LAJU DEKOMPOSISI SERASAH DALAM DUA SISTEM BUDIDAYA KARET PADA LAHAN GAMBUT DI KAWASAN RIMBO PANJANG, RIAU

Abstract

This study focused on two smallholder rubber systems in Riau, i.e. “rubber jungle” and “rubber garden,” which have contrasting vegetative structure. Owing to the absence of weeding, rubber jungle may become as dense as 1100-1200 trees/ha, consisting of around 28.80% non-rubber trees. In rubber garden, stand density is retained at usually 500-600 trees/ha and as monospecific stands. Such differences have been suspected to affect decomposition process beneath each system. The purpose of this study was to determine and compare the rate of litter decomposition and nutrient changes in rubber forest and rubber garden. This research has been done throughout the period of February-August 2012 (180 days) on a peatland area situated at Rimbo Panjang, Kampar Regency, Riau. Dried naturally-fallen rubber leaves were used as litter, which was exposed to field conditions in nylon litter bags. In both rubber growing systems, litter rapidly lost substantial amount of its mass (averagely 34.59%) during the first 30 days, but the decomposition slowed down thereafter until the end of the experiment on the 180th day, where the average remaining litter mass was 43.13% of the initial mass. Litter decomposition rate in earlier phase was 1.16%/day and slowed down to 0.32%/day to the 180th day. C/N ratio declined through time, starting from 40.41 to 27.42. P content did not change much through time, while K fluctuated slightly. In contrast, Ca increased in earlier phase to the middle of decomposition process and decreased afterwards. Mg decreased though time