Trees occurring on steep slopes often possess stem inclination or sprouting ability as adaptive responses to slope inclination. These behaviors might be crucial for the growth and survival of species living on unstable and erodible surface. However, little is known about how tree architecture responds to topographic conditions. In this study, we measured tree architecture for nine species of broad-leaved deciduous trees on Mts. Tanzawa.

Almost all stems inclined towards down-slope azimuth, and stem inclination was larger for smaller stem size, shallower soil, and steeper slope. Average stem inclination ranged from 5 to 38 degrees for each species, and species with larger stem inclination had smaller stems and were distributed on thinner soils. Soil depth and slope inclination strongly explained stem inclination of species found on relatively deep soils and those on gentle slopes, respectively. This tendency might suggest that stem inclination is a passive response of species that inhabit mild topographic conditions. On the other hand, species with high sprouting ability occurred on thin soil. These suggest that species found on harsh environment have higher abilities to respond to topographic conditions.