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

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