Oak mast production and animal impacts on acorn survival in the central hardwoods

As part of the Hardwood Ecosystem Experiment we measured mast production in white (Quercus alba) and black (Q. velutina) oak, and quantified the impacts of seed predators on acorn survival over a 3-year period. Specifically, we measured the proportion of acorns of each species infested with weevils (Curculio spp.), and the probability of acorn removal by seed predators from a system of semipermeable exclosures. The 3 years of the study included 2 years of high mast production in both species (2006-07) and 1 year of mast crop failure (2008). Across all 3 years, 19 percent of acorns were infested. The rate of weevil infestation was slightly higher for black oak than for white oak in each year, but infestation peaked for both species during the year of mast failure (2008). Overall, 39 percent of acorns in the exclosures were removed by seed predators. The probability of acorn removal was lower when squirrels were excluded, providing support for additive effects of different seed predators. The probability of removal was highest in 2008 during the year of mast failure. In the future, these pre-harvest data will be compared to data obtained following timber harvests conducted in winter 2009.