Next part- How much root dieback can be expected when roots are cut, eg., for a trench? Do you expect (again, with the caveats of species, etc.) a general amount of dieback? One foot? Two feet? Does it change as you get closer to the tree (larger roots die back more)? Is there a maximum or minimum amount of dieback you allow for? Again, I'm looking for comments on generalities you use to quantify the damage.

Reply to post by Russ Carlson, on August 30, 1999 at 22:43:59:

On Dougfir in Pac.NW I expect to see decay progressing at about 1 ft. per year towards the origin, for any root over 3 inches diameter, culmninating in brown rot of the root crown/butt. About 50% of the time.

Reply to post by Russ Carlson, on August 30, 1999 at 22:43:59:

Based on what (little) I've read on this, in addition to species and environmental variables do you need to consider the nature of damage. The consumer literature pretty routinely no says to cleanly cut all roots (root prune) not to simply hack, break or rip them with an excavator. I beleive the first time I heard this was from Shigo. A number of sources have shown photos with cleanly cut roots, even, large ones, resprouting at the point of cut.

So, 1) is dieback a given or is it dependent on species, specimen vigor and treatment protocol and 2) as with tops must we distinguish die back-loss of function on the one hand from structural degradation on the other?

Without getting into the semantics of pathogens vs. saprophytes, do all root attacking fungi attack both function and structure or is it like a branch where health can be good but structure degraded?

Reply to post by Scott Cullen, on August 30, 1999 at 22:43:59:

All good and valid questions. And I sure don't have the answers.

A progressive rate of dieback would seem logical, but that would be species/vitality/environment/pathogen dependent.

As to root fungi, my understanding of those pathogens/saprophytes that I've studied a bit, is that a pathogen may or may not decay the wood, but the root will quickly decay of breached from the outside.

In many cases I've seen roots that were decayed from the bottom up. Once locked in place by soil, the root cannot continue to grow in diameter past a certain size. The lower tissues die, and decay starts working upward, at the same time new tissue continues to grow across the top of the root. The result is a cresent with decay beneath. This should probably be considered more often than it is in assessing high risk trees. But to the pint, what effect will this condition have on further diebak (extent and rate) on a root cut where there is only a cresent remaining?

Reply to post by Russ Carlson, on August 31, 1999 at 07:13:35:

"A progressive rate of dieback would seem logical, but that would be species/vitality/environment/pathogen dependent."

I'd re-word that: A progressive rate of dieback might logicallly follow from certain patterns of species/vitality/environment/pathogen/nature of damage.

Certainly we see continually progressive root dieback, as Peter describes. Perhaps we see progression to a point followed by stabilization. Perhaps we see regressivie dieback... an initial dieback in x period followed by less and less per period until stabilized. This would be complicated by continued root growth on non-injured roots.

I don't see why we might not also discover virtually no die back, just regrowth. I keep thinking of Shigo's slide of new root growth from a cleanly cut root. Is that root going to rot after or despite early resprouting? I don't know.

In the eary 70's I was pruning a fair sized elm next to a church. My sales manager remembered that in the early 50's when he was in the field his manager had him in a hole up to his head to bury dead men to guy the tree after extensive root cutting to accomodate an addition to the church. The guys were long gone. the tree survived and prospered both health and structure wise until DED got it in the late 70's. Did that tree experience progressive root dieback and decay?

Reply to post by Russ Carlson, on August 31, 1999 at 07:13:35:

I understand that, if you see root decay on top of a tree's roots, be extra careful because it's typically much worse on the bottom of the root.
Good useless information: Last year at ISA an.mt. I read of a church in England where an ancient yew stands. Archeologists found an archway built around the yew's roots by the Romans that serves as the church's foundation.

Reply to post by Peter Torres, on August 30, 1999 at 22:43:59:

So certain infections will cause continuing, progressive disease or decay?

I'm trying to get a feel for how much (little?) we understand the deterioration of root sturcture. Do root compartmentalize as does trunk and limb wood? We can make good estimates of decay in trunks, can we do the same for the roots yet?

Reply to post by Russ Carlson, on August 31, 1999 at 00:05:10:

Russ, when you say certain "infections" I think you mean certain cases (infecting organism - pathogen if you will, host species, host vigor, type of damage or impact, root treatment protocol & environmental conditions) rather than just the specific infecting organism. Is that correct?

Reply to post by Scott, on September 05, 1999 at 22:36:16:

Correct- by infections I meant the general complex of whatever organisms may be affecting/infecting the roots.

Reply to post by Russ Carlson, on August 31, 1999 at 00:05:10:

Yes roots compartmentalise and in general they
do so better than above ground wood. It wood seem that
they are better adapted to growing in environments often
more favourable to fungi.

Mark