Regional changes to forest understories since the mid-Twentieth Century: Effects of overabundant deer and other factors in northern New Jersey

•Forest understories in northern NJ were compared to prior data from 1948 to 1973.•Major declines occurred in young tree densities and shrub, herb and large seedling cover.•Major increases were observed in exotic shrub, liana and herb cover.•Major changes in tree species composition occurred in relation to browse preference.•Deer exclosures returned large seedling densities and species composition to historic levels.