Impacts of white-tailed deer on regional patterns of forest tree recruitment

18 Local, shortto medium-term studies make clear that white-tailed deer can greatly suppress 19 tree growth and survival in palatable tree species. To assess how deer have broadly affected 20 patterns of tree recruitment across northern Wisconsin, we analyzed recruitment success in 11 21 common trees species that vary in palatability across 13,105 USFS FIA plots sampled 22 between 1983 and 2013. We also examined how recruitment in these species covaried with 23 estimated deer densities here. Saplings of five palatable species were scarce relative to less 24 palatable species and showed highly skewed distributions. Scarcity and skew provide reliable 25 signals of deer impacts even when deer have severely reduced recruitment and/or no reliable 26 deer density data are available. Deer densities ranged from 2.3-23 deer per km over a 30 27 year period. Sapling numbers in two maples (Acer) and aspen (Populus) with intermediate 28 palatability declined sharply in apparent response to higher deer density. Path analysis also 29 reveals that deer act to cumulatively depress sapling recruitment in these species over 30 successive decades. Together, these approaches show that deer have strongly depressed 31 sapling recruitment in all taxa except Abies and Picea. As these impacts are now propagating 32 into larger sized trees, deer are also altering canopy composition composition and dynamics. 33 The tools developed here provide efficient and reliable indicators for monitoring deer impacts 34 on forest tree recruitment using consistent data collected by public agencies. 35 36