"Wind thinning" on PNW conifers

Re: \"Wind thinning\" on PNW conifers

[ QUOTE ]
I'll keep my discussion to Doug firs as that's what's commonly "wind-sailed" around here.

What no-ones really touched on is the effect on thinning on what goes on in the root zones when the wind blows. So, let's say a mature tree is heavily pruned, around 1/3 removed. Wind comes and blows through those remaining branches. The physical force of the wind is actually stronger now on the remaining branches.



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I think that a model would show that the force on the trunk and roots would be less, if limbs are thinned. Sort of how the wind tugs like crazy at an umbrella, but cut holes in it and the force to the wrist is not so much.

Its pretty evident that branches on one side could have extra protection if other limbs on the other side were not removed.

As far as "shock load" and trees returning to original position, the return sway (sway) is generally slow and gentle. A return sway is rarely as great as the intitial push and lean from the initial burst of wind.

The thing with wind --- it's not a light switch or an electric window switch where it goes on and off instantaneously, or reverses on a dime. Winds increase and subside with a transition in most cases.

It would be interesting to take photos of a Douglas fir out here before and after thinning, through wind storms of nearly identical wind speeds. And measure the angle of the trunk in the photos from it's max lean.

For Leyland Cypress, which I think few people should plant out here, I've found both thinning and branch length reduction to be priceless to salvage many of the better looking ones that had gathered a bit of lean.

Also, if arborists don't remove more than 10% to 15% canopy volume at one time, I think it's pretty inconsequential.

For trees in groups / groves, other than corrective pruning, I think that "wind-sail" thinning would be pointless.
 
Re: \"Wind thinning\" on PNW conifers

Sean, go for it! Getting that verbiage re. EWR into the brains of the school system would be great.

And I agree with you on the 25% rule guideline. I used 1/3 referring to what some of those "wind-sailed" trees look like how much was removed after pruning :)
 
Re: \"Wind thinning\" on PNW conifers

"I'll cut back to a much smaller lateral on the black oaks around here than I would on a ponderosa or a doug fir."

Thanks Michael, I agree that fractions mean nothing to a tree. They don't know how to do the math, so why should we?
So what are the general criteria for locating reduction cuts? Here's one list:

Size of wound. The smaller, the sooner it will close and the less it will decay.
Sunlight, and space to grow into and mature.
Vitality. Color, brightness and quality of buds, show vitality
Thickness of collar-type tissues at the bud protection zone. The more incipient callus tissue there is, the sooner the cut will close.
Angle of attachment. A lateral growing at a 90 degree angle may develop an unstable and unsightly “hollow elbow”, so cutting at the next node out may be advisable.
Angle of cut. Sloping cuts capture less moisture and spores. Upright laterals generally preferred.
Exposure of cut. Shaded cuts are less likely to crack and decay.
Size of remaining lateral branch. One-third the diameter of the parent branch is a common guideline—not a Rule--where one dominant branch is desired.


[ QUOTE ]
I have a bid to submit including EWR on Doug-fir over school buses ($103,000 each when new, with very involved repairs when the roof gets punctured/ damaged).
Thoughts anyone?

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Did the county write any specifications? If not, then it's up to you. How would you use this template to communicate your intent?

"Pruning shall be done in accordance with ANSI A300 (Part 1) Pruning." Work procedures will follow the requirements (indicated by the word "shall") and recommendations (indicated by the word "should") of the ANSI A300 Part 1 Pruning standards. Note: On occasion, the arborist is allowed to deviate from a recommendation based on the unique needs of a particular job, tree species, or work site.


1. Tree(s) to be pruned: ______________________________________________________________

2. State Pruning Objective(s).
Risk reduction, explain: _____________________________________________________________________
Manage Health, explain: _____________________________________________________________________
Clearance, explain___________________________________________________________________________
Structural Improvement/correction, explain:______________________________________________________
View improvement, explain:___________________________________________________________________
Aesthetic improvement, explain________________________________________________________________
Restoration, explain: ________________________________________________________________________
Structural, explain___________________________________________________________________________
Other, explain______________________________________________________________________________

