Kl. Borgmann et al., Does balsam fir (Abies balsamea) facilitate the recruitment of eastern hemlock (Tsuga canadensis)?, AM MIDL NAT, 141(2), 1999, pp. 391-397
Eastern hemlock (Tsuga canadensis) was a major component of mesic forests i
n the Upper Great Lakes region, but presently persists in only a few locati
ons, Many of these stands experience poor regeneration due to herbivory by
white-tailed deer (Odocoileus virginianus), suggesting that hemlock will be
come progressively less common in these stands. We tested the hypothesis th
at balsam fir (Abies balsamea) facilitates establishment of eastern hemlock
at 11 sites in northern Wisconsin. Hemlock saplings are three times as den
se and twice as tall when growing within patches of balsam fir compared to
growing outside such patches. Hemlock saplings growing outside balsam fir p
atches are also four times as likely to exhibit deer browsing damage as tho
se growing inside. These results suggest that patches of balsam fir create
a physical or visual barrier to deer and thus provide a refuge for hemlock
saplings from white-tailed deer browsing. Because balsam fir saplings are m
uch more abundant than hemlock in northern Wisconsin forests and establish
on a wider range of sites, foresters could use patches of balsam fir to fac
ilitate local hemlock establishment and so promote restoration of this impo
rtant forest type.