Prescribed fire promotes acorn survival and seedling emergence from simulated caches

Abstract

Prescribed fire increasingly is used to promote oak (Quercus) establishment in many hardwood forests across North America. However, how prescribed fire affects several key components of the oak regeneration process, including acorn survival and germination, is relatively unknown. Acorn mortality during a prescribed fire is likely affected by acorn dormancy, burn season, and previous burial (caching) by scatterhoarding rodents. We assessed the effect of fall and spring prescribed fires on seedling emergence for artificially cached and un-cached northern red oak (Q. rubra) and white oak (Q. alba) acorns in situ in granivore-proof exclosures through eight prescribed fires over two years at two sites in central Indiana. The odds of cached acorn emergence were 3.4–12.1 times higher following fall and spring prescribed fires than the unburned control. Red oak emergence was 1.7 times higher following fall burns than spring burns, whereas white oak emergence was unaffected by burn season. Lower winter temperatures following fall burns may have driven observed differences between burn seasons for northern red oak acorns. Our study links the oak-rodent conditional mutualism hypothesis with the oak-fire hypothesis, by suggesting that prescribed fire may produce environmental conditions that shift interactions between oaks and scatterhoarding rodents toward a more mutualistic relationship.