Fire-related recruitment in stagnant Quercus douglasii populations

Age structure, stem analysis and fire-scar history from >500 blue oak individuals on 2 sites in central California revealed: 1) meager tree recruitment since the 1940s and few trees older than 150 yr; 2) increased fire frequency following Anglo-American settlement in 1848 until fire suppression efforts in the 1940s; 3) a positive association between tree ages and fire dates; and 4) superior vertical growth to 135 cm of postfire sprouts (trees with ground-level ages within 1 yr after fires) on the site with less livestock browsing pressure. The association between tree ages and fire dates may have resulted from temporal concentration of postfire seedling sprouts, and faster vertical growth of postfire sprouts compared with true seedlings. However, sampling from existing trees may dampen the difference in vertical growth rates between sprouts and true seedlings where there is heavy browsing, because only true seedlings that grew as fast as sprouts survived and were available for sampling. -from Authors