Kevin Smith's review "An organismal
view of dendrochronology" in Dendrochronologia mentions examples of
white rings that develop in poplar and birch in response to insect defoliation
or crown loss in winter storms.
I am not sure what would cause dark
rings in oak, but agree that it is something that is activating a compartmentalization
response and/or creating a barrier zone. Because these occurrences
are a complete, single growth ring that encompasses the whole tree, I suspect
an environmental factor.
Mike, you might check for a correlation
between the year of the ring and winter injury, late or early frost, an
extreme winter or summer temperature event, or maybe even flooding or insect
defoliation.
In response to Ed Barnard, I don't think
these rings indicate oak wilt, as infections in white oaks that survive
the first year generally show up as incomplete and spotty dark rings, with
additional partial dark rings in the same affected areas the following
year in surviving white oaks. Among oaks, red oaks die very quickly of
oak wilt, so you wouldn't see this long term survival.
On a different dendrochronology note:
If anyone is familiar with "islands"
of enclosed phloem in red or live oaks that apparently generate a
new layer of xylem-generating cambium after cambium injury please let me
know. I have found this response in several oak species after attack by
the cambium-feeding gold-spotted oak borer (GSOB), Agrilus coxalis, which
is now a problem pest in Southern California.
I am developing methods of back-dating
such enclosed phloem to reconstruct the history of the pest's residence
and spread within and among stands, and determine onset of tree mortality
after attacks. So I need to know other factors -- biotic or environmental
-- that may generate similar new layers of xylem external to patches of
enclosed phloem. I have enclosed pictures of the enclosed phloem and response
wood that develops after GSOB attack if inner phloem has not been killed
by very heavy attacks and/or pathogens associated with this decline.
Thanks!
Paul Zambino
><><><><><><><><><><><><><><><><><><><><><
Paul Zambino, Ph.D.
Plant Pathologist, Forest Health Protection
Southern California Shared Service Area
San Bernardino NF - SO
602 S. Tippecanoe
San Bernardino, CA 92408-3430
Ph: (909)382-2727 FAX: (909)383-5586
Cell: (909)215-0394
Email: pzambino@fs.fed.us
><><><><><><><><><><><><><><><><><><><><><
| "Barnard, Ed"
<barnare@doacs.state.fl.us>
Sent by: rg70300-forent-bounces@lists.iufro.org 11/21/2009 11:09 AM
|
|
Very interesting! I really have no idea, being for the most part a Pathologist in Florida dealing primarily with pines. As a pathologist, a thought comes to mind, but you should try to verify even the possibility of this with someone who deals with oak wilt (caused by Ceratocystis fagacearum). You are (as I understand it) in an area where this disease occurs, and red oaks are susceptible hosts, often displaying vascular staining or streaking. Most of the time infected red oaks die, but I do know that if infections of some vascular wilts are not lethal, recovery can occur, sometimes “compartmentalizing” the pathogen in interior vascular tissues – together with its associated vascular staining. Any chance that these trees might be oak wilt survivors? This could possibly be evaluated in a laboratory.
Ed
Any idea what would cause dark rings in
red oak logs as in the attached pictures?
The dark rings run the length of the logs.
So far this has been seen on a number of sites in 3 or 4 counties
in Minnesota. Not all red oak trees on a site have the dark rings.
My first guess is that it is a barrier zone
resulting from a wound or injury of some type. However it seems strange
that it forms a complete cylinder that reaches the ends of the logs. I
didn't see any logs where the dark ring only went part way around a log.
Also there were some logs that had obvious injuries with decay and
discoloration but these logs did not form rings or even have distinct barrier
zones going even part way around the log.
I've only looked at logs like this while
in the mill, not on the site where they were harvested. At first, the thought
was that these rings were the result of something happening 16 to 17 years
ago. This will take more investigation, but it looks to me like the
time period varies anywhere from 6 to 35 years. Also at this time
I can't say if the time period varies ibetween sites, or if the time period
varies from log to log on the same site.
Any suggestions would be appreciated.
Mike Albers
Forest Health Specialist
MN DNR-Forestry
1201 E. Hwy. # 2
Grand Rapids, MN 55744
(218)-327-4115_______________________________________________
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