Hardwood even-aged/un-even aged

[flatrock]

I see alot of material regarding un-even aged mgmt. in hardwoods and I have a few questions I hope the board may have ideals on. My first question is, if your forest is primarily a stand of even-aged shade intolerant species is  un-even aged mgmt. still the right approach?  I have a tract of oak/hickory no maples, cherry or other commerical shade tolerant species.  I would think scattered group selection openings or small clearcuts would be a better way to maintain the oak species.   It seems you would get the stump sprouting from the smaller stems harvested as well as lots of sunlight. Or, is there an uneven aged method that really opens up the canopy and would work in regenerating with shade intolerant species like oak?   Presently the dominant harvest method in the community where my forest is located is the diameter limit cut.  The higher diameter limit cuts that I have seen (14" or 16") to me look visually appealing quicker after harvest but every thing I read indicates this is the worst possible way to harvest and you are condemning your forest to decline by doing this.  Which leads to my final question. In even-aged stands  of shade  intolerant hardwoods is diameter limiting cutting or some variation of diameter limit cutting ever the best harvest strategy?

[Ron Wenrich]

Its really hard to convert over from an even aged forest to that of an uneven aged.  Your group selection would be one method.  Think of your forest as being a lot of smaller forests that are managed at different ages.  This can also work for other species, but you have to vary the size of your openings, depending on the species you're trying to regenerate.

One of the hardest thing to get through people's head is the need for regeneration cuts.  I have been on several jobs that have no regeneration.  They had a "thinning" which they were told would result in a new forest.  But, if the thinning is too hard, and the openings are too big, then you end up with weeds and vines with very little chance for natural regeneration.  Stump sprouts are not necessarily a good regeneration source.  They usually end up with multiple sprouts or deformed butts.

Diameter limit cutting is silvicultural suicide.  If you are working in an even aged forest, then you will be taking all the good growing trees and leaving the slower growing trees as a seed source.  If they couldn't beat out the other trees when they were juvenille, do you really think they are a good seed source?  Never kill your best milkers. 

When you cut at 18" and up, you are taking the cream of the crop.  That is where hardwoods make the veneer grade. 

There are some regeneration cuts that use a diameter limit cut.  You cut all trees under a certain size.  That allows them to seed in under a canopy of good quality trees.  Then, you remove the overstory and release the seedlings.  It doesn't happen very often on private lands. 

[LeeB]

Very interesting topic. I didn't know I need this information till now.

[Gary_C]

How do you determine if you have an even aged forest vs. an un even aged. Certainly not by same diameters. Is it height of trees?

[SwampDonkey]

Red oak is not as intolerant to shade as our aspen and whit birch here in the north. Red oak lives at least twice as long as aspen. I can't really say that about white birch as a general rule because we have some really old white birch on good sites to. A lot of those old bruits died off here 70 years ago, but you still find the odd one. Getting back to red oak shade tolerance, it's considered intermediate like our yellow birch. In this area red oak and yellow birch alike do best on sites with a fluctuating water table on finely textured soil with good lateral flow. And associated with sugar maple, yellow birch, white ash and basswood and commonly with softwood such as balsam and white pine. Usually, small, relatively pure stands of red oak are found on shallow rocky soils. Right now I'm thinking of the sites I know with almost pure red oak and it fits those shallow rock outcropped soils, usually on ridge tops or southerly aspects of big hills. It's regenerating well on my woodlot, which was clearcut in 1993 and never had an oak on it until the wildlife and myself planted them. I blame bear and moose and maybe the odd blue jay as I'm not far from a pure stand of red oak. Neighboring woodlots that were cut at the same vintage as mine have some oak seeding in to. We aren't talking huge numbers, but they are common. I try to save every one.

As Ron says size of harvested openings means a lot. Big open areas cut on rich sites can mean poor regen and lots of raspberry, elder, weeds and such. I would limit the open sizes to a couple tree lengths and smaller, but go for irregularity of the shape of the opening. Most often if your opening a mature stand of red oak up there was no regen under it, due to shade.  Possibly, you release the seed of some weed species that may be dormant for decades or get wind blown seed coming in of undesirable species.

As Ron says, avoid the diameter limit game. Short term gain for long term demise. That's what we have experienced on most active woodlots here in my area. On lots with a long cutting history, Hardwood have been high graded to death or simply cleared off. Those best trees split a lot easier than the knarly ones for firewood. We never really had much of a hardwood sawlog market here until the last 15 years. It was pulp and firewood. Thousands of acres chewed up by chipping operations for peanuts on crown lands and 100" or treelength off harvested woodlots.

