Posted by: chrismaser | December 10, 2009

ROOTS

Unlike the crowns of my pear and apple tree or those of the maples, which periodically require my attention during any given year, none of the trees’ roots make such demands. Although there is nothing I need do directly to or with the roots in the sense of gardening, I must understand something about their relationship to both the soil and the aboveground portion of the trees they support, lest I inadvertently compact the soil and thereby hinder their ability to function.

As a tree’s leaves caress the sky and harvest momentarily the sun’s energy, so its roots are fastened in the Earth, where they grip the soil while harvesting the sun’s energy stored in darkness from millennia past. The soil, where nonliving and living components of the landscape join, is also where past and present flow one into the other and determine a tree’s future.

Soil supports the plants and animals that in turn create and maintain the myriad hidden processes that translate into soil productivity. Into this incredibly thin band of seething activity, the very ferment of terrestrial life, a tree thrusts its roots that it may withdraw energy long stored in Nature’s warehouse and replace energy derived from the present net worth of its photosynthetic exchange, the leaves of its crown.

But here one might ask, “What is a root?” Most people probably think of a root as the underground portion of a plant that serves as support, draws food and water from the surrounding soil, and stores food, all the while holding the soil together. A root is far more than this simple description, however.

To examine the notion of a root, we will venture into a largely unknown, hidden world with the slightly buried seed of a Douglas-fir as our guide. It is spring and the seed begins to swell as it absorbs moisture from the warm soil. The seed’s coat splits, and a tiny root begins to penetrate the bosom of the Earth as small, green seed leaves reach toward the sun. Thus the seed of the tree becomes the seedling of the tree in its first spring of life.

As the seedling’s roots spread through the soil, the new nonwoody root tip of a tiny feeder root comes in contact with a week-old fecal pellet of a deer mouse. The deer mouse had dined on a truffle (the belowground fruiting body of a fungus) the night before it deposited the pellet. The pellet, packed full of the truffle’s spores, is still soft from the moisture in the soil, and the root tip has little difficulty penetrating it.

Inside the pellet, the root tip comes in contact with the spores that have passed unscathed through the mouse’s intestinal tract. Meanwhile, the yeast (a fungus) in the pellet is growing and producing a substance called yeast extract that is food for the nitrogen-fixing bacteria. (“Nitrogen fixing” means to capture gaseous nitrogen and convert it into a form usable by the plant.) As the root tip contacts the spores, the yeast helps stimulate the spores to germinate and grow into and around the root tip; the nitrogen-fixing bacteria and yeast become enveloped in the fungal tissues. Once inside the fungal tissue and in the absence of oxygen, the nitrogen-fixing bacteria are nurtured by the extracts of both the yeast and the truffle’s non-reproductive tissue. The bacteria in turn fix atmospheric nitrogen that can be used by both the fungi and the host tree.

The non-reproductive tissue of the truffle, called mycelia, forms a mantle around the tree’s feeder root; this symbiotic association is called mycorrhiza, which literally means, “fungus-root.” As the mycelia grow into and around the root tips, they also grow out into the soil where they join billions of miles of gossamer threads from other mycorrhiza-forming fungi. These mycelial threads act as extensions of the seedling’s root system as they wend their way through the soil absorbing such things as water, phosphorus, and nitrogen and sending them into the seedling’s roots. As the seedling grows, it produces sugars that feed the fungus, which in turn expands through the soil as it is nourished by and nourishes the seedling. The tree is therefore a product of both the sun’s light and soil’s darkness; the nutrients of darkness feed the tree’s top in light and the sugars of light feed the tree’s roots and their fungi in darkness.

Although as a young man I knew nothing about this tree/fungal association and doubt that I had ever really considered the functional aspects of a tree’s roots, I learned about their tenacity the year I was confronted by an old cottonwood stump on a ranch in northwestern Colorado, where I worked as a ranch hand. This particular cottonwood stump was in a small grove of its kind along the little stream that supplied water to the main ranch house. I forget the reason now, but the old rancher wanted the stump taken out, and removing it fell on my shoulders.

“Well,” I thought to myself with the surety of youth, “this will be easy. All I have to do is chop through its roots with my ax, and I can pull it out with a team of horses.” That’s what I thought until the first day I hacked unceremoniously at the stump and the blade of my ax got so deeply buried in the soft wood that I couldn’t get it out no matter how hard I tried.