3. Select Pruning Method(s) and Create Specification(s) to accomplish the objective(s). (Italicized fields are required.)
Clean (Pruning to remove one or more of the following non-beneficial parts: dead, diseased, and/or broken branches).
Location: _________________________
Size range of parts to be removed: _________________________
Other: _________________________
Raise (Selective pruning to provide vertical clearance).
Clearance distance:_________________________
Location: _________________________
Size range of parts to be removed: _________________________
Other: _________________________
Reduce (Selective pruning to decrease height and/or spread).
Location/Clearance: _________________________
Size range of parts to be removed: _________________________
Other: _________________________
Thin (Selective pruning to reduce density of live branches).
Location: _________________________
Percentage of foliage to be removed: _________________________
Other: _________________________

4. Specialty Pruning
Restoration (Selective pruning to redevelop structure, form, and appearance of severely pruned, vandalized, or damaged trees.)
Size range of parts to be removed: _________________________
Location: _________________________
Percentage of sprouts to be removed: _________________________
Other: _________________________

Vista/View (Pruning shall consist of the use of one or more pruning methods(types) to enhance a specific line of sight.)
Pruning Methods(s) to be used: _________________________
Size range of parts to be removed: _________________________
Location: _________________________
Percentage of foliage to be removed: _________________________
Other: _________________________
 
Re: \"Wind thinning\" on PNW conifers

MD Vaden .. with all respect, Sean asked for data. Currently the PNW Tree Risk Assessment course (with flaws, given) cites several studies and publications dealing with tree mechanics etc. I encourage you to take that course or peruse it's manual.

Here's a quote for you: "While a dense crown 'sail' catches more wind, it also allows the tree to return to its initial position more slowly. If the sail suddenly becomes very porous, the damping motion is greatly reduced and the tree may flex back and forth very rapidly - often much faster than the root system can accept, thus creating a string of unusually strong pulsed forces acting on the roots."

Trees aren't umbrellas or boats. Punching holes in material makes a ton of sense to those objects, not to tree canopy though - they have adapted in other ways to deal with wind, far before we starting punching holes in their canopies.

Not sure we can compare Leyland Cypress to Douglas fir here either, super different heights and habits.

I stand by new science here ...
 
Re: \"Wind thinning\" on PNW conifers

[ QUOTE ]
...

Here's a quote for you: "While a dense crown 'sail' catches more wind, it also allows the tree to return to its initial position more slowly. If the sail suddenly becomes very porous, the damping motion is greatly reduced and the tree may flex back and forth very rapidly - often much faster than the root system can accept, thus creating a string of unusually strong pulsed forces acting on the roots."

Trees aren't umbrellas or boats.

[/ QUOTE ] I know trees are not umbrellas. Did you learn that in a class - LOL.

What I wrote still stands based on what I've seen here for over 3 decades. Back and forth motion is still pretty much swaying. Plus, wood is impressively strong: and why we use it to make floor joists and other stuff. Even fragments of a trunk are highly durable.

Be sure not to omit the 10% to 15% that I included in the context too.

[ QUOTE ]
"While a dense crown 'sail' catches more wind, it also allows the tree to return to its initial position more slowly. If the sail suddenly becomes very porous, the damping motion is greatly reduced and the tree may flex back and forth very rapidly - often much faster than the root system can accept, thus creating a string of unusually strong pulsed forces acting on the roots."

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Heard that before. Note the suddenly and how that contrasts with the moderate foliage removal I mentioned. Even if foliage was rapidly thinned, if the tree went over, that may be what that tree deserves. The top wouldn't be the real crux of the problem.

I went back and bold printed the 10% to 15% in my previous reply just to make sure that folks note it. Because my approach to trees is moderate changes.

Its surprising how many tree services in our area tend to change trees in big ways, rather than lightly tinkering with them. Often, the best approach is incremental changes while getting to learn the certain tree. Especially with some of the older or big established ones.
 
Re: \"Wind thinning\" on PNW conifers

[ QUOTE ]
"While a dense crown 'sail' catches more wind, it also allows the tree to return to its initial position more slowly. If the sail suddenly becomes very porous, the damping motion is greatly reduced and the tree may flex back and forth very rapidly - often much faster than the root system can accept, thus creating a string of unusually strong pulsed forces acting on the roots."

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This is such garbage. So the worst case scenario would then be a tree virtually stripped of all its limbs, it's going to just wiggle right out of the ground and fall back against the wind?

The real point to consider in this is whether or not a pruning practice can reduce the force of the wind on tree. Does spiral pruning? Sometimes, maybe, depends on the tree and the number of limbs removed as well as the shape and species. Some species/individuals maintain a habit that deforms under high winds to lower drag. Pruning that inhibits that ability is unwanted. Other species develop a habit that features few limbs, often short, sturdy and on the leeward side of the stem. Others have the characteristic of losing limbs during high winds, lowering drag immediately and then recouping the lost foliage with epicormic shoots.

