Decline of Betula ermanii with Special Reference to Ozone Concentration at Mt. Mae-Shirane, Oku-Nikko, Japan

During June to October 2000 and 2001 we measured the height, Diameter at Breast Height (DBH) and stand density of Betula ermanii trees at Mt. Mae-Shirane, Japan and the ozone concentration there to explore the relationship between ozone concentration and the decline of B. ermanii trees on the mountain. Height, DBH and stem volume were lower on the southeast-facing slope than on the northwest-facing slope. Stand density on the southeast-facing slope was 1/8 that on the northwest-facing slope. Serious forest decline was observed on the southeast-facing slope. The ozone concentration was higher on the southeast-facing slope than on the northwest-facing slope during the period of measurement. Experimental exposure of B. ermanii to ozone showed that at the concentration levels observed at Mt. Mae-shirane this pollutant significantly damages the growth of B. ermanii. It is concluded that ozone is one factor that damages the growth of B. ermanii at Mt. Mae-Shirane.