Thursday, 4 May 2017

Instream wood dynamics in Carpathian headwater streams

New results were published from ongoing research of instream wood in Czech Carpathian headwaters. Our recent article in Geomorphology prepared in co-operation with colleagues from the University of Geneve (Dr. Ruiz-Villanueva and Prof. Stoffel) deals with the residence time of typical tree species of Carpathian forests (Norway spruce and European beech) in small channels of Mazácký Grúnik Natural Reserve, Moravskoslezské Beskydy Mts (Fig. 1). We investigated that spruce logs indicated more than two times longer mean and maximal residence times as compared to European beech based on the successful cross-dating of 127 logs (Fig. 2). Maximum obtained residence time in the headwaters was 128 years for spruce and 59 years for beech, whenlog age and log diameter played the most important role in the preservation of wood in the fluvial system.Instream wood creating steps or logs accumulated in jams did not show any differences in residence time as compared to nonfunctional pieces. Shorter residence time was found for hillslope-stabilized wood when compared to unattached wood entirely located in the channel or pieces stabilized by other wood or sediments. We also documented that large flood events recorded by nearby gauging station or by dendogeomorphic methods (dating of exposed roots by channel erosion) were not always responsible for tree mortality and delivering of wood into local channels and thus, another important agents of wood recruitment than lateral erosion (e.g. windthrows, mass movements) should be considered.

During last days, we measured topography of the Mazák Stream and installed RFID pit-tags into fifty logs in order to observe their movement during future hydrogeomorphic events (Fig. 3). To compare wood and sediment dynamics, we also added ca. 70 stones with pit-tags (ca. D50 grain-size) on channel bed.

Fig. 1. Cross-dating performed in the headwater channel

Fig. 2. Depletion rate of European beech and Norway spruce in the studied channels

Fig. 3. Geodetic measurements and pit-tags installation


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