THE EFFECTS OF LITTER DISPLACEMENT ON RIVERBANK VEGETATION

Along a stretch of the unregulated Vindel River, in N Sweden, amount of leaf litter left on the river bank after flooding was significantly correlated with soil organic matter. Wood litter mass and total litter mass were not correlated with riverbank features such as soil organic matter, riverbank slope or stem density. Species richness, species diversity, and the proportions of stemmed and nonstemmed species showed quadratic relationships with leaf litter mass, whereas ground vegetation cover decreased monotonically with increasing leaf litter mass. Tall stemmed species were most frequent at eroded sites with low amounts of leaf litter and at sites where leaf litter had accumulated. The highest proportion of low-growing species was found at sites with intermediate leaf litter masses. Community characteristics such as species richness, species diversity and the proportions of stemmed and nonstemmed species were less strongly correlated with wood litter mass and total litter mass. Density and richness of seeds increased with increasing litter mass. Flooding in pristine rivers may exert a considerable influence on riverbank vegetation as a result of litter displacement. -from Authors