ASSESSING AND RESTORING MISSISSIPPI RIVER BLUFFLAND OAK SAVANNAH USING GIS

Kirkpatrick, C., Powell, L. University of Dubuque, Environmental Science/Biology 
Dept., 2000 University Ave. Dubuque IA, 52001
Mills, D. Iowa Natural Heritage Foundation. Land Conservation Specialist

Keywords: Oak Savannah, Mississippi River Bluff, Historical 
Land Use, Land Management, GIS/Arcview applications

We worked with the Iowa Natural Heritage Foundation and the Four Mounds 
Foundation to plan, carry out, and assess the restoration of prairie remnants in 
a historic oak savannah on the Mississippi River bluff land north of Dubuque.  
We obtained vegetation databases from the Iowa Dept. of Natural Resources that 
allowed us to determine the past history of land use on approximately 15 acres 
of land overlooking Lock and Dam No. 11.  Our goals were to remove the invasive 
native and non-native tree species in an attempt to open up the forest canopy to 
its original savannah condition.  Prairie grasses and forbs would be encouraged 
by this management scheme.  We also desired to connect four isolated patches of 
nearby prairie remnants within the savannah.  The final goal was to manage the 
remaining oak, hickory, and walnut populations.  To begin restoration efforts 
that would result in a more native, presettlement vegetation cover, we first 
sampled the savannah to obtain tree diversity, density, and size. The data were 
transcribed into GIS databases to provide a spatially referenced view of the 
area.  We then conducted selective tree thinning and prescribed burns during 
2001.  Following these management practices, we re-sampled the area to assess 
the success of restoration efforts.  The oaks and hickories were our main 
species to manage for, and their dbh values were 16.7 and 20.6cm, which were 
third and fifth largest respectively. Several species were reduced in their 
occurrences within transects of the study area. Red cedars were reduced from 75 
down to 8 percent, buckthorn from 78 to 16 percent, black cherry from 31 to 18.6 
percent, and elm species from 52 to 26 percent. Black locusts remained on the 
site, but 100% were girdled and treated with herbicide.  Walnuts were thinned 
from a 50 percent occurrence rate to 33 percent.  This thinning and removal 
should allow the release of younger oaks as competition for resources decreases.  
The available space will also in time release forbes and grasses from the seed 
bank for further habitat improvement.