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Lynx and snowshoe hare response to spruce-beetle tree mortality: Evaluating habitat suitability and timber salvage in spruce-fir forests

October, 2015

Canada lynx on the Rio Grande National Forest, Colorado, 2015
Canada lynx on the Rio Grande National Forest, Colorado, 2015
By 2013, a spruce beetle outbreak impacted 85% of the mature spruce-fir forests on the Rio Grande National Forest.  In many cases, the forest canopy is 90-100% dead.  The Rio Grande National Forests was also the location that 85% of the Canada lynx reintroduced to the state by Colorado Parks and Wildlife from 1999 - 2007.  These spruce-fir forests provided some of the highest quality lynx habitat in the state.  Thus, the uncertainty of how lynx, and their primary prey snowshoe hares, will respond to insect-impacts to spruce-fir forests has important management and conservation implications.  Many key management assumptions for this species may or may not remain valid.  Hundreds of thousands of acres of lynx habitat in the Southern Rocky Mountains was likely reduced in quality as mortality to overstory spruce trees approached 100%.  However, the subalpine fir component and understory spruce in many of these forests survived the initial insect outbreak, and anecdotal observations indicate lynx and snowshoe hare are still present.  Biologists are in the very difficult position of being required to evaluate the consequence of management actions to lynx, such as timber salvage, without a scientific basis to support their decisions relative to recent changes to lynx habitat due to insect infestation.  The key question is how can the expected increase in proposed timber salvage be conducted in ways that also facilitate lynx conservation and species’ persistence on the Rio Grande National Forest.

In addition to the applied management questions, it is scientifically important to determine how increased disturbance processes as the result of climate change affect lynx conservation in the Southern Rocky Mountains.  The boreal forests that support lynx and snowshoe hares are structured by disturbance processes that include fire, insects, disease, wind, and human-actions.  Climate change is expected to greatly increase the amount of fire and insect infestation in the montane forests that support lynx.  However, scientific data are lacking that investigate how changes in forest structure and composition from spruce bark beetle impact resource-use patterns of lynx and snowshoe hares. 

To address this information need, the Rocky Mountain Research Station, in cooperation with the Rio Grande National Forest, Colorado Parks and Wildlife, and the Montana State University, initiated research to investigate how lynx and snowshoe hare respond to changes in forest composition and structure from spruce bark beetle outbreaks.  In 2015, lynx were trapped and instrumented with GPS collars to document their movements and resource-use.  These collars transmitted lynx-movement data to aircraft for future analysis.  In addition, state-of-the-art methods will be used to map the structure and composition of insect-impacted forests relative to lynx resource-use based on satellite remote sensing and field data.  In addition, forest attributes at lynx GPS locations within insect-impacted forests will be quantified to provide detailed understandings of resource-use characteristics.  The new knowledge provided from investigating lynx resource-use of insect-impacted forests combined with remotely-sensed and plot-level evaluations of habitat characteristics will allow managers to formulate prescriptions that guide timber salvage in ways that also facilitate lynx conservation. 

Key research objectives:  

  1. Determine if Canada lynx exhibit seasonal (winter vs. summer) changes in resource use of insect-impacted spruce-fir forests in the San Juan Mountains, Colorado;

  2. Determine how the structure, composition, and time-since-disturbance of insect-impacted spruce-fir forests affect relative patterns of snowshoe hare abundance in the San Juan Mountains, Colorado;

  3. Identify areas outside high-quality lynx habitat in insect-impacted spruce-fir forests that accommodate timber salvage with minimal impacts to Canada lynx.

Project Contact: 

Principal Investigators:
Jake Ivan - Colorado Parks and Wildilfe
Randy Ghormley - Rio Grande National Forest Service
Rick Lawrence - Montana State University

Scott Jackson - U.S. Forest Service - National Carnivore Program

Funding Contributors:
Rio Grande National Forest
U. S. Forest Service - National Carnivore Program