Effect of Understory Dwarf Bamboo on Seasonal Changes in Soil

The effect of understory dwarf bamboo (Sasa kurilensis) on the seasonal changes in soil temperature was studied in a dense secondary forest of Betula ermanii in northern Japan. Four plots were established in the Betula ermanii forest with Sasa kurilensis in the understory, and Sasa was removed in two plots of the four. The soil temperatures at 5 em below the surface were monitored in the four plots from May 1999 to September 2000, and were compared between the plots with and without Sasa. The daily maximum soil-temperature was ca. 0.5'C lower in the plots without Sasa than in the plots with Sasa during the snow-cover period. On the contrary, the daily maximum soil-temperature was ca. 3-4'C higher in the plots without Sasa than in the plots with Sasa just after the snowmelt in mid-May 2000. The difference in soil temperature between the plots with and without Sasa decreased gradually from the snowmelt toward the snow-cover period. The solar radiation was highest at around late Mayor early June 2000, and decreased toward winter. In addition, much solar radiation penetrated through the overstory layer from the snowmelt till early June when the leaf emergence of overstory trees started. Therefore, the absolute difference in solar radiation on the soil surface between the plots with and without Sasa was thought to be highest after the snowmelt, and gradually decreased till the snow cove