LEAF LITTER DECOMPOSITION BY TERMITES IN DRY DIPTEROCARP FOREST AT LAINAN SUBDISTRICT, WIANG SA DISTRICT, NAN PROVINCE

Abstract

The litter productivity and the litter decomposition by termites were investigated in the dry dipterocarp forest at Lainan Subdistrict, Wiang Sa District, Nan Province from November 2012-December 2013. Litter traps and litter bags with two mesh sizes, 0.5 mm (non-accessible by termites) and 2.0 mm (accessible by termites), were installed in four 40x40 m2 plots dominated by Dipterocarpus tuberculatus Roxb. Aboveground biomass averaged at 81.4±13.5 tons/ha with 4.2% increase per year. The average of leaf litter production was 7.9±0.9 tons/ha/yr with the highest leaf litter production measured in March 2013. Average litter mass in 0.5 and 2.0 mm litter bags was significantly reduced from 40 g to 15.53±0.85 and 11.89±0.65 g in 13 months, respectively. The litter mass loss in 2.0 mm litter bags was significantly higher than in 0.5 mm litter bags (F=4.85, df=1, 96, p=0.03). Leaf litter decomposition rate calculated as Olson’s decomposition constant (k) from November 2012-December 2013 were 0.87 for 0.5 mm bags and 1.12 for 2.0 mm bags, respectively. Soil fauna, such as springtails, beetle larvae, and mites were found in significantly higher abundance in 0.5 mm litter bags than 2.0 mm litter bags. Mesh size, air temperature, termites, humidity, and beetle larvae had positive effect on the litter mass loss (F=5.556, df=11, 261, p<0.001) while rainfall, bark lice, springtails, mites, soil temperature, and soil pH had negative effect on the litter mass loss. Only 70% of leaf litter was decomposed over 13 months, so the remaining leaf litter could be accumulated as fuel for bushfire. In conclusion, the results suggested that termite is an important biological factor in leaf litter decomposition in dry dipterocarp forest. In addition, air temperature and humidity may directly affect leaf litter decomposition as well as influencing the activities of termites in leaf litter decomposition in dry dipterocarp forest.