Genetic Potential and High Grading   Don Bertolette
  Mar 31, 2006 16:21 PST 

Bob/Lee-

It occured to me that this would be an easier question to answer, if the
forests had remained essentially undisturbed by man's influence over the
last several centuries...the biggest and best, and other superlatives, have
for the most part been removed. The remnants are not necessarily the best
representatives of the genetic potential.

-DonB
Re: From weather to trees - more questions for Lee   Edward Frank
  Mar 31, 2006 19:10 PST 

Don,

I am not Lee or Bob, but want to take a shot at your question anyway. I
don't think the removal of trees through timbering has changed the genetic
make-up of the forest in most areas and that the best representatives of the
genetic potential are still there. There are several arguments supporting
this hypothesis.

1) If the largest trees were removed from the forest, they do not
necessarily represent the greatest genetic potential. They may be in the
upper portion, but in a given set of trees the greatest potential for
maximum growth is most likely to be in one of the smaller trees not yet at
full height, because numerically they far out number the largest mature
trees. The largest trees simply represent those individuals that are the
largest at that time of harvesting, not necessarily the largest potential of
a given population.

2) Assuming the greatest potential was in the largest tree, and that tree
was removed. Chances are that if it were a superior tree, and had lived
long enough to express this potential, then it likely is the parent of many
of the smaller trees in its immediate vicinity. The genetic potential
therefore would still be preserved even if the maximum expression of that
potential were removed. To remove the genetic potential of an individual
from the gene pool, it must be removed before it reproduces and passes those
genes on to the next generation.

3) In North America, given the long natural life span of most trees,
people have not been logging these trees for long enough of a time to cause
a dramatic shift in the make up of the gene pool. To achieve significant
change in a population, as can be demonstrated in breeding attempts on
everything from dogs to roses, require multiple generations of selective
breeding. I don't think the haphazard, removal of big trees has made much
of an impact on the genetic make-up of the entire population in this short
of a time frame - one that spans only a generation or two.

4) Most of the tree removal has not been selective, but one in which all of
the trees, or all of the trees above a certain size were removed. There was
no selection, so the net result on the general population in these areas
would not result in a net shift in the gene pool in these areas.

Now with that being said, there are some arguments that would suggest a
potential for loss of the maximum potential genes from the gene pool.

1) If the trees that held exhibited the maximum potential for that species
were found in a limited area, removing all of the trees in that area due to
clear cutting and replanting with different species, urbanization, farming,
or other change in land use could remove these representatives from the gene
pool.

2) Invasive species or blights with a high mortality rate could easily
remove the individuals representing the maximum growth potential for that
species from the gene pool. Those that survive would represent the
individuals most resistant to the invasive species or blight, rather than
the individuals with the most growth potential.

3) Given global warming, the potential exists in the near future for the
loss of a number of species at the southern end of their range. In many
cases the southernmost specimens are the largest. These species being
larger in the southern portion of there range is likely a large part due to
climatic conditions, but there could be some genetic elements involved as
well. If the climate warms, these specimens may no longer be able to
reproduce, they may be out competed by other species moving northward, or
other effects can cause these southern representatives to die. If the
offspring of these individuals can not "migrate" northward faster than the
rate of change in the climate (given some leeway for the degree of
adaptability in that species), then the genetic potential and signature of
these specimens will be lost. Other related climatic changes could
adversely effect other populations, also with the result of losing their
genetic signature.

So, in summary, I don't believe the genetic potential of most species has
been affected by timbering operations. However other effects have in the
past, and could in the future shift the genetic characteristics of a tree
species.

Ed Frank
Re: From weather to trees - more questions for Lee   Bruce P. Allen
  Apr 01, 2006 05:34 PST 

Ed, Don,

If the fastest growing eastern white pine are the most susceptible
ozone (acid deposition or sulfur dioxide), the fastest growing gene
combinations could be removed from a population, particularly if
trees were affected before they produced seeds. Fragmented
populations would be more susceptible to the loss of genetic
diversity through highgrading. In terms of the duration of
highgrading, portions of the Northeast have been influenced for ~300
years. New Hampshire was only 10% forested in 1890 and most of the
remaining forest was in the White Mountains and areas north. Forests
south of Spruce-Fir went through a significant bottleneck. Similar
bottlenecks occurred in many areas of the Northeast. Has anyone seen
what Ohio looks like from the air? Tree ranges have been
significantly fragmented.

