home reconstruction and damage to a sugar maple's root system

[pshea1]

We are contemplating a home remodeling task that will affect a 100 yr old sugar maple whose trunk is within 10 ' of our 200 year old house. The house sits right on a country road so the tree is also bound by a macadam roadway within 6 feet in the other direction. Our remodeling contractor would ideally like to dig a traditional 36" deep foundation through the root field of the tree. We feel this would kill the tree so we asked for alternatives other than removing the tree. He suggested pier construction where he would sink two 12-16" diam pillars into the root field to support the new addition. Our question is how much damage will these pillars cause to the tree? Is there anyway to minimize the damage by sheilding the pillars in some way? If we find a major root limb(6-10: diam") in the location of the pillar can it be severed without killing the tree? This tree is beautiful and has full healthy foilage. It has survived the encroachment of our home and the roadway for many years, is that signal that it could withstand one more "attack"? We know there are no easy answers to any of these questions but would be interested in anybodys opinion or experiences with similar situations. Thanks for your help.
Peter Shea, West Chester, PA

 

[Dan F]

The piers are probably the best answer.

Before beginning the project, contact a local arborist (make sure they are a certified or consulting arborist), and have them look at the tree. Without seeing the tree, it is hard to give specific instructions. The arborist should be able to give more specific instructions than I can. Have the arborist meet with the contractor to make sure all are on the same page.

In general though, what probably needs to be done is a general crown thinning (not topping!) before any work begins. Spread a very healthy layer of wood chips or mulch around the tree to cushion the soil from compaction. AT LEAST 6", preferably 12. Remove all but 3 or so inches after the project is done. DO NOT fertilize the tree, water only, and make sure it is an adequate amount.

Most likely, cutting one or two 6" diameter roots will not be very detrimental to the overall health of the tree. What will really hurt it is compaction of the soil. Stress to the contractor that only those people and machines that are ABSOLUTELY necessary be on the root zone of the tree. If machinery is needed, insist that the machine have dedicated rubber tracks (such as skidsteers), or the widest tires possible.

You may also want to check into insuring the tree, the arborist should be able to help in that respect.


Dan

 

[John Paul Sanborn]

The best thing to do is to get a ASCA Registerd Consulting Arborist to developing a tree preservation plan specific to the project, and to monitor the progrees with you to ensure that subcontractors do not encroach on the tree.

Some of the things that would be involved may be hand digging for the peirs and hand cutting th roots (or at least a chainsaw) we dont want an excavator or auger that will rip the roots up. This may cause a big jump in cost, but it sounds like the tree is worth it to you.

I would not fertilize either, but amend the soil with organic products that contain a wide spectrum of minor and trace elements, such as seaweed or fish emultions.

here is the ASCA siite to search for a RCA.
http://www.asca-consultants.org/directory/index.cfm?fuseaction=searchResults

 

[Tom Dunlap]

Dan,

You wrote: In general though, what probably needs to be done is a general crown thinning
(not topping!) before any work begins.

Dan you share your justification for "a general crown thinning"? What exactly to you mean by that diagnosis and what is involved?

Tom

 

[Kneejerk Bombas]

If the posts are set to prevent cutting the roots, then a structure is built over the root area, the soil underneath will dry up and no longer support root growth anyway.

I would not recommend any actions that cause stress to the tree, including trimming any live limbs, or burying the roots with 6-12" of chips.
Most people don't realize the anaerobic conditions that exist under a pile of woodchips. Although 12" of woodchips would help reduce compaction from a piece of equipment, is anyone going to put them there and remove them by hand?
If you can figure out how to put them down, I would strongly recommend removing them as soon as possible, as in hours or days, not weeks, or you may end up with an area of dead roots the size of the chip bed and beyond.

Besides giving off CO2 and blocking oxygen, the chips will suck up nitrogen like mad, another stress, so do a soil test to make sure you have the basic soil nutrients in check and add extra nitrogen in moderation if chips are to be used.

