instream wood, headwater stream, cross-dating, Western Carpathians

The effect of instream wood on stream hydraulics and geomorphic processes depends on wood and channel dimensions. We investigate the abundance and geomorphic effects of large and small wood (LW/SW) in four steep tributaries of the Mazák Stream (Moravskoslezské Beskydy Mts., Western Carpathians). The volume and frequency of LW depend on channel confinement (i.e., available space in the valley floor to store instream wood) and adjacent hillslope gradient which enhances lateral supply of wood. The presence of a deciduous tree canopy in two studied tributaries was reflected in higher abundance of SW due to the continuous supply of branches instead of entire dead trees. In these streams, morphological steps ? created exclusively by SW ? were more frequent than LW steps. Norway spruce samples indicated more than two times larger mean and maximal residence times as compared to European beech based on the successful cross-dating of 127 logs.