Monday, 17 November 2003
Pine regeneration following prescribed and wild fires: the role of seed dispersal by animals
After disturbances, dispersal of seeds by animals may enhance the probability of seedling establishment and survival. This study examined the effects of prescribed and wild fires on the interactions between Jeffrey pine (Pinus jeffreyi) and forest rodents such as chipmunks (Tamias spp.) and deer mice (Peromyscus maniculatus). On prescribed burn plots at Incline Village, Lake Tahoe, NV, small mammal populations declined significantly for only 1 yr after burns, with species composition remaining relatively constant as numbers increased to pre-burn levels over 3 yr. Similarly, the rate at which animals removed seeds on the forest floor decreased for only 1-5 mo after burns. Seed caching occurred on freshly burned plots but was difficult to detect due to drought. However, an artificial cache study found significant advantages for seeds planted both before and after fires at the depths and in the microsites (mineral soil under shrubs) often used by animals. Seeds placed on the forest floor (typical of wind dispersal) experienced high mortality both during and after burns. After burns, the seedlings that emerged from caches survived significantly longer on burned plots than on unburned controls. At the site of a nearby wildfire in Floriston, CA, rodent populations declined for 2.5 yr after the fire, and deer mice dominated the post-fire community. Foraging rates reflected population size. Emergence and survival of seedlings from artificial caches was significantly greater on the burn than in adjacent unburned forest. Our results suggest that seed-caching animals may play an important role in facilitating pine regeneration shortly after both prescribed and wild fires.