Effects of Long‐Term Deer Exclusion on a Pinus Resinosa Forest in North‐Central Minnesota

Trees, shrubs, and herbs were sampled inside and outside an exclosure in a 230—year—old Pinus resinosa forest in north—central Minnesota from 1946 to 1969. Prior to the building of the exclosure in 1937, white—tailed deer had existed at or above starvation population densities for 10 or more years. Overbrowsing continued outside the exclosure until 1945 when the deer were virtually eliminated by hunting. Since then deer numbers have gradually increased. Before 1937, severe browsing had apparently removed all tree reproduction greater than 1—2 years old. Since 1937, inside the exclosure the occurrence of seedlings and samplings has increased greatly and has followed a normal successional sequence dominated by Pinus strobus with lesser amounts of Betula papyrifera, Acer rubrum, Quercus borealis, and Abies balsamea. Outside, tree reproduction was scarce until after 1945; then Pinus resinosa, P. strobus, and Betula papyrifera saplings increased substantially. Only P. resinosa and B. papyrifera have grown above the sapling class in appreciable numbers, probably because B. papyrifera is of low preference as deer browse compared with the other intermediate species, Pinus strobus, Acer rubrum, and Quercus borealis. Thus, moderate—to—high browsing has continued to inhibit successional development.