When are shade-tolerant trees ready for full sun?

twistedtree · December 30, 2005, 05:32:16 PM

I've got a stand with mature pioneer trees (mostly aspen and some birch), and a bunch of sugar maples that have established in the shade. It was a field 50 years ago. The maples are 1"-2" in diameter, and 10'-20' tall. The aspen are 1-2 feet in diameter and probably 60-80 feet tall.

The question is how long Maples need to stay in the shade before it's OK to give them full sun, in this case by removing the aspens. The maples are pretty dense so I think the ground will still be shaded by the maples alone if I wack the aspens.

Any thoughts or guidance?

Thanks

SwampDonkey · December 30, 2005, 06:33:52 PM

That's a hard call twistedtree. I have seen stands with aspen and birch with understory sugar maple. Usually the size difference isn't that extreme. You must have alot of sugar maple in surrounding stands. I will say that the sugar maple is not likely to scald as badly compared to having an overstory of mature maple. This is because the aspen and birch don't cast as intense shade. If you go at removing all the overstory aspen then you'll end up with alot of root suckered aspen taking over. If you go that route, I would let the suckered aspen catch up to the maple 6-10 years and get out the spacing saw. I've seen some nice sugar maple develop in aspen stands. Trouble is those big aspen are gonna do alot of damage unless you take a systematic approach to their removal by using spaced trails, directional felling and bucking in place. In ten years time it won't be that difficult to thin the new stand. The slash will likely be well rotted. Beware, that any white birch left standing if the overstory is opened up alot will suffer from scald and their crown will thin and eventually die. Dominant trees aren't as susceptable to scald. Typically, birch die-back takes about 3-5 years. Once it begins the bole of the tree will get pocket rot. However, depending on where your located you can grow some nice white birch veneer if you do a light harvest. If your on the southern fringe of white birch then they probably won't get real big. Often they are multi-stemed and as crooked as cork-skrews when regenerating in fields, because they get alot of browse from wildlife competing with aspen for light. So basically, if your gonna take all the aspen, take the birch or loose it. Just be carefull and use directional felling and spaced trails to your advantage.

Have fun

twistedtree · December 30, 2005, 07:14:53 PM

Good call on the surrounding Maple stands. It's a small field of 2-3 acres with lots of surounding maple. The birches are small and mostly inconsequential so removing them won't be a big deal. However, I'm a bit confused about why they will suffer if I remove the apsens. I thought birches liked full sun (they are pioneer thress right?). I'm slowly learning this stuff, but I have a long way to go.

I agree removing the aspen will be a trick to minimize damage. I may want to haul out the logs and slash since I look at this area from my house so it's appearance is important. That will only agrevate the damage. My only alternative is to leave it to nature, but when the aspen dies and falls it will trash the maples just the same.

SwampDonkey · December 30, 2005, 07:55:14 PM

Quote from: twistedtree on December 30, 2005, 07:14:53 PM
The birches are small and mostly inconsequential so removing them won't be a big deal. However, I'm a bit confused about why they will suffer if I remove the apsens.

The bole of the tree becomes over heated, and the leaves in the crown are conditioned to grow in shade by having a larger leaf surface area than those growing in full sun. This stresses the tree because of increased water loss.

QuoteMy only alternative is to leave it to nature, but when the aspen dies and falls it will trash the maples just the same.

I wouldn't be too concerned there, they won't all fall down at once unless there is a major wind storm. They are shallow rooted and when they get over mature they can be toppled by heavy winds. But, most times they die back and decay loosing a little of their tops at a time. It will be less damaging than harvesting the stand, it's part of the natural seccession. Poplar and birch are nurse trees.

twistedtree · December 30, 2005, 09:47:05 PM

Thanks again, this is very helpful. As I said, I'm learning more and more all the time about this.

I've seen what you describe as the trees die. Some of these aspen died as a result of ice damage in the '98 ice storm we had, and they have been coming down in chunks.

I'm assuming that after the maples are established, removing the over story trees will accelerate their growth, correct? Because this is part of the viewscape from my house, getting the dead trees out quicker is desirable.

The more I think about it, the more I think I need to better describe the situation. The really big aspens are along the edge of the old field, as much as 30 feet into the edge woods. This edge area has been growing longer than the field. There are other smaller, but more interesting trees in this edge area, including some maples, beech, yellow birch, and cherry. The field, which is probably no more than 200' across, has sprouted up with maple and other saplings. Some of the big aspen in the edge area are dead and starting to come down, but others are still healthy, though topping out everything else.

It seems removing the aspens would benefit the established and more valuable hardwoods in this edge area, so that suggests removing them is a good idea. But, these same aspen have provided much of the shade that has enabled the field saplings to take hold, so I don't want to take them out pre-maturely. Plus of course there's the issue of damage while removing the trees rather than let them die naturally. I guess this is what makes foresty interesting - there are no clear answers. I know they play an important role in establishing new forests, but once their job is done, I'd prefer not to have to look at them.

Minnesota_boy · December 31, 2005, 07:45:57 AM

I'm not a forester, so this may be all wrong, but if you don't have a huge number of the aspen and don't have a good market for them, could you use an herbicide on them to kill them and let them come down in pieces as other trees that have died are doing? Doing it this way will eliminate the suckering from the roots too.