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inhabitant& of this precious spiuning jewel, our Earth, we need to
<br />deepen our moment-to-moment consciousness--our daily walk--
<br />by developing a working respect for other forms of life, like the
<br />tree beings, whose very presence is life-enhancing for all of us. I
<br />hope the steps I have presented will start the deeper dialog. A
<br />
<br />Andrew Goodheart Brown describes himself as a practical mystic
<br />--first and foremost; tree healer, gardener, 'eMer-in-training,
<br />permaculture fool, soil enhancer, bread.baker, beer maker,
<br />gourmet vegetarian cook, and all around general biophiliac.
<br />
<br />Rhizosphere Wars
<br />
<br />Alex Shigo
<br /> The rh~zosphere is the absorbing re°t-soil interface. It is the zone,
<br />about one millimeter in width,,surrounding the epidermis of living root.
<br />hairs and the boundary cells of myeon'hizae as well as hyphae growing
<br />out from some mycorrhizae.
<br /> The rhizoplaae is the boundary where soil elements in water are
<br />absorbed into the tree. Under an electron microscope, the rhizoplane
<br />appears as a jelly where microorga.nlsms and tree cells mix, making it
<br />impossible to tell which side is tree and which is soil.
<br /> A eoustanfly changing mix of organisms inhabit the rhizosphere and
<br />surrounding soil. Bacteria, actinomycetes, fungi, protozoa, slime molds,
<br />algae, nematodes, enchytraeid worms, earthworms, millipedes, ~
<br />centipedes, insects, mites, snails, small animals, and soil viruses
<br />compete constantly for water, food, and space.
<br /> The rhizosphere is a battleground and the wars are continuous.
<br />Amoebae are eating bacteria. Some bacteria are 'poisoning other
<br />bacteria. Fungi are killing other fungi. Nematodes are spearing roots.
<br />Fungi are trapping nematodes. Earthworms are eating anything they can
<br />find. Sometimes the victors benefit tho tree and sometimes they do not..
<br /> Every tree treatment affects the rhizosphere in some way. The more
<br />you know about the rhizosphere, the better the chances are that your
<br />treatments will lead to benefits rather ~han harm.
<br />Declines and the Starving Rhizosphere
<br /> Go anywhere in the world and you will learn that some local trees
<br />have a "new" decline problem. I)eclines usually mean the trees are sick
<br />because there is a problem in the rhizosphere.
<br /> Trees die, as all organisms do, in three basic wayS: depletion,
<br />dysfunction, and disruption. DiSrUption means wounding, severe
<br />mechanical impacts and fracturing. Dysfunction means some parts and
<br />processes of the living system have developed problems that retard or
<br />prevent their functioning and growth. Depletion means that the basic
<br />substances for life begin to decrease to the point Where injury and death
<br />are certain. One of the ways depletion injures organisms is by starvation.
<br /> Soils and wood share a common problem: They ate thoUght of as
<br />dead substances. This has come about because wood-products research
<br />gained an early lead over research on wood in living trees. Many texts
<br />still define soils as "loose material of weathered rock and other minerals,
<br />and also partly decayed organic matter that covers large parts of the land
<br />surface on Earth." ·
<br /> Sapwood in living trees has many more living 'cells than dead cells.
<br />In upper layers where most absorbinf' roots of plants grow, soils have'
<br />more soil organisms than grains ofw~hered rock. In great disrespect,
<br />most people still refer to soil as dirt! When researchers first discovered
<br />the great value of soil microorganisms for human antibiotics and profit,
<br />the living nature of the soil.began to emerge.
<br /> A more correct definition of soil should be that it is a substance made
<br />up of sands, silts, clays, decaying organic matter, air, water and an
<br />enormous number of living organisms. Survival of all living systems
<br />depends greatly on synergy and efficiency to optimize the functioning of
<br />all processes and to keep waste as low as possible. When synergy and
<br />efficiency begin to wane, declines follow. Trees are dependent on the
<br />light from the sun for their energy; water and 14 elements from the soil
<br />
<br /> for their building blo~ks'0flife. Some trees decline when
<br /> incorrect treatments or abiotic injuries lead to 'starvation
<br /> of organisms in the rhizoSPhere, When them are troubles
<br /> in the rhizosphere, there will be troubles with the tree.
<br /> Energy & Root Exudates
<br /> Microorganisms compete in the rhizosphere, an area
<br /> rich in exudates from the tree. The exudates contain
<br /> carbohydrates, organic acids, vitamin.q and many other
<br /> substances essential for life. From 5-40% of the total dry
<br /> matter production of organic carbon from photOsynthesis
<br /> may be released as exudates! When trees begin to decline,
<br /> the amount of organic carbon released as exudates
<br />. increases. Mineral deficiencies, low amounts of soil air,
<br /> and severe wounding are major causes for the increase.
<br /> Another way to say this is that an increase in exudates
<br /> would be caused by OVer-pruning, construction injury,
<br /> planting too deeply, over-watering, compaction, and
<br /> planting trees in soils that have a pH too high or too low
<br /> for their optimal growth..
<br /> You would think that a tree in decline would decrease,
<br /> not increase, exudates. A possible explanation might
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<br /> NEW FORESTRY., DI~EMBER 1998 25
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