Biotic and microsite factors affecting whitebark pine establishment

Abstract

To enhance establishment of future whitebark pine (Pinus albicaulis) forests, information is needed on the physical and biological factors affecting whitebark seed germination and seedling establishment. This paper summarizes the first-year results of field examinations designed to evaluate predator and seedbed factors affecting whitebark pine establishment. Predator effects were estimated by recording seedling emergence under four levels of predator exclusion (free predator access, rodents excluded, birds excluded, and both rodents and birds excluded). Rodents ate or removed 100 percent of available surface-sown seeds. Emergence was higher on plots excluding rodents only and significantly higher on plots excluding rodents and birds. Seedling emergence did not differ significantly between mineral (although numerically higher) and litter seedbeds. The effects of three seedbed factors were also examined by comparing seedling emergence under three light levels (open, 25, and 50 percent shade cover), two seedbed conditions (mineral and litter), and two sowing depths (on surface and 0.8 to 1.6 inches beneath surface). Buried seeds had significantly higher emergence rates than did surface-sown seeds. Even though the first season was hot and dry, 78 percent of seedlings survived.