Litter production by mangroves. I: Mgeni Estuary

Abstract

Litter fall was measured in two mangrove communities: one dominated by Avicennia marina (Forsk.) Vierh. and the other comprising an almost pure stand of Bruguiera gymnorrhiza (L.) Lam. Mean litter production for the A. marina community was 1,91 g dry matter m− 2day− 1 or 6,98 tons ha− 1year− 1 over a 3-year period, while the values for the B. gymnorrhiza stand were 2,26 g dry matter m− 2day− 1 or 8,24 tons ha− 1year− 1 over 4 years. Highest litter values in both communities were obtained when seedlings were shed in autumn. The A. marina community produced extremely variable yields of litter components and total litter from year to year, whereas the yields from B. gymnorrhiza were more consistent. Mean annual leaf yield comprised 59,0% and 62,5% of the total litter in the A. marina and B. gymnorrhiza communities respectively. In the B. gymnorrhiza stand stem material constituted only 6,0% of the total litter yields, while in the A. marina community the contribution was 17,8%. From the 44 ha occupied by mangroves it is calculated that total litter production is 334,2 tons year− 1, of which approximately 200 tons year− 1 is leaf litter. This is considered to provide a significant input to this system.