Long-term effects of riparian forest harvest on light in Pacific Northwest (USA) streams

Abstract

AbstractRiparian forests exert strong influence on abiotic and biotic processes in adjacent streams by regulating light. Harvesting of riparian forests was once common practice, and consequently, many streamside forests across North America are in varying stages of development as they regenerate, thereby affecting stream light regimes. We used 2 approaches to evaluate the influence of riparian forest harvest and stand recovery on light availability in small mountain streams. We estimated light and canopy cover every 25 m along 11.5 km of a 4th-order stream network dominated by late-successional riparian forests that included 7 streamside harvest units 50 to 60 y old. Estimates of stream light fluxes were lower in harvest units than in up- and downstream sections bordered by old-growth forests even though only 1 stream bank was harvested in 5 of 7 units. Differences in stream light between harvested reaches and adjacent old-growth sections were greater when both banks had been logged. We also conducted a s...