Does understory vegetation reflect the history of fluvial disturbance in a riparian forest?

Abstract

AbstractWe have examined the relationship between the history of fluvial disturbance and understory vegetation in a riparian forest. The study site was divided into three sites, by use of aerial photographs and topographical maps, with different histories of fluvial disturbance: (1) Fagus‐type on land that has not been flooded for the last 39 years, at least; (2) Populus‐type on land that has not been flooded since debris flow occurred 34 years ago; and (3) Salix‐type on land that has been flooded periodically from an abandoned channel since debris flow occurred 34 years ago. Species richness in the Salix‐type was significantly higher than in the other types. Detrended correspondence analysis revealed obvious floristic differences among the three canopy types. Canonical correspondence analysis showed that herbaceous species were mainly found on lower plots with high moss cover, implying that moss layers may capture seeds transported by the stream. Tall herbs occurred in less shaded plots and on higher plots, suggesting that their rapid growth prevented the occurrence of other species. Fagus‐type was dominated by species with ingested fruits which depended on animals for their dispersal. Populus and Salix‐types were dominated by species with wind dispersal or no dispersal mechanism, which depended on physical phenomena for dispersal. Attributes of current understory vegetation were connected with historical events, suggesting that riparian vegetation reflects the history of fluvial disturbance.