PARENT SESSION
Symposium 4: Ecosystem ecology at the watershed scale: Linking biogeochemical cycles across the terrestrial - aquatic divide
Organized by: ES Bernhardt and MH Valett
Tuesday, August 9, 8:00 AM - 11:30 AM, Meeting Room 517 A, Level 5, Palais des congrès de Montréal

The watershed-ecosystem approach: Historical perspectives and future opportunities and challenges.

Likens, Gene^*,1, ¹ Institute of Ecosystem Studies, Millbrook, NY, USA

ABSTRACT- The watershed-ecosystem approach, pioneered by the Hubbard Brook Ecosystem Study, provides an ecosystem-based framework to think about landscape units (ecosystems) and to quantify the input-output budgets (mass balances) of water, chemicals and energy for large, complicated ecosystems. A relatively simple measurement at the base of a watershed can integrate the complexity of the catchment above and reveal interactions among atmospheric, terrestrial, and aquatic components, thereby extending the analytical framework. Sustained monitoring of input/output parameters and experimental manipulation of these ecosystems at the watershed scale have been powerful in identifying extreme events, in generating new and important mechanistic questions from inside the black box, in elucidating critical connections among air, land and water, in detecting environmental change, and in providing critical data to decision makers. Early, it was recognized that, (. . .the vegetation (upland terrestrial portion) of a watershed and the stream draining it are an inseparable unit functionally) (Bormann and Likens 1967), but rarely has this concept prevailed in actual studies. Now, it is clear that the aquatic/terrestrial interface at the watershed scale is an exciting opportunity/challenge for developing increased overall understanding of the functioning of a landscape (e.g. nitrogen retention). Moreover, deeper quantitative comparison of undisturbed and experimentally manipulated watershed-ecosystems across biomes to find common processes and interactions among hydrology, biogeochemistry and ecology, the creative application to urban-suburban ecosystems, and analysis of interactions among element cycles, present some exciting opportunities for the future. Applying this approach to integrated monitoring, assessment and management of large catchments with complicated land-use patterns, can provide the understanding needed to sustain the health of these watershed-ecosystems.

Key words: watershed-ecosystem approach, hubbard brook ecosystem study, sustained monitoring, aquatic/terrestrial interface