Saturday, July 23, 2011

Eastern deciduous forest bottomlands

Pulpit Rock in the foreground and the Upper Iowa River floodplain and bottomlands in the distance.  Northeastern Iowa near Decorah.
Eastern Deciduous Forest bottomlands can be quite the interesting place to visit.  If you were dropped off in the middle of one of these forests during the summer probably the first thing you would notice would be the mosquitoes.  Secondly, you would notice thick vegetation and in most cases the soggy ground.  Some areas would be dry but most areas would be at least moist, if not so muddy that you could never imagine walking through them.  As you tried to hike out of the forest you would find yourself bushwacking through thickets of stinging nettles and poison ivy.  You would also walk through tall grassy areas or cross over nearly barren ground due to the thick tree canopy above or recent flooding that killed ground vegetation.  

These forests are always quite flat except for depressions where small ponds or drainages form.  This flat structure is a result of decades to centuries of river flooding (or more).  The nearby river is what defines the bottomland forest and makes it a quite inhospitable place.  As any river flows it erodes away soil and deposits it elsewhere, especially during floods.  Typically this eroded soil is deposited where the water slows along the river banks.  Year after year, flooding deposits sediments along the river bank resulting in the formation of a floodplain, which is where bottomland forests are found.  A newly formed floodplain will first be colonized by ragweed and grasses.  If it is stable and isn't washed away by river flooding, Willows will begin to colonize it, often forming quite dense stands.  Cottonwoods will shortly follow.  Very few of these trees will ever reach maturity.
A dense stand of Willow and Cottonwood trees.  The earliest stage of bottomland forest succession.  These trees require full sunlight to grow.
If the area is heavily disturbed by flooding year after year the stand of Willows and Cottonwoods may persist.  But if the area is slightly drier and not as strongly disturbed for many years other trees may move in like Ash, Elm, Swamp Oak, Walnut, or Basswood.  If the floodplain remains stable even longer, many decades after these trees are established Maple trees will become the dominate tree.  This progression of tree species is called succession.
Not the greatest picture but shows a dense thicket of Maple trees (left half of photo) growing under the canopy of more mature Ash trees (the larger stump on the right).  Most of these Maple trees will die, but due to their ability to grow in shade, the Maples will one day replace the Ash trees.  One day this Ash tree forest will be a Maple forest.  This is an intermediate stage of Bottomland Forest succession.  This bottomland is located adjacent to the Cedar River in the Wikkiup Hill Natural Area in Eastern Iowa.

A Bottomland Eastern Deciduous Forest composed almost exclusively of Silver Maple with a few Elm, Sugar Maple, and Cottonwood trees.  This is nearly the latest stage of bottomland forest succession.  This bottomland is also at Wikkiup Hill Natural Area in Eastern Iowa.
As you can probably tell from the description, the Bottomland Forest is not somewhere you would want to pitch a tent and camp out for the night due to its in-hospitable nature.  However, this wild in-hospitality is what makes it so interesting and exciting to explore.  Exploring it with a good amount of bug spray, some waterproof boots, a hiking trail, and the ability to identify Poison Ivy and Stinging Nettles makes these areas more accessible.  Not many people brave the mud and bugs of bottomlands so they become tremendous wildlife refuges.  Deer, Turkey, Raccoons, beaver, otters, muskrat, ducks, and a whole host of birds are in abundance in bottomlands.  On recent hiking trips I saw several Whitetail Deer fawns in bottomlands and absolutely none in drier more hospitable upland forests.  
An ephemeral pond in a Bottomland Forest left over after flooding.  Ephemeral ponds are temporary in nature, forming in spring with flooding and drying out later in the summer.  These ponds are home to a wide variety of organisms including, salamanders, frogs, toads, and ducks.  Picture is from Cedar River floodplain located at the Indian Creek Nature Center in Eastern Iowa.
Based on the above description of the bottomlands you can probably tell that these areas form quite diverse habitats.  Annual flooding disturbs some areas more then others and makes some areas wetter then others.  This creates a variety of different forest types in differing stages of succession and a variety is different water habitats.  All kinds of interesting animals can be found in their preferred habitat type (also called a niche) and the greater diversity of habitats, the greater diversity of organisms you will find.  Yet another great reason to explore the bottomlands.  

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