Treesearch

Site index is one of the more easily measured indicators of the productive capacity of an area for a given species. In mixed stands, the site index of one species can be used to predict the site index of another. Site index also illustrates growth differences among species.

When you "thin" an even-aged stand, or "restructure" an all-aged stand by thinning out certain size classes (both are sometimes called "improvement cuttings"), how much basal area should you leave?

For long it was assumed that deer browsing on the terminal shoot of sugar maple was detrimental to height growth, stem form, and vigor. Does browsing permanently damage sugar maple in northern hardwood stands?

Good site index estimates are necessary for intensive forest management. To get tree age used in determining site index, increment cores are commonly used. The diffuse-porous rings of northern hardwoods, though, are difficult to count in cores, so many site index estimates are imprecise. Also, measuring the height of standing trees is more difficult and less accurate than measuring the height of felled ones.

Clearcutting can be one of the most effective hardwood management systems in the Lake States-if an essential criterion is adhered to. That criterion is: Regeneration must be established-that is, 2 to 4 feet high before you clearcut, before the overstory can be removed.

How do you deal with stump sprouts in second-growth hardwood stands? Although thinning them takes special effort to avoid causing decay, stump sprouts are the only way to regenerate certain species such as basswood. Generally, you should thin them early and preferably when potential crop stems are 3 inches d.b.h. or less. But if you delay thinning until they are pole-size, leave those with vigorous co-dominant crowns, and those joined to the stump at the lowest point.

Sometimes a name creates a problem. The name of a silvicultural system usually refers to the way a stand is cut to get regeneration-"single tree selection"-for example. Trouble is, the name suggests that the regeneration cut will be the first treatment applied to the stand. Not so. We are now mostly making "intermediate" cuts in our Lake States stands and bringing them to maturity; then we can make the "regeneration" (or "harvest) cuts to reproduce them.

The 2-cut shelterwood silvicultural system is the most reliable method we have for regenerating even-aged hardwoods. Unlike other systems it can be used for all hardwood species, both small- and large-seeded, but will probably be used most often for the small-seeded ones such as yellow birch, paper birch, and hemlock.