Canopy leaf area index and litter fall in stands of the mangrove Rhizophora apiculata of different age in the Mekong Delta, Vietnam

Leaf area index (LAI) and seasonal patterns of litter fall, leaf production and seed (propagule) production were measured in monocultures of the mangrove Rhizophora apiculata aged from 6 to 36 years in Ca Mau Province, southern Vietnam. There was no clearly defined seasonal pattern in leaf fall, but leaf emergence was significantly correlated with the monthly precipitation/evaporation (P/E) ratio. Propagule production was markedly seasonal, with more than 80% of the propagules being shed in the wet season period of May-November. Total annual litter fall ranged from 941 g dwt m(-2) year(-1) to 1879 g dwt m(-2) year(-1). Leaf litter was the main component of litter fall in all the stands, twigs and branches being a significant component of litter fall in only one stand which was undergoing self-pruning of the lower branches. Propagules were a significant component of litter fall only in the two older stands of 21 years and 36 years, which produced an average of about 40 and 68 propagules m(-2) years(-1), respectively, highlighting the importance of older forests of R. apiculata as seed stands. Stand LAI decreased with age, ranging from 4.9 in the younger stands down to 3.3 in older stands. These leaf area indices are comparable to those of Rhizophora stands elsewhere, (C) 2000 Elsevier Science B.V. All rights reserved.