Thursday, August 25, 2011

Looking into the Iowa Deciduous Forests Past

In 1846 Iowa gained statehood and migrants rushed to the prairie taking advantage of free land made available by the government.  That same year, my German ancestors journeyed  across the Atlantic, through the eastern U.S. to the mighty Mississippi.  The country and forests look much different from what we have been discussing in previous blog entries on deciduous forests.  The Mississippi likely would have been the largest muddiest river they had ever seen.  Being the railroad would not have crossed into Iowa for four more years, migrants would have had to pass through the river bottomlands on foot or by wagon and cross the river by ferry.  Just thinking of crossing it would have been a daunting task.  Even if trails had already been blazed,  swamps, backwaters, islands, and mud in the bottomlands lining the mile or so wide river made crossing into Dubuque, Iowa from Illinois or Wisconsin quite an adventure.  The entire journey through bottomland muck and across the river could have been many miles.  Logging of the bottomlands would have begun at a larger scale 12 years prior to this time when the first sawmills were built in Dubuque, but the forests still would have largely been untouched by logging at this time.
A muddy bottomland forest.
First Steps in Iowa
Once crossing the Mississippi and setting foot in Iowa for the first time, it is likely migrants first entered an area covered with early successional Cottonwood and Willow forests along the river banks.  Being near the river, frequent flood disturbance and soggy soils would have maintained this forest type.  Heading inland, areas with slightly less soggy soils and less flood disturbance Boxelders, Ashes, Silver Maples, and Elms would have increased in abundance.  Elms of that time were very different from today.  Large, often several hundred year old Elms would have been common at that time.  Today however, Elms have been resorted into small understory trees only living a few decades at most due to the introduction of Dutch Elm Disease into the Midwest during the 1900's.  Further inland, less disturbed areas would have likely had more Sugar or Red Maple dominated forest than we see today.  Sugar and Red Maple, being a late successional climax species, would have likely been more abundant simply due to the lack of logging, allowing for succession to come to climax.

Moving upward, away from the river, more rarely flooded terraces would have had Oak-Hickory type forests.  Many types of Oaks would have been present including Swamp and Pin Oaks in wetter areas, White, Red, and Bur Oaks in the drier areas.  Bitternut Hickory would also have been in wetter areas and Shagbark Hickory in drier areas.  Some of the trees common below the terrace such as the Maples, Boxelder, and Elms would have also been present in this area, especially in moister locations.
Mature White Oak forest with widely spaced trees.  After coming out of the Mississippi River bottomland forests settlers likely found forests such as this one where wagons could easily move through the trees.  The floor of this forest is burned every few years, removing non-fire resistant vegetation.  Larger fire resistant oaks however survive the fires.
Entering the Prairie
Marking the end of the Mississippi river bottom, 200 to 300 foot steep limestone bluffs rise into the Tallgrass Prairie.  Moving up the bluff, the land became drier, and fire rather than flood became the major disturbance type.  All other species of trees slowly left the forest except for several species of Oaks.  White, Bur, and Red Oaks formed a woodland to savanna forest type.  These Oaks, due to their thick barks, easily survived the frequent prairie fires.  Non-fire adapted trees and shrubs, as well as smaller trees and seedlings of fire adapted species, were killed off by fire.  Larger Oaks however survived.  These forests were filled huge magnificent widely interspersed Oaks several hundred years old.  Today, most Midwestern forests are thick with vegetation and one could never imagine driving a wagon through them without running into a tree.  In 1846 however, the trees were so widely inter-spaced along the river bluffs that wagons were easily driven through.  Moving further from the river, trees likely became limited to valley and creek bottoms where they were protected from fire.  Ridge-tops, where it was driest and fires most frequent were primarily un-plowed prairie at this time.

Most free government issued homesteads were on these prairie ridge-tops.  This is simply because hills and valleys became less frequent and prairie became the most abundant ecosystem type the further away from the Mississippi you moved.  Prairie grass was so thick and tall it was difficult and dangerous to navigate through.  This grass was easy to get lost in and was home to buffalo and rattlesnakes, among other dangers.  Settlers often could not find their homesteads in this sea of grass.  So the Army Corp of Engineers at that time would burn the grass and mark the corners of the homestead.
An Oak Savanna, likely similar to what 1800's settlers would have seen.  These oaks have thick bark that  helps  these trees to survive frequent prairie fires.  
It is unknown how extensive Oak Savannas were prior to settlement.  These savannas contained relatively few Oaks, widely interspersed in the prairie grass.  Being Oaks were the most readily available building material these savannas were the first to be logged.  It is likely there were extensive savannas in Eastern Iowa, they were however logged prior to any scientific investigation.  The first settlers built their log homes, sheds, and barns out of these oaks.

Today, Oak Savannas are gone for the most part and only about one third of the overall Iowan forests remain.  These forests are almost all likely in earlier successional stages than they were in the mid-1800's.  This is simply due to the fact of logging and agricultural disturbance over the past 150 years.  Bottomland forests are about half what they were prior to settlement simply due to development within old bottomlands.  Oak-hickory forest types, once limited to bottomland terraces have expanded into uplands due to lack of fire disturbance.  But none of this is to be negative about Iowa's forests.  Though very different from what they were 100 plus years ago, they are still magnificent displays.
A large White Oak, similar to ones Iowan settlers would have seen in the 1800's.

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