Decomposition of bamboo and Rang (Shorea siamensis Miq.) leaf litters in mixed deciduous forest and their decomposition fungi

Study on decomposition of bamboo and Rang (Shorea siamensis Miq.) leaf litters in mixed deciduous forest and their decomposing fungi was carried out by the litter bag method at Mae Klong Watershed Research Station, Amphur Thong Pha Phoom, Changwat Kanchanaburi. The remaining leaf litters in the litter bags were oven-dried and weighed every month for one year period. Dry bamboo and Rang leaves collected from the forest floor at the beginning of the experiment and the remaining leaf litters in the litter bags at every 3 month-interval were sampled and analysed for mineral content. Total species and isolates of fungi growing on the dry leaves and the remaining leaf litters at every 6 month-interval were also isolated by the dilution plate technique. Results of the study revealed that Rang leaf litter was decomposed faster than bamboo leaf litter. Decomposition rate of the former equaled 95.14 percent per year and the latter equaled 85.03 percent per year. The decomposition constants (k) of Rang and bamboo leaf litters were 3.03 and 1.90, respectively. Dry-weight loss per month of both litters had a positive correlation with temperature, relative humidity and precipitation of the area. The concentrations of N and Ca in the 2 leaf litters were quite stable at the early stage of decomposition and increased at the later stage while the concentrations of P, K and Mg tended to decrease with the longer decomposition time. At the beginning, the percentages of mineral content (percent dry weight) of the dry bamboo leaves were K Ca N Mg P and the dry Rang leaves were K N Ca Mg P. The orders of mineral content of the 2 leaf litters remained constant until the end of the experiment. The losses of N, P, K, Ca and Mg per year of the former were 0.561, 0.051, 1.031, 0.638 and 0.202 percent, respectively and of the latter were 0.773, 0.060, 1.039, 0.366 and 0.119 percent, respectively. There were 42 species of decomposing fungi isolated from the two litters. Aspergillus was the highest in number of species and isolates and followed by Penicillium. The highest fungal species diversity was at 6 months after decomposition. The similarity index between the fungal community on bamboo leaf litter and Rang leaf litter was about 50 percent. The similarity values among the different stages of decomposition were low. Most of the fungal species at the early stage of decomposition disappeared at the later stages. It showed that a fungal succession occurred throughout the period of decomposition process.