Breakdown of mangrove leaf litter in a managed mangrove forest in Peninsular Malaysia

Decomposition of Rhizophora apiculata, Rhizophora mucronata, Bruguiera parviflora and Sonneratia alba leaves was studied in situ using litter bags in both Cleared and Virgin Jungle Reserve (VJR) mangrove forests in Peninsular Malaysia. A single exponential model best described the rate of decomposition for each species. All leaf species decomposed faster in the VJR site than in the Cleared site (R. apiculataP <0.05, R. mucronataP <0.01, B. parvifloraP <0.01, S. alba not significant and mixed bags P <0.05). The rate of decomposition was species specific: Sonneratia alba leaves decomposed the fastest (P <0.001) in both sites. The time in days required for the loss of half the initial dry mass (t50) was Cleared site: R. apiculata 76, R. mucronata 122, B. parviflora 122, S. alba 22, mixed 51; VJR: R. apiculata 43, R. mucronata 34, B. parviflora 70, S. alba 15 and mixed 32. Increasing litter diversity, by mixing leaves of different species in bags, had no effect on decomposition rate. The mass of air controls showed an initial decline to 65% in 14 d but then remained fairly constant (t50=108 d). This initial loss may represent the leaching of dissolved organic matter. Water controls (mixed litter bags submerged in seawater) had a t50 of 10 d, a rate significantly different (P < 0.01) from air controls. Our results show that breakdown of leaf litter is site and species dependent. This affects ecological functioning of the mangrove ecosystem and may have implications for management and conservation of mangroves.