an individual-based forest model (UVAFME) to simulate forest response to changing climate at the northern treeline in interior Alaska and to assess the potential for a northward treeline shift. UVAFME has been previously used in interior Alaska and comparisons with inventory data and other abiotic characteristics show good agreement with observations.  UVAFME is updated for this study to simulate seed rain from a source grid cell to adjacent grid cells, dependent on the density of and distance to reproductively active trees. Model results predict a northward shift in the treeline, though the speed of this shift is sensitive to local-scale conditions as well as the parameters used for seed dispersal. These results have implications for changing biogeophysiology at the broader tundra-taiga ecotone, as increasing forest cover would alter energy and water fluxes, soil conditions, as well as the fire regime.

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