Trees Above and Below

Trees Above and Below

    Somehow, in a review from somewhere I can't recall, I picked up a copy of Hope Jahren's recent book, Lab Girl.  Didn't expect much, another book about botany and plants and soils and trees.  But since I had just mentioned trees in my recent post (having given them "a haircut," as I wrote), I was surprised to quickly read in her book that an average tree has as many leaves as we humans have hairs on our heads (well on average, anyway); this was quickly followed by her mentioning that the average birch tree, that one with paper-like peeling bark, will drop about 250,000 seeds each spring.  Hmm, so I wasn't exaggerating about my elm (sweeping up 250,000 seeds can seem like a million!).  I was shall we say, intrigued. 

    So here I sat on the deck with my wife, reading Jahren's book, the slight droll of an overhead Piper plane going back and forth, mimicking the bee that occasionally came by to make sure that I hadn't moved.  And when I read those sections of her book, I stared up at my trees, marveling at the changing colors the setting sun was painting them with shadows and slivers of light that somehow turned the simple color green into a rainbow of so many different hues of green each beyond description, as if every leaf and seed or walnut was almost crying out, look at me.  And as surely as I think that I had witnessed that rare spectrum of green towering above me, Hope Jahren began to describe her digs in soil, heading down and getting dirty as surely as I simply looked upward.  Maybe I should have looked down as well. 

    I wrote a review of her book for our library (you know, one of those "reader" reviews that people post on Amazon and such) and I began with, "It doesn't seem fair."  Which is how I felt, for she begins her book telling about her love of slide rules (for those of you not old enough to remember those calculus rulers, think back not too long ago and you'll discover that they were used by NASA as a backup to their computers, their engineers verifying their calculations with them, all for landing and returning a man on the moon).  Then she goes into her love of a windowless room for her lab, a place to be alone and to conduct her experiments as if she might be Mary Wollstonecraft Shelley reborn in the flesh.  Brainiac, Nerd. Whatever.  But it is when you begin to read her writing that you realize the unfairness...not only can she write but she can write well; and before long, you recognize that you are begin to learn something (plants! of all things!).  So excuse the extended sample of her writing but I'm putting it here to give you a basic idea of her style of writing...and teaching.

    From Chapter 5: Let's consider a modest, unremarkable tree -- the one living on your street, perhaps.  A decorative maple tree, about the height of a streetlight --not a majestic maple reaching its full height in the forest-- a demure neighborhood tree that's only one-quarter the height of its regal counterpart.  When the sun is directly overhead, the little maple in our example casts a shadow about the side of a parking space.  However, if we pluck off all the leaves and lay them flat, side by side, they would cover three parking spaces.  By suspending each leaf separately, the tree has stacked its surface area into a sort of ladder for light to fall down.  Looking up, you notice that the leaves at the top of any tree are smaller, on average, than the leaves on the bottom.  This allows sunlight to be caught near the base whenever the wind blows and parts the upper branches.  Look again and you'll notice that leaves low in the canopy are of a darker green; they contain more of the pigment that helps each leaf absorb sunsihine, allowing them to harvest the weaker rays that penetrate shade.  When building foliage, a tree must budget for each leaf individually and allocate for each position relative to the other leaves.  A good business plan will allow our tree to triumph as the largest and longest-living being on your street.  But it ain't easy, and it ain't cheap...the leaves on our little maple, all taken together, weigh thirty-five pounds.  Every ounce therein must be pulled from the air or mined from the soil --and quickly-- over the course of a few short months.  From the atmosphere, a plant gains carbon dioxide, which it will make into sugar and pith.  Thirty-five pounds of maple leaves may not taste sweet to you and me, but they actually contain enough sucrose to make three pecan pies...the pithy skeleton within the leaves contains enough cellulose to make almost three hundred sheets of paper...Our tree's only source of energy is the sun: after light photons stimulate the pigments within the leaf, buzzing electrons line up into an unfathomable long chain and pass their excitement one to the other, moving biochemical energy across the cell to the exact location where it is needed.  The plant pigment chlorophyll is a large molecule, and within the bowl of its spoon-shaped structure sits one single precious magnesium atom.  The amount of magnesium needed for enough chlorophyll to fuel thirty-five pounds of leaves is equivalent to the amount of magnesium found in fourteen One A Day vitamins, and it must ultimately dissolve (it) out of the bedrock, which is a geologically slow process.  Magnesium, phosphorous, iron, and the many other micronutrients that our tree needs can be gained only from the extremely dilute solution that flows in between the tiny mineral grains within the soil.  In order to accumulate all of the soil nutrients that thirty-five pounds of leaves require, our tree must first absorb and evaporate at least eight thousand gallons of water from the soil.  That's enough to fill a tanker truck.  That's enough to keep twenty-five people alive for a year.  That's enough to make you worry about when it is next going to rain.

    Phew!  That's a lot to take in (and to type); but that is just about a page and a half of her book.  There's more, much more, and as you can read, it is far from a droll science lecture while still filled with her years of study.  But more than anything, it is books such as hers that captivate and allow you to think about something you might never have thought of, such as the "spines" of the cactus actually once being their leaves, conditioned through evolution to turn into spines because of the tough growing conditions they face, that of heat and dryness and a general lack of moisture.  She goes into a tree, then into the soil, then into the roots, then into the unknown (the mushrooms we harvest are merelya tiny sex organ that appears and yet hides a complicated web structure underneath, one which often stretches for miles).  And suddenly, you are facing education...learning unexpectedly, and delightfully.  How it should be.  And certainly, as in this case, plant life and tree life and what's happening in the ground below you may not be your cup of tea...but it's there, all around us whether in a desert or a jungle, a city street or a remote fjord.  All of it is happening, independent of us...and in basically one book, you can take a peek at this marvelous mystery.  Or you can simply look up at the trees and watch...the discovery will come on its own.