Plant Communities of the Midwest - NatureServe

The development of a standard vegetation classification for conservation, resource management,
and vegetation ecology research is not without controversy. Concerns range from continuum issues to
single versus multi-factor approaches, and to questions about the most practical ways to protect
biodiversity above the species level. For example, should conservation be based on ecological
communities, ecological land units, or functional landscapes The rationale for the approach used by the
ICEC/USNVC, of which the Midwest classification is a part, is more fully explained by Grossman et al.
(1998). However, a core feature of this approach is that it provides the tools needed to define
“naturalness” or “ecological integrity” of an ecological community. The classification categorizes types
based on existing or actual vegetation, thereby describing the current condition of the system, including
whether the vegetation is native, planted, or exotic, and whether it is maintained by disturbances (e.g.,
fire, grazing, or flooding), either natural or cultural (Grossman et. al. 1998). By using this approach to
describe the natural ecological communities across the Midwest, we can define the native assemblages of
species that occur there and the ecological processes that they depend on. Naturalness, which is not a
static or discrete concept, doesn’t preclude human activity in native systems, but it emphasizes the degree
to which native systems function without regular human intervention (Grossman et al. 1998, Angermeier
2000). It is a key criterion for assessing the conservation status of systems, from global to local scales
(Hannah et al. 1995).
Although the USNVC, and the Midwest portion described here, was developed primarily to
address conservation and resource management issues, it also provides a systematic way to describe
natural vegetation patterns and processes across the region. The descriptions provided here attempt to
place the midwestern vegetation in a new perspective. Such an effort is sorely needed. Braun’s (1950)
approach to describing the eastern deciduous forests of North America—an outstanding work in its day—
is still widely used whenever syntheses of forest patterns in the eastern United States are needed (Greller
1988, Barnes 1991, Delcourt and Delcourt 2000). However, early on it was recognized to have some
limitations because of the climax approach used (Whittaker 1957). The seminal work by Curtis (1959),
who described the vegetation of Wisconsin, led to no other comparable state-level efforts in the Midwest.
The hundreds of more local vegetation studies have not been integrated into any single, coherent
framework to interpret the diverse and dynamic patterns of vegetation, although many Natural Heritage
programs have developed systematic classifications and descriptions for conservation applications in their
states (White and Madany 1978, Anderson 1982, Nelson 1985, Minnesota Natural Heritage Program
1993, Lauver et al. 1999, Steinauer and Rolfsmeier 2000). The North American-wide surveys edited by
Barbour and Billings (1988, 2000), although very valuable, are broadly synoptic, and omit many of the
more regional and local vegetation patterns, such as cliff communities, alvars, and “Great Lakes Dunes.”
The approach used here works from broad-based to fine-scale patterns, and relies on existing vegetation
concepts to describe the patterns and condition of the midwestern landscape. In this way, users can
compare the vegetation patterns defined here to ones defined by others, whatever the scale of
presentation. We hope this first qualitative synthesis of midwestern natural terrestrial vegetation will spur
others to review, critique, and refine the patterns of vegetation—at all scales—that are outlined here.
The Midwest classification presented here is an integral part of the USNVC. Through that
system’s hierarchy, associations can be organized hierarchically based primarily on their floristic and
physiognomic relationships (Grossman et al. 1998, Anderson et al. 1998). Such an arrangement is
important for many purposes, many of them of national or international scope. However, when
attempting to convey the information available at the association level to a wide audience of midwestern
ecologists, we have found that such a vegetation-based, international framework is unfamiliar and can be
somewhat cumbersome. As the purpose of this report is to present detailed descriptions at the association
level within the Midwest, we chose to organize the associations by a more ecological, or habitat-based,
approach that we call “ecological groups.” Developing this alternative arrangement for associations,
based on the purpose and audience, is not new; such alternatives have been used when presenting similar
association-based approaches in Europe (e.g., Ellenberg 1988; Rodwell 1991, 2000; Muchina 2001). The
decision to use ecological groups to organize the associations was made late in the classification process
PLANT COMMUNITIES OF THE MIDWEST – 2001
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