Surprise!! Trees Grow

I am a fan of Sherlock Holmes, having read and reread all the Conan Doyle stories many times.  Conan Doyle was indisputably a very intelligent man and his stories are real lessons in the power of deductive reasoning.  However, even a learned man such as he suffers from some common misperceptions about trees as living, growing, changing things.  In the story "The Musgrave Ritual" Holmes is attempting to solve a riddle (written 200 years prior) that he thinks will lead to some sort of hidden treasure.  One of the clues in the riddle involves the shadow cast by an old elm tree.  Even though the poor tree was struck by lightning and died a few years earlier, the owner of the estate recalls that as a child he was required as part of his math lessons to calculate the height of all the trees around the house.  He tells Holmes that the tree was 64 feet tall.  With this information Holmes calculates the length of the shadow that would have been cast by the tree at a certain time if it had still been standing. From this he locates the "treasure" and solves the mystery.  Pretty clever.  

Except,  that  this would only work if trees did not grow.  Holmes (or rather Conan Doyle) was like many people and their perceptions of trees as something more akin to a statue or large lawn ornament than a living thing. We remember those big, old trees from our youth that we can go back to as adults and still see standing there like "sentinels" guarding the past. In some cases they may seem to have not changed much since we have grown too.  I recall a woman when I worked on the Prescott National Forest whose family had operated a youth camp south of Prescott for many decades.  She grew up there and when we proposed a thinning to reduce fire hazard and improve the health of the pine forest she was skeptical.  She had lived there all her life and she did not want us to change her beloved forest.  At the time she must have been in her 50's and the trees she was discussing were mostly about 70 to 90 years old.  When she was a child, say 45 years ago then, these same trees would have been only 30 to 40 years old, probably 20 to 30 feet shorter and much smaller in diameter. The forest would have been much denser in terms of numbers of trees per acre.  So, just from the natural growth of individual trees and the natural thinning from competition the forest she was in as an adult was quite a different thing than she would have experienced in her youth. 

You can get a general idea of the age of a young pine tree by counting the "whorls" of branches from bottom to top.  Each year a pine tree grows a central leader branch vertically, surrounded by a layer of horizontal branches.  One layer of horizontal branches per year.  Once trees get very old (say 30 to 50 years) the lower branches begin to die off and eventually even the dead branches drop and any remnant is covered up by wood and bark as the tree grows in thickness. Up until then you can look at the tree and do a quick count of branch layers (whorls) and see how old the tree is.  One thing that is very interesting to do is to count back from the top of the tree to estimate the height of that tree at a point of time in the past.  I first came to the Kaibab National Forest in 1975, nearly 42 years ago.  I have what I think are vivid memories of my first years here.  When I count backward as I have described, I find how much shorter the forest was when I came. In fact, though I discuss tree growth a lot in my profession, I am surprised at not only the height change but the fact that many trees I am looking at now where not even here or were very small seedlings back then.  

So what do we make of this natural change in things.  Well, for one thing, it teaches us the futility of expecting that somehow we can "preserve" nature.  Prevent change.  And that change in the natural world is a very bad thing.  I see this in the discussion of the repercussions of climate change.  I will not discuss the merits of the arguments for and against human influence being the main factor behind recent measured changes in climate.  I do, however, take exception to the idea that whatever changes have a occurred or will occur will invariably result in something bad. Maybe like that woman in Prescott we are afraid to lose what we think we had in our youth.  But we must realize that what we think we had and could keep "preserved" is an illusion.  Nature will change things. Nature has changed things.  Just look around. Take a lesson from the trees.