Decadal‐scale changes in suspended wood after riparian recruitment in managed stands in headwater streams of coastal British Columbia, Canada

Abstract

Large wood (LW) affects several ecological and hydrogeomorphic processes in streams. The main source of LW is riparian trees falling inside channels. However, in confined valley floors, falling trees are more likely to be suspended above the channel. Eventually, these suspended trees will decompose and break to finally fall into the channel to better provide functions for streams. We evaluated changes in wood decay, length, diameter, and suspended status (suspended or non‐suspended) 17 years post‐harvest and nine years after the first sampling occurred in 2006 in 12 headwater streams of coastal British Columbia, Canada. We also evaluated whether changes differed among riparian management treatments (no‐harvest buffers of 10 and 30 m in width, thinning, and unharvested reference sites), and identified the factors affecting wood changes and suspended status. Wood pieces advanced in decay, became shorter, and 34% of them (n = 108) changed status from suspended to non‐suspended. Non‐suspended wood pieces were more decayed and shorter than suspended wood. Suspended wood was longer, thicker, less decayed, and represented 46.5% (n = 147) of the wood sampled in 2006. Our findings revealed limited influences of riparian management on many aspects of wood changes considered in this study. Changes in wood characteristics were more likely for pieces that were smaller in diameter, longer, and suspended closer to the water. The transition from suspended to non‐suspended LW can be a long‐term process that can increase wood residence time and reduce LW in‐stream functions particularly in confined stream valleys. The suspended stage is also an important mechanism underlying time lags in stream ecosystem responses to riparian tree fall. © 2020 John Wiley & Sons, Ltd.

Too much, too soon? Two Swedish case studies of short-term deadwood recruitment in riparian buffers

“…This aspect is essential to include in best-practice-management considering that vast majority of the deadwood we encountered in both studies was fresh spruce and most of the new deadwood was suspended above the streams (Fig. 5e), not currently benefiting aquatic habitat and organisms (Grizzel and Wolff 1998;Rossetti de Paula et al 2020). Ideally, deadwood should vary in age, species composition and location within the riparian-aquatic environment to support high diversity of organisms utilizing the wood in the decades to come (e.g., Bisson et al 1984;Dynesius and Hylander 2007).…”

Introduction to the Wood in World Rivers special issue

“…The first WWR conference focused on field studies, physical‐biotic interactions, and numerical modeling of wood recruitment to channels. These remain focal topics of riverine science research that explicitly includes the role of large wood, as illustrated by papers in this special issue examining controls on wood load and spatial distribution of wood in diverse field settings (Galia et al, 2020; Iroumé et al, 2020; Máčka et al, 2020; Picco et al, 2021; Rossetti de Paula et al, 2020) and on the geomorphic (Booth et al, 2020; Gurnell et al, 2019; Hinshaw et al, 2020; Iroumé et al, 2020; Zhang & Rutherfurd, 2020) and ecological (Ader et al, 2021; Shirey et al, 2020) effects of large wood.…”