Factors associated with seed cone production in Pinus ponderosa were reviewed to identify broad patterns and potential effectiveness of restoration activities. Cone and seed production are quite variable, with differences between (1) years, (2) sites, and (3) individual trees. Between-year, population-wide crop failures suggest large-scale triggers for cone and seed production, perhaps high temperatures and dry weather. Stem diameter is the most important determinant for cone production at the tree level, with other factors such as genetic disposition, moisture, soil nutrients, and insect pests and disease playing a smaller role. Some extrinsic factors affect growth rate, indirectly affecting cone production. For example, less competition and lower stand densities result in P. ponderosa trees that increase in diameter more quickly, possibly because of more light, and produce seeds earlier. This literature suggests that restoration activities, especially thinning, will result in trees better able to produce larger seed crops. The effect of prescribed fire is less clear, with contradictory effects depending on site conditions, burn severity, and nutrient status of the site.
Krannitz, Pamela G. and Duralia, Thomas E.
"Cone and seed production in Pinus ponderosa: a review,"
Western North American Naturalist: Vol. 64
, Article 8.
Available at: http://scholarsarchive.byu.edu/wnan/vol64/iss2/8