Enough rambling for now

Bruce
Re: From weather to trees - more questions for Lee   Don Bertolette
  Apr 01, 2006 07:26 PST 
Ed-
If you don't mind, I'll respond to your well thought out points below, in the body of your text, IN SMALL BOLD ITALICIZED CAPS...:>}
----- Original Message -----
From: "Edward Frank" <ed_f-@hotmail.com>;
To: <ENTST-@topica.com>;
Sent: Friday, March 31, 2006 8:10 PM
Subject: Re: From weather to trees - more questions for Lee


I am not Lee or Bob, but want to take a shot at your question anyway. 

I DIDN'T MEAN TO BE EXCLUSIVE, SHOOT AWAY!    

I don't think the removal of trees through timbering has changed the genetic make-up of the forest in most areas and that the best representatives of the
genetic potential are still there. There are several arguments supporting
this hypothesis.

1) If the largest trees were removed from the forest, they do not
necessarily represent the greatest genetic potential. They may be in the
upper portion, but in a given set of trees the greatest potential for
maximum growth is most likely to be in one of the smaller trees not yet at full height, because numerically they far out number the largest mature
trees. The largest trees simply represent those individuals that are the
largest at that time of harvesting, not necessarily the largest potential of
a given population. 

I SUPPOSE IT DEPENDS ON WHEN IN THE DEVELOPMENTAL STAGES OF A FOREST THAT YOU MAKE YOUR "ENTRY"...GOING BACK TO PRE-EUROPEAN SETTLEMENT FORESTS (I'M TRYING TO GET AT A TIME WHERE HUMAN TECHNOLOGY DIDN'T OVERWHELM THE FOREST'S ECOSYSTEM RESILIENCE), THE BIGGEST TREES WEREN'T JUST THE BIGGEST TREES THAT GREW IN THE FIRST COHORT RESPONDING TO A STAND LEVELLING DISTURBANCE. THESE TREES REPRESENTED THE SYNERGY THAT CAME FROM AN ENTIRE ECOSYSTEM'S INPUT, OVER A GREAT NUMBER OF GENERATIONS WHERE MAXIMUM POTENTIALS (IN THE CONTEXT OF A RELATIVELY STABLE ENVIRONMENT) WERE REACHED, PARTICULARLY THOSE THAT CONTRIBUTED TO WHAT I CALL ECOSYSTEM RESILIENCE. IF MAXIMUM TREE/FOREST HEIGHT EQUATED TO PROTECTION OF THE ECOSYSTEM THAT LIE BELOW THE PROTECTIVE 'UMBRELLA', THEN LET'S CALL HEIGHT/SIZE A CONTRIBUTER.

2) Assuming the greatest potential was in the largest tree, and that tree
was removed. Chances are that if it were a superior tree, and had lived
long enough to express this potential, then it likely is the parent of many
of the smaller trees in its immediate vicinity. 

IN AN UNDISTURBED (PRE-EUROPEAN SETTLEMENT), TREES WERE REMOVED AT RANDOM BY THE ELEMENTS, FROM INDIVIDUAL TREE FALL GAPS TO STAND-WIDE DISTURBANCE EVENTS, PROVIDING AN INCREDIBLY VARIABLE MOSAIC THAT EFFECTIVELY PROVIDED A VERY WIDE ARRAY OF GROWTH OPPORTUNITIES AND OVER TIME, AND OVER TIME, A WIDE EXPRESSION OF "GENETIC POTENTIAL". PERSISTENT SELECTION FOR THE TALLEST STRAIGHTEST BOLES OVER SEVERAL GENERATIONS OF THESE INDIVIDUALS FROM THE GENE POOL WOULDN'T ELIMINATE "TALLNESS" GENES, BUT IT WOULD CERTAINLY EFFECT THEM...INITIAL LOGGING PRACTICES WERE TECHNOLOGICALLY LIMITED AND FORCED AN ECONOMY OF EFFORT...LOGGERS WOULD FIRST TAKE THE MOST VALUABLE INDIVIDUALS (READ LARGE/TALL), AND OVER TIME REMOVE SUCCESSIVELY LESS PROFIT-LADEN TREES

The genetic potential
therefore would still be preserved even if the maximum expression of that
potential were removed. 

