Comparison of litter decomposition rate constant for Yagirala and Horton Plains natural forests of lowland wet zone a nd montane zone of Sri Lanka

Abstract

An estimation of rates of litter decomposition was carried out in two forest types Yagirala ForestReserve (FR) in the Low Country Wet Zone and Horton Plains natural forest (NF) n montane zoneof Sri Lanka. Yagirala forest reserve was located between 6°21' to 6°26' north alt tude and 8006'to80°1 I 'east longitude in the lowland wet climatic zone in Sri Lanka. Horton Plains natural forest waslocated between 6047'_ 6° 50' north latitude and 80' 46'- 80' 51' east longitude in mid country ofSri Lanka.

Three 300m line transects with three plots (100 m distance between 2 plots) were established in eachforest. Litter decomposition rates were determined using the mixed species litter bags method. A totalof 54 bags were placed in the both Forests (9 replicates for one plot). The experiment was conductedfor a period of 8 months. The rates of decomposition of litter recorded during this were fitted to theexponential decay model proposed by Olson (1963).

X X = e

Where, x is the weight of litter remaining after time 't", XO is initial weight of litter and k isdecompos ition rate constant. Results revealed that the mean annual 1itter decomposition rate constantfor moderately exploited Yagirala forest reserve was 2. i9 year' I while the value for Horton Plainsnatural forest was 1.35 yearl.Litter accumulation rates for Yagirala Forest is 668.86 tons ha' year:'.and this value for Horton Plains natural forest is equal to 226.54 ha' year:'. According to the results,it was clear that Yagirala forest reserve situated in the low country wet zone recorded higher litterdecomposition rates compared with Horton Plains natural forest situated in the Montane zone of thecountry.