DECREASED CARBON AND NUTRIENT INPUT TO BOREAL LAKES FROM PARTICULATE ORGANIC-MATTER FOLLOWING RIPARIAN CLEAR-CUTTING

The plankton communities of oligotrophic Canadian Shield lakes are str ongly regulated by the allochthonous supply of total phosphorus (TP) a nd dissolved organic carbon (DOC), a proportion of both of which origi nate from particulate organic matter. Although decreased inputs of all ochthonous leaf litter have been documented for small streams whose ri parian forests have been removed, no such data exist for boreal lakes. Through estimates of airborne litter input from forested and clear-cu t shorelines and laboratory measurements of concentrations released fr om leaf leachate, we determined that riparian deforestation resulted i n reductions of DOC from 17.8 to 0.4 g/m shoreline/yr and of TP from 2 .9 to 0.3 g/m shoreline/yr. Previous predictive models indicate that s uch reductions may be substantial enough to decrease basic metabolic p rocesses of lake plankton communities by as much as 9% in primary prod uction and 17% in respiration.