I'M NOT SURE I WOULD USE THE WORD PRESERVED HERE, AS IT IMPLIES UNDISTURBED, UNIMPACTED 

To remove the genetic potential of an individual
from the gene pool, it must be removed before it reproduces and passes those
genes on to the next generation.

REPRODUCTION IN 'TREE FALL GAP' SCENARIOS IS INCREDIBLY COMPLEX AND VARIABLE, WITH LIKELYHOOD OF SAME SPECIES REPRODUCTION NOT AS LIKELY AS SAY, SPECIES MORE ADAPTED TO 'PIONEERING'.

3) In North America, given the long natural life span of most trees,
people have not been logging these trees for long enough of a time to cause
a dramatic shift in the make up of the gene pool. To achieve significant
change in a population, as can be demonstrated in breeding attempts on
everything from dogs to roses, require multiple generations of selective
breeding. I don't think the haphazard, removal of big trees has made much
of an impact on the genetic make-up of the entire population in this short
of a time frame - one that spans only a generation or two. 

THIS WOULD BE MORE COMPELLING IF THE REMOVAL OF BIG TREES WERE HAPHAZARD...FOR A GREAT NUMBER OF REASONS, REMOVAL OF BIG TREES WAS SYSTEMATIC FROM EARLY LOGGING HISTORY, THROUGH TODAY WHERE SUCH REMOVAL IS VERY SYTEMATIC...IS THREE HUNDRED YEARS OF HIGH-GRADING EFFECTIVE IN REDUCING GENETIC POTENTIAL? I THINK THE JURY IS IN ON THIS ONE.

4) Most of the tree removal has not been selective, but one in which all of
the trees, or all of the trees above a certain size were removed. There was
no selection, so the net result on the general population in these areas
would not result in a net shift in the gene pool in these areas.

OF COURSE, BY NOW YOU REALIZE THAT WE ARE VERY MUCH IN DISAGREEMENT ON HOW SELECTIVE TREE REMOVAL HAS BEEN HISTORICALLY...YOUR COMMENT ABOUT 'TREES ABOVE A CERTAIN SIZE BEING REMOVED' IS PRACTICALLY THE DEFINITION OF SELECTIVE REMOVAL...ADD IN SPECIES, GRADE, EASE OF ACCESS AND YOU COVER MUCH OF THE SPECTRUM OF SELECTIVITY.

Now with that being said, there are some arguments that would suggest a
potential for loss of the maximum potential genes from the gene pool.

I GUESS HERE, YOU'RE PLAYING DEVIL'S ADVOCATE WITH YOURSELF?

1) If the trees that held exhibited the maximum potential for that species
were found in a limited area, removing all of the trees in that area due to
clear cutting and replanting with different species, urbanization, farming,
or other change in land use could remove these representatives from the gene
pool. 

YOUR MENTION OF 'FOUND IN A LIMITED AREA' I THINK GETS AT THE POTENTIAL REACHED AS A RESULT OF QUALITIES IN THE ECOSYSTEM THAT ARE ENVIRONMENTAL AS OPPOSED TO GENETIC...MANY TIMES, THAT IS ALL THAT IS LEFT TO BE DISCOVERED, AND WE RUN THE RISK OF EXTRAPOLATING THAT ENVIRONMENTAL POTENTIAL TO THE SPECIES WIDER RANGE, PERHAPS INCORRECTLY?

2) Invasive species or blights with a high mortality rate could easily
remove the individuals representing the maximum growth potential for that
species from the gene pool. Those that survive would represent the
individuals most resistant to the invasive species or blight, rather than
the individuals with the most growth potential.