Once the construction starts, remember that soil piles cause anaerobic conditions just like chip piles, maybe even worse because it's weight will also cause compaction. Even if the pile is only temporary, the compaction is permanent, and it only take a short time to kill the roots below, from oxygen deprivation.

It may not be technically correct, but I like to think about mature trees as having a low ratio of leaves to total biomass, and young trees as having a high ratio. A young tree can withstand heavy pruning and come right back, where as a mature tree gets to a point where it has just enough leaves to sustain itself, and after that point it's health begins to spiral downward to death. Those few leaves, that low ratio, mean that removing a small percentage of a mature trees leaves can be very stressful, even causing it's eventual death.
Limbs and leave are not a liability to a tree, they are the source of the tree's food. Photosynthisis cannot take place on leaves and limbs once they get pushed through the chipper. That food is what will drive the growth on those roots which will be damaged and removed during the construction.

 

[Dan F]

Dan you share your justification for "a general crown thinning"? What exactly to you mean by that diagnosis and what is involved?

From what I remember from my classes (it has been a couple of years though), if you are going to be cutting roots, thinning of the crown needs to be done.

Plain and simple, if you are cutting roots, you are going to be affecting the ability of the tree to uptake water. Now, depending on how many piers need to be poured and what the spacing will be, thinning the crown may not be needed. If only 2 are going to be dug and poured, it probably won't be needed. Without seeing the sight, I can't say for sure.
My guess is that if the tree is indeed 100+ years old, it has never been touched as far as cleaning out dead limbs or eliminating crossing branches, etc. I'm not suggesting taking out 50% of the branches, what I'm talking about is removing around 10-15%. Enough to reduce the amount of water needed until the root system recovers, but not enough to adversely affect the health and shape of the tree.

As for not mulching around the tree, when did this thinking come about? If everything can be done by hand, do it, but you still should spread a good 3" around the tree. Foot traffic will compact the soil just as fast (or faster) than machine traffic. A Bobcat 864 with dedicated 18" rubber tracks that wieghs 6-7k pounds has a LOT less ground pressure than you or I ever will, unless we are laying down.

If removing the mulch in a timely manner is a concern, it can be written into someone's contract before any work is begun.

What keeps coming to my mind is the bank up in Chicago that added on a new section. They actually built (literally) around some trees that were ~24-36" DBH (or larger). The new section was set on piers and had a concrete floor 2-3' above ground. It's kind of hard to pour a pad that far above grade without some filler, right? Well as filler they brought in pea gravel, 2-3' worth. They poured the concrete on top of that and when it set up, the pea gravel was dug out BY HAND (this may not be politically correct) by midgets.

So, this new addition to the house is most likely do-able. I think we all agree that despite what has been said here and the differing opinions we might have, the one thing we can all agree on is that Mr. Shea needs to contact a consulting arborist before any work begins.


Dan

 

[John Paul Sanborn]

Originally posted by Mike Maas
If you can figure out how to put them down, I would strongly recommend removing them as soon as possible, as in hours or days, not weeks, or you may end up with an area of dead roots the size of the chip bed and beyond.

I guess this depends on how long the project lasts, some small studies have shown that raised grade changes dont significantly diminish gas exchange if soil compaction does not take place when making the change. One of the major mechinisms of soil gas exchange is water percolation. Though I would definatly agree with keeping the chip pile in place for as short of a time as possible, watering it regularly to reduce microbila heating.

Once the construction starts, remember that soil piles cause anaerobic conditions just like chip piles, maybe even worse because it's weight will also cause compaction.

This depends on how the pile is put in place and why I recomend having the RCA involved in the project from start to finnish. As for the soil moisture problem under the new addition, the RCA might suggest drip emittor, or like irrigation in the crawlspace

It may not be technically correct, but I like to think about mature trees as having a low ratio of leaves to total biomass, and young trees as having a high ratio.

