Fungal ingrowth on forest floor and decomposing needle litter of Chamaecyparis obtusa in relation to resource availability and moisture condition

Fungi play an important role in litter decomposition in forest ecosystems and studies are needed to follow the changes in hyphal abundance during litter decomposition and examine the factors regulating the ingrowth of hyphae in litter. The purposes of the present study are to demonstrate the patterns of needle decomposition of Chamaecyparis obtusa in terms of the vertical distribution of fungal biomass and chemical properties within litter horizons (L1, L2, F, and H layers) and fungal ingrowth and succession in relation to organic chemical and nitrogen dynamics during needle litter decomposition over a one-year period. A further aim is to assess the effect of moisture and availability of organic matter on live hyphal length, during 1 year of decomposition. Live hyphal length was correlated to holocellulose concentration in four litter horizons. In a litter bag experiment, total (live plus dead) hyphal length increased during decomposition which was correlated to the concentrations of nitrogen, lignin, holocellulose, and soluble carbohydrate in the litter. The 12-month period over which decomposition was measured was divided into four seasons and the correlation between the water content and live hyphal length was evaluated for each period. The length of live hyphae was correlated to the water content of litter in all four periods. The slopes of regression lines between the water content and live hyphal length were positively correlated to the mean concentrations of soluble carbohydrate of each period, suggesting that the growth of live hyphae was highly dependent on the moisture condition of litter, and under moist conditions on the availability of soluble carbohydrate in the litter. The decrease in the slopes during decomposition can be ascribed to ecophysiological traits of fungi responsible for decomposition in these periods.