Living woody vegetation as a storage element for large wood in the channel

The stability of large wood (LW) in the channels is a prerequisite for its persisting geomorphic and ecological effects. This study analysed the factors influencing the storage of LW by living woody vegetation while still interacting with the active channel (and consequently, having potential geomorphic and ecological impact in the channel). It was conducted through field inventory of sixteen European channel reaches across various environmental settings. On the reach scale, the volumes of LW pinned by woody vegetation per channel area (0.1-18.2 m³/ha) followed global trends for total LW volumes., As the catchment area and channel width increased, and bed slope decreased, LW volumes pinned by vegetation decreased. However, the volumetric proportion of LW pinned by vegetation (1.5-30.3 %) did not increase solely as a simple function of the increasing LW mobilisation rate (represented by the increasing catchment area and channel width) or the increasing density of woody vegetation in the fluvial corridor. Instead, the specifics of the disturbance regime had an additional impact on the distribution of LW and its potential pinning on living vegetation in fluvial corridors. Moreover, stable vegetated patches in the channel were detected as significant features responsible for the pinning of LW. Only two tested reaches indicated significantly smaller dimensions of LW pinned by vegetation compared to unattached LW. This implied a possible equimobility mode of LW transport based on their sizes during flood pulses, suggesting somewhat 'random' dimensions of LW trapped by woody vegetation. This study demonstrated that woody vegetation occupying fluvial corridors cannot be solely regarded as sources of LW recruitment, but these trees and shrubs also play a crucial role as retention elements for mobilised wood during floods or other hydrogeomorphic events.