What strategy to follow for thinning a woodlot?

Question

I have a woodlot roughly 10 acres (4 hectares) from which I harvest firewood. From a permaculture perspective, this is my Zone 4; Zone 5 lies along the back edge of the woodlot. I'm in the northeast USA, USDA Zone 5 -- it was recently -10°F (-20°C) during a cold snap. Acidic, loamy, gravelly soil.

The species makeup is mainly beech and Eastern hemlock; with significant amounts of sugar maple and white pine; and smaller amounts of black cherry, ash, paper birch, and spruce. I harvest using a selective cutting strategy -- removing diseased or damaged trees first, then less-desirable species (hemlock has lower energy density than beech or maple), and paying attention to the amount of light and wind that I'm letting in via cuts as well as which mature species are left in place to scatter seed.

The woodlot is just for firewood and wildlife; it is not used for other crops or pasture.

I do not plant anything back there. Actually, in areas where I have thinned and lots of sunlight is reaching the floor I think I am "overstocked". Many seedlings are growing up very densely -- which leads me to the question: What guidelines should I follow for thinning?

• How do I know how densely various species should be growing for optimum yield? It seems obvious that beech shouldn't be grown 4-6" apart, but how many should I remove?
• Which seedlings should I (de-)select? (I.e. which to cut and which to keep.)
• Is it sensible to deselect the (less energy dense) softwoods and encourage the hardwoods? I don't want to destroy biodiversity, but I don't want to maintain the current ~30-50% hemlock makeup -- or, in one area, ~80% white pine saplings. Also, encouraging sugar maple makes the land more valuable -- sugaring businesses are active in the area, and these trees provide ongoing yields without having to cut them down.
• Should I thin in phases? E.g. aim for a certain density when the seedlings are under 6' (2m) and then a certain lower density when they get to say 15' (5m).
• Is there an ideal time of year to thin? I don't think seedlings are strong enough to regrow when cut, but perhaps some slightly larger trees would -- timing thinning to minimize regrowth (and rework) would be nice.
• Is there any consideration I should give to yields that I can get from thinning? It's quite a bit of work, and I'd love to be able to get something out of it now, instead of waiting to get everything 40 years from now. (Note that I'm obviously in this for the long haul, but I'm more than willing to get a yield from what would otherwise be waste.)

Answer 1

I am not sure I am qualified to answer all your questions but here are the ones I feel qualified to answer.

Phased selection

The first point I would make is that trees in the wild do start off in dense thickets and naturally self-select as they get larger. I would expect that this has a number of benefits for the soil such as reduced erosion. I would suggest phasing the thinning. This has a few benefits including the fact that you may get more initial growth for things like kindling out of the initial high speed growth.

I would suggest during the thinning phase, assuming young trees, that a simple rule might be that if the heads of the trees are touching, you can probably afford to thin half of the trees. That gives them room to grow for the next phase without thinning them so far you might worry about too much erosion in the spring with the runoff.

I would suggest also removing the weaker and smaller saplings if there is a difference there.

As for yelds, if you can saw the small logs on a jig and dry them out they can be useful for kindling in a wood stove. We heat our house in Chelan with apple wood which cannot be easily split due to the way it has been pruned, and we just use smaller rounds as kindling.

Species Selection

I share your concerns here. I don't think there is a problem with selecting based on species in order to shift yields. This is a more tricky subject and probably pretty locally dependent so rather than try to provide a definitive answer, I will mention a few things to keep in mind.

Many forests have an internal species progression where established trees of one species group enable the next stage of the progression to become established. These progressions can take hundreds of years in some forests to reach maturity and obviously you don't want to wait that long. In fact I know of old growth forests in national parks in Washington State, where such a progression has not reached maturity and probably won't for another few hundred years, assuming no fires or the like (for example in Mt Ranier National Park a lot of the old growths in the lower areas are doug fir-dominated, but the next phase will be Western Hemlock).... At the same time you may want to be familiar with it because you may be trying to either back things out or push things forward. Being aware of such cycles is the first step in trying to harness them and it may shape the way you look at species selection.

As I understand it, in your area, beech and maple are probably the pinnacle species, so one thing you should keep in mind is that eventually these trees will likely dominate the other species. Additionally these species are co-dependent, each reproducing best in the shade of the other.