Northern Prairie Wildlife Research Center
of 6.1. These results are similar to those found in the Chicago region, Illinois,
and Michigan where 11%, 17%, and 15% (respectively) of the native plant species
were assigned C values of 3 or less and the native floras had s
of 7.3, 6.4, and 6.5 (Swink and Wilhelm 1994, Herman et al. 1996, Taft et al.
1997).
| Figure 1. Distribution of the 1309 native plant taxa occurring in North and South Dakota (excluding the Black Hills) by coefficient of conservatism designation. |
Grouping taxa by physiognomic class reveals that most native species in the Dakotas are perennial forbs, followed by annual forbs, perennial sedges, perennial grasses, and shrubs, respectively (Figure 2). Conversely, our region's non-native taxa are dominated by annual forbs. Also, although only 16% of our native grasses are annuals, over half (55%) of the non-native grass taxa are annuals. Of the 129 perennial grasses in our area of consideration, only 18 (14%) are non-native; however, of the 44 annual grasses, half are non-native. Much of our current landscape favors annual plants whereas annual species were less prevalent in our region's pre-settlement plant communities. The shift from habitats favorable to perennials to those providing competitive advantages to annuals is clearly reflected in the physiognomic composition of the non-native plant taxa that have successfully invaded our region.
By applying the coefficients of conservatism supplied here and calculating
Floristic quality assessment may help to better focus our efforts in areas
of greatest potential benefit as competition for limited natural and financial
resources continues. For example, drainage of a wetland with a long history
of cropping in the basin during periods of below average precipitation may
be easy to mitigate in terms of the native plant communities it supports.
The species inhabiting this wetland will be limited to those that can tolerate
the extreme disturbances associated with periodic cropping and will quickly
repopulate a created or restored basin with minimal effort. However, a similarly
sized wetland with soils that have never been tilled may support a native
plant community rich in conservative species and be beyond our current abilities
to create or restore; loss of this wetland should be considered an immitigable
event. Floristic quality assessment allows us to identify high quality natural
areas and to measure the quality of native plant communities we have attempted
to restore and/or manage, thus providing an objective assessment of our current
restoration and management efforts.
Figure 2. Distribution of native and
non-native plant taxa occurring in North and South Dakota (excluding
the Black Hills) by physiognomic class.
and FQI, an effective means of evaluating the
quality of plant communities in our region is obtained. Changes in quality,
either positive or negative, can be identified by repeating surveys and calculations
over time. Through the use of floristic quality assessment, a preserve manager
reintroducing fire to a landscape in a manner approximating pre-European settlement
conditions can determine, through changes in
and FQI, if the change in management is allowing conservative plant species
to repopulate the area. Similarly, a regulator attempting to estimate the
consequences of draining a wetland can obtain a clearer idea of the likelihood
of recreating a wetland with a comparable plant community elsewhere, and a
real estate specialist will have reliable information for ranking tracts of
land when acquisition funds are limited.
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U.S. Department of the Interior |
U.S. Geological Survey
URL: http://www.npwrc.usgs.gov/resource/plants/fqa/resdisc.htm
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