WILL-WOLF, SUSAN. Department of Botany, University of Wisconsin, Madison, WI 53706-1381. - Lichen communities of old-growth vs managed forests in the northern Great Lakes states.
We have compared lichen communities in three layers (canopy, trunk,
ground) of 15 old growth and managed Northern Hardwood and
Hemlock-Hardwood forest plots in Michigan and Wisconsin, to develop an
old-growth forest indicator system and to assess the impact of forest
management. Old-growth stands of both forest types have more lichen
species than managed stands. Equivalent stands of the two forest types
have about equal numbers of species and of nitrogen-fixing
cyanolichens. Hemlock-Hardwood stands have species evenly distributed
among forest layers, while Northern Hardwood stands have more species
in taller layers. All managed stands of both forest types have fewer
and less abundant cyanolichen species than do old-growth stands.
Species loss occurs most in canopy and trunk layers of managed
Northern Hardwood stands, but trunk and ground layers of managed
Hemlock-Hardwood stands. Large, long-dead standing snags and large
partially-decayed coarse woody debris (CWD: especially mossy logs) are
particularly important substrates fostering increased species
diversity of forest lichen communities. Bark-living lichen species
tend to be substrate-selective both with respect to tree species and
to tree age, so a wide range of tree sizes as well as a variety of
tree species fosters increased lichen community diversity. Lack of
snags and CWD is more critical in Hemlock-Hardwood stands because
trunks and bases of living hemlocks are too shady for most lichens.
Management of forest stands which leaves abundant snags and old-tree
islands, and leaves or enhances large CWD should deter loss of lichen
community diversity. Nitrogen-fixing lichens and ground-layer lichens
are two identifiable lichen "guilds" whose diversity is
negatively impacted by logging.
Key words: forest, lichen communities, lichens, management, old-growth