EVOLUTIONARY!

3) Given global warming, the potential exists in the near future for the
loss of a number of species at the southern end of their range. 

I DON'T KNOW IF THE JURY IS IN ON THIS...GRADIENT ANALYSIS WOULD SUGGEST THAT ALL RANGE EXTREMES WOULD BE MORE SENSITIVE TO ENVIRONMENTAL CHANGE...IT'S MY UNDERSTANDING THAT WE'RE GOING INTO GLOBAL CLIMATE CHANGE...AND THE RESPONSE (IN A GAIA-LIKE WAY) WON'T FOR ANY GIVEN GEOGRAPHIC POINT BE WARMING PERSE, BUT CHANGE...SOME AREAS WILL BE PREDISPOSED TO BE COOLER OR WARMER OR MORE VARIABLE, OR LESS VARIABLE, DEPENDENT ON THE HOST OF INFLUENCES THAT SURROUND THAT GIVEN POINT. 

In many
cases the southernmost specimens are the largest. These species being larger in the southern portion of there range is likely a large part due to
climatic conditions, but there could be some genetic elements involved as well. If the climate warms, these specimens may no longer be able to
reproduce, they may be out competed by other species moving northward, or other effects can cause these southern representatives to die. If the
offspring of these individuals can not "migrate" northward faster than the
rate of change in the climate (given some leeway for the degree of
adaptability in that species), then the genetic potential and signature of
these specimens will be lost. Other related climatic changes could
adversely effect other populations, also with the result of losing their
genetic signature. 

I THINK THAT ALL THESE THINGS MAY BE TRUE, HARD NOT TO SPECULATE...

So, in summary, I don't believe the genetic potential of most species has
been affected by timbering operations. However other effects have in the
past, and could in the future shift the genetic characteristics of a tree
species.

I THINK WE CAN AGREE TO DISAGREE...I'D BE SURPRISED IF OUR POST/REPOST DIDN'T GENERATE FURTHER DISCUSSION...;>}
-DON
Ed Frank

Re: From weather to trees - more questions for Lee   Edward Frank
  Apr 02, 2006 03:26 PDT 
Don,

I have some comments to make in response, particularly with regard to the jury, but will wait until others have had a chance to comment. I was using hieght as an example of potential, not meaning to imply it was the only measure of genetic potential to be consider. It is easier to discuss one specific first before moving on to a general case.

Ed
RE: From weather to trees - more questions for Lee   Edward Frank
  Apr 03, 2006 15:47 PDT 

Don and ENTS,

There are a couple of fallacies, in my opinion, in the arguments you
present. First is the assumption that the largest trees present at a
particular time embody the genetic potential of the species. The second
is that genetic shifts that affect the height structure of the general
forest population are also applicable to individual trees. I will
address these two points first then some of the other comments made in
your reply. I agree with many of your observations, but donít feel they
impact the discussion. I understand you are talking about a mixture of
characteristics that represent ecosystem resilience, but for simplicity
in phrasing the arguments I will talk about height, but the same
arguments would apply to other genetic characteristics or combinations
of characteristics.

I initially was talking about an undisturbed forest prior to European
settlement. A mature forest has trees of a variety of ages as canopy
openings occur and refill in a dynamic process. Stand leveling
processes also occur over larger areas. The recovery process of the
forest from these small and large scale disturbances are somewhat
different . I agree with your comments about synergy, ecosystem
resilience, but donít see how the Ēpoint of entryĒ relates to any of the
arguments. Again I will speak on height - as one factor of the larger
concept of ecosystem resilience.

The largest trees obviously represent the portion of the total
population of a species that have the potential to reach great height,
given the fact they have succeeded in doing so. There are a number of
factors besides genetics that affect whether an individual tree reaches
itís maximum potential: environment, temperature, light availability,
water availability, stand history, stand density, the presence of
insects, animals, and a variety of other factors. If everything goes
right for a tree with a genetic potential for height, then that tree
will grow tall. If things are not ideal for another tree with the same
potential, it will not grow as tall, or may not even survive. But the
genetic potential for height is present in the second shorter tree.
Offspring from this tree which receive the ďgeneĒ for height will have
the same potential for reaching a great height as the offspring of the
tree that actually achieved the greater height. There is no validity in
the Lamarckian concept of passing acquired characteristics on to the
next generation.

