Thursday, May 2, 2013

Spring ephemeral a day - Hepatica

Shelburne Bay

What: The most fascinating thing for me about hepatica is that as it comes up some of the leaves don't quite make it above the leaf-litter, or make it just part way. Where the leaves are exposed to the sun they are a dark purple, while the shaded parts are a bright green.

Another common adaptation of spring ephemerals is fuzziness (lots of species of ferns have some similar adaptation covering their fiddleheads). The fuzz is analogous to the loft of a down jacket. It creates a buffering layer around the plant. I'm convinced that this layer - ecologically called a boundary layer - is one of the most significant factors that plants and animals have adaptations for. We experience a boundary layer in cold water. If we stand in calm cold water we feel it get warmer and warmer the longer we stand there. Our body heat radiates out and warms the water, effectively increasing our boundary layer. The boundary layer can dwindle if we start walking or if the water is moving (e.g. wind action or water flow in a river). Wearing a wetsuit creates a thin boundary layer between the suit and our bodies that helps warm us.

Regardless of how strong the wind or current is, we always have at least a thin layer of no friction around us. It's why even on the highway, that layer of dust stays pressed against the hood of our car. It's also why at the top of Camel's Hump, all the plants hug close to the rocks to shelter from the wind. It's also why the reproductive part of the moss up there sticks up above the moss, to get out of the boundary layer and let the wind drag the spores away.

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