Abstract:

Background and Aims Decomposition of mixed leaf litters in Xishuangbanna tropic rain forest was studied both in the field and laboratory. Negative exponential model x_t/x₀=exp(-k_t) and binomial exponential model x_t/x₀=a×exp(-k₁t)+b×exp(-k₂t) were used to simulate the observed decomposition process with. Bio-models were introduced to analysis the contribution of biotic and abiotic factors to the decay rates of leaf litters.

Methods Coarse (with mesh size of 1 mm) and fine (with mesh size of 100 μm) litterbags were used in the field to examine the effects of different components of soil fauna on litter decomposition by restricting access by most soil macrofauna and mites, respectively, i.e. feasible for most mites to coarse mesh and nematodes to fine mesh. In the laboratory, sterilization and inoculation were adopted to investigate the effects of nematodes and microbiota on leaf litters.

Key Results The decomposition process was a course fast incipiently then slowdown with stagnation periods. The decay rate of mixed leaf litters fluctuated over the decomposing period with the magnitude of fluctuation positively related to complexity of food-web. The binomial exponential model simulated the two different courses of leaf litter decomposition whereas the negative exponential model did not simulate the initial stage well and overestimated the long-term decay process. Soil fauna accounted for 78.1% of the decay rates while abiotic factors for 14.1% and microorganisms only for 7.8%.

Conclusions This study suggests that the decomposition of leaf litters was a cascade process and binomial exponential model can describe the process better than the negative exponential model. Soil fauna played a dominating role in litter decomposition in tropic rain forest.

Key words: Xishuangbanna, Tropic rain forest, Mixed leaf litter, Decomposition, Model