18
Landscape and Regional Biogeochemistry:
Approaches
Ingrid C. Burke
Introduction
Landscape- or regional-scale biogeochemistry is a
subfield of biogeochemistry that focuses on the
large-scale spatial variation in the fluxes and distribution of elements. The application of ecosystem
ecology to such large spatial scales is inherently
problematical because processes are difficult if not
impossible to measure at these scales (Rosswall et
al. 1988; Groffman and Wagenet 1994). Biogeochemical processes at such scales are important determinants of regional-to-global earth system dynamics, and are the best indication of atmospherebiosphere interactions and economic processes that
result from food and other natural resource production (Schimel et al. 1988; Matson et al. 1989; Burke
et al. 1991; Riebsame et al. 1994; Walker 1994).
There are three general types of questions that
are addressed in landscape or regional biogeochemistry. First, we seek to understand patterns in the
distribution and flux of elements in currently existing landscapes or regions (discussed in section on
pattern analysis). This type of study often utilizes
the spatial and temporal variability that occurs
across large scales to study the controls over biogeochemical processes (e.g., Jenny 1941; Lieth
1978; Meentemeyer et al. 1985; Zak et al. 1986;
Groffman and Tiedje 1989; Burke 1989; Knapp et
al. 1993; Schimel et al. 1991; and many others).
For instance, a landscape or region may have strong
variation in soil water availability, soil temperature,
soil texture, and land use, all of which are important
controls over net primary productivity, decomposition, soil organic matter, and trace gas flux. The
landscape provides an experimental framework in
which we can ask how these controls interact to
influence the flux and distribution of elements. This
experimental framework is simpler than conducting
a manipulative analysis. It is also confounded however, since most of the major controls over biogeochemical processes (i.e., microclimate and soils)
vary together across the landscape (Groffman et al.
1988; Burke 1989), making it difficult to isolate the
influence of individual control factors.
In a second type of analysis, we address the biogeochemical connections among components of the
landscape (discussed in section on spatially explicit
analysis). In this case, components of the landscape
are spatially dependent; changes in one place influence the flux and distribution of elements in another. Water is most often the important vector for
transporting elements among landscape components, so this type of study often addresses the
terrestrial-aquatic interface. Wind may also be an
important vector, particularly for soil erosion. This
type of study is fundamentally different from the
pattern analysis described above because the biogeochemical processes studied are so-called "spatially explicit," or represent spatial redistribution
within or among landscapes and regions.
Finally, in a third general type of study in landscape or regional biogeochemistry, we attempt to
extrapolate our understanding the controls over biogeochemical pools and fluxes over large scales (discussed in section on extrapolating to regional or
landscape scale). Landscapes and regions correspond with the scales at which many important processes and perturbations occur, including land-use
management, fires, flooding, and some severe
weather events. Simple empirical modeling or
277
Landscape and Regional Biogeochemistry:
Approaches
Ingrid C. Burke
Introduction
Landscape- or regional-scale biogeochemistry is a
subfield of biogeochemistry that focuses on the
large-scale spatial variation in the fluxes and distribution of elements. The application of ecosystem
ecology to such large spatial scales is inherently
problematical because processes are difficult if not
impossible to measure at these scales (Rosswall et
al. 1988; Groffman and Wagenet 1994). Biogeochemical processes at such scales are important determinants of regional-to-global earth system dynamics, and are the best indication of atmospherebiosphere interactions and economic processes that
result from food and other natural resource production (Schimel et al. 1988; Matson et al. 1989; Burke
et al. 1991; Riebsame et al. 1994; Walker 1994).
There are three general types of questions that
are addressed in landscape or regional biogeochemistry. First, we seek to understand patterns in the
distribution and flux of elements in currently existing landscapes or regions (discussed in section on
pattern analysis). This type of study often utilizes
the spatial and temporal variability that occurs
across large scales to study the controls over biogeochemical processes (e.g., Jenny 1941; Lieth
1978; Meentemeyer et al. 1985; Zak et al. 1986;
Groffman and Tiedje 1989; Burke 1989; Knapp et
al. 1993; Schimel et al. 1991; and many others).
For instance, a landscape or region may have strong
variation in soil water availability, soil temperature,
soil texture, and land use, all of which are important
controls over net primary productivity, decomposition, soil organic matter, and trace gas flux. The
landscape provides an experimental framework in
which we can ask how these controls interact to
influence the flux and distribution of elements. This
experimental framework is simpler than conducting
a manipulative analysis. It is also confounded however, since most of the major controls over biogeochemical processes (i.e., microclimate and soils)
vary together across the landscape (Groffman et al.
1988; Burke 1989), making it difficult to isolate the
influence of individual control factors.
In a second type of analysis, we address the biogeochemical connections among components of the
landscape (discussed in section on spatially explicit
analysis). In this case, components of the landscape
are spatially dependent; changes in one place influence the flux and distribution of elements in another. Water is most often the important vector for
transporting elements among landscape components, so this type of study often addresses the
terrestrial-aquatic interface. Wind may also be an
important vector, particularly for soil erosion. This
type of study is fundamentally different from the
pattern analysis described above because the biogeochemical processes studied are so-called "spatially explicit," or represent spatial redistribution
within or among landscapes and regions.
Finally, in a third general type of study in landscape or regional biogeochemistry, we attempt to
extrapolate our understanding the controls over biogeochemical pools and fluxes over large scales (discussed in section on extrapolating to regional or
landscape scale). Landscapes and regions correspond with the scales at which many important processes and perturbations occur, including land-use
management, fires, flooding, and some severe
weather events. Simple empirical modeling or
277