Litter production and decomposition in a subtropical mangrove swamp receiving wastewater

Litter production in a mangrove swamp was estimated by litter trapping for 2 years in 2 sites, one receiving wastewater and the other was the control. Mean annual litter production was about 11.7 t · ha^-1 with leaf and reproductive materials contributing more than 70% of total litter production. A distinct seasonal pattern was found in both years with peak litter fall occurring in the summer rainy season, in particular, August. In terms of total litter production, variations between years and sites were statistically not significant: (at P ≤ 0.05 level). Total litter biomass in 1991-92 and 1995-96 were 1149 and 1187 g · m^-2 , respectively. Sites receiving wastewater did not show any significant changes in litter production. Leaf litter decomposition rates in different locations within the mangrove swamp were similar. Neither wastewater discharge nor distance from land had any effect on the decay process. When the two plant species were compared, leaves of Kandelia candel (L.) Blanco degraded more rapidly with more nutrient released and exported to the foreshore environment than those of Aegiceras corniculatum (L.). The decay constant (k) of K. candel and A. corniculatum was 0.052 and 0.015 day^-1, respectively. The high litter production and rapid turnover of leaf litter indicated the importance of this mangrove swamp in supplying nutrients and organic matter to the estuarine ecosystems.