The largest tree of the species in a forest was not always the largest.
It started as a seedling, then sapling, and all the age and size stages
until reaching itís present size. That brings up the question of
whether there are other trees in the forest that are not yet fully
mature that could potentially equal or exceed the size of the current
largest tree, and what would be the distribution of trees with this
potential among the general population? Assuming that 5% of the
population of trees have the potential to reach great height, the
distribution of that potential can be determined among the total
population. The chance of a particular tree being among that 5% would
be equally distributed among all age ranges. The population of older
trees with the potential to reach that height is 5%, the mature trees
have a 5% potential, saplings have a 5% potential, and seedlings have a
5% potential. Now look at the numbers of the tree themselves. There
are fewer old trees than younger trees. For each successively younger
set of trees, there are greater numbers of individuals, and therefore
greater numbers of trees with potential for great height. There are
more mature trees than old trees, more saplings than mature trees, and
more seedlings than sapling. Numerically the seedlings have far more
trees with the genetic potential to reach great height than any other
age category. For the older trees which represent only a small
percentage of all the trees overall with the great height potential, and
even smaller amount actually achieve their optimum height potential.
What does this mean? It means that the oldest and biggest trees in the
forest represent only a small percentage of the genetic potential for
height of all the trees in the system. In fact given the relative
numbers, there is only a miniscule chance that the current tallest tree
represents the maximum potential for height in the forest at any one
time.

If the biggest trees were removed, only small percentage of the
population of trees with the potential for great height would be gone
from the stand. The removal of these tallest specimens for a thousand
generations would not remove the genetic potential from the general
population. If the genetic potential of this tree was removed by
logging, chances are that if it were a superior tree, and had lived long
enough to express this potential, then it likely is the parent of many
of the smaller trees in its immediate vicinity. The genetic potential
therefore would still be present in the population, even if the large
tree itself were removed. To remove the genetic potential of an
individual from the gene pool, it must be removed before it reproduces
and passes those genes on to the next generation.

Don made some comments about the trees filling in the canopy opening
after the removal of the big tree. Some of the offspring bearing the
genetic marks of the parent large tree may be adversely affected by
quick growing pioneer species filling the opening. At other times the
opening might occur at a point where it would free the younger tree to
grow rapidly into the new canopy opening. I think this is a wash. But
the effects on the gene pool of a tree is not necessarily limited to the
immediate vicinity of the big tree. Tree production is commonly a
sexual process. I know of young chestnut trees actively producing nuts,
where the individuals are separated by others of their species by miles.
Pollen can carry a long way.   Seeds can be distributed by birds,
animals, wind, water, and gravity for long distances. So a canopy
opening, if it did have an adverse effect on tree sprouts in the
immediate vicinity, would not affect all of the trees that could have
been descended from the large tree.

I donít believe that selective removal of the tall specimens would
result in a significant shift in the genetic pool of the forest given
the small percentage of the total population bearing the same genetic
potential for height. Short of removal of almost all of the specimens
of a species in a given area, removal of a specific genetic potential
from the population is difficult.

Suppose that the majority of the trees bearing one genetic trait were
somehow removed from the population, how would this be expressed in the
forest itself? Again I will speak of height for simplicity of
expression. If most of the height genes were removed from the
population of a species, that would affect height structure of the next
generation of trees. With fewer numbers of the height gene in the
population, fewer trees would have both this gene and grow in areas
environmentally conducive to growing trees of great height. The average
height of the trees in the forest overall would be affected downward.
The variability of the heights would be unchanged. The trees with the
height gene would still have the potential to grow as tall as they did
before, and some percentage of them would still do so. These trees
would still pass on their genetic traits to their offspring. So the
genetic potential of trees to grow a certain height would be unchanged.
The height structure of the forest would change, but not that of
individual trees. Just because the forest was on average 20% shorter
would not mean that the tallest trees in the forest would be any shorter
than they were before, just fewer in number.

