Litter production by mangroves. III. Wavecrest (Transkei) with predictions for other Transkei estuaries

Abstract

Litter fall was measured in a mixed mangrove community in which Avicennia marina (Forssk.) Vierh. was dominant over Bruguiera gymnorrhiza (L.) Lam. Mean litter production was 1.24 g dry matter m - 2 day - 1 or 4.51 tons ha - 1 yr - 1 over a 3-year period. Mean annual leaf yield comprised approximately 72% of total litter. Generally greater leaf fall occurred in the summer than in the winter. In both A. marina and B. gymnorrhiza propagule production was variable from year to year. In both species, reproductive material was present on the trees almost throughout the year. This behaviour and the low litter yields appeared to indicate that the community is approaching its southern limits. From the 14 ha of mangroves in the estuary it is calculated that total litter production is 50.7 tons yr - 1 , of which approximately 36.8 tons yr - 1 is leaf litter. The total litter production of the larger stands of mangroves in Transkei’s estuaries was calculated. Mangrove litter is considered to provide a significant input to these systems.