HR: 10:45h
AN: B52A-02    [Abstracts]
TI: Characterizing Dimensions and Abundance of Channel and Riparian Coarse Wood in Rocky Mountain Watersheds: Consequences of Spatial Variation
AU: * Young, M K
EM: mkyoung@fs.fed.us
AF: Rocky Mountain Research Station, Forestry Sciences Laboratory, 800 East Beckwith Avenue, Missoula, MT 59801 United States
AU: Mace, E
EM: emace@fs.fed.us
AF: Rocky Mountain Research Station, Forestry Sciences Laboratory, 800 East Beckwith Avenue, Missoula, MT 59801 United States
AU: Ziegler, E
EM: eziegler@fs.fed.us
AF: Rocky Mountain Research Station, Forestry Sciences Laboratory, 800 East Beckwith Avenue, Missoula, MT 59801 United States
AU: Sutherland, E K
EM: esutherland@fs.fed.us
AF: Rocky Mountain Research Station, Forestry Sciences Laboratory, 800 East Beckwith Avenue, Missoula, MT 59801 United States
AB: Coarse wood is widely recognized as a critical component of aquatic environments in forested ecosystems and fundamental to fish habitat formation, diversity, and stability, as well as sediment dynamics, hydrologic response, and channel complexity. Its significance has resulted in prescriptions for coarse wood abundance in streams, yet few studies have addressed the spatial variation in coarse wood counts and volumes, with many relying on samples taken from reaches of a few hundred meters. To examine these patterns and relations at the scale of individual pieces and in consecutive 50-m reaches, we continuously censused channel large wood and at 250-m intervals sampled riparian large wood along 1- to 5-km reaches in 13 western Montana basins with varying disturbance histories. Although most coarse wood in channels appeared to originate from riparian zones, frequency distributions of dimensions of channel coarse wood compared to those of riparian pieces indicated substantial in-stream processing. Despite apparent transport of coarse wood shorter than bankfull width in nearly all streams, frequency distributions of counts and volumes of channel coarse wood tended to be normal. Surprisingly, in most streams there was no correlation among counts or among volumes of wood in adjacent 50-m reaches, and although correlograms revealed large-scale coarse wood patches in several streams, patch size was unique to each stream. Finally, relations in piece counts (and volumes) between channels and riparian zones were erratic. Sample sizes necessary to estimate mean length and maximum diameter of individual pieces within 25% of the mean were modest (fewer than 30 pieces in most basins), whereas estimating piece volume required sampling over 150 pieces. To characterize coarse wood abundance with similar precision on average required sampling over 1.3 km of stream; to characterize volume required sample sizes exceeding 2.7 km. Consequently, we regard estimates from short stream reaches as unreliable predictors of total coarse wood abundance. Similarly, models predicting coarse wood abundance based on such estimates likely underestimate variation and may yield unrealistic results.
DE: 0400 Biogeosciences
DE: 1824 Geomorphology (1625)
DE: 1851 Plant ecology
SC: Biogeosciences [B]
MN: 2005 Joint Assembly