You should always do a preliminary inventory before you go toting a chainsaw. Get a feel for the quality of the standing trees, the density and distribution of tree diameters and ages. Then, plan the cutting to improve the stand quality by taking so many trees or basal area of each diameter class and age group and encourage a wide range of each so you can make multiple entries to your woods in your life time. And not just one entry that you may regret down the road. What good is a family woodlot to the family if you have to wait 2 more generations for the next crop? It likely won't stay with the family long. That's what I see here a lot. People just move on and sell out without worrying about the next guy.

I know I rambled on a bit more than necessary, but food for thought. 

[SwampDonkey]

How do you determine if you have an even aged forest vs. an un even aged. Certainly not by same diameters. Is it height of trees?

Height is a pretty good guess for pure stands of some species if the trees being assessed are free to grow, not over topped or show signs of long suppression and the soil type is similar. I wouldn't rely too heavily on it in mixed stands. That little balsam could be 50 years old and 6 feet tall, while that aspen over there is 15 years old and 50 feet tall.  Well managed balsam fir stands growing on a known soil type are known to achieve a certain size at a known age, that's just site index.

Get out the 'inky' borer, tried and true. 

[Phorester]

GARY, the definition we use in VA: an evenaged forest is one in which the dominant trees are all within a 20 year age spread.  You cannot go by height or by diameter.  You need to count the rings.  We use an increment borer (Swamp's "inky" borer) for that.

About height and diameter,  first you have to compare trees of roughly the same age.  Then, height is determined by the site.  Good sites produce tall trees, poor sites produce short ones.  Diameter is determined by growing space.  That's why thinning is important. You give more growing space to the trees you want on that spot so they grow faster in diameter than if they were not thinned.  Thinning produces a faster growing tree, thus a healthier tree and one that reaches commercial value quicker.

FLATROCK:  In the hundreds of management plans I have written over 33 years, I have recommended a diameter limit cut only once.  It was in a 25 acre stand of almost pure chestnut oak, evenaged.  Since all the trees were the same species and the same age, growing on the same soil,  a diameter limit cut would work there.

Otherwise it is indeed a slow decline in the health and commercial value of a forest, as Ron describes.  It's the worst way to harvest timber if the landowner is at all interested in the future health and value of his forest. 

[tonich]

GARY, the definition we use in VA: an evenaged forest is one in which the dominant trees are all within a 20 year age spread.   

Looks like the same here, in BG.
We have so called “age classes”, which are as just as Phorester described them – 20 years for high-stem management, and 5 years for low-stem management (coppice stand).

As for uneven management: You really need strong shade tolerant tree species, in order to introduce it successfully. Although Red Oak is less light demanding, comparing to our local oaks, I would never consider it a shade tolerant tree…
There were some efforts in the past for turning oakeries into uneven management, which were not so successful. The general rule is: If you need uneven-aged forest, deal with shade tolerant trees for it!

Red Oak is supposed to be the leading tree species in you stand, I assume. Others should be spouses. The approach should be everything, but diameter limit cutting.
After I’ve been described this method, I can only second:

Diameter limit cutting is silvicultural suicide

[Gary_C]

Thank you for the replies. Would it be true that just about all uneven aged stands are created by man and not the result of natural events?

[tonich]

Would it be true that just about all uneven aged stands are created by man and not the result of natural events?

No.
Uneven-age forest appeared by nature originally. With no human disturbance.
Small gaps are being opened by biotic and abiotic factors, causing start of self-regeneration process on very small area. Repeating this many times, leads to complex pattern of tree of different age and dimensions
It is man, that is trying to follow natural processes nowadays, by means of so called Uneven-age Management.

[Ron Wenrich]

I had a guy try to tell me he could prove that there was no such thing as forest succession due to shade intolerance.  It was also the basis for his perceived notion that forest science was just a bunch of hooey.

His facts were that he was on the Tionesta wilderness in NW Pennsylvania.  The area is a virgin forest.  He came upon a spot that had a white pine and a hemlock growing side by side.  How could that be?  Isn't the hemlock shade tolerant and the white pine shade intolerant?

My reply was imagine 2 seedlings standing underneath a really large hemlock or other such tree.  Now imagine a lightnings stike killing the big tree.  An opening appears and both the shade tolerant and shade intolerant trees are released.  His reply was "Never thought of that".

The point is, a lot of those shade intolerant species remain viable in the understory for a very long time.  All it takes is some sort of natural calamity to release new trees.  That could be a fire, ice storm, tornado, flood, etc.  Depending on how old the forest, there should be several different ages present, along with a lot of different species. 

[tonich]

The point is, a lot of those shade intolerant species remain viable in the understory for a very long time. 

