Interactive Effect of Canopy and Fluvial Disturbances on Sapling Community Structure and Species Diversity in a Montane Riparian Forest1

Abstract: Montane riparian forests exhibit a higher diversity of tree species than adjacent stands. This pattern is thought to be generated by the unique disturbance regime of riparian forests, including canopy gap formation and fluvial disturbance (e.g., transport of boulder/gravel sediments), which provides a variety of habitat conditions for regeneration (habitat niche segregation). Although segregation of micro-environmental conditions for seedling establishment has been confirmed, habitat segregation for saplings remains untested. Thus, to determine if the composition and structure of the riparian sapling community is influenced by canopy and fluvial disturbances, we sampled 11 canopy-gap sites and 3 fluvial boulder-deposit sites, as well as beneath-canopy sites that had not been disturbed recently, in a temperate mixed-species deciduous forest. We analyzed the distribution patterns of saplings for 31 canopy and subcanopy species. Saplings were found mainly on the disturbed sites compared with the be...