Input—Output Budgets

Abstract

Because our ecosystems are watersheds, the flux of chemicals into the system may be simplified to that in precipitation (meteorologic vector) and the output to that in drainage waters (geologic vector), at least for those nutrients without a prominent gaseous phase (Bormann and Likens, 1967; Likens and Bormann, 1972). Theoretically, then, the difference between annual input (I) and output (O) for a given chemical constituent tells whether that constituent is being accumulated within the ecosystem, I > O; is being lost from the system, I < O or is quantitatively passing through the system, I = O. By this definition weathering products do not represent an input to the ecosystem; instead, weathering is considered as a process internal to the ecosystem and a part of the intrasystem cycle (Figure 1; Bormann and Likens, 1967; Likens and Bormann, 1972).