It is true, Shigo phrases it as dynamic mass, that wich is photsynthetic and static mass, that which is supportive and conductive. Only that which is on the ouside of the tree can be productive, and as the bark thichens, the trunk and branches can no longer add to the net gain.

A young tree can withstand heavy pruning and come right back, where as a mature tree gets to a point where it has just enough leaves to sustain itself, and after that point it's health begins to spiral downward to death.

A healthy mature tree that puts out small incremental terminal growth is in a state of balance. It makes carbs to support itself and store for next years leaf growth. The can live in this state for years before senescnce sets in. Heavy thining can precipitate decline in such trees because that balance is lost.

Consider the Consulting Arborist as a advocate, or guardian ad litum for the tree.

 

[Greg]

Great info Mike, JPS!
As has been mentioned soil compaction is one of the greatest risks to the health of the tree. Being that construction will take place so close to the root zone I would build a wooden fence around the tree to protect the areas of root zone that you can. Those flimsy screen type fences typically used to protect trees are too often moved for a few hours to allow heavy equipment access to the work site, and then put back in place. A wooden fence is not as easily moved around, and may provide better protection while construction is underway.
Greg

 

[ksu_chainsaw]

Originally posted by Dan F
A Bobcat 864 with dedicated 18" rubber tracks that wieghs 6-7k pounds has a LOT less ground pressure than you or I ever will,

The bobcat may have less ground pressure since it is on tracks, but it does the same amount of compaction that a wheeled bobcat would do. The tracks just make the surface more compacted, and the wheels just have a vertical compaction area, which is narrower on the surface. both machines have the same amount of weight to compact the soil, so they both do the same amount of compaction, just in different areas. also, if the ground is wet, it won't make a difference if the bobcat is on tracks or not beacure the soil will compact easier when it is wet.

 

[Jay Banks]

My first question. Peter, you say that the tree has withstood the construction of the house and road. Have you had the tree looked over professionally? A consulting arborist should look at the tree and evaluate it to see if this next onslaught will be the last straw for the tree.

If the tree is in decline now, construction of this addition could finally collapse the tree's ability to recover.

 

[Dan F]

The bobcat may have less ground pressure since it is on tracks, but it does the same amount of compaction that a wheeled bobcat would do. The tracks just make the surface more compacted, and the wheels just have a vertical compaction area, which is narrower on the surface. both machines have the same amount of weight to compact the soil, so they both do the same amount of compaction, just in different areas. also, if the ground is wet, it won't make a difference if the bobcat is on tracks or not beacure the soil will compact easier when it is wet.

Have you ever run either one? From what you said, I doubt it.

First of all, the described 864 has (if I remember correctly) around 2.7 psi ground pressure (gp). You and I have around 7-8 psi gp on foot. The reason the tracked 'cat has less gp is because the same weight as the wheeled 'cat is spread out so much. I have no idea what the gp is of the wheeled 'cat is, but I am reasonably sure that it is much higher than 7-8 psi. Will the tracked 'cat compact the soil? Sure, but a LOT less than you or I will by walking on it. And a heck of a lot less than a wheeled 'cat.

I guess you might be right about the tracked 'cat doing more compaction than the wheeled 'cat when the soil is wet. The only reason though would be because the tracked 'cat will get anywhere you want it to go and the wheeled 'cat will get stuck shortly after getting off of pavement.

Case in point: I have personally had a tracked 864 in a ravine bottom to place a 4000 pound sandstone rock to be used as a bridge. The ravine bottom where the access was, was so wet that if you tried to walk across it, you would have sunk to your knees. The 864 floated across effortlessly. Hardly left a rut. Even used it to grade out ruts that other equipment left. You would be hard pressed to do that with a wheeled 'cat, even if it had 3' wide tires on it.

Second case in point (probably a better example): A large landscape project I was on about 2 years ago. We were there strictly for planting. Another contractor was hired to do the finish grading and seeding. This required him to get numerous tri-axles of topsoil brought in. Know what he used to spread it? An 864 with 18" tracks. Know what I could do with the soil after he graded it out and left tracks where he had been? I could move the dirt in his tracks with my foot. I KNOW that wouldn't have been possible with a wheeled 'cat. You sure couldn't even think about it with our John Deere 250, which weighed less than the 864.


