Timing of Peak Acorn Yield in Northern Red Oaks at Flat Rock Forest in Relation to Small Mammals

Abstract

Oak trees can produce pulsed, synchronous and large seed yields; a phenomena coined "masting" . Among the diversity of trees in northeastern forests, mast events from northern red oak (Quercus rubra) have been linked to wildlife demographics. In years of surplus seeds, oak species may satiate granivores and thus enhanced germination rates occur in those years. Variation in annual seed yield, within populations of northern red oaks has been well studied. However, we sought to better understand the within-year timing of peak sound acorn maturation from a population of northern red oaks near their northern range limit in upstate New York. Further, we compared the timing of sound acorn maturation with small mammal trapping data. We installed then monitored ten seed traps weekly from September 10th to October 30th 2013. We collected acorns via seed traps and counted on-the-ground acorn abundance, and compared these data with small mammal presence. Peak seed rain of sound acorns and maximum small mammal captures, occurred around October 9th, 2013. Deer and white-footed mice (Peromyscus spp.) were the most captured granivore species (n =15 captures). When compared to density of acorns collected in seed traps, those on the ground were clearly depredated most likely attributed to small mammals or other acorn predators. The number of sound acorns recorded on the ground during the final week of this study was 75% less than the cumulative number of acorns found in the seed traps during the sampling season. There was no significant relationship between tree size (DBH) and acorn yield. We did however find a significant inverse relationship between crown area and acorn yield. Our baseline data will eventually be used to help understand the mechanics of masting and result in optimization of management practices of valued northern red oak in addition to growing a better understanding of the complex community dynamics of this foundational species.