ajaake said:
Will some or all of these trees die? What can I do to help them make it?
Over ninety percent of tree roots grow in the top 12" of soil. This is where the soil Oxygen is at a high enough level to support growth. If you put 12" or more fill over existing roots, you have essentially lowered the O2 level to a point that will kill all the roots.
How long can the fill be on the roots before they die? Smaller roots start dying immediately, while larger diameter roots can hang in there for weeks, even months.
Another problem with fill is compaction. Once you put huge loads on the surface of the soil, whether it's a pile of fill, or the machine that pushed it there, you compress the air spaces out of the existing topsoil. This limits the Oxygen that can make it into the soil.
The tree pictured, that has 6 feet of soil piled on it, will need to have the fill removed. Whatever equipment that is used needs to stay away from the critical root area.
Removing the bulk of the fill will be simple, an excavator could be parked 30 feet or so away and pull the soil off the roots. The problem is when you get near the original grade. A large piece of equipment will easily dig into the original grade and damage roots. When you get down to the last foot of fill, it needs to be removed by hand to avoid digging in. Don't be temped to run a bulldozer or bobcat over the roots to push away the last of the fill, use a scoop shovel and rake.
Once you're back to grade, you're still in hot water. The top soil is now compacted and it will not un-compact on its own. The best tool is an air spade, or similar device, along with an experienced arborist operating it.
He will use the tool to work the soil with a jet stream of air that displaces soil with minimal damage to roots. Depending on what he finds, he may need to spend several hours loosening soil and adding amendments, all while keeping the area moist.
Finally, he will top dress with compost and mulch.
Because the project is not finished, he will need to build a sturdy fence around this and any other trees that are being preserved. Not a little plastic fence either. To be respected, it will need to be something heavy duty, like a chain link fence with posts pounded several feet into the ground.
If you follow these steps, I'd give the tree better than 50% chance of survival.
To address the huge bark injuries, I'll first let you know that trees can survive such injuries, but how well they do is dependent on age of the tree, its health and vigor, growing conditions, and the species of tree.
When I see a photo of a tree with a large trunk injury, and then notice the entire root area is ripped up and/or buried by heavy construction equipment, I know it has a very dim future. The tree is spending all its energy repairing roots, there won't be much left over for the bark damage or other disease defense.
So again, the trees best chance is with a qualified arborist repairing the root and soil damage.
If you remove these trees, it only opens up the next row of trees to damage, so I'd be tempted to leave them stand as protection.
Even if soil is removed it will need aeration. Might want to check out armillaria as well. As far as wounds, made by heavy equipment?, compaction, they will need to be cleaned up and inspected as they are severe. Research cambium and its function and location. Is oak wilt an issue in your area? There is much research on tree paint and general consensus is that it is no good unless to mask the hormones scent the tree produces during attempt to close, in a oak wilt area so bugs will have harder time finding.
