Characterizing and contrasting instream and riparian coarse wood in western Montana basins

The importance of coarse wood to aquatic biota and stream channel structure is widely recognized, yet characterizations of large-scale patterns in coarse wood dimensions and loads are rare. To address these issues, we censused instream coarse wood (≥2 m long and ≥10 cm minimum diameter) and sampled riparian coarse wood and channel characteristics in and along 13 streams in western Montana. Instream coarse wood tended to be shorter but of larger diameter than riparian pieces, presumably because of fluvial processing. Instream coarse wood also displayed highly variable spatial patterns. Most segments lacked significant spatial correlation in coarse wood abundance in adjacent 50 m reaches and when present, coarse wood patch sizes (100–1200 m) were specific to particular streams. Estimation of instream and riparian piece dimensions within 25% of the mean required samples of 13–314 pieces, whereas estimation of wood loads instream segments required samples of 8–210 reaches (400–10 500 m). If these results are representative of other systems, few previous studies have used sample sizes adequate to characterize instream coarse wood loads.