Species habitat associations in an old-growth beech forest community organised by landslide disturbances

In order to understand the processes that govern tree species’ spatial associations with habitats in landslide-affected forest communities, we investigated the habitat associations of six major tree species in an old-growth beech forest community located on a steep flank slope where landslides had occurred. All stems ≥ 5cm in diameter at breast height were mapped on a 1.14 ha polygonal plot and the topographic conditions (slope inclination and convexity), canopy state, and forest floor vegetation (i.e. dwarf bamboo and fern cover) were assessed. Most stems of Fagus crenata and Acer japonicum as well as many stems of Magnolia obovata belonging to the canopy layer were located on sites with low fern cover, whereas many stems of M. obovata below the canopy layer were associated with sites having high dwarf bamboo cover. The locations of the two Acer species belonging to the canopy and lowest layers coincided with sites having convex topography. Stems of Aesculus turbinata below the canopy layer were generally found on sites with gentle slopes, whereas most stems of Quercus crispula coincided with steeply sloping sites. While the results demonstrate that steep slopes created as landslide headscarps provide suitable habitats for species with less shade tolerance, it should be noted that there were few consistent patterns of habitat association across the layers. Our results suggest that unpredictable sporadic landslide disturbances with varying intensities and spatial scales, and their recursiveness, are at least partly responsible for habitat association patterns observed in the forest community.