Large, Old Trees Best Suited For Wildlife
In wet forests that are dominated by ancient red cedars, 22 to 30 percent of trees offer enough habitat for birds and mammals to be classified as a wildlife tree.
Among trees over 100 cm diameter in the Interior Cedar-Hemlock biogeoclimatic zone of central British Columbia, the proportion reaches 64 percent.
Certain features such as tree cavities that are used by birds, bats, squirrels and weasels, mainly occur in trees over 62.5 cm diameter, which tend to be over 300 years old. The researchers warn that this type of wildlife habitat will become rare under the 80 to 100-year forest harvesting rotations that are planned for this ecosystem, unless patches of older trees are retained.
Different tree species offer different types of habitat. Subalpine fir snags are well-suited for bat roosts as they decay and the bark loosens. Hybrid spruce, in particular, can develop large concealed spaces amid the roots near the stem, providing cover for grouse and hares. Red cedar boles feature cracks, but lack decay inside. Slow-growing western hemlock most often contains decayed heartwood.
Logging had little affect on the volume of coarse woody debris lying on the ground in these forests near McBride, BC. The average length of pieces, however, declined during harvesting by about one-third in clearcuts and group retention blocks. Harvesting also resulted in a smaller proportion of the log debris being suitable for wildlife habitat. The changes in coarse woody material were less pronounced in blocks with more tree retention.
Susan K. Stevenson, Michael J. Jull and Bruce J. Rogers. 2006. Abundance and attributes of wildlife trees and coarse woody debris at three silvicultural systems study areas in the Interior Cedar-Hemlock Zone, British Columbia. Forest Ecology and Management. 233(1): 176-191.