3.2 General Description of Ecosystem Characterization
Ecosystem :characterization is not itself a goal,
but is a primary tool for ecological assessments and
monitoring (see discussion of different approaches
in Klijn, 1994; Sims et al., 1996; Grossman et aI.,
1999). The characterization process can be either
static (e.g., physical land evaluation) or dynamic
(e.g., see Chapters 18, 19, Chapter 23, and 26).
However, all applications must somehow relate the
patterns of interest to the agents of pattern formation (sensu Urban 'et aI., 1987) or to the causes of
ecological changes. Whereas ecosystems are characterized as functional units, ecological units must
be delineated as their spatial expression (Bailey et
aI., 1994). These,ecological units represent a stratification of landscapes for efficient data collection
and analysis, as well as for presentation of results
(e.g., Bunce et a1\,.1996).
3.2 General Description of
Ecosystem . Characterization
Ecosystems are groups of interacting, interdependent parts (e.g., species, resources) linked to each
other by the exchange of energy, matter, and information. Such 'systems are considered complex
because they are characterized by strong interactions amongc,components and intricate feedback
loops, as well as significant time and space lags,
discontinuities, thresholds, and limits (Costanza et
aI., 1993). Ecosystems can be described at many
different scales.(see Chapter 2; also Levin, 1992),
and therefore the spatial and temporal relationships
of particular ecosystems or their components
should be clearly defined. Describing ecosystems
is a routine scientific endeavor that leads to the generation of classifications and maps (e.g., Klijn,
1994; Sims et al., 1996; Grossman et aI., 1999).
Making predictions about future states of ecosystems under various scenarios requires elucidating
the relationships between patterns and hypothesized causal factors, that is, processes or agents of
pattern formation. Once a correlation or a causeeffect relationship between pattern and process is
determined, predictions are made using (1) data
summarization resulting from classification and/or
mapping, (2) statistical or simulation models, or
(3) a combination of these approaches. Many scientists establish a relationship between pattern and
processes to make predictions, but the approach
taken may lack rigor and standardization. Nevertheless, the formulation of recommended land and
watershed management practices is accomplished
by integrating predictions into proposed conservation and management actions.
41
Complex ecosystem patterns and the multitude
of processes that form them exist within a hierarchical framework (see Chapter 2; also Allen and
Starr, 1982; Allen et aI., 1984; O'Neill et aI., 1986).
Scale dependency is very significant in the context
of assessments conducted to understand relationships among patterns and processes, because such
relationships change as spatial scale changes
(Turner, 1990; Davis et aI., 1991). In recent years,
considerable attention has been directed toward describing the hierarchical organization of terrestrial
and aquatic ecosystems (see Chapters 22 and 24;
also Frissell et al., 1986; Amoros et aI., 1987; Urban et aI., 1987; Minshall, 1988, 1994; Naiman,
1988; Pringle et aI., 1988; Wiens, 1989; Poff and
Ward, 1990; Bayley and Li, 1992; Gardner et aI.,
1992; Holling, 1992; Lathrop and Peterson, 1992;
Klijn, 1994; Sims et al., 1996; Grossman et aI.,
1999). As applied to landscape ecology, hierarchy
theory provides a framework for characterizing the
components of an ecosystem or set of ecosystems,
as well as for detecting the linkages among different scales of ecological organization (see Chapter
2; also Allen and Starr, 1982; O'Neill et al., 1986;
Urban et aI., 1987).
Ecosystem characterization (Levin, 1992) is carried out to map and conduct landscape evaluation
at scales ranging from the site to the continent. Ecological classifications are developed to delineate
ecological units at multiple scales using criteria appropriate to the objectives of the project. Terrestrial ecological units are defined using terrestrial
variables (e.g., ECOMAP, 1993; Bailey et aI.,
1994; Bailey, 1995). Aquatic-hydrologic units are
defined using variables relevant to aquatic systems
(e.g., Maxwell et aI., 1995; Jensen et aI., 1996). In
all cases, boundaries are drawn around ecosystems
to delineate the ecological units at appropriate ecological and planning scales (Omernik, 1987; Zonneveld, 1989; Maxwell et al., 1995; Jensen et aI.,
1996). Major ecological classification and mapping
systems and their goals, objectives, and uses are
presented in Klijn (1994), Sims et a1. (1996), and
Grossman et a1. (1999).
Most ecological assessments and land management practices are concerned with patterns or static structures, but the dynamic nature of ecosystems
cannot be ignored. It has long been documented
that ecosystems are rarely in equilibrium. Nonequilibrium dynamics include succession along
multiple pathways, discontinuities, and surprises as
ecosystems track constantly changing environmental conditions (Holling, 1986; Kay, 1991; Costanza
et al., 1993). Examples of dynamic processes that
can lead to nonequilibrium behavior for terrestrial
Ecosystem :characterization is not itself a goal,
but is a primary tool for ecological assessments and
monitoring (see discussion of different approaches
in Klijn, 1994; Sims et al., 1996; Grossman et aI.,
1999). The characterization process can be either
static (e.g., physical land evaluation) or dynamic
(e.g., see Chapters 18, 19, Chapter 23, and 26).