Yes, this is what Uneven-aged management is based on.
But I was considering mainly shade tolerant tree species, though:

I wouldn’t consider any small size tree a “junk”, since it is the future stand of the selected wood. For example the Silver Fir (Abies Alba) is able to stay/be kept suppressed (selective cutting is a combination of suppressing and releasing) for up to 70 years of age, without loosing its growing potential at all.

(http://www.forestryforum.com/board/index.php?topic=24761.0)

[Tom]

I'm told that release is viable only to a certain age.  Pine that has been "Stunted" will not respond to release after a few years. (not my statement)

If this were true, would hardwoods find themselves permantly stunted?

Now, I have to add that I've cut many pines from swamps that had twenty or thirty growth rings in their first 3 inches of growth and still burst out into 1" rings and make a 20" tree after a supposed release.  Would this be a normal thing?

[SwampDonkey]

Balsam fir is notorious for sitting in suppression for decades and live on. Once released it can take 5 or 6 years before growth rate picks up. Those trees are usually rotten in the middle. If you can catch them by 25 years or so, and release them they will be a lot better tree. On the other hand red spruce will respond well from long suppression and not suffer from but rot so much. White ash, which I've posted a pic of the end grain, shows one board that had rings about 25 to the inch, yet it became a dominant tree. It is quite shade tolerant as a young tree, becoming less shade tolerant with age. Similar to white pine. Nothing could be more shading than 7 foot tall raspberry canes over topping white pine seedlings. I have some in that situation that are still green, but grow very little. The seedlings would be 7 years old now and compound this with browsing by snow shoe hare. It's amazing how they live. 

[Ron Wenrich]

I've always heard the same thing.  I think all trees respond, just some respond slower.  Now, if they respond too slow, they'll get overtopped again.  It probably has something to do with juvenille trees vs older trees.  

I've seen the same rings in oak trees.  I once gave a talk to a 5th grade class about trees.  So, I took in a cross section of a tree.  About the only person that was interested was the teacher, and she was amazed.  From the rings, I could tell when the stand was probably cut, and when there was a hard gypsy moth defoliation.  Each time, the tree responded to the release.

The only time a tree will expand its diameter is when it has room to expand its crown.  

[Gary_C]

So that leads me to the next question. Are all even aged stands only the ones created by man as in plantations or pure stands of aspen after clearcuts? Are you saying that all even aged stands will revert to uneven aged in time?

[Ron Wenrich]

I would think the incoming forests after Mt St Helens would qualify as an even-aged stand.  Same goes for a lot of ingrowth after a forest fire.  A lot would depend on how big of an area you want to classify as a forest.  If you are looking at a rather small area, then the amount of trees you have to work with are limited.

Will an even aged stand revert to uneven aged?  I would think that depends on the amount of outside influences and the size of the disturbance.  Minor disturbances would tend to more uneven aged structure.  Major disturbances would tend to more even aged.

[Tom]

Still, inversly, a stand of highly invasive, fast-growing trees will form a dense forest that disallows or chokes out any competitors.  Brought to mind is Chinese Tallow where there is no outside disturbance.  I've seen acres of it come up almost simultaneously and be so dense that nothing, including its own progeny, can survive in the shade below.

[flatrock]

Thanks for all the replies.  Have made me think of other questions.  I understand the need not to wipe out all the big ones for genetics.  So, then is the trick in a southern oak hardwood dominated even aged stand cutting a little heavier across diameter classes to let the sun in?  Im thinking of the forestry term residual basal area.  Assuming adequate stocking to begin with cut to lower RBA than say you would in the NE and harvest across diameter classes.?  My concern here would be the smaller stems are really the same age as the bigger ones.  Is the reason they are smaller due to genetics and will an even aged cut like this leave  a forest with smaller trees that have bad genetics as well as good big ones.  If the small trees do not respond  & grow well it would seem the better course of action would be large group selection cuts.

[SwampDonkey]

Again, I can think of aspen stands. Often I come across sites copiously regenerating with aspen at a density approaching 20,000 stems per acre. Hmmm.....through self thinning from over crowding, competition, shade intolerance, and cankers the stand density declines with age and height. Low and behold in 10 years time I see a carpet of sugar maple.  or a carpet of balsam fir establishing even more  Very shade tolerant tree species will establish at the 'opportune' moment. 

Go to a hardwood stand, mixed with sugar maple, beech and yellow birch.....concentrate on harvesting the beech out for firewood while leaving the maple and yellow birch in the canopy and retaining 60% plus crown closure. See what the regen is in 10 years. Beeeeeeech!!  So thick and nasty you can't begin to walk through it.