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Forum » Public Boards » General Discussion » Deciduous versus Evergreen

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Deciduous versus Evergreen
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Evolution (or the lack thereof) is a fascinating subject. Science commonly recognizes two distinct varieties of trees; deciduous varieties that shed their leaves in fall, and evergreens that don't.

If you compare the leaves of a deciduous tree with those of an evergreen the "rationale" behind each should be apparent. Deciduous leaves are obviously designed to act as efficient solar collectors. Since sunlight provides both the wavelengths that the tree needs to grow and heat energy, the leaves evolved into a thin structure that can readily dissipate heat, and which have the ability to sweat to aid in cooling. The unfortunate side effect of this design is that the leaves are prone to freezing in cold weather. So the evolutionary strategy is to collect massive amounts of energy during the warm months, and sacrifice the leaves when the weather turns cold, rather than try to heat leaves that are designed to dissipate heat.

By comparison, evergreen leaves are thin needles with a waxy insulation layer. Since the amount of energy from sunlight that any object absorbs is dependent on its surface area, it seems like a silly design at first glance. But unlike deciduous leaves, where the upper surface is the primary collector, evergreen needles are designed to collect equally from all directions. This, combined with their different pigmentation, provides a unique alternative to collecting sunlight directly from the source, namely allowing the absorption of the wavelengths of light required for growth from indirect sunlight, which for the most part lacks the infrared component (heat) that deciduous leaves struggle to eliminate. Although the needles are less efficient than broad leaves, they are designed to absorb much less heat energy and thus lack the massive cooling structures of a deciduous leaf, which allows them to operate without freezing. And, in winter when the sun's energy is considerably lessened, a snow-blanketed environment provides a near-perfect reflector to the wavelengths the needles are designed to absorb.

These are two quite different approaches to the same problem; one is to grab as much as you can while you can, and then cut your losses and wait for the next opportunity. The other is to adapt to a changing environment by getting by with less, and taking only what is required, regardless of how much is available. Are evergreens conservative?
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