Seasonal variation of monoterpene emissions from forest floor and its contribution to whole canopy flux in a Larix kaempferi forest

摘要

To understand monoterpene emission from a deciduous coniferous forest floor, we measured monoterpene emission rate of the forest floor and monoterpene content in needle litter in a Larix kaempferi forest, Japan in spring, rainy season, summer, and late autumn. Six soil chambers were set up on the L. kaempferi forest floor, and experimental plots were left undisturbed (no removal of needle litter and fine roots). The dominant compound in all seasons was alpha-pinene. The monoterpene emission rate from the forest floor depended on temperature. The highest standard monoterpene emission rate (at 21 degrees C) from the forest floor was observed in late autumn, and the lowest occurred in summer. The seasonality of standard monoterpene emission rates was similar to that of monoterpene content in the needle litter. We calculated the ratio of monoterpene emissions from the forest floor to canopy scale monoterpene fluxes. The highest ratio was observed in late autumn (28%), whereas the lowest ratio was observed in summer (0.07%). Our results suggest that the forest floor of a deciduous coniferous L. kaempferi forest is an important source of monoterpene emission in autumn, and the contribution of forest-floor monoterpene emissions to canopy-scale monoterpene flux depends on the season.