Effects of litter type, origin of isolate, and temperature on decomposition of leaf litter by macrofungi

The dependence of hyphal growth and litter decomposition on litter type and incubation temperature used as substratum were compared for litter-decomposing macrofungi originating from subtropical (ST), cool temperate (CT), and subalpine forests (SA) in Japan. In the first series of pure culture decomposition tests using a total of 39 litter types as substrata inoculated with six fungal isolates from the three climatic regions, the fungal decomposition of litter was negatively affected by the content of acid-unhydrolyzable residues (AUR) or extractives and positively by N content in the litter. Secondly, cross-inoculation tests were performed to examine the mass loss of leaf litter of broad-leaved trees from ST, CT, and SA, each inoculated with three Mycena species from the three climates and incubated at seven temperatures between 5 and 35 A degrees C. Fungal isolate, litter type, incubation temperature, and their interactions significantly affected the mass loss of litter during the incubation. The greatest values of mass loss were found at 20 or 25 A degrees C, and were generally consistent with the optimum temperatures of colony diameter growth rate of these isolates. Isolates from cooler regions were more sensitive to higher temperature than isolates from warmer regions. The decomposition of recalcitrant compounds (as acid-unhydrolyzable residues, AUR) by Mycena sp. from ST was also affected by litter type and incubation temperature, but the degree of selective decomposition of AUR relative to other components, such as cellulose, was insensitive to the range of temperature tested.