Abstract
Scattered populations of Avicennia marina can be found in the Arabian Gulf, occupying one of the driest mangrove habitats in the world, in which salt concentrations may reach levels that are beyond the physiological limit for other species. These ecosystems are poorly known, in particular, what levels of productivity can be attained and whether there are any indications of genetic adaptation to these exceptionally severe conditions. We have estimated standing biomass as varying between 70 and 110 t ha