Decomposition of leaf litter of four tree species in a subtropical evergreen broad-leaved forest, Okinawa Island, Japan

The leaf litter decomposition of four indigenous tree species, such as Castanopsis sieboldii, Schima wallichii, Elaeocarpus japonicus, and Daphniphyllum teijsmannii, was monthly monitored using the litterbag technique over a 12-month period in a subtropical evergreen broad-leaved forest of Okinawa Island, Japan. The decomposition rate constant (k) was 1.19 +/- 0.19 for D. teijsmannii, 1.09 +/- 0.07 for C. sieboldii, 0.94 +/- 0.05 for E. japonicus, and 0.66 +/- 0.05 (S.E.) yr(-1) for S. wallichii. The decomposition rate constant was significantly lower in S. wallichii than the other three species (P < 0.01). It might be attributed to the low number of micro-fauna. The fastest rate of decomposition of the leaf litter of D. teijsmannii can be attributed to collembola whose number was almost twice compared to the number of collembola observed in the other species leaf litters. The remaining carbon of leaf litter decreased with increasing incubation time and its concentration was ca. 50% over one year. The remaining nitrogen of C. sieboldii, E. Japonicus, and D. teijsmannii showed three phases: leaching, net gain, and net loss, while S. wallichii showed two phases without net loss phase. The leaf litter of D. teijsmannii, which had the highest initial N concentration of 0.97%, showed the highest decomposition rate constant. Concerning the other species of leaf litters, however, their initial N concentration did not reflect on their decomposition rate constant. The critical value of C/N ratio ranged from 31 for D. teijsmannii to 33 for C. sieboldii. (C) 2004 Elsevier B.V. All rights reserved.