Seed crops may be reduced by feeding insects, birds, and mammals. Some of these animals also serve as dispersal agents, and successful seedling establishment often results from neglected food caches. Fall-dispersed seed overwinters and germinates the next growing season when moisture and temperature conditions are optimal. Such a covering facilitates precipitation penetration and prevents excessive soil drying. In Arizona, germination coincides with the advent of July rains.
Early germination appears crucial for successful seedling establishment in the Southwest.
Seedlings that emerge in late summer develop shallow root systems and eventually succumb to fall drought, frost heaving, or winter kill. Successful establishment requires adequate soil moisture through two growing seasons. The growth rate of newly established seedlings is rather slow, but growth of advanced reproduction is generally moderate to rapid. During initial establishment partial shade benefits seedlings by conserving moisture. In contrast to the unreliable regeneration in the Southwest, interior ponderosa pine in the Black Hills is characterized by prompt and abundant regeneration.