Friday, March 9, 2012

Flood Damage - Plants

My greatest concern following a major flood event is the recovery of the streamside plant communities.  The plants must recover in order for the animals to recover.  Billions of small organisms were swept away with the leaf litter and topsoil.  Those that were left behind have lost the environment they need to survive.  Roots that once gathered nutrients from the decomposing leaves are left exposed to dry out and die.  It could be tough growing for some of the plants this spring.  The bare soil will dry out much more quickly and will heat rapidly when exposed to the sun.  Conditions will improve some when plants grow enough to shade the ground.  Soil creation can begin anew next autumn when falling leaves fill in the space between plants.

While some places lost their topsoil, others gained soil material.  Plants must now push their way up through a thick layer of sediment.

Both situations involve this stuff.  At one point these crumbs were all neatly stacked and arranged to form a cohesive block of soil.  In that condition they provided the structure needed for a healthy soil ecosystem.  Now they’re like shards of glass from a broken drinking glass; Recognizable pieces of what they once were, but no longer functional as a whole.  It will take a long time for these crumbs to be broken down and reformed into healthy soil.

In some cases, leaf litter was also redistributed.  Shallow water flows pushed leaves together to form tightly packed drifts several inches deep.  I moved some leaves aside to show the thickness of this pile and found a plant buried beneath.  Leaves packed at this density can form an effective mulch that blocks the upward movement of growing plants.

These Downy Rattlesnake Plantains were perched at the top of the bank at the high water line.  One still holds the stalk and seed capsules from last year’s flower.

Rhizomes that were just beginning to reach out into the surrounding soil, now have nowhere to go.

Plants farther from the stream were threatened by sheets of water flowing from the hillside.

Some areas closer to the channel hardly seem capable of supporting plants.  Had a logjam not developed directly upstream, there might not have been anything left here.

Just a few feet downstream of the logjam is the site of a single Large Flowered Trillium that has been growing here for about ten years.  It has bloomed several times during that period and flood water has flattened it about an equal number of times.  Hopefully it will be poking its way through in a few weeks.  I sometimes wonder if I should relocate plants growing in such precarious positions, but I figure there must be a reason for the plant to be growing on this site, instead of the many places I believe to be better suited. 

This Swamp Milkweed grows in the center of the creek channel where it’s anchored by one stout root in a crack between the rocks.  Most of its roots are exposed on the creek bed.  I figured it wouldn’t last long at all in this location.  Despite my opinion, the plant has flourished and flowered for the past several years.  It’s occasionally battered by flood water, but it bounces right back up and produces a beautiful floral display.  I’m hoping the rest of the plants along the creek follow its example.

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