An estimation of rates of litter decomposition was carried out in two forest types; Yagirala Forest Reserve (FR) in the Low Country Wet Zone and Horton Plains natural forest (NF) in montane zone of Sri Lanka. Yagirala forest reserve was located between 6°21′ to 6°26′ north altitude and 80°6’to 80011’east longitude in the lowland wet climatic zone in Sri Lanka. Horton Plains natural forest was located between 6° 47′- 6° 50′ north latitude and 80° 46′- 80′ 51′ east longitude in mid country of Sri Lanka.
Three 300m line transects with three plots (100 m distance between 2 plots) were established in each forest. Litter decomposition rates were determined using the mixed species litter bags method. A total of 54 bags were placed in the both Forests (9 replicates for one plot). The experiment was conducted for a period of 8 months. The rates of decomposition of litter recorded during this were fitted to the exponential decay model proposed by Olson (1963).
Where, x is the weight of litter remaining after time ‘t’, x0 is initial weight of litter and k is decomposition rate constant. Results revealed that the mean annual litter decomposition rate constant for moderately exploited Yagirala forest reserve was 2.19 year-1 while the value for Horton Plains natural forest was 1.35 year-1.Litter accumulation rates for Yagirala Forest is 668.86 tons ha-1 year-1, and this value for Horton Plains natural forest is equal to 226.54 ha-1 year-1. According to the results, it was clear that Yagirala forest reserve situated in the low country wet zone recorded higher litter decomposition rates compared with Horton Plains natural forest situated in the Montane zone of the country.
L A M C Amarasekara and D M S H K Ranasinghe
Department of Forestry and Environmental Science, University of Sri Jayewardenepura, Sri Lanka.