The impact of extreme run‐off events from the Sakasagawa river on the Senjogahara ecosystem, Nikko National Park. V. The importance of adventitious root systems for burial tolerance of different tree species

We surveyed the morphological responses of tree species buried by alluvial deposits, and measured the physicochemical properties of alluvial materials which buried each of the individual trees, on Senjogahara moor, Nikko National Park, Japan. The results showed that these species had a different capcity to form adventitious roots. Malus toringo Sieb. individuals, which had survived in spite of heavy deposits over the past 10 years, developed many adventitious roots from the buried parts of their trunks. However, Larix kaempferi Carr. and Betula platyphylla Sukatchev var. japonica Hara, which both died in heavy deposit areas, were inferior to M. toringo in the formation of adventitious roots. From these facts, we presumed that the ability to develop adventitious roots contributed to the survival of trees and resulted in the difference in burial tolerance among each species. Adventitious roots tended to form in the depositional layers which consisted of fine particle size materials. It is thought that these layers prevent gas exchange between soil and air, causing a lack of oxygen to the rhizosphere. Thus, we concluded that adventitious roots have a physiological importance in reducing the obstruction, and in the survival of buried trees.