3
Ecosystem Characterization
and Ecological Assessments
Patrick S. Bourgeron, Hope C. Humphries, and Mark E. Jensen
3.1 Introduction
Ecological assessments are an important component of any strategy for making or reevaluating land
management and regulatory decisions (see Chapters 1,9, and 35; also Slocombe, 1993; Jensen and
Bourgeron, 1994; Bourgeron et aI., 1995). An important objective of ecological assessments is the
identification, location, and description of the biotic and abiotic features of a landscape. Landscape
features exhibit heterogeneity at a variety of scales
(Turner et aI., 1995). This heterogeneity is characterized by identifying relevant patterns and the
processes that produce patterns in a landscape
(Bourgeron and Jensen, 1994). Distinct patterns
and processes occur at a variety of spatial and temporal scales of organization (see Chapter 2). For
ecological assessments, an explicit understanding
is needed of the scaled relationships of biological
and biophysical characteristics from site to regional
scales (Lessard, 1995; Lessard et aI., 1999). Therefore, the characterization process is a multi scaled
approach conducted within a hierarchical framework (Bourgeron and Jensen, 1994; Hann et aI.,
1994; Bourgeron et aI., 1995; Jensen et aI., 1996).
The emerging approach for land and resource
management (e.g., O'Neill et al., 1997; Lessard et
aI., 1999) recognizes ecosystems as the context for
assessment and monitoring of various commodities, species, and other resources (Lubchenco et aI.,
Patrick S. Bourgeron and Hope C. Humphries wish to
acknowledge partial funding provided by a Science to
Achieve Results grant from the U.S. Environmental Protection Agency ("Multi-scaled Assessment Methods:
Prototype Development within the Interior Columbia
Basin").
40
1991; Franklin, 1993; Mladenoff and Pastor, 1993;
Jensen and Bourgeron, 1994; Stork et aI., 1997).
Such an ecosystem approach requires methods for
characterizing the landscape attributes that influence ecosystem integrity and sustainability at various spatial scales (Zonneveld, 1988, 1989; Levin,
1992; Franklin, 1993; Mladenoff and Pastor, 1993;
Bourgeron et aI., 1994b, 1995; Bunce et aI., 1996;
Mladenoff et aI., 1997). Regardless of their specific
objectives and scope, all ecological assessments require the delineation of broad-scale land units to
provide a context for the evaluation and management of commodities or elements of biodiversity;
this is the process of regionalization (Omernik,
1987; Jensen et aI., 1996; Bailey, 1995; Maxwell
et aI., 1995). Ecological assessments also require
delineation of fine-scale ecological units to describe the basic landscape patterns and characteristics that are important for the issues at hand (Zonneveld, 1989, 1994).
This chapter presents general principles pertaining to two aspects of ecosystem characterization,
classification and regionalization-mapping of ecosystem units, that are central to ecological assessments (Bailey, 1996; Rowe, 1996). As a consequence of the hypothesis that ecosystems can be
characterized at different scales (hierarchically
arranged), ecosystem units can be arranged in a hierarchy of sizes, can capture links between biotic
and abiotic ecosystem components, and can link
terrestrial and aquatic systems. Ecosystem characterization conducted for regional ecological assessments combines the principles of ecosystem
theory and landscape ecology (see Chapter 2) with
the methods developed in geography for describing tracts of land. This chapter includes discussion
of issues of definition and prediction of ecosystem
properties and extrapolation of results.
Ecosystem Characterization
and Ecological Assessments
Patrick S. Bourgeron, Hope C. Humphries, and Mark E. Jensen
3.1 Introduction
Ecological assessments are an important component of any strategy for making or reevaluating land
management and regulatory decisions (see Chapters 1,9, and 35; also Slocombe, 1993; Jensen and
Bourgeron, 1994; Bourgeron et aI., 1995). An important objective of ecological assessments is the
identification, location, and description of the biotic and abiotic features of a landscape. Landscape
features exhibit heterogeneity at a variety of scales
(Turner et aI., 1995). This heterogeneity is characterized by identifying relevant patterns and the
processes that produce patterns in a landscape
(Bourgeron and Jensen, 1994). Distinct patterns
and processes occur at a variety of spatial and temporal scales of organization (see Chapter 2). For
ecological assessments, an explicit understanding
is needed of the scaled relationships of biological
and biophysical characteristics from site to regional
scales (Lessard, 1995; Lessard et aI., 1999). Therefore, the characterization process is a multi scaled
approach conducted within a hierarchical framework (Bourgeron and Jensen, 1994; Hann et aI.,
1994; Bourgeron et aI., 1995; Jensen et aI., 1996).
The emerging approach for land and resource
management (e.g., O'Neill et al., 1997; Lessard et
aI., 1999) recognizes ecosystems as the context for
assessment and monitoring of various commodities, species, and other resources (Lubchenco et aI.,
Patrick S. Bourgeron and Hope C. Humphries wish to
acknowledge partial funding provided by a Science to
Achieve Results grant from the U.S. Environmental Protection Agency ("Multi-scaled Assessment Methods:
Prototype Development within the Interior Columbia
Basin").
40
1991; Franklin, 1993; Mladenoff and Pastor, 1993;
Jensen and Bourgeron, 1994; Stork et aI., 1997).
Such an ecosystem approach requires methods for
characterizing the landscape attributes that influence ecosystem integrity and sustainability at various spatial scales (Zonneveld, 1988, 1989; Levin,
1992; Franklin, 1993; Mladenoff and Pastor, 1993;
Bourgeron et aI., 1994b, 1995; Bunce et aI., 1996;
Mladenoff et aI., 1997). Regardless of their specific
objectives and scope, all ecological assessments require the delineation of broad-scale land units to
provide a context for the evaluation and management of commodities or elements of biodiversity;
this is the process of regionalization (Omernik,
1987; Jensen et aI., 1996; Bailey, 1995; Maxwell
et aI., 1995). Ecological assessments also require
delineation of fine-scale ecological units to describe the basic landscape patterns and characteristics that are important for the issues at hand (Zonneveld, 1989, 1994).
This chapter presents general principles pertaining to two aspects of ecosystem characterization,
classification and regionalization-mapping of ecosystem units, that are central to ecological assessments (Bailey, 1996; Rowe, 1996). As a consequence of the hypothesis that ecosystems can be
characterized at different scales (hierarchically
arranged), ecosystem units can be arranged in a hierarchy of sizes, can capture links between biotic
and abiotic ecosystem components, and can link
terrestrial and aquatic systems. Ecosystem characterization conducted for regional ecological assessments combines the principles of ecosystem
theory and landscape ecology (see Chapter 2) with
the methods developed in geography for describing tracts of land. This chapter includes discussion
of issues of definition and prediction of ecosystem
properties and extrapolation of results.