However, all applications must somehow relate the
patterns of interest to the agents of pattern formation (sensu Urban 'et aI., 1987) or to the causes of
ecological changes. Whereas ecosystems are characterized as functional units, ecological units must
be delineated as their spatial expression (Bailey et
aI., 1994). These,ecological units represent a stratification of landscapes for efficient data collection
and analysis, as well as for presentation of results
(e.g., Bunce et a1\,.1996).
3.2 General Description of
Ecosystem . Characterization
Ecosystems are groups of interacting, interdependent parts (e.g., species, resources) linked to each
other by the exchange of energy, matter, and information. Such 'systems are considered complex
because they are characterized by strong interactions amongc,components and intricate feedback
loops, as well as significant time and space lags,
discontinuities, thresholds, and limits (Costanza et
aI., 1993). Ecosystems can be described at many
different scales.(see Chapter 2; also Levin, 1992),
and therefore the spatial and temporal relationships
of particular ecosystems or their components
should be clearly defined. Describing ecosystems
is a routine scientific endeavor that leads to the generation of classifications and maps (e.g., Klijn,
1994; Sims et al., 1996; Grossman et aI., 1999).
Making predictions about future states of ecosystems under various scenarios requires elucidating
the relationships between patterns and hypothesized causal factors, that is, processes or agents of
pattern formation. Once a correlation or a causeeffect relationship between pattern and process is
determined, predictions are made using (1) data
summarization resulting from classification and/or
mapping, (2) statistical or simulation models, or
(3) a combination of these approaches. Many scientists establish a relationship between pattern and
processes to make predictions, but the approach
taken may lack rigor and standardization. Nevertheless, the formulation of recommended land and
watershed management practices is accomplished
by integrating predictions into proposed conservation and management actions.
41
Complex ecosystem patterns and the multitude
of processes that form them exist within a hierarchical framework (see Chapter 2; also Allen and
Starr, 1982; Allen et aI., 1984; O'Neill et aI., 1986).
Scale dependency is very significant in the context
of assessments conducted to understand relationships among patterns and processes, because such
relationships change as spatial scale changes
(Turner, 1990; Davis et aI., 1991). In recent years,
considerable attention has been directed toward describing the hierarchical organization of terrestrial
and aquatic ecosystems (see Chapters 22 and 24;
also Frissell et al., 1986; Amoros et aI., 1987; Urban et aI., 1987; Minshall, 1988, 1994; Naiman,
1988; Pringle et aI., 1988; Wiens, 1989; Poff and
Ward, 1990; Bayley and Li, 1992; Gardner et aI.,
1992; Holling, 1992; Lathrop and Peterson, 1992;
Klijn, 1994; Sims et al., 1996; Grossman et aI.,
1999). As applied to landscape ecology, hierarchy
theory provides a framework for characterizing the
components of an ecosystem or set of ecosystems,
as well as for detecting the linkages among different scales of ecological organization (see Chapter
2; also Allen and Starr, 1982; O'Neill et al., 1986;
Urban et aI., 1987).
Ecosystem characterization (Levin, 1992) is carried out to map and conduct landscape evaluation
at scales ranging from the site to the continent. Ecological classifications are developed to delineate
ecological units at multiple scales using criteria appropriate to the objectives of the project. Terrestrial ecological units are defined using terrestrial
variables (e.g., ECOMAP, 1993; Bailey et aI.,
1994; Bailey, 1995). Aquatic-hydrologic units are
defined using variables relevant to aquatic systems
(e.g., Maxwell et aI., 1995; Jensen et aI., 1996). In
all cases, boundaries are drawn around ecosystems
to delineate the ecological units at appropriate ecological and planning scales (Omernik, 1987; Zonneveld, 1989; Maxwell et al., 1995; Jensen et aI.,
1996). Major ecological classification and mapping
systems and their goals, objectives, and uses are
presented in Klijn (1994), Sims et a1. (1996), and
Grossman et a1. (1999).
Most ecological assessments and land management practices are concerned with patterns or static structures, but the dynamic nature of ecosystems
cannot be ignored. It has long been documented
that ecosystems are rarely in equilibrium. Nonequilibrium dynamics include succession along
multiple pathways, discontinuities, and surprises as
ecosystems track constantly changing environmental conditions (Holling, 1986; Kay, 1991; Costanza
et al., 1993). Examples of dynamic processes that
can lead to nonequilibrium behavior for terrestrial