Treesearch

Small trees in even-aged northern hardwood stands suffer the most mechanical damage when stands are thinned for the first time. From 15 to 35 percent of the trees may be damaged; a quarter of the trees (but usually less than 20 per acre) can be seriously damaged by having at least 50 square inches of the cambium exposed. Bole damage is most common, followed by root and then crown damage.

Maple decline (i.e. maple blight, maple dieback) has periodically caused significant losses of sugar maple in northern hardwood forests. The first major outbreak of maple decline was reported in northeastern Wisconsin and upper Michigan in the late 1950's. The disease reappeared in the same general area during the late 1970's and early 1980's.

Since its discovery in the United States in 1930, Dutch elm disease has killed thousands of native elms. The three native elms, American, slippery, and rock, have little or no resistance to Dutch elm disease, but individual trees within each species vary in susceptibility to the disease. The most important of these, American elm, is scattered in upland stands but is more abundant on wetter sites and along river bottoms.

In commercial terms, trees change in three ways: by growing in diameter, growing in merchantable height, and changing in grade. So when you are marking a stand for thinning and you have to choose between two trees of the same species, you estimate what the future diameter, height, and tree grade will be for each tree if the other is cut. Then you compare the predicted changes and decide which to cut and which to leave.

Managed old-growth northern hardwoods have few insect and disease problems Insect damage is only occasional and any major decay from diseases can be eliminated in three cyclic cuts.

Several properties of wood are affected by moisture content-weight, fuel value, electrical conductivity, strength, and shrinkage. Differences in these properties are commonly observed in wood in service. For example, a green 2 X 4 weighs more than a kiln-dried 2 X 4, dried wood burns more easily and hotter than green wood, etc.

As the demand for wood products increases, hardwoods will be used in larger amounts and trees more completely utilized. As a result, foresters will have a greater need to predict weight yields of hardwood stands.

How large is an economically mature tree?

Yellow birch needs moisture, nutrients, overhead light, and enough space for the crown to expand in order to compete successfully with faster-growing northern hardwoods. By releasing crowns early, you can increase the number of future veneer and saw log trees in a stand and double the growth rate, thus cutting rotations in half. If you delay crown release too long, growth response is poor. After 45 years most birch trees in unmanaged stands occupy such poor crown positions that little can be done to improve them.

Thin too much the first time and you are likely to get a surge of epicormic sprouts. These small branches that can mar a clean bole and cause serious degrade often develop profusely in pole and small sawtimber before and after initial thinning, particularly under even-age management.