sensing, led to enormous progress in our knowledge of terrestrial ecosystems at large scales.

Regional-scale studies have been crucial in understanding the role of atmosphere-biosphere exchanges in tropospheric chemistry. Field campaigns such as the Arctic Boundary Layer Expedition series,93 the Canadian Northern Wetlands Studies, and studies of biomass burning (South African Fire-Atmosphere Research Initiative and Transport and Chemistry near the Equator over the Atlantic) transformed our knowledge of tropospheric chemistry. Long-term regional monitoring for atmospheric deposition of acidic species and ozone is key to understanding the regional impacts of atmospheric change on ecosystems. Regional analyses should include both biophysical and biogeochemical interactions of ecosystems and the atmosphere. The biophysical and biogeochemical processes are naturally linked because biophysical processes are critical regulators of trace gas exchange and biogeochemical processes influence biophysical exchanges. Although site measurements of trace gas flux are useful for detecting change and testing models, regional measurements using atmospheric techniques are crucial for constructing budgets. Regional trace gas budgets are naturally estimated in multiscaled studies, such as the Large-Scale Biosphere-Atmosphere Project in Amazonia (see Figure 2.7), where the regional measurements may be tied to local process studies.

Remote sensing should be integral to multidisciplinary studies. Both terrestrial and oceanic remote sensing techniques provide high-resolution information, such as information on land cover (see Plate 3), relevant to regional processes. Integrated regional studies also provide an ideal venue for transferring knowledge about advanced remote sensing capabilities to new user communities, if the research is initiated by interdisciplinary teams.

Modeling at the regional scale is also essential to integrated regional studies. 94 As discussed earlier, it also provides an organizing framework and detailed information complementary to global models. Models provide an encapsulated, or planned, form of disciplinary knowledge in interdisciplinary investigations. The regional scale provides a venue where the critical processes in human-ecosystem-physical interactions may profitably be explored. Models designed for regional application can contain substantially more spatial and biological detail than global models (although this level of detail may only be available in certain regions).

Summary: Key regional measurements

  • High-resolution mapping of land cover (for terrestrial systems) or of physical and optical properties (for aquatic and marine systems).

  • Atmosphere-biosphere exchange of trace gases, toxics, and nutrients.

  • Field programs measuring ecosystem fluxes at organism to regional scales.

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