Nitrogen fixation during litter decomposition was studied for 34 months using litterbags containing newly fallen litter of
coniferous species
Cryptomeria japonica and
Pinus densiflora and that of deciduous species
Quercus serrata. Litterbags were set in contact with the forest floor in a deciduous broad-leaved forest near the top of a slope and in a
C. japonica stand at the middle of the slope at a watershed in eastern Japan. Nitrogen-fixing activity, estimated by acetylene reduction
after 16 and 19 months of incubation, was 62.65–3.86 nmoles C
2H
4 h
−1 g
−1 DW in
Cryptomeria litter, but only 1.07–0.09 in
Pinus and 0.72–0.04 in
Quercus. The rate of N increase in decomposing litter was highest in
Cryptomeria. Fungal biomass in decomposing litter, estimated by ergosterol content, increased during the initial 16 months of incubation
in
Cryptomeria and
Quercus, and during the initial 19 months of incubation in
Pinus. The litter decomposition rate was highest in
Cryptomeria among the three species, due to increased N content and fungal biomass in
Cryptomeria litter. Thus, N increase in decomposing
Cryptomeria litter affects the subsequent N dynamics and decomposition pattern.
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