Assessing the Drivers of Mortality and Regeneration for a Threatened Conifer
Whitebark pine (Pinus albicaulis, WBP) is an important species in many high-elevation environments in western North America. It is recognized as both a keystone species and ecosystem engineer because it retains and re-distributes snow, promotes biodiversity and provides beneficial conditions for many plant and animal species. However, WBP has experienced substantial mortality in many regions and rates appear to be accelerating. In light of these declines, WBP has been categorized as endangered by IUCN and the Canada Government, and was recently listed as threatened in the U.S. under the Endangered Species Act.
The decline of WBP has been attributed to a complex mixture of interacting factors: infection by an exotic pathogen that causes white pine blister rust, outbreaks of the mountain pine beetle, altered wildfire regimes, decreased effectiveness of its obligate avian seed disperser (Clark’s nutcracker), and the increased heat and drought associated with anthropogenic climate change. In addition, studies are mixed as to whether WBP seedlings benefit from associating with shrubs and trees. State and federal agencies are eager to implement management activities that promote the health and regeneration of WBP. However, we currently lack sufficient knowledge about best management practices.
To address this situation, the Cushman lab is addressing the following questions: 1) What abiotic and biotic factors best predict adult mortality and seedling recruitment of WBP? 2) How does wildfire severity affect the recruitment and survival of WBP seedlings across landscapes of varying aridity? 3) Do shrubs and other trees act as competitors with or facilitators of seedlings of WBP across landscapes of varying aridity? and 4) Do current forest thinning practices promote or suppress seedling recruitment of WBP and does this vary across topographic/environmental gradients?
Whitebark pine (Pinus albicaulis, WBP) is an important species in many high-elevation environments in western North America. It is recognized as both a keystone species and ecosystem engineer because it retains and re-distributes snow, promotes biodiversity and provides beneficial conditions for many plant and animal species. However, WBP has experienced substantial mortality in many regions and rates appear to be accelerating. In light of these declines, WBP has been categorized as endangered by IUCN and the Canada Government, and was recently listed as threatened in the U.S. under the Endangered Species Act.
The decline of WBP has been attributed to a complex mixture of interacting factors: infection by an exotic pathogen that causes white pine blister rust, outbreaks of the mountain pine beetle, altered wildfire regimes, decreased effectiveness of its obligate avian seed disperser (Clark’s nutcracker), and the increased heat and drought associated with anthropogenic climate change. In addition, studies are mixed as to whether WBP seedlings benefit from associating with shrubs and trees. State and federal agencies are eager to implement management activities that promote the health and regeneration of WBP. However, we currently lack sufficient knowledge about best management practices.
To address this situation, the Cushman lab is addressing the following questions: 1) What abiotic and biotic factors best predict adult mortality and seedling recruitment of WBP? 2) How does wildfire severity affect the recruitment and survival of WBP seedlings across landscapes of varying aridity? 3) Do shrubs and other trees act as competitors with or facilitators of seedlings of WBP across landscapes of varying aridity? and 4) Do current forest thinning practices promote or suppress seedling recruitment of WBP and does this vary across topographic/environmental gradients?