Gravel bars: A key habitat of gravel-bed rivers for vegetation

This paper examines the importance of gravel bars in terms of a substrate for
recruitment, colonisation and development of ground flora and woody vegetation via two European case studies. Experimental work on the River Tagliamento in Italy is used to explore the role of substrate particle size and elevation on recruitment and growth of seedlings and cuttings (Populus nigra L. and Salix elaeagnos Scop.). Meanwhile on the River Tummel in Scotland, the pattern of vegetation communities was related to bar morphology and sedimentology via field survey. Both studies reveal the critical importance of bar morphology and substrate particle size, via their control on inundation frequency, substrate stability and moisture availability, in terms of vegetation development on gravel bars from the initial colonisation stage to vegetation communities present after more than decade.