I donít think that Don and I really disagree about whether or not the
removal of trees in early European settlement times was systematic or
haphazard. I believe it is a simple disagreement over terminology.

I was not playing Devilís advocate with myself. I was trying to answer
a question and look at different aspects of that question. In more
complex issues not every factor pulls the same direction. The question
is which of these multiple factors dominates.

  Don writes: IS THREE HUNDRED YEARS OF HIGH-GRADING EFFECTIVE IN
REDUCING GENETIC POTENTIAL? I THINK THE JURY IS IN ON THIS ONE.

I donít think so, except in conjunction with other process. Selective
logging of the best specimens in and of itself over this limited time
frame would not reduce the genetic potential of a population. In my
opinion, if the jury is in on this one, the jury is wrong.

One last elaboration concerning my comments on southern trees being
taller. I guess I did not express myself well, or complete my thoughts.
In a given population across its entire range, there are genetic
variations. In different areas natural selection may have concentrated
certain of these genetic traits in greater numbers. If height were
selected for by environmental factorsÖ.

Ed Frank

Genetic Potential- High Grading   Edward Frank
  Apr 07, 2006 19:13 PDT 

Don,

Sorry it looks like nobody wants to debate genetic potential with us. It is really hard to remove a genetic trait from a population. First the trait needs to be strongly linked to a particular gene. There needs to be an aggressive attempt to remove the gene from the population, including all specimens, of all sizes, and whether the gene is actively expressed or not. These trees in our hypothetical forest may have been selectively cut in terms of timber production, but I don't believe they were selectively cut in terms of genetic characteristics. Even if most of the trees of a particular species were removed from the ecosystem, those trees remaining should have much of the genetic potential of the original population. Of course there are caveats - a particular subset of the population holding a particular genetic sequence may be completely eliminated, without eliminating the entire population, but in general terms, I don't think high-grading is removing genetic potential. There may very well be some change in the relative abundance of a particular gene within the population. For example, IF there was a specific gene linked to height. Selectively removing all the trees above a certain height would could decrease the frequency of that gene in the population - but to what extent? The actual mechanism for the change would be those trees whose maximum height was less than the specified cutting height would increase in frequency, while all other populations would decrease. This would be small increase of a small percentage of a small number of trees, and I don't believe the change in most cases would be significant.   I just don't see any mechanism for dramatically altering the make-up of these forest stands.

Why then does the regrown forest after high grading have such poor quality trees? Lee Frelich would be the one to give the best explanation as that is one of his areas of research. I can speculate on the issue. When these forests are high-graded there is stress put on those trees that are left behind and those that regrow in this first generation to repopulate. Small trees are broken and injured. Trees with multiple trunks grow from stump sprouts. Trees are subject to different light, and temperature regimes than those grown from an opening in the forest. The soil and soil water capacity can be affected. Invasive species can be introduced.   This stress makes the trees more susceptible to disease and insects. The seedlings and saplings are subject to browse damage from spiking populations of deer and other herbivores. Stand density in the initial growth period may be high. All of these things and others combine to make it difficult for the first generation after high-grading to grow well. A tree's form shows adaptations to the physical conditions under which it is grown. A tree in an open field tends to grow wide spreading branches and not develop great height. In a forest setting a tree may grow rapidly taller to reach a small opening in the canopy. These represent variability in form within each trees genetic make-up. What I am suggesting is that given the environmental conditions after high-grading, these trees are likely just doing the best they can under the circumstances. I don't believe it is a loss of genetic potential that has resulted in the poor timber quality, rather environmental conditions. I will just need to wait a couple hundred years to see what some of these high-graded forests, if they survive, look like after a second generation of trees grow. I would anticipate they would be of similar quality to the forest prior to the initial timbering operations.

I am interested in alternative or additional arguments relative to what I have suggested above.

