Multi-scale approach for restoring endangered riparian forests of the Skeena River Floodplain.
Haeussler, Sybille*,1, 2, de Groot, Adrian1, 1 Bulkley Valley Centre for Natural Resources Research & Management, Smithers, BC, Canada2 University of British Columbia, Vancouver, BC, Canada
ABSTRACT- Floodplains of major rivers are ideal systems for studying multi-scale linkages among ecological processes and structures. The Skeena River in British Columbia, Canada (watershed area 54,432 km2; mean annual discharge 1730m3/sec) is the largest free-flowing temperate zone river in the world with a floodplain largely unmodified by urban and agricultural development. On the lower floodplain, 20th century logging replaced 85% of old growth Sitka spruce (Picea sitchensis) riparian forest with secondary black cottonwood (Populus balsamifera ssp. trichocarpa)-dominated stands, now in high demand for fibre production. Riparian Sitka spruce forests are red-listed in British Columbia, while cottonwood forests are blue-listed. To guide adaptive management of the floodplain and restoration of endangered old growth ecosystems, our research is examining regional- to microsite-scale factors affecting the stability, recruitment and restoration potential of Sitka spruce and black cottonwood forests. We used hydrological records (1928 - 2004), digitally mapped 1947- 2005 aerial photos (16,000 ha) and soils, stand structure and vegetation data from 3 stand types (old growth spruce; primary deciduous; secondary post-logged deciduous) to update a traditional state-factor model of floodplain succession (based primarily on bench height) into a more comprehensive model that links phenomena at regional (hydrologic regime), landscape (spatial pattern of erosion, deposition and log jam development) and within-stand (coarse woody debris recruitment, exotic earthworm activity) scales to prioritize stands for either conservation, active restoration or commercial harvest. Although superficially similar, primary and secondary deciduous stands differed in floodplain stability, species diversity, and conifer recruitment patterns. Thus, although secondary deciduous stands are most attractive for commercial harvest, they also appear to have better potential for successful restoration of endangered old growth Sitka spruce.
Key words: endangered ecosystems, restoration, disturbance dynamics, riparian
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