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Exceptional in this respect are palm trees, whose trunks can suffer circumference damage up to their breaking point without the trees' health diminishing. This is because the palm family's phloem conduits are arranged in scattered bundles throughout the stem instead of in a circle around it. None of the moisture carried downward in the sapstream to the roots is returned into the soil. But in nature's economy, trees do reciprocate earth's gift of water by holding soil, and thus moisture, in place with their root meshes, and by lessening ground evaporation with their shade. This is why trees are planted around reservoirs, to check erosion and parching. Evergreens are most used for this purpose because they will grow fastest and densest with the least water requirement for themselves, and their roots run nearer the surface, where erosion begins. |
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