Summary and Conclusions

Abstract

Figure 11.1 summarizes the ideas about the spatial and temporal variability of ecosystems presented in this book. From these ideas, we can draw the following conclusions:

• 1. We recognize all natural ecosystems by differences in climatic regime. Climate, as a source of energy and moisture, acts as the primary control for the ecosystem. As this component changes, the other components change in response. The primary controls over the climatic effects change with scale. Regional ecosystems are areas of essentially homogeneous macroclimate that biogeographers have traditionally recognized as biomes, life zones, or plant formations.

• 2. Landform is an important criterion for recognizing smaller divisions within macroecosystems. Landform (with its geologic substrate, its surface shape, and relief) modifies climatic regimes at all scales within macroclimatic zones. It causes the modification of macroclimate to local climate. Thus, landform provides the best means of identifying local ecosystems. At the mesoscale, the landform and landform pattern form a natural ecological unit. At the microscale, we can divide such patterns topographically into slope and aspect units that are relatively consistent in soil moisture regime, soil temperature regime, and plant association (i.e., the homogeneous “site”).

• 3. Present vegetation and land cover are useful for describing the status of the ecosystem in terms of age or disturbance, not to delineate the boundary of the system.

• 4. Aquatic and riparian systems are closely associated with terrestrial systems and therefore do not need a separate classification, mapping, and/or description mechanism. They are all part of the same landscape ecosystem pattern. All landscapes as ecosystems include both wet and dry, plus warm and cold, extremes within a region. As such, they are neither terrestrial nor aquatic, but geographic units.

• 5. The land is conceived as ecosystems, large and small, nested within one another in a hierarchy of spatial sizes. Management objectives and proposed uses determine which sizes are judged important. The aim of useful land classification and mapping is to distinguish appropriately sized ecosystems. Land units will differ significantly from one another, according to resource production capability and the needs of land management.

• 6. Smaller systems are encompassed in larger systems that control the operation of the smaller systems. We must examine the relationships between an ecosystem at one scale and ecosystems at smaller or larger scales to predict the effects of management prescriptions on resource outputs. A disturbance to an ecosystem affects smaller component systems.