1999 Proceedings
DEVELOPING A GIS DATABASE TO MONITOR PLANT POPULATION DYNAMICS IN THE FLOODPLAIN: A MODEL BASED ON BOLTONIA DECURRENS, A THREATENED SPECIES
Southern Illinois University Edwardsville
Abstract Plans for restoration of large-river floodplain ecosystems must include strategies to restore the integrity of the vegetation of the area (Olson and Harris, 1997; Russell et al., 1997); however, restoration and conservation efforts are difficult due to the dynamic nature of the systems (Sparks et al., 1998). This study applied geographic information system (GIS) technology to develop a model to predict current and potential population sites for Boltonia decurrens, a wetland plant species endemic to the floodplains of the Illinois River and its confluence with the Mississippi River. Populations of B. decurrens, a fugitive species, vary annually in size and location, depending upon the timing and severity of annual floods (USFWS, 1990). Over the past 100 years, a net decline in population numbers has resulted from the reduction of suitable floodplain habitat (Bellrose et al., 1983; Schwegman and Nyboer, 1985; USFWS, 1990). Because the Illinois floodplain system is large and extremely dynamic, predicting the location of populations or selecting suitable sites for restoration is time-consuming and costly. The primary purpose of this study was to develop a predictive model,
based on environmental constraint criteria, which could enable conservation
biologists and government agencies to locate unknown populations, predict
areas that may be colonized after a flood event, or select suitable sites
for reintroduction of the species. A 90 km2 site containing
two known B. decurrens populations was selected to determine the
feasibility of utilizing GIS technology and readily available data to create
a predictive model based on habitat criteria, and to apply that model to
the study area to assess its accuracy. A database, organized by site location,
was established in ArcView 3.1. Soil series type, as defined by the U.S.
Department of Agriculture (USDA) Soil Conservation Service (SCS), National
Wetland Inventory (NWI) classifications, and distance to surface water
were identified for the two known sites and used to define the environmental
constraint criteria of the model. Another data layer defining the extent
of surface water during the 1993 flood was initiated to determine if the
population which predated the 1993 flood could have been the seed source
for the second population which emerged in 1994. Genetic analysis was begun
to test the seed dispersal hypothesis, but the results of the isozyme data
are incomplete. Study areas which met environmental constraint criteria
were identified and ground-truthed. Site inspection of predicted areas
confirmed that the model is capable of identifying potential locations
of suitable habitat. Of the locations that met the three habitat criteria,
71% had populations of either B. decurrens or B. asteroides,
a closely related species with similar habitat requirements. Of the total
study area, 2.7% was identified as suitable habitat, reducing the searchable
area by 97.3% and therefore reducing the cost of field surveys. The approach
used in this study could be adapted for use with any species of concern,
or for groups of plants or animals which share similar habitat requirements.
The database development is continuing and will be used to answer additional
questions concerning plant population dynamics on the floodplain.
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