Natural and logging disturbances in the temperate rain forests of the Central Coast, British Columbia

Abstract

Natural disturbances frame the spatial and temporal processes of ecosystems and are the foundation for ecosystem-based management. In the coastal temperate rain forests of British Columbia, landscape patterns of natural disturbances and their contrasts with logging are not well documented. Stand-replacing disturbances over the past 140 years were investigated for the Central Coast (1.5 million ha) at regional and local scales using a combination of aerial photograph interpretation and forest management GIS databases. At the regional scale, stand-replacing natural disturbances affected 3.1% of the forested area. The extent of natural disturbances was not strongly affected by the scale of analysis. In contrast, spatial pattern and scale were essential for discerning the full impact of logging. At the regional scale, logging affected 5.4% of the forested area. Within watersheds, however, logging occurred primarily in valley bottoms (81% ± 4%) with 59% ± 10% of valley bottom areas logged, 10 times the area of natural disturbances. Watershed size strongly affected riparian zones, with active floodplains comprising 53% ± 5% of valley bottom area in large (>20 000 ha) watersheds. In physiographically diverse landscapes, geomorphic features (such as watersheds, valley bottoms, and fluvial landforms) are crucial for determining disturbance processes and effects of logging at ecologically relevant scales.