Event Title

Natural regeneration of whitebark pine: Factors affecting seedling density across Idaho, Montana, and Wyoming

Presenter Information

Sara A. Goeking
Deborah K. Izlar

Location

USU Eccles Conference Center

Event Website

www.restoringthewest.org

Abstract

Whitebark pine (Pinus albicaulis) is an ecologically important species in high-altitude areas of the West due to the food source it provides for Clark’s nutcrackers, red squirrels, grizzly bears, and other animals. Whitebark pine stands have recently experienced high mortality due to wildfire, white pine blister rust, and a mountain pine beetle outbreak, leading several researchers and managers to question the species’ long-term viability. This study examined regeneration at over 1,000 Forest Inventory and Analysis (FIA) plots containing a whitebark pine component (i.e., any dead whitebark pine trees larger than 5 inches d.b.h. or live whitebark pines of any size) in the northern Rocky Mountains. Objectives were to characterize the population’s age and size structures, as well as identify factors that influence whitebark pine regeneration. Mean seedling density at FIA plots ranged from zero to over 3,000 seedlings per acre, with a mean density of about 300 seedlings per acre and a median density of about 110 seedlings per acre. At the landscape scale, whitebark pine’s age classes and size classes both show a steep reverse-j distribution. A two-stage modeling approach was used to relate site-specific and climate variables first to presence/absence of whitebark pine seedlings, and then to seedling density. Preliminary results suggest that regeneration is most strongly related to the density of understory vegetation, particularly the shrub Vaccinium scoparium, as well as seedling density of other tree species. Species composition of the overstory was more important than indicators of overstory density, including tree canopy cover and basal area. With respect to temperature and precipitation, the relative importance of mean versus variability metrics differed by season.

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Oct 16th, 12:30 PM Oct 16th, 12:35 PM

Natural regeneration of whitebark pine: Factors affecting seedling density across Idaho, Montana, and Wyoming

USU Eccles Conference Center

Whitebark pine (Pinus albicaulis) is an ecologically important species in high-altitude areas of the West due to the food source it provides for Clark’s nutcrackers, red squirrels, grizzly bears, and other animals. Whitebark pine stands have recently experienced high mortality due to wildfire, white pine blister rust, and a mountain pine beetle outbreak, leading several researchers and managers to question the species’ long-term viability. This study examined regeneration at over 1,000 Forest Inventory and Analysis (FIA) plots containing a whitebark pine component (i.e., any dead whitebark pine trees larger than 5 inches d.b.h. or live whitebark pines of any size) in the northern Rocky Mountains. Objectives were to characterize the population’s age and size structures, as well as identify factors that influence whitebark pine regeneration. Mean seedling density at FIA plots ranged from zero to over 3,000 seedlings per acre, with a mean density of about 300 seedlings per acre and a median density of about 110 seedlings per acre. At the landscape scale, whitebark pine’s age classes and size classes both show a steep reverse-j distribution. A two-stage modeling approach was used to relate site-specific and climate variables first to presence/absence of whitebark pine seedlings, and then to seedling density. Preliminary results suggest that regeneration is most strongly related to the density of understory vegetation, particularly the shrub Vaccinium scoparium, as well as seedling density of other tree species. Species composition of the overstory was more important than indicators of overstory density, including tree canopy cover and basal area. With respect to temperature and precipitation, the relative importance of mean versus variability metrics differed by season.

https://digitalcommons.usu.edu/rtw/2013/Poster/6