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Temporal dynamics of a commensal network of cavity-nesting vertebrates: increased diversity during an insect outbreak
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Network analysis offers insight into the structure and function of ecological
communities, but little is known about how empirical networks change over time during
perturbations. ‘‘Nest webs’’ are commensal networks that link secondary cavity-nesting
vertebrates (e.g., bluebirds, ducks, and squirrels, which depend on tree cavities for nesting)
with the excavators (e.g., woodpeckers) that produce cavities. In central British Columbia,
Canada, Northern Flicker (Colaptes auratus) is considered a keystone excavator, providing
most cavities for secondary cavity-nesters. However, roles of species in the network, and
overall network architecture, are expected to vary with population fluctuations. Many
excavator species increased in abundance in association with a pulse of food (adult and larval
beetles) during an outbreak of mountain pine beetle (Dendroctonus ponderosae), which peaked
in 2003–2004. We studied nest-web dynamics from 1998 to 2011 to determine how network
architecture changed during this resource pulse.Cavity availability increased at the onset of the beetle outbreak and peaked in 2005. During and after the outbreak, secondary cavity-nesters increased their use of cavities made by five species of beetle-eating excavators, and decreased their use of flicker cavities. We found low link turnover, with 74% of links conserved from year to year. Nevertheless, the network
increased in evenness and diversity of interactions, and declined slightly in nestedness and
niche overlap. These patterns remained evident seven years after the beetle outbreak,
suggesting a legacy effect. In contrast to previous snapshot studies of nest webs, our dynamic approach reveals how the role of each cavity producer, and thus quantitative network architecture, can vary over
time. The increase in interaction diversity with the beetle outbreak adds to growing evidence
that insect outbreaks can increase components of biodiversity in forest ecosystems at various
temporal scales. The observed changes in (quantitative) network architecture contrast with the
relatively stable (qualitative) architecture of empirical mutualistic networks that have been
studied to date. However, they are consistent with recent theory on the importance of
population fluctuations in driving network architecture. Our results support the view that
models should allow for the possibility of rewiring (species switching partners) to avoid
overestimation of secondary extinction risk.
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The Benefits of Opening Forest Canopies
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Learn about the benefits of creating open canopy in oak forested areas -- for livestock, aesthetics, and wildlife -- with Dwayne Elmore from the Oklahoma State University Extension.
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The Planning for Growth and Open Space Conservation Webinar Series
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Planning for Climate Change Adaptation: Considerations for Forests, Wildlife, and Land Use
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The Planning for Growth and Open Space Conservation Webinar Series
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Session #26: Using Social Marketing and Micro Targeting to Engage and Move Woodland Owners to Stewardship.
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Tree mortality predicted from drought-induced vascular damage
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The projected responses of forest ecosystems to warming and drying associated with twenty-first-century climate change vary widely from resiliency to widespread tree mortality (1–3). Current vegetation models lack the ability to account for mortality of overstory trees during extreme drought owing to uncertainties in mechanisms and thresholds causing mortality (4,5). Here we assess the causes of tree mortality, using field measurements of branch hydraulic conductivity during ongoing mortality in Populus tremuloides in the southwestern United States and a detailed plant hydraulics model. We identify a lethal plant water stress threshold that corresponds with a loss of vascular transport capacity from air entry into the xylem. We then use this hydraulic-based threshold to simulate forest dieback during historical drought, and compare predictions against three independent mortality data sets. The hydraulic threshold predicted with 75% accuracy regional patterns of tree mortality as found in field plots and mortality maps derived from Landsat imagery. In a high-emissions scenario, climate models project that drought stress will exceed the observed mortality threshold in the southwestern United States by the 2050s. Our approach provides a powerful and tractable way of incorporating tree mortality into vegetation models to resolve uncertainty over the fate of forest ecosystems in a changing climate.
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U.S. Endowment for Forestry and Communities
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The Endowment is committed to keeping working forests as forests and advancing family-wage jobs in forest-rich rural communities. Through strategic and deliberate investment, the Endowment supports research and development in traditional forest product markets, ensuring that forests and forest-based economies grow and thrive.
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U.S. Fish and Wildlife Service Region 5 Endangered Species Act Update
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Featuring general news, incidental take permit, and classification information pertaining to the Endangered Species Act in Region 5.
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U.S. Fish and Wildlife Service and The Nature Conservancy Establish New National Agreement for More Controlled Burning
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The U.S. Fish and Wildlife Service (Service) and The Nature Conservancy announce a new partnership that will for the first time increase and better coordinate controlled burn activities, also known as prescribed fire, on their respective lands to enhance wildlife values. The agreement will encourage more efficient use of personnel and equipment while treating lands that might otherwise not get the benefit of controlled burning.
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US Forest Service Proposes New Management Practices for Stewardship of Water Resources
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The U.S. Forest Service today announced its intent to strengthen agency management direction for groundwater resources and the use of best management practices to improve and protect water quality on national forests and grasslands. This action is an integral component of watershed stewardship and land management.
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USDA Reports Synthesize Literature on Climate Change Effects and Adaptation Strategies for U.S. Agriculture and Forests
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The U.S. Department of Agriculture (USDA) released two comprehensive reports today that synthesize the scientific literature on climate change effects and adaptation strategies for U.S. agriculture and forests.
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