Remediation and prevention of compacted soil near trees

[Es Anderson]

Greetings, All,

I have ten acres in the Seattle area, approximately three of which is pasture. I have a tractor (4500 lbs with loader and backhoe) that I need to be able to move around to various parts of the property, but doing so is difficult because there are enough trees (that I do not want to remove) that it is difficult to drive past them without infringing on their critical root zone. I have carefully plotted several paths that maximize the distance from the trees, however it still may be a bit too close to avoid damage. I'd like to learn how to remediate and/or mitigate -and possibly prevent- any such damage.

The paths I've plotted keep me out form under any trees (i.e., I am outside of the drip lines), but if calculating critical root zone as a 1' radius per 1" DBH my paths enter outer reaches of CRZ of several trees (infringing by perhaps 15-20% of the CRZ). The affected trees are western hemlocks, western red cedars, douglas-firs, and bigleaf maples.

If I am worrying needlessly, and this single path (quickly becoming a road) will not likely be problematic, please let me know. I will happily not worry about it if the consensus here is that damage will be limited. Or if some of those trees are unlikely to be bothered that would be useful to know, as I could alter my path to protect the more sensitive trees. If I do have cause for concern, how can I deal with the situation? Here are some ideas I have dreamed up:

I could plan my incursions into various parts of the property so as to do all the work that needs done in bursts of activity, then loosen the ground where the tractor has compacted soil near a tree with a broadfork (or etc), adding mulch and/or wood chips. This is obviously inconvenient but I will do it if need be; there are only a handful of trees affected, so it can be done. My thinking is that it would un-compact the soil and introduce both air and material that would serve to amend the soil. I also considered that perhaps adding 6" of wood chips occasionally might limit damage in future by serving as a sort of cushion. I don't know if this would work, however, as it is fairly heavy for a compact tractor.

What do y'all think?

PS - Someone please let me know if I've posted this in the wrong forum.

 

[greengreer]

Honestly I don't think a 4500lb tractor is going to put a ton of psi's into the soil.
Check out the isa info on construction site management. They usually recommend creating boundaries and putting thick layers of mulch or trips where the equipment will be.

 

[BC WetCoast]

I wouldn't worry too much about the Douglas fir and cedars. They can handle some compaction ok. The hemlocks can be a little more sensitive to root compaction. The bigleaf maples should be ok, if they are stessed they will sucker like crazy - a good indicator.

I would be observant of the hemlocks. From what I've seen, here in Vancouver, they haven't handled the last two dry summers well. If you are seeing them with a heavy cone crop and looking a little peaked, start saving your pennies cause they are on their way out and will have to be removed. If they die, they don't stay solid very long and you have to be wary of stem breakage.

I would put down a trail of mulch and just drive on that. Put down a 6" trail and the roots will barely notice the impact.

 

[Es Anderson]

I'll keep a close eye on them. The hemlocks in this area are prone to windfall due to shallow roots: If the lone hemlock tree near the trail starts looking bad I will likely cut it down proactively. I don't currently have any hemlock drying, so the wood will be a consolation if I lose one. There is one maple along the path that is already looking a little grim; one of the multiple trunks has some dead pieces up high. However that is on the other side of the tree from the path. The rest of the trees are in good shape, and I'm happy hear that it may not be a problem for them.

The tractor has dug a decent couple of little ruts in one place, so this is why I am concerned. I think this area is still a bit wet and that has aided the compaction. Is my broadfork plan unnecessarily ambitious?

Also, when you say mulch, do you mean plain wood chips? I hear a lot of people here (Seattle area) referring to mulch as a shredded/chipped wood and compost mixture, but that doesn't seem like it would do as much in terms of cushioning.

 

[ATH]

Staying off of the trail when the soil is wet would be step #1.

Use coarse wood chips...not the "fancy" triple ground stuff.

Is this a permanent road or temporary?

If it is less than 20% of the total rooting area for any given tree, as you said, and you are relatively far away from the trunk (you said outside of the dripline...) I wouldn't be too terribly concerned.

 

[Es Anderson]

It needs to be permanent for the moment, because it's the least detrimental access to 80% of my property available. If a tree goes somewhere I might be able to plan a different route, but for now I'll need to use it at least a few times a year. I could/will try to limit my travel so that I do everything that needs done down there at once rather than using it every week.

I thought the ground was dry, but after a few trips back and forth it started getting moist. I am new to the area and the ability of the land to retain moisture after a full week of sun is impressive to me. It is definitely less than 20" of the critical root zone. I suspect maybe 10-15%, and possibly less; given that the soil holds moisture so well, the trees may not have needed to root quite that far out. I'm going to look around for a truck load of wood chips. Thanks for that clarification.

