Wildlife Trees and Downed Wood
Any tree or group of trees with more than average wildlife use should be retained. Dead and dying trees are particularly attractive to fungi, insects, birds and small mammals. In addition to providing food and habitat, downed wood releases nutrients and moisture slowly, moderates temperature and moisture fluctuations and builds soil. In this way (in our region), over the long run they also reduce the intensity of any potential fires and in times of fire and drought provide fungi, bacteria, insects, amphibians and plants with potential refuge. One method for increasing downed wood is to retain wind thrown trees on the ground. This also has the beneficial effect of retaining small hummocks where the trees have been uprooted. These areas create micro-site differences in moisture holding and nutrient pooling and the exposed soil increases the probability of Douglas-fir regeneration. Where possible downed trees should be left full length as they don’t desiccate and decompose as fast as smaller sections. Trees decomposing over a longer period of time tie up the least amount of soil nitrogen (a limiting nutrient). Thus the benefits of downed wood are expressed over a longer time period. Creating snags by girdling some trees is also valuable (especially in small groups. Pick areas where you want more light (i.e. Areas with bare ground, but no tree regeneration or under-story shrubs; or pick dense areas with a lot of inter-tree competition). If the risk of fire hazard from human use is high, branches on downed trees could be cut and dropped to the forest floor.
Natural seeding is preferred because locally adapted genes are retained in the stand. It is also inexpensive. The dominant trees are good candidates to consider as seed trees. At the end of their lives they also become good wildlife trees. Merv feels good forester manipulates the canopy, opening it up to light when necessary. This benefits the trees that remain and also lets new seedlings get started (usually in patches).
Retaining the tallest trees in the stand is beneficial in reducing wind velocities and therefore damage to tree leaders (particularly those approaching the top of the canopy). The tallest trees are often the best seed trees as well. Retaining the tallest trees means the stand height will remain high or get taller thus better economically in the long term, and also better ecologically because more habitat opportunities exist.
Candidates to Harvest
Our understanding of ecosystem functioning is not sufficient to say with certainty what harvest levels can be maintained for hundreds (or thousands) of years. But any time you cut more than the growth you are in a deficit position. It is desirable to allow sufficient light to reach the forest floor (in a patchy fashion) to allow for the regeneration of the desired plant species. This criterion will have to be balanced with the desire to keep the stand sufficiently dense so that the trees lose lower limbs and develop less juvenile wood. A helpful way to decide which trees to remove is to consider what in the stand would be next to die naturally. This may include some (but not all) diseased or suppressed trees. Typically trees with less than 25 percent of their length in live foliage have a higher probability of dieing next. Lack of foliage density and a poor (yellowish) colour are also indicators of our native conifer trees in decline. In Douglas-fir as the tree grows its red inner bark becomes exposed. Those trees showing a lot of red between the grooves of bark are faster growing. Those trees showing little red in the grooves of bark are slower growing and could be considered for harvest. One should keep in mind that some of these trees should be left for wildlife use and nutrient cycling. Also, diseases are a part of the forest too and should not be eliminated. Many diseases are fungal and play an important role in recycling nutrients.