Topping will always lower the wind force a tree experiences. It's rarely the preferred solution long term, but in some species and circumstances it is the best
method.

I think that end weight reduction is often a good solution if the tree and site/budget allow it. Pruning the fluff out of the middle probably does next to nothing except maybe appease a nervous homeowner.

I've pruned thousands of conifers in forestry settings, and it's a plain as the sun in the sky that reducing windsail causes trees to move less in the wind, and fewer pruned trees blow down than unpruned (proved in a study.)

Sean I think there's no doubt that there's value in pruning trees with the aim to reduce windsail. The tricky part is balancing the clients' needs with the trees' qualities.
 
Re: \"Wind thinning\" on PNW conifers

Hey Gord and MD, no need to get snarky, nice to meet you too.

G - So, sure you take all the foliage off a tree and it's going to stand there not catching wind but then you've just messed with the corresponding roots and it will likely topple in a few years or so, maybe less due to how fast it was stripped of tissue making abilities (all the roots die, tree can't stand up).

Topping, well that doesn't actually lower the wind force, it shortens the bending moment - ie. where on the trunk the tree will bend or break. Here we distinguish that from topping as crown reduction which often is very specific and prescriptive to the tree/species being pruned. Most topping practices are indiscriminate cutting of the tree trunk without much more crown management.

I think we were essentially saying the same thing, based on your second paragraph - can a pruning practice reduce force on trees? Maybe and in some instances, absolutely, but really trees been adapting to do manage environmental forces on their own for far longer than us. EWR seems to work on managing limbs breaking out better than thinning out entire branches.

MDV - Tree swaying is more like oscillation, moving around as well as just over in one direction.

Removing any foliage in one day from a mature DF is pretty much sudden defoliation but I agree if pruning is done, that 15 percent is acceptable.

The point of my comment was to indicate that when we talk about pruning, the rest of the tree is forgotten, especially what the effect is on the rooting area - something hard to study but not to be ignored.
 
Re: \"Wind thinning\" on PNW conifers

[ QUOTE ]
Hey Gord and MD, no need to get snarky, nice to meet you too.

...


MDV - Tree swaying is more like oscillation, moving around as well as just over in one direction.

...

The point of my comment was to indicate that when we talk about pruning, the rest of the tree is forgotten, especially what the effect is on the rooting area - something hard to study but not to be ignored.

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10% to 15% snarky is usually okay - LOL

Some others may forget about roots and other. I usually have the whole tree in mind. Hence pages like this:

Achilles Heel of Redwoods

At least the oscillation is not quite like flicking a metal car antennae, which would truly seem speedy. Although speeding up a video of a conifer could make it look that way. And maybe double-speed would be the most interesting way to review it.

Keeping the entire tree in mind is generally why I like to implement changes over a span of 3 to 5 years in stages. Most recently: one maple tree in Tigard, where I finally removed one limb on the sidewalk side, having waited 7 years for the right time.
 
Re: \"Wind thinning\" on PNW conifers

My turn to chime in here. MD Vaden is correct in pointing out that smaller amounts of affect on the tree are more appropriate.
However, the only science supporting wind thinning of NW Conifers is from Ken Byrne. The focus of his study is on thinning of the edge of forestry parcels to prevent windthrow within the stand. He also has a formula to find a factor of safety for a particular tree based on Species, CBH, Height of lowest Branch, canopy spread - measured in four quadrants of the tree height, and some other factors as well. His formula will give a very specific percentage of thinning for each quadrant, say 10% in the top, 5% in each of the lower three, in order to raise the factor of safety from a low 100% number up to perhaps 200%. (Just making these numbers up for illustration purposes) Very very prescriptive pruning based on an exhaustive measurement before pruning. Here is my big point, most trees are already strong enough and need now pruning to make them stronger. The ones that have a low factor of safety, often don't have much crown to play with, and thus not much pruning. Also, Ken's formula admittedly has a flaw in the calculations that does not factor in height or spread reductions.
Dr Kane and Gillman both have published studies that show effects of different pruning treatments. Gillman's shows conflicting results for thinning to be effective as reducing stem movement, Kane's wind drag study showed greater applied forces on pruned trees vs, unpruned. Both studies were on small angiosperms (birch, oak, horsechestnut) and on small numbers.

