Instream large wood loads across bioclimatic regions

Drivers of Low Instream Large Wood Retention and Imprints of Wood Mobility in Mountain Nonperennial Streams of a Mediterranean Semiarid Environment

“…In general, we observed a gradual downstream decrease in LW volumes based on (i) increasing channel width, (ii) changing valley settings from canyon‐like confined to unconfined, and (iii) declining conifer trees in the riparian corridor. The link between the increasing channel width and decreasing LW volume fits well into the conclusions of compilation studies summarizing general predictors of LW retention across the globe (Ruiz‐Villanueva et al, ; Wohl et al, ). Increasing valley floor width and decreasing confinement allows potential out‐of‐channel storage (Benda & Sias, ; Martin & Benda, ; Wohl et al, ), but this LW loss was not as evident in the field, likely due to overall low LW abundance in the studied fluvial corridors.…”

“…We investigated predictors of LW frequencies and volumes in steep intermittent and ephemeral streams of semiarid Mediterranean environment. In general, a very low LW frequency (6.5 LW/100 m) and LW volume (9.06 m 3 /ha) were found in the studied reaches in comparison with those found in compilation reports that include steep streams draining various bioclimatic regions (Ruiz‐Villanueva et al, ; Wohl, ; Wohl et al, ). The initial LW inventory in the Lefka Ori Mountains took place in the 4‐km‐long ephemeral reach of the Sfakiano Gorge, which was influenced by intensive sediment transport and considerable morphological changes during the last major flood event in 2000 (Galia, Škarpich, et al, ).…”

“…Some fundamental questions for sustainable management of stream and river channels (e.g., to restore habitats for target fish species or predict flood hazards in relation to possible LW transport) are how much wood we should expect in the channel and what the local driving factors of LW occurrence are. Although there are a limited number of LW inventories from sites outside temperate bioclimatic regions, previous compilation reports suggest the following global trends: (i) Unmanaged channels surrounded by old‐growth forests usually have much higher LW volumes than managed channels or channels with human‐altered structure of riparian corridors, and (ii) environments with relatively high biomass production and simultaneously slow decay rates of wood have higher LW volumes than other regions (Ruiz‐Villanueva et al, ; Wohl et al, ). At the same time, specific LW volumes per channel area generally decrease with increasing catchment area and/or channel width; these parameters represent a proxy for stream transport capacity (Martin & Benda, ; Piégay et al, ; Wohl et al, ; Wohl & Jaeger, ).…”

“…Although there are a limited number of LW inventories from sites outside temperate bioclimatic regions, previous compilation reports suggest the following global trends: (i) Unmanaged channels surrounded by old‐growth forests usually have much higher LW volumes than managed channels or channels with human‐altered structure of riparian corridors, and (ii) environments with relatively high biomass production and simultaneously slow decay rates of wood have higher LW volumes than other regions (Ruiz‐Villanueva et al, ; Wohl et al, ). At the same time, specific LW volumes per channel area generally decrease with increasing catchment area and/or channel width; these parameters represent a proxy for stream transport capacity (Martin & Benda, ; Piégay et al, ; Wohl et al, ; Wohl & Jaeger, ). By contrast, a lack of correlation between LW abundance and bed slope has been reported by using a large worldwide data set (Wohl et al, ), although this parameter is perceived as an important predictor for the mobility of bed sediments.…”

“…At the same time, specific LW volumes per channel area generally decrease with increasing catchment area and/or channel width; these parameters represent a proxy for stream transport capacity (Martin & Benda, ; Piégay et al, ; Wohl et al, ; Wohl & Jaeger, ). By contrast, a lack of correlation between LW abundance and bed slope has been reported by using a large worldwide data set (Wohl et al, ), although this parameter is perceived as an important predictor for the mobility of bed sediments. This underlines the importance of the channel width versus wood length ratio as the main factor controlling wood stability in the channel (Braudrick & Grant, ; Gurnell et al, ).…”