Altitudinal Differences in Organic Matter Mass Loss and Fungal Biomass in a Subalpine Coniferous Forest, Mt. Fuji, Japan

Abstract

In order to study the long-term effect of climatic conditions on organic matter decomposition, the difference in the mass loss rate of organic substrates was examined along the altitudinal temperature gradient (1500–2400 m) of Mt. Fuji, Japan. Two standard substrates, cellulose filter paper and wood chips of beech (Fagus crenata), were placed in the L and FH layers at each altitude. The mass loss rates tended to be smaller with increasing altitude and were significantly correlated with the annual mean air temperature in a log-linear fashion. The temperature dependence of the mass loss rates was much larger than that of microbial respiration. The initial increase in ergosterol content (an indicator of fungal biomass) of organic substrates was more rapid at low altitudes than at higher altitudes. The effects of fungal biomass and freezing temperatures on the temperature dependence of decomposition were examined using a simple simulation model. The results suggest that the effects of temperature increase on decomposition could be much larger than those estimated from the temperature-microbial respiration curves.