Re-reading your post for the third time, I understand now what you are trying to say. However, there will not be the same amount of compaction between the two machines. I do agree however that they will impact the soil in different areas. The tracked skidsteer will impact the soil a lot less. Probably less than a riding lawnmower will when you mow, and that happens every week!

More food for thought.


Dan

 

[ksu_chainsaw]

Have you ever run either one? From what you said, I doubt it.

I have lived on a farm my entire life and operate my own farm currently. i have run just about every piece of equipment that is available for farm use.

The reason the tracked 'cat has less gp is because the same weight as the wheeled 'cat is spread out so much.

Yes i was trying to say something similar, i know that the ground pressure of the rubber track is less, but that does not change the amount of compaction that there is.

However, there will not be the same amount of compaction between the two machines

An example of this would be someone on snowshoes in deep powder snow. If you walk into that powdered snow in regular shoes(wheeled bobcat), you would sink in deeper than if you had a large snow shoe on(rubber-tracked bobcat).

In a labratory situation, the same amount of weight creates the same amount of compaction, it can either be concentrated or spread out over a wider area. The advantage to speading it out with a tracked viehicle is that you can go in and break up the compaction from a tracked viehicle easier than from a wheeled viehicle. (most people don't want a 3' subsoiler going through their yard, but they don't complain when a core aerator goes through the yard.)

tracked 'cat doing more compaction than the wheeled 'cat when the soil is wet.

both machines will do the same amount of compaction when the soil is wet, as the soil structure is weakened when it is wet.

charles

 

[ksu_chainsaw]

compaction

here is a link that explains what i was trying to a little better

http://ohioline.osu.edu/b301/301_2.html

hope this is clearer

Charles

 

[John Paul Sanborn]

The comparison between the PSI of a foot print and a track tread is a marketing red herring.

With foot traffic you can get a small single path, witth a 10000# machine you end up with 2 wide continuouse paths.

Yes I have made crews walk in one sinlge drag path to the shipper to reduce the "footprint" of our operation. I explain it as less raking for them.

Sometimes mechanizing the operation is the only way to meake it economicly feasable. Most of the time it causes more peobelms then it solves.

I remember a talk by Kim Coder, where he quoted a study where the did compaction analisys of a small truck. 5 passes over the same area casued 80% loss of soil porosity.

Compaction is a microscopic occurance, anything we do is on the macroscopic scale wich can only assis the worms and other macrobiota in separating the particles at the smaller level.

One interesting compaction remidiation theam I've seen is planting giant thistle in the area and deadheading the blooms so that the deep rooting can can help with water and gass excahnge and allow deeper biotic activity.

 

[Dan F]

I fully understand what you are trying to say, and I think you are right about the same amount of compaction. It is just that the compaction caused by a tracked skidsteer is a lot easier to fix! Run a core aerator over it and it ought to be about back to normal...

Can I use the excuse of lack of sleep caused by a 3-week-old daughter who is mandating when I can and can't sleep?


Dan

 

[ksu_chainsaw]

The comparison between the PSI of a foot print and a track tread is a marketing red herring.

It is just that the compaction caused by a tracked skidsteer is a lot easier to fix! Run a core aerator over it and it ought to be about back to normal...

i agree with the both of you, companies are out there to make more money. I spent this last semester in a soils class, and over half of the semester was talking about compaction, how to reduce it, and how to prevent it.

i agree that tracks are better, for the point that you have.

charles

 

[John Paul Sanborn]

Once again, the compaction is microscopic. The core aeration may help speed up the prosess some, but you still have the particles sticking together.

add in a topdress of good organics and some native worms and such and you will speed it up more.

I read some studies that show it takes 5-8 years for compacted soil to regain porosity.