PRESETTLEMENT AND CONTEMPORARY VEGETATION PATTERNS
ALONG REACHES 4 AND 8 OF THE UPPER MISSISSIPPI RIVER

John C. Nelson1, Catherine McKeever1, and Melvin Bower2
1Illinois Natural History Survey, LTRMP Reach 26 Field Station, 4134 Alby St.
Alton, IL 62002.  Biological Resources Division, 2U.S. Geological Survey,
Environmental Management Technical Center, 575 Lester Ave., Onalaska, WI
54650.

Assessing the current ecological status of the Upper Mississippi River System
(UMRS) is an ongoing process, but to-date, little effort has focused on assessing
the presettlement characteristics of this nationally significant large river-floodplain ecosystem.  Since so much of the UMRS is altered and modified,
historical baseline data is critical for answering some of the most basic questions
regarding how to maintain and enhance the biological integrety  of the UMRS;
i.e., what have we done and how can we best restore it? This study used General
Land Office (GLO) Survey records to reconstruct the landscape and tree
community patterns that existed over 150 years ago along two reaches of the
UMRS in Wisconsin and Minnesota.  GLO surveyors described much of the
upland vegetation as "oak openings" or as "scattered timber" -- a likely reference
to the savanna communities that covered much of  the region prior to Euro-American settlement.  The dominant tree taxa were white oak, bur oak, and black
oak.   Very low tree density estimates (~13 trees/ha), obtained from bearing tree
distances, provide additional evidence that savannas were once widespread. 
Surveyors also encountered prairies in the uplands and according to plat maps,
these prairies varied greatly in shape and size.  The cities of Onalaska and
LaCrosse, WI and Red Wing, MN were all built on or near former prairies.  Some
mesic forest communities containing basswood, sugar maple, and elm were also
encountered in the uplands, but according to the importance values of these
indicator species, mesic forests were much less extensive than the open savannas.  
On the floodplains, a different mix of tree species were encountered.  Dominant
tree taxa included; bur oak, silver maple, ash, elm, birch, black oak, and willow. 
Surprisingly, despite a different compliment of tree species, the floodplain shared
a pattern consistent with the surrounding uplands -- savanna communities
predominated.  Floodplain tree density estimates were only 19 and 5 trees/ha
(Reach 4 and 8, respectively).  Fire was likely an important disturbance factor
influencing landscape and community patterns in the uplands as well as on the
floodplains - especially during periods of drought.   The modern upland
landscapes are highly fragmented and the former savanna matrix has been
replaced by a predominantly agricultural matrix among forested patches.  This
type of habitat conversion and fragmentation has been especially severe in the
uplands surrounding Lake Pepin.  The modern floodplain landscapes indicate
varying degrees of change from their presettlement conditions.  For example,
Reach 4 still retains a large percentage of its presettlement forest area despite river
impoundment, but Reach 8 has lost thousands of acres due to the same
modification.  Most of the remaining floodplain prairies and marshes are much
smaller than their presettlement counterparts, while others have been replaced by
forest - likely the result of fire cessation.  The results of this study confirm that
many of the resource problems of the Mississippi River are attributable to land
management practices directly outside the river-floodplain environment.  If  we
are to successfully preserve, protect, and restore the biological integrity of the
UMRS,  we must integrate management strategies across both upland and river-floodplain landscapes.