A HABITAT MATRIX CONCEPTUAL-MODEL FOR STREAM PERIPHYTON

In this paper we suggest a conceptual model for the evaluation of peri phyton communities in unshaded temperate streams based on the primary habitat variables of flood disturbance, nutrient resource supply and i nvertebrate grazing. The core of this model is a classification of 35 periphyton tars into four main functional groups bused on the C-S-R li fe history strategies of Grime. Possible successional trajectories fol lowing system-wide disturbances under different nutrient supply regime s are also discussed. The interaction of disturbance and nutrient supp ly on species membership, productivity and accrual time results in a p redicted gradient from low biomass in frequently disturbed, unenriched habitats to high biomass in infrequently disturbed, enriched habitats . This prediction is verified empirically using literature data. Herbi vory can strongly modify such periphyton responses to disturbance and resource supply. However, these grazing effects could vary greatly dep ending on the dominant invertebrate grazer and their total abundance, which inturn, is also sensitive to changes in disturbance and nutrient resource supply. This interaction is also discussed. The conceptual m odel complements other more general habitat templet and dynamic equili brium concepts in ecology.