large wood; small wood; headwater stream;

Besides the well-known significance of large wood (LW), also small woody pieces (SW; here defined as pieces with dimensions at least 0.5 m length and 0.05 m diameter), can play an important role in steep narrow headwaters. We inventoried instream wood in the 0.4 km long Mazák headwater channel, Moravskoslezské Beskydy Mts, Czech Republic (2<W<4.5 m; 0.20<S<0.40 m/m) with very steep adjacent hillslopes (0.6<S<1.1 m/m), where the parameters of wood dimensions, orientation, decay status (four classes), stability (unattached/contact with hillslopes/attached by bed sediments or other wood), % of influenced channel width by a wood, the geomorphic function of a wood (step, wood jam) and % of length of a wood in channel were assessed. The total number of inventoried instream wood was 90 LWs and 199 SWs. In addition, dendrogeomorphic dating of 36 LWs and 17 SWs was performed to obtain residence time of local instream wood and to provide some insights into its mobility.