The upshot is that I had to dig out each root on which I then cut, hacked, and sawed. In addition to my physical assault on its roots, I muttered at that infernal stump for the better part of the summer and autumn until the day came when I thought that I could in fact pull it out with a team of workhorses.

With the team hitched and anchored securely to the stump by a chain, I gave the word and the horses began to pull. I had, over the course of time, dug so far under the stump that I thought it would snap out in a twinkling. The old stump groaned and shivered, rose and fell until the chain broke, but would not release its grip in the soil. It had, I found, a monstrous taproot, which I could see only when the horses were pulling on the stump. I therefore had to dig the hole deeper.

Then came the day in early October when the old stump finally relinquished its hold, and the horses pulled it free of the soil. That was a bittersweet moment because it wasn’t just a stump anymore; it had become a stump with a personality. I had unknowingly developed an honest-to-goodness relationship with it, one that challenged not only me but also technology and a team of powerful horses.

But I don’t think I really ever conquered it, because I have long had the distinct feeling that at some point in our relationship the old cottonwood stump decided, for whatever reason, to let me cut it out. That stump, perhaps more than any other, caused me to focus on roots. Yet as I chopped at the old stump’s roots, I had no inkling of how vitally important tree roots are to the health of the forest beyond the individual trees.

Decomposing woody roots of tree stumps have distinct functions. Tree roots contribute to the shear strength of the soil, which is a root’s ability to hold soil in place. Declining shear strength of decomposing woody roots increases mass soil movement after such disturbances as catastrophic fire and clear-cut logging.

Another related function of decomposing tree stumps and roots is the frequent formation of interconnected, surface-to-bedrock channels that rapidly drain water from heavy rains and melting snow. The collapse and plugging of these channels as roots decay may force more water to drain through the soil matrix, which reduces soil cohesion and increases hydraulic pressure, which in turn may cause mass soil movement. Because these plumbing systems are necessary to the stability and sustainable productivity of the soil in a forest and cannot be replaced by young trees with their relatively small roots, grandparent trees are necessary to mediate the relationship between water and soil.

Although the pear and apple trees in my garden hardly qualify as a forest, their roots perform similar functions in the soil, many of which I know nothing about. What I do know, however, is that the care I take of my fruit trees aboveground affects directly the health of their roots belowground. In addition, how I choose to participate with the aboveground environment of my garden is a choice, my choice and nothing more. But the consequences of my choices will in many unknown and hidden ways affect not only the trees but also the next person to call this small piece of ground “my garden.”

Mark Collins, of the World Conservation Monitoring Center, says that “forest destruction is the key threat to species worldwide,” including ten percent of the world’s species of trees. One-tenth of the known species of trees in the world are in danger of extinction, yet fewer than one in four species benefit from any kind of protection, according to the 650-page report World List of Threatened Trees.1

According to the study, which was financed by the Dutch government and released in Geneva, Switzerland, on August 25, 1998, 8,753 of the world’s estimated 80,000 to 100,000 species of trees are vulnerable. Of these, 1,000 are classified as critically endangered, reduced to less than 100 living individuals. Some of the species threatened with extinction have yet to be investigated scientifically. What will society lose with these secret extinctions?

It is my hope that whoever reads these words will pause for a moment before putting his or her saw or ax to a tree and in that moment pay homage to the being whose life is about to be severed. I say this because it is through the consciousness with which we act, and not the acts themselves, that we honor the Creation of which we are all an inseparable part.


 

Related Posts:

• Trees: The Quintessential Plant

• Trees In Time And Space

• Leaves

• Flowers And Fruits

• Branches

• Trunk

• The World Is In My Garden–My Garden As Metaphor

• What Is A Commons?

• Biodiversity–The Variety Of Life

• Soil–The Great Placenta

• Air–The Breath Of Life

• Water–A Captive Of Gravity
 


ENDNOTE

  1. The Associated Press. 1998. 10 percent of tree species under threat of extinction. Corvallis Gazette-Times, Corvallis, OR. August 26.


Smaller plants may feed and sustain us, but in trees we see ourselves.
Thomas Campanella


Text and Photos © by Chris Maser, 2006. All rights reserved.

Protected by Copyscape Web Copyright Protection


If you want to contact me, you can visit my website. If you wish, you can also read an article about what is important to me and/or you can listen to me give a presentation.



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