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Mast-seeding conifers such as Picea glauca exhibit synchronous production of large seed crops over wide areas, suggesting climate factors as possible triggers for episodic high seed production. Rapidly changing climatic conditions may thus alter the tempo and spatial pattern of masting of dominant species with potentially far-reaching ecological consequences. Understanding the future reproductive dynamics of ecosystems including boreal forests, which may be dominated by mast-seeding species, requires identifying the specific cues that drive variation in reproductive output across landscape gradients and among years. Here we used annual data collected at three sites spanning an elevation gradient in interior Alaska,...
Mast-seeding conifers such as Picea glauca exhibit synchronous production of large seed crops over wide areas, suggesting climate factors as possible triggers for episodic high seed production. Rapidly changing climatic conditions may thus alter the tempo and spatial pattern of masting of dominant species with potentially far-reaching ecological consequences. Understanding the future reproductive dynamics of ecosystems including boreal forests, which may be dominated by mast-seeding species, requires identifying the specific cues that drive variation in reproductive output across landscape gradients and among years. Here we used annual data collected at three sites spanning an elevation gradient in interior Alaska,...
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Obtaining useful estimates of wildlife abundance or density requires thoughtful attention to potential sources of bias and precision, and it is widely understood that addressing incomplete detection is critical to appropriate inference. When the underlying assumptions of sampling approaches are violated, both increased bias and reduced precision of the population estimator may result. Bear (Ursus spp.) populations can be difficult to sample and are often monitored using mark‐recapture distance sampling (MRDS) methods, although obtaining adequate sample sizes can be cost prohibitive. With the goal of improving inference, we examined the underlying methodological assumptions and estimator efficiency of three datasets...
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In 2009 and 2010, the National Park Service (NPS) Arctic and Central Alaska Networks tested aerial distance sampling and hierarchical modeling to estimate Dall's sheep (Ovis dalli dalli) abundance in Gates of the Arctic National Park and Preserve (GAAR). This report details the field methods and summarizes results for the 2010 survey. Further information regarding data analysis and interpretation for both surveys can be found in Schmidt et al. (2011). In 2010, we flew 318 20-km long contour transects generated on a 9-km grid across available sheep habitat in GAAR (26,921 km2 survey area). We detected 220 groups totaling 557 individuals on 86 transects. Data were analyzed using spatially-explicit Bayesian modeling,...
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Survey data for trumpeter swans were collected throughout Alaska since 1968, but due to design difficulties and past analytical limitations, previous analyses were limited to simple summary statistics. The main purpose of my work was to rigorously analyze these data using advanced methods and determine rates of population change, the effects of environmental change on habitat use, and the influences of habitat features on habitat occupancy. I estimated that the adult population grew at a rate of 5.9% (95% credible interval = 5.2% to 6.6%) and production of cygnets increased at 5.3% (95% credible interval = 2.2% to 8.0%) annually. I also found evidence that variation in occupancy was positively related to average...
    map background search result map search result map The effects of climate change on the population dynamics of trumpeter swans Climate sensitivity of reproduction in a mast-seeding boreal conifer across its distributional range from lowland to treeline forests Landscape-scale patterns in tree occupancy and abundance in subarctic Alaska Using distance sampling and hierarchical models to improve estimates of Dall's sheep abundance A diverse alpine species pool drives a 'reversed' plant species richness-elevation relationship in interior Alaska Environmental and Human Influences on Trumpeter Swan Habitat Occupancy in Alaska Dall’s sheep in Gates of the Arctic National Park and Preserve, Alaska: 2010 survey report Reducing Effort While Improving Inference: Estimating Dall’s Sheep Abundance and Composition in Small Areas Possible Secondary Population-Level Effects of Selective Harvest of Adult Male Muskoxen Accounting for incomplete detection: What are we estimating and how might it affect long-term passerine monitoring programs? Species richness of multiple functional groups peaks in alpine tundra in subarctic Alaska Effects of control on the dynamics of an adjacent protected wolf population in interior Alaska Improving inference for aerial surveys of bears: The importance of assumptions and the cost of unnecessary complexity Effects of control on the dynamics of an adjacent protected wolf population in interior Alaska Improving inference for aerial surveys of bears: The importance of assumptions and the cost of unnecessary complexity Landscape-scale patterns in tree occupancy and abundance in subarctic Alaska A diverse alpine species pool drives a 'reversed' plant species richness-elevation relationship in interior Alaska Accounting for incomplete detection: What are we estimating and how might it affect long-term passerine monitoring programs? Species richness of multiple functional groups peaks in alpine tundra in subarctic Alaska Using distance sampling and hierarchical models to improve estimates of Dall's sheep abundance Dall’s sheep in Gates of the Arctic National Park and Preserve, Alaska: 2010 survey report Climate sensitivity of reproduction in a mast-seeding boreal conifer across its distributional range from lowland to treeline forests Possible Secondary Population-Level Effects of Selective Harvest of Adult Male Muskoxen Environmental and Human Influences on Trumpeter Swan Habitat Occupancy in Alaska The effects of climate change on the population dynamics of trumpeter swans Reducing Effort While Improving Inference: Estimating Dall’s Sheep Abundance and Composition in Small Areas