| False
Rings and Missing Rings |
wad-@comcast.net |
| Nov
22, 2005 19:14 PST |
Neil
First let me say I know very little about dendrochronology.
Would the missing rings on one side of a tree represent previous
damage and healing over? Maybe another tree falls and clips the
side of the tree, the one side continues life as normal, the
other has no rings for a while until it heals over? How do trees
create extra rings, or lose them???? I am very interested in
your work.
Scott
|
| Re:
False
Rings and Missing Rings |
Neil
Pederson |
| Nov
24, 2005 07:38 PST |
Scott,
The missing rings could represent the lack of growth following
an
injury. Stress is the primary cause of missing rings, whether it
is
climate, insect outbreaks, fire, etc... A tree clipping another
and
knocking out most of the crown could cause a missing ring. A
study
from NH following the severe ice storm of the late-1990s,
however,
did not mention too much about missing rings. In fact, unless a
tree
lost a majority of its crown, growth recovered rapidly [<
5yrs] in
most species.
Missing rings occur occasionally following a fire; actually, a
grad
student at Lamont saw this in pitch pine from the NJ pine
barrens.
Several years were missing in some trees following fire. I am
not as
familiar with trees in fire-dominated systems in the eastern US
outside of longleaf pine, yet.
Most missing ring issues that I have first hand experience with
are
related to severe climatic conditions and insect outbreaks in
Russia
and Mongolia. During severe droughts or could periods, trees in
Russia and Mongolia at treeline can drop a few to several rings
over
the course of a decade. Insect outbreaks in Mongolia cause all
kinds
of growth and crossdating issues.
In the eastern US, missing rings seem to be more related to
overstory competition or drought. Red maple and the particular
cucumbertree I mentioned dropped rings [didn't form growth rings
consistently] when suppressed (I've nicknamed them zombie trees
for
now). Oak and hickory, because of their ring-porous nature,
rarely
drop rings.
False rings are triggered by an abrupt change in weather/climate
within one season. If I recall correctly, A.E. Douglas, the
founder
of modern dendrochronology, recognized this in the eastern US
during
the first half of the 1900s. Since then, Dave Stahle clearly
demonstrated false ring production in post oak in the midwestern
US
during years with 'false' springs. In this case, spring would
start
fairly normally and radial growth would commence. A late, severe
frost would injure or slow down growth in some trees. The return
to
'normal' growing conditions would trigger normal radial growth.
The classic example of a false ring is found in conifers. In
southwest GA, I found that a severe, early-season drought, say
in
June, followed by the commencement of 'normal' precipitation
would
produce false rings. Early-season drought sometimes triggers the
growth of latewood or summer wood. The return of regular rain
would
sometimes trigger production of earlywood [springwood]cells.
Resulting rings would look something like this:
http://www.geo.arizona.edu/palynology/geos462/tringtaxfalse.gif
Drought as a cause of false rings have been documented several
times; most notably by Douglas and Ricardo Villalba.
The false rings I've observed in diffuse porous trees
[Liriodendron,
Magnolia, Betula] are similar to the pattern of
earlywood-latewood-earlywood-latewood. In the case of diffuse
porous
trees, it appears to be a change in cell density and ring
structure.
I'm not sure what is exactly happening in these trees, but
crossdating verifies these 'false' rings. I'll send Ed a pic to
post
of a tulip-poplar false ring in the year 1910. The blue lines
show
true ring boundaries. The yellow oval encompasses part of the
false
growth band. This isn't the best image, but it conveys the
concept
fairly well. We have been fooled many times by trees from the
genera
listed above.
Bob Keeland and Joy Young showed that flooding can cause false
rings
in baldcypress, too.
Here is a decent page giving an overview of dendro and locally
absent and false rings.
http://www.geo.arizona.edu/palynology/geos462/09dendrochron.html
I don't think we are confusing 'barrier' zones or the healing of
wounds from tree rings. Most dendrochronologists determine rings
by
ring structure. Growth over wounds, calluses or compartmental
areas,
look very different from growth rings.
Happy Turkey Day all!
Neil
|
| Dendrochronology |
Neil Pederson |
| Nov 22, 2005 |
|
Ed,
Cookies are much better for figuring out false/missing rings than cores.
The best book for an intro to dendrochronology is "An Introduction to Tree-Ring Dating" by Stokes and Smiley, 1968:
http://www.uapress.arizona.edu/books/bid1007.htm
A couple other things I neglected to mention. Tulip, cucumber and sweet birch need to be sanded to at least 600 grit sand paper. A rough sanding will not do it. Ring boundaries can be difficult to define without complete sanding. You need to be able to see all the cells and terminal parenchyma...
Neil
|
| wood
types |
John
A. Keslick, Jr. |
| Nov
26, 2005 16:01 PST |
| Re:
Question for Neil |
Neil
Pederson |
| Nov
27, 2005 22:12 PST |
Hi Bob,
Looks like John gave you a good definition of
diffuse and semi-diffuse porous ring structure.
