Drivers of variability in large wood loads along the fluvial continuum of a Mediterranean intermittent river

Abstract

AbstractAlthough in‐channel and floodplain large wood (LW) has been recognized as an important component of lotic ecosystems, there is still limited knowledge on the recruitment, mobility and retention of LW in rivers with an intermittent hydrological regime. In this study, we analysed the LW characteristics and related reach‐scale variables of 22 reaches in a Mediterranean intermittent river (Evrotas, Greece) in order to identify predictors of in‐channel and floodplain LW distribution. Our results indicated high downstream variation in LW volumes in the fluvial corridor (0.05–25.51 m3/ha for in‐channel LW and 0–30.88 m3/ha for floodplain LW). In‐channel and floodplain LW retention was primarily driven by the hydrological regime of the studied reaches (i.e. perennial or non‐perennial) with higher volumes of LW observed in perennial sections. The width of the riparian corridor was an important predictor of LW storage at the reach scale. Non‐perennial reaches had a disproportionally larger number of relatively small‐diameter living trees at the expense of mature trees with larger diameters typical for riparian stands functioning as LW recruitment areas in perennial reaches. The smaller dimensions of in‐channel LW in non‐perennial reaches, coupled with the dominance of loose LW pieces, implies frequent LW transport during ordinary flood events. Nevertheless, overall low LW retention in the fluvial corridor under non‐perennial flow regime predicts low volumes of mobilized LW. In contrast, the recruitment of relatively long and large‐diameter LW from mature riparian stands in perennial reaches, together with additional LW stabilization by banks, bed sediments, living trees or other LW pieces decreases the potential for further LW transport. © 2020 John Wiley & Sons, Ltd.