I think it would probably kill it eventually. On one of the housing developments we maintain the builders did this to 2 mature ash trees and they are both dead now, i assume it would be the same for oaks.
my thoughts exactly
If it's mature then you could use some kind of raised collar to maintain an air space around the tree. I'd opt for a minimum of 30cm but access into this would be needed to stop soil/debris building up against the bark.
I do concur that death may result if you cover the nursery mark by too much.
The quickest killer is the combination of oxygen starvation of the roots and compaction due to the weight above them - so the roots basically start to rot and die back in the anaerobic environtment resulting. The compaction at the depth the roots are already at prevents new growth.
Can be a slow death, the tree may linger on for 3-5 years but will ultimatly die due to such bad practise.
The speed of death varies, most Quercus species will hang on for abit before dying, Birch go almost very quickly, while Willow and Poplar seem to drag and will often survive (Note how these willow and poplar also grow from cuttings easily).
To a lesser extent the trunk bark can rot and any open wounds would certainly be infected.
Great explanation David, thanks!!!!
As per other comments I have personally seen a v mature oak tree that was killed by landscapers who built up a bank approx 3/4 ft encompassing the tree. Beautiful old tree was killed for no reason and I hate to think what the tree surgeon's bill was, it was huge. Stupid.
Thanks and agree with all of you. Now I just have to convince my client that the the work I have been asked to assessthat has been done by another contractor has not only been done incorrectly but will result in a beautiful Oak tree dying. Any further supporting info would be much appreciated
Has it got a TPO on it? Is so, let the council Tree Officer convince the client!
I should also add - Think about the soil type, If it is clay, or quite dense and loamy the tree is almost certainly doomed, as the density of the soil will ensure compaction and suffocation of the roots quickly.
A very sandy loam or a peat may actually be light enough to avoid some compaction and be able to breath at least a bit, giving the tree some time, and it may possibly grow roots into the new soil over time, however you are talking in the 10+ year time frame for any recovery, during which time it will look, well, crap, and be so weak as to probably succumb to another ailment.
agree with David, and there is an added complication that if you decide to reduce the soil level back to what it was originally, you may encounter new tree roots have grown into the fill, so you will need to excavate with great care and judge when the damage to new roots outweighs the damage to the original roots that you are trying to remedy...