Damaging Factors–Regeneration — Abstract of Paper


Arboreal Seed Removal and Insect Damage in Three California Oaks
Walter D. Koenig,¹ Johannes M. H. Knops,² William J. Carmen³


We investigated arboreal removal and insect damage to acorns in an undisturbed oak woodland in central coastal California. Arboreal seed removal was determined for four to eight individual Quercus lobata over a period of 14 years by comparing visual estimates of the acorn crop with the number of acorns caught in seed traps. Insect damage was assessed by sampling acorns from trees of all three species of oaks common in the study site (Quercus lobata, Q. douglasii, and Q. agrifolia). Patterns were generally similar for both sets of data: more acorns, but a smaller proportion of the crop, were removed or damaged as the productivity of an individual tree increased. However, we found no evidence that trees outproducing local conspecifics attracted a disproportionate number of arboreal seed or insect predators. Acorn removal was not significantly correlated with population sizes of either California scrub-jays (Aphelocoma coerulescens) or acorn woodpeckers (Melanerpes formicivorus), two common arboreal seed removers that are also potentially important dispersal agents. These patterns are partially in accord with predator satiation, but not the attraction of seed dispersers, being an important factor potentially influencing the reproductive strategies of oaks in central coastal California.