Simply put the science does not (yet) support wind thinning.

In practice, wind thinning can best be described as overpruning. I am in the Puget Sound and have yet to see a Douglas-fir after it was "wind thinned" "wind sailed" "spiral pruned" or whatever you want to call it that wasn't in worse shape than before. Most of the tree pruners thin heavily on the lower 2/3rds of the canopy leaving a dense upper crown. If you are going to argue for this practice, it would definitely need to go the other way - a little more off the top please.

And.... There is plenty of science that supports reduction in height and spread as very effective for reducing canopy loading.

OK, I am ready and wearing body armour (Canadian spelling out of respect for my esteemed colleagues up north). Bring it on!
wink.gif
 
Re: \"Wind thinning\" on PNW conifers

I have seen, and even done some fairly aggresive spiral pruning on Dougs for wind sail. Works fine, wind does not redirect itself toward an obstacle when there is a path through.

The problem, as I have experienced it, is when these thinned trees get that rare wet coastal snow loading. With fewer branches to share that load, branch failure is much more pronounced than with it's non-thinned neighbors, in extreme cases, "branch pancaking".

Which is why I maintain that an agressive spiral prune or windowing for view on a Doug fir WITHOUT EWR is setting the tree up for eventual branch failure.

Northind
 
Re: \"Wind thinning\" on PNW conifers

Agreed, Zebhaney, A little more of the top please!

You can't leave the top thick, you need to be climbing to 4" diameter trunk with a pole pruner/saw.

Northwind
 
Re: \"Wind thinning\" on PNW conifers

[ QUOTE ]


OK, I am ready and wearing body armour (Canadian spelling out of respect for my esteemed colleagues up north). Bring it on!
wink.gif


[/ QUOTE ]

Doubt you need the body armour. Glad you mentioned the studies too. I recalled those being posted like a year or two ago when this or a related topic came up.

Best I can tell, effort to help roots should often be the focus of attention, rather than the top.

One project that came to mind was a back yard of Shore Pines. Much shorter, but still fits this topic.

A lady had a pseudo-Japanese style landscape in the back, where about 30 ro 40 Shore Pines were planted in rectangular raised beds. about 15 of them leaned over during an Oregon wind storm. Rather than pulling them back, I pruned them to redirect, leaving the lower trunks with a lean. Then I asked the home owners to cull the irrigation system she was watering them with.

Not long after, when the trees were taller and bigger, another wind storm hit that was equally as strong if not stronger. The pine trees did not budge.
 
Re: \"Wind thinning\" on PNW conifers

Thanks to all; I'm hearing agreement on dose and the need to get to the tips and tops, all good.

"Gillman's shows conflicting results for thinning to be effective as reducing stem movement,"

In one study, thinning resulted in a 17 improvement and reduction in a 23 (i forget the units). He called the treatments statistically equivalent. I asked gosh that difference sure seems significant to me. He answered no they are too close; no difference.

I got a C in statistics and did not pursue the matter. Naybe now's the time; I firmly believe reduction in general is more effective than thinning. Good topic for debating over a brew or two.

"Ken's formula admittedly has a flaw in the calculations that does not factor in height or spread reductions."

Reminds me of folks condemning trees primarily based on shell wall thickness....apologies if that sounded snarky!
 
Re: \"Wind thinning\" on PNW conifers

The point I was trying to make is that if you are windthinning trees, unless you have a prescription for amount to be removed and where, you are guessing at best. Same for EWR. Take for example a typical Douglas-fir here. Average dimensions for an urban DF might be 30" DBH x 120'. That tree is stable without any modifications. Unless you have a reason to factor in poor soils or root zone issues, no pruning necessary. The range for normal extends well beyond this example. I saw a DF a couple months back, 95' x 18" with first branch at 50 feet. Very narrow but dense crown. Obviously am interior tree left behind during the construction of the home 20 years previous. Whipping around in the wind like crazy. Marginal at best, but has withstood both the December 14, 2006 storm and the January 20, 1993. As well as countless other less destructive storms. I am sure that if it were wind modified by a well meaning arb it would begin suffering from CADS.

Looked at another tree today, going to have Ken Byrne run the numbers on this tree through his windcalc model. Here is what I have to collect to get a prescriptive pruning regimen for this tree:
Height
DBH
Height to lowest live crown
height of surrounding trees
Prevailing wind direction
Soil makeup
slope
Average canopy spread in four vertical quadrants

Now we can get a baseline to analyze potential thinning or reduction.