 

[ropensaddle]

Wood chips,wood chips,wood chips I use them for everything even breakfast. One day wood chips will rule the world I'm convinced. Seriously they help greatly with soil compaction two fold cushioning is just one way but add in the under ground biology created and you end up with worm beds digging and churning the soil! Also areas that have been sown in wood chips just feel great on the feet. When I get home from my job out here and before I fly back I got to make more wood chips lol

 

[Es Anderson]

Sounds like I need to get some wood chips!

 

[ChoppyChoppy]

I've never given it any thought when working in the woods. Can't think of any tree we killed from packing down the dirt. Not sure the ground psi but the feller buncher is around 40 tons, the skidders are around 15 tons.

 

[ATH]

That is not a year round road though...right? Short term use every several years is drastically different than running the same area over and over and over.

Also noteworthy that he's already cut ruts. Ruts from a 4000LB tractor will cause more damage than a 40 ton machine on solid soil. I send the logging crew home when the ruts start showing up if they can't find a dryer part of the woods for the day...its just part of the deal.

 

[Es Anderson]

I would prefer it to be a year round road, but I have resigned myself to using it mainly in the summer. It gets very moist Nov-Apr, so it's probably best to avoid it, as it will not only damage the trees, but tear up the pasture. The ruts aren't bad yet. I stopped when I realized I was compacting the soil.

For the moment, I am planning to get a pile of wood chips to deploy as needed, then loosening the soil near those trees (only 6 of them that I get close to) once per year.

 

[ropensaddle]

I've never given it any thought when working in the woods. Can't think of any tree we killed from packing down the dirt. Not sure the ground psi but the feller buncher is around 40 tons, the skidders are around 15 tons.

Damage done takes at least two years to show up look at construction sites 2 years old and you will see dead trees caused by compaction and construction.

 

[ropensaddle]

I would prefer it to be a year round road, but I have resigned myself to using it mainly in the summer. It gets very moist Nov-Apr, so it's probably best to avoid it, as it will not only damage the trees, but tear up the pasture. The ruts aren't bad yet. I stopped when I realized I was compacting the soil.

For the moment, I am planning to get a pile of wood chips to deploy as needed, then loosening the soil near those trees (only 6 of them that I get close to) once per year.

What do you mean loosening the soil and with what ? The mulch bed and its worms will take care of any minimal compaction you have done. You can use a small auger bit in a grid watching out for roots but imo is un-necessary. I think your compaction will be localized not like you are continually circling the tree!

 

[Es Anderson]

I was going to loosen the soil manually, with a broadfork, but I must admit half of that plan was motivated by having an excuse to buy a broadfork. I've wanted one for a while, but it's hard to justify a $200 hand tool.

I think based on everybody's input it sounds like I need not worry, especially considering a new development in the situation: A family of moles or gophers has moved into the area and is digging up mounds right smack in the middle of the area I was worried most about. So... soil aeration is being accomplished with no effort on my part. I'm going to hold off on the wood chips until they move on, I think, and just try to limit trips as described above to times when conditions are right.

 

[BC WetCoast]

Oh for sure you NEED a broadfork. All the trees on your property will die immediately if you dont buy one.

 

[Es Anderson]

A year plus later, an update and another question.

I created a 40' strip of road where I have to roll over these trees. I piled up fallen limbs on either side to form a sort of curb to contain the wood chips, then I put a truckload of 'cedar play chips' (big, coarse chips) in between those edges. In the end, I suspect they are on average 6" deep. It seems to have worked pretty well... I don't know much about any compaction under all the chips, but they have stayed in place. I'll eventually need to add more chips, I suspect, and give the success of the operation I'm now looking to expand roads into other areas on my land.

One problem however: Wood chips are expensive! I cannot keep buying truckloads of chips to make roads and then having to buy more to top them off once in a while. Therefore, I am now looking into wood chippers and am hoping to get some advice. What I have found is that most wood chippers yield smaller chips than I purchased. The larger wood chips seem to be generated by the huge and expensive trailered chippers (which I cannot afford). I am presently sitting at a playground typing this, however... and note that the chips in use here are fairly small... maybe 1/4-1/2 inch by 2 inches (little sticks, really) --- they seem to make for a pretty good cushion!

I have a 35hp tractor for 30hp at the PTO. I also have a 2-wheeled tractor that has some chipper options, too. Woodmaxx has a fairly inexpensive model that is appealing at under $3k, but their rep indicates that most of their wood chips will be about pumpkin seed size. My questions, then: 1) How big of chips do you need? 2) Does anyone have thoughts on chippers in the $3k area? 3) Are chipper/shredders worth considering, or is the dual function going to mean that neither of them is done well?

Thanks again!