Annual cone and seed development for the four PJ species is highly variable both temporally and spatially and requires at least two growing seasons to produce mature seed. Pinyon pines have short-lived seeds, and junipers produce relatively long-lived seeds, which affects the longevity and abundance of seed in the seedbank. For singleleaf pinyon (Pinus monosperma), a typical mean seed crop during a year of heavy cone production ranges from 2,000 to 8,000 filled seeds per tree, but values for individual trees vary tremendously. Pinyon and juniper seeds are well adapted for dispersal by both birds and small mammals, with distances commonly ranging from several feet to several miles. Competition from forbs and grasses can reduce seedling emergence, but once established, competition from forbs and grasses has little effect on survival.
For more detailed information and citations refer to: Miller, R.F. and others. 2019. The Ecology, History, Ecohydrology, and Management of Pinyon and Juniper Woodlands in the Great Basin and Northern Colorado Plateau of the Western U.S. US Forest Service, Rocky Mountain Research Station. RMRS-GTR-403. 284 pg.