If you are spiral pruning or wind thinning without an idea of where you are starting out, you are not helping trees. Maybe making customers fell better. Maybe making wood chips for mulch, but the trees are suffering. Trees move, why try to make them stop?
 
Re: \"Wind thinning\" on PNW conifers

In one study, thinning resulted in a 17 improvement and reduction in a 23 (i forget the units). He called the treatments statistically equivalent. I asked gosh that difference sure seems significant to me. He answered no they are too close; no difference.

In one study is the key wording here. And this was a study of 20 foot southern live oaks in full leaf with wind blowing in a straight line. I asked him if he had a way to simulate wind gusts. In a nutshell he replied yes, but that the data from anything beyond a straight line wind was too much for the models to handle.

Both his and Kane's studies are of too small a number of trees to make a cross species assumption that spiral pruning of conifers is effective.

I'll take you up on that beer, Guy. After I qualify!
 
Re: \"Wind thinning\" on PNW conifers

I think arborists get hung up on the rhetoric of topping in some cases - the best way to reduce the hazard level of an urban conifer in the PNW, especially a newly exposed tree, is to top it. Call it a reduction or whatever you want, but you're topping it. You come back 5 years later, and maybe remove it, but more than likely, re-top it, and move on. No big deal. I can see some of these statistical approaches to thinning working in forestry applications, like reducing windthrow on cutblock edges or something, or maybe on open grown trees that have new targets. I'm all ears though. .

I get more requests to thin conifer canopies for light than for wind. i.e. "I can't grow tomatoes in the back yard because the front yard row of firs blocks the sun. Can you thin them because I've heard topping is bad. . ." Not to de-rail the thread, but you've got to top the trees or move to a sunnier spot.

"(Canadian spelling out of respect for my esteemed colleagues up north)" - Hey Zeb, we all know you want to make the jump up here, spelling is a good start. If Randy Quaid can do it, so can you!
 
Re: \"Wind thinning\" on PNW conifers

"If you are spiral pruning or wind thinning without an idea of where you are starting out, you are not helping trees. Maybe making customers fell better. Maybe making wood chips for mulch, but the trees are suffering. Trees move, why try to make them stop?"

Zeb - Thinning usually starts with making the customer feel better. I don't get calls to help trees w/o a target below. It may be a good thing that peope are choosing an approach to their trees that does not include topping. If I thin a tree, I am not trying to keep it from moving... I am trying to keep it from falling over.
It is all a guess. It is not a bridge I can inspect and replace rusty bolts. Maybe I am just closer to Canada than you, but I am for thinning Firs... :)
 
Re: \"Wind thinning\" on PNW conifers

[ QUOTE ]
I think arborists get hung up on the rhetoric of topping in some cases - the best way to reduce the hazard level of an urban conifer in the PNW, especially a newly exposed tree, is to top it. Call it a reduction or whatever you want, but you're topping it. You come back 5 years later, and maybe remove it, but more than likely, re-top it, and move on. No big deal. I can see some of these statistical approaches to thinning working in forestry applications, like reducing windthrow on cutblock edges or something, or maybe on open grown trees that have new targets. I'm all ears though. .

I get more requests to thin conifer canopies for light than for wind. i.e. "I can't grow tomatoes in the back yard because the front yard row of firs blocks the sun. Can you thin them because I've heard topping is bad. . ." Not to de-rail the thread, but you've got to top the trees or move to a sunnier spot.

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Good post Jeff. I've worked for companies that sell thinning for light, what a waste of time and money.



Study of wind pruning effectiveness in forestry.

This study (relevant portion at p205) notes that crown modification reduced windthrow around logging cutblocks by an average of 40%. It also says that no increased mortality was noted for three years, then in some places a slight increase was noted in the fourth year. Probably not statistically significant.
 
Re: \"Wind thinning\" on PNW conifers

If someone wants more light for their yard, there are lots of options short of topping. This is where you would decide to what degree you are willing to affect the tree negatively to make a customer happy. In my case, I make sure I am getting paid to give my opinion, so I can feel free to give them an answer that does not require me to find material to pout through a wood chipper.

I'll say it again, if you think that science is behind windthinning trees, you are wrong. The studies do not point to generalized treatments for individual trees. Unless you can quantify some variables ahead of time and come up with a prescriptive approach based on a particular tree having a low factor of safety, you are "harming" the tree by reducing its ability to do what trees do best, that is, adjust to their surroundings.
 
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