Herbivory and seedling establishment in post-fire southern California chaparral.

A caging experiment was conducted to determine the effects of herbivorous insects and small mammals on first-year establishment of Ceanothus greggii (ceanothus) and Adenostoma fasciculatum (chamise) seedlings in post-fire chaparral. Insect herbivory had no effect on either species. Observations of tagged seedlings revealed that nearly all herbivory was due to small mammals, and was preferentially greater for ceanothus. When seedlings were protected from herbivory chamise experienced higher mortality. Small-mammal herbivore pressure on ceanothus seedlings tipped the survivorship balance for unprotected seedlings in favor of chamise, allowing a relatively higher establishment of chamise seedlings during the first growing season after chaparral fire.