Ed Frank
Re: Genetic Potential- High Grading   Don Bertolette
  Apr 07, 2006 20:11 PDT 

Ed-
I think part of our disparate views come from different perceptions of the
history of Eastern forests...it's my impression that most everywhere has
been repeatedly logged, not in the western clearcut model, but in the many
small loggers going in and cutting selectively the most
cost/energy-effective trees that the market suggests yields the highest
profit. Year after year, century after century...

I'd also like to hear fellow ENTS members weigh in on this, as my
perceptions of Eastern forest logging history come from my three years at
UMASS...

-DonB

Re: Genetic Potential- High Grading   Lee Frelich
  Apr 08, 2006 13:14 PDT 

Ed, Don:

You are both partly right. Few genes are removed from a population by
highgrading. Tree populations have to go through an incredibly small
bottleneck to eliminate genes. However, this varies among species. Some
species are hexaploids and it is almost impossible to cause them to lose
genes. Other species lose genes more easily. With the type of highgrading
practiced in New England it would take several centuries to cause
populations of most species to lose genes.

Although few genes are removed at the population level, highgrading can
cause a high proportion of the next generation to have certain genes
absent, even though those genes are still present in a few individuals.
Since the stand growth characteristics are a summation of all the
individuals, this can have an impact on stand growth.

In addition, in certain circumstances trees do go through very tiny
bottlenecks. In some areas of the Midwest whole townships were logged and
burned and the entire forest over many square miles was reseeded by a
handful of self-pollinated parent trees, leading to genetic impoverishment.
In other places dozens of parent trees were able to cross pollinate each
other after logging and genetically healthy populations have recovered
(this is the case in most areas).

Loss of nutrients and mycorrhizas, etc., after an area has been farmed can
also affect tree growth in some second-growth stands, and the trees can
look stunted even if the population is genetically healthy.

Overall, I would say that looking at the current landscape from the
perspective of genetic health, its a complex mosaic of forests that are
genetically healthy, those with altered gene frequency among individuals in
the population, those that are genetically impoverished, and those that
have degraded site conditions that are hard to tell from a genetically
impoverished population without an expensive study. I have not seen any
studies that put all these conditions in perspective across the landscape.

Lee

Re: Genetic Potential- High Grading   Michele Wilson
  Apr 13, 2006 06:46 PDT 


I am interested in discussing genetic potential, a matter I've been dealing
with since at least 1975, but right now I simply don't have time!
Michele Wilson
Re: Genetic Potential- High Grading   Fores-@aol.com
  Apr 13, 2006 06:58 PDT 
Ed:

I do not have much time for a debate on the issue but I am convinced that
high grading is harming the genetic potential of the forest, reducing diversity
and hindering overall productivity and forest health. I get to visit
degraded woodlands on a daily basis and I have reached the point where it has
become easier to notice a healthy and undegraded woods than a "normal"
patch of woods. This will be the case especially when visiting a patch of
woods where the trees are older than the chestnut blight....1925 or about 80
years old

With the timber industry moving out of forest ownership and management and
the entire harvest process being dominated by real estate speculators and trust
funds there is a rapidly escalating interest in deferring long term forest
health, productivity and management costs and concerns to future owners....the
numbers can really work well if you stick to a 7 to 10 year ownership
horizon like most of the investment funds and as long as there will be willing
buyers...who's to notice.

Russ
Re: Genetic Potential- High Grading   Fores-@aol.com
  Apr 13, 2006 07:10 PDT 
Ed:

I just finished inventorying a property in Lewis County, WV where about half
the property was unlogged and half of the place was severely high graded. A
consulting forester had marked everything down to 12" DBH (except hickory,
black gum and beech. For commercially desirable species like red oak, black
oak, sugar maple and yellow poplar the foresters marked the trees even
smaller. The timber company was unable to finish their contract but I have some
excellent information on the condition of the pre cut and post cut portions of
the woods as much of the land the foresters marked was never harvested.


In a majority of the land, five to seven years after the commercial clearcut
was done by the consultants there is limited regeneration because of a very
high deer population and all of the skid trails and roads have developed into
a carpet of Microstegium with only scattered spice bush sprouts poking
through.