In case you need more information:
http://www.woodanatomy.ch/ident_key.html
How do I distinguish false rings in diffuse
porous wood? I key in on the terminal parenchyma.
The terminal parenchyma is the last line of cells
in the annual ring and signifies the end of a
true ring. It typically has a strikingly solid
and smooth boundary [no alliteration, intended],
though its appearance can differ by species. I
recall the tulip-poplar having a greenish-yellow
line at the end of growth ring. The image online
is ok, but not as good as what I see in the
microscope. Hmm, this is hard to put into words.
Diffuse porous species can have tricky
boundaries and, in some cases like in black gum
[black tupelo], have a nearly absent boundary on
the growth ring. So, we dendrochronologists use a
tool called crossdating. This is an objective
method of identifying the pattern of narrow and
wide rings in a species in one stand. Here is a
very good page on crossdating:
http://www.ltrr.arizona.edu/skeletonplot/introcrossdate.htm
In the birches, Liriodendron and Magnolia
species crossdating is crucial for determining
true and false rings. The image provided shows a
somewhat obvious false ring. There is a change in
cell density and size and what looks like a
terminal parenchyma. Some false rings in these
species are almost impossible to identify by
sight, even with significant experience; they
look very real. So, by identifying the pattern of
narrow and wide rings through time in a
population will help identify these rings. It
takes a lot of work, patience and, most
importantly, good sample preparation. These
species sometimes need to be sanded with 2400
grit sandpaper or finer.
The baldcypress situation you describe is the
result of not understanding dendrochronology or
the excellence of Dave Stahle. He is one of
dendrochronologists in the world. No doubt. His
work with baldcypress is amazing. It is a tough
specie to work with. Dave has mastered it.
Hope this helps a bit. It is hard to translate
this stuff sometimes. I'll keep working on it.
Please keep asking if I don't accomplish this
goal. I'll be out of town for a few days, so I
apologize in advance if there is another delay in
responding.
Neil
this feature
| |
Neil,
Excellent description. Thanks.
Dendrochronology is such a fascinating
science and we are incredibly lucky to have dendro
science so well
represented on the ENTS list. Just for those on the list
unfamiliar with
the terminology, could we ask you to explain what is
meant by diffuse
porous and how that feature helps you distinguish false
rings?
Your mention of baldcypress
forming false rings after flooding
reminded me of a silviculturist from Stephen F. Austin
State University
turned popular science writer who openly doubted in a
book that he wrote
that baldcypresses that others have declared to be 1000
years old or
older are anywhere near that old because of false rings.
If I recall, he
thought they were not much over 300, which would suggest
an average of 2
or more false rings per season. I didn't take the
professor's
proclamations very seriously. He spent most of his time
in a popular
guide to forest ecology that he wrote lobbying for
clearcutting and
making favorable comparisons between fire and
clearcutting.
Bob
|
|
| Re:
Question for Neil |
John
A. Keslick, Jr. |
| Nov
28, 2005 13:33 PST |
Re:
Question for NeilNeil
I have dissected a couple of trees (ring porous) that for many
years the tree only produced early or spring wood and then shut
down growth without forming late of summer wood. It was very
difficult to count the increments of growth. I have only seen
this survival feature once or twice. Any comments on this?
Sincerely,
John A. Keslick, Jr.
|
| using
stumps for dendrochronology work |
Robyn
Darbyshire |
| Dec
02, 2005 00:28 PST |
Neil may chime in here too - but stumps are commonly used for
dendrochronology work here in the west where the forests are
conifer-dominated (hardwood stumps tend to decay more rapidly) -
most
people tend to either do their counting in the field or collect
just a
small triangle from the pith to the bark to take to the lab. One
of the
most impressive wood collections I have seen is the wood storage
room at
the University of Arizona Tree Ring Lab - it's an experience I
won't
soon forget!
Also, Ed mentioned joining the tree ring mailing list - and for
anyone
else who joins that list, it is used to advertise the North
American
Dendrochronology Field Weeks. I highly recommend the
Dendrochronology
Field Weeks (BVP even led at project at the one that I
attended). They
have them in a different part of North America each year and
they are
great learning experiences. The best part is that you carry out
a
project from start to finish during the week and learn all of
the
techniques from some very knowledgeable people.
While it's not dendrochronology, one person I know came up with
an
interesting technique to count rings quickly on conifer stumps
in the
field (but it probably misses very narrow and/or missing rings).
The
method relies on the greater hardness of the latewood (vs. the
earlywood). They use wire brushes to clean off the stump and
scrape
away much of the earlywood. Then, then use a pencil tip and
start at
the bark or the pith and count the number of "bumps"
as they drag the
pencil tip across the stump radius. |
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