Rentmeester, Steven. 2004. An assessment of large woody debris and riparian forest resources at Ellsworth Creek Watershed and a comparison of riparian management options. M.S.
Selecting and prioritizing large woody debris enhancement projects requires the ability to stratify instream habitat and riparian forests based on current conditions and ecosystem recovery pathways. During the summer of 2003, we inventoried large woody debris, habitat, and geomorphological characteristic of all fish bearing water at Ellsworth Creek Watershed (24.1km). Additionally, the spatial distribution, stand structure, and species composition of riparian forests along main-stem channels were characterized using aerial photos and field data. Trees, saplings, and topography were measured within fifty-seven, 500m2 riparian forest transects. Headwater and main-stem channels (15.9 km and 8.2 km, respectively) were delineated along a 200 ha upstream drainage area breakpoint. As compared to unmanaged basins, headwater channels at Ellsworth Creek had higher than expected abundance of instream wood and key pieces (p-values < 0.001). Main-stem channels were deficient in wood abundance, volume, and key pieces (p-values < 0.001).
Riparian forests within 50 meters of main-stem channels occupy 77.8 hectares. The history of road building and timber harvest left a distinct spatial pattern on these forests. Stands younger than 20 years old accounted for 19.1% of the total area. Stand 20-40 years old covered 22.4%, 40-80 year-old stands covered 33.3%, and stands older than 200 years covered 23.2% of the total area. Average basal area ranged from 24.6 m2/ha in 15 year-old stands to 70.2 m2/ha in stands greater than 200 years old. Stem density ranged from 700-2480 TPH in 25 year-old and younger stands. Density ranged from 140-1000 TPH in older stands. Quadratic mean diameter increased from 14.3 cm in 15 year-old stands to 43.2 cm in stands greater than 200 years old. Channel confinement and stream adjacent landform were important factors influencing species composition.
Effects of thinning on riparian forests were simulated using the Pacific Northwest Coast variant of the Forest Vegetation Simulator (FVS-PNC). Thinning from below increased production of large diameter snags by 28-74% over a “no touch” silviculture. Although thinning from below increased diameter growth in the simulations, it has also been shown to increase wind firmness and has the potential to decrease instream wood recruitment originating from wind disturbance.
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