Friday, October 14, 2011

Looking Into Midwestern Deciduous Forest Future

An Oak-Hickory forest, historically this was the most common upland forest, along with oak savanna in Iowa.
Looking at a forest, we naturally get the idea that the present state of that forest will continue forever.  Historically, Iowa and much of the Midwest has been characterized by Oak-Hickory upland forests and mixed bottomland forests.  Today, even after 100 plus years of drastic change, the forests remain predominately Oak-Hickory uplands and mixed bottomlands.  Of course, its a little more complex than this and we have in-fact lost many original forests to development.  The structure and details of these communities have changed right along with changes in land use, but the overall communities remain relatively similar.  Flood control systems, agricultural practices, and urban development have more or less already "set" their effects on the land so huge impacts like ones of the past century are not expected in the coming century.  As odd as it may sound, compared to today's doom and gloom environmental lookouts, Iowa's forests are expanding in acreage and relatively healthy.  Not everything is "rose petals and teacups" however, there are problems.  But considering the states present forest conditions, what should we look for in the future?
An old Oak-Hickory woodland being taken over by Sugar Maples and Basswood due to the lack of fire disturbance over the last century.  Palisades State Park near Cedar Rapids, Iowa.
Most forests in Iowa are in the 100 to 150 year old age range, growing out of logging and fire disturbances of the late 1800's.  While these disturbances were common 100 years ago, they no longer are common today.  Out of these disturbances grew the upland Oak-Hickory forests.  Both hickory's and especially oaks are well adapted to the full sun and lack of competition common after logging or fire.  One logging event, or several low intensity fires, can establish an Oak-Hickory forest that can survive fore potentially a few hundred years.  With settlement of the state, fire was suppressed and nearly eliminated.  Logging also became far less common, simply because all the forests in Iowa were already logged and most converted to farmland.  So without fire and logging, oaks and hickories have not continue to regenerate themselves.  So in the absence of these disturbances, trees such as Sugar Maple and Basswood begin to take over.  These trees easily establish in the shade of old oaks and hickories.  Then without forest floor fire disturbance they will eventually overtake the forest.  Due to these facts, Oak-Hickory forests are rapidly declining in the state as well as in much of the rest of the Eastern United States, and Maple-Basswood forests are increasing.  And as of now, it appears this trend will continue into the future.

Fortunately for land managers in Iowa, as well as the rest of the Eastern United States, are realizing the value of low burning fires as a management tool in prairies, savannas, and most recently Oak-Hickory forests.  Today even, this management tool is fitting being almost all fires prior to settlement were also human started, also often to manage the growth of Oak-Hickory forests.  Native Americans and many early settlers understood the value and importance of fire in maintaining quality, productive habitats and frequently set ground fires.  Today, similar to these presettlement fires, these fires are not the raging hundred foot flames that consume everything in their path.  Rather, they were low burning, lower temperature fires.  Fire intolerant shrubs, trees, and thick accumulations of herbaceous plant materials were killed and cleared.  Fire adapted trees such as oaks and hickories survive, and herbaceous plants survive as roots, all proliferated as a result of fire.  Hopefully, the reintroduction of fire as a management tool will again cause the regeneration of Oak-Hickory forests.  Time will tell.
Oak woodland restored through controlled burns of the forest floor.
Bottomland forests continue today to have a similar disturbance pattern of flooding and wet soils.  While flooding patterns have changed during the past century due to human development of river channels, flooding still remains and will remain in the future.  Bottomland forest therefore remain a similar mix of trees such as Ash, Elm, Willow, Cottonwood, Maple, and certain types of oaks.  The future of these forests seem to be a continuation of of the past more or less.  However, there is one major up and coming problem for ash trees, the Emerald Ash Borer.  This exotic insect bores inside of ash trees and kills them.  Currently, the Emerald Ash Borer has only been found in one location in Iowa.  Managing this insect appear to be only slowing its spread.  Very likely the spread of this insect will greatly reduce the number of ash trees in bottomland forests in the future.

The future of Iowa and other Midwestern forests has its dark spots but there is good reason for hope.  While there doesn't seem to be much hope for the bottomland Ash tree, there is great hope for upland Oak-Hickory forests with the reintroduction of fire.  This doesn't automatically mean Oaks and Hickories will start regenerating, but does greatly increase the likelihood.  Our increased understanding and concern for our land will hopefully translate into healthy forests.  Increased human management today, is similar to human management of the past, and this is good for us and our forests.  These forests have been managed by humans for thousands of years, and a return to past healthy forests with the return to past management practices is very hopeful.
White Oak leaves.

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