Factors affecting emergence and first-year survival of seedlings of Carry oaks (Quercus garryana) in British Columbia, Canada

Regeneration is essential to sustain populations of Garry oaks (Quercus gar ryana). Processes that mediate oaf; regeneration can be influenced by where acorn-hoarding animals take acorns and how deep scorns are buried at hoard ing sites. We planted acorns to determine the rule of habitat type and buri al depth on emergence and first-year survival of Carry oak seedlings. In al l habitats that we examined, vertebrates removed >53% of acorns placed on t he ground surface. However, in approximately one half of the habitats, vert ebrates removed only between 7 and 48% of acorns buried in the ground cover or soil. Habitats with high predation varied in trims of vegetation struct ure, but included all those with sparse herb, dense shrub, and moderate to high tree cover. Predation on buried acorns was low in habitats with variou s structural characteristics, including those with dense herb sever and spa rse shrub and tree cover. The mortality rate of buried acorns that were not removed by predators was low (<17%) in all but one habitat. Perhaps becaus e of desiccation, the mortality rate of surface acorns was >40% in all but one habitat. Regardless of burial depth, once seedlings emerged, seedling s urvival was >65% in most habitats. Some habitats with high seedling emergen ce had relatively low seedling survival, and vice versa. In habitats on a s outh-facing slope, characterized by rocky outcrops and absence of conifers, many seedlings died from desiccation. other seedling mortality may have be en caused by shoot browsing, root browsing, or insect herbivory. Seedling s urvival was not related to percent cover of overstorey vegetation, indicati ng that first-year Garry oak seedlings were not protected by shade and can survive in habitats with low light. (C) 2000 Elsevier Science B.V. All righ ts reserved.