In a forest that formerly supported a stand that was 30% red oak and 60%
yellow poplar that now has an overstory that is 80% hickory and black gum and
20% beech, red maple and cull white oak and a forest floor with nearly a 100%
cover of Japanese stiltgrass the future does not look bright.

Russ
Re: Genetic Potential- High Grading   Joshua Kelly
  Apr 13, 2006 08:19 PDT 

Russ,

Chilling description of the combined effecunsustainable logging and
Microstegium viminium. Below is a piece on Microstegium that I recieved
from a friend a few days ago.

Josh

Though you all might enjoy this.



Some of you professionals are probably already aware of this but for the
rest of the team, Southeastern Biology, April 2006 abstracts a paper by
Patrice Cole, UT, Knoxville- The non-native grass, Microstegium vimineum,
suppresses woody seedling recruitment in understory habitat as follows:

"The non-native grass, Microstegium vimineum, is established throughout the
Eastern United States. The open understory characteristic of forested
habitats dominated by M. vimineum suggests that this grass may be
suppressing woody seedling recruitment. As mature trees in these habitats
die, the absence of woody seedlings and saplings could result in gaps in
forest cover dominated by M. vimineum. Although shade-tolerant, M. vimineum
thrives in high light environments. Seed dispersal would likely enlarge the
gap in forest cover and create additional populations farther into
surrounding understory habitat. In this scenario, large areas of forest
might be converted to open grassland dominated by this non-native species.

I conducted a 2-year field experiment to test the hypothesis that M.
vimineum suppresses woody seedling recruitment by reducing light at the soil
surface. Fifteen 1-m2 plots were established iin an understory site
dominated by M. vimineum and all plants were removed from 10 plots. Seeds
of 5 native tree species were planted into each of the 15 plots. Five of
the plots from which M. vimineum had been removed were covered with shade
cloth of a density that resulted in light reduction comparable to that
beneath the intact M. vimineum. Seedling emergence and survival were
monitored through two growing seasons. Seedling survival and the number and
biomass of other woody and herbaceous species were greater in the in the
unshaded removal plots than in the other plots.

These findings indicate an urgent need for control of M. vimineum to avoid
significant loss of forested ecosystems."

So, another nomination for public enemy number one. And thanks to Dr. Jim
Perry for sharing.
Re: Genetic Potential- High Grading   Edward Frank
  Apr 13, 2006 18:00 PDT 
Russ and Michele,

I am not arguing that the forests after high grading are not changed. But a more reasonable comparison should be made after a second generation of trees have regrown on the affected property - in time frames like 150 to 200 years to access any change in genetic potential. The forests after high-grading are crappy. After this first generation grows it is still crappy. I am saying this is a result changed environmental conditions - the examples you cited browsing, invasion of stilt grass are all environmental effects of the logging - not genetic. High grading, short of removing a species all but entirely from an area is not effective in changing the genetic potential of the remaining population of trees. At worst there will be a slight - slight - change in the frequency of certain genetic traits, but there will not be any net loss of any genetic potential from the population as a whole.

The problem in these discussions is that changes that are being seen, while real. are being attributed to loss of genetic potential, but they are not genetic. The gene pool is basically unchanged as a direct result of logging. Changes may take place as a consequence of the logging - but these are from environmental changes and not related in any measure to change in genetic potential. Species may be lost entirely as a consequence of these environmental factors. The ratio of tree species in a population may change, but these are not because of genetic material removed from the population. If there is any significant amount of a species still present in the overall population, its genetic potential will essentially be the same as the species had before the population decline. The remaining sample will be distributes in the same proportion as the original population. Only if the population is reduced to next to nothing and then is repopulated by just a few trees, will there be a loss of genetic potential. This concept of genetic loss may have been repeated again and again until the myth has achieved acceptance as fact, but that does not make it true. In previous posts I have tried to explain in terms of numbers of individuals, population pools, etc. to the best of my ability the basis for this assessment. I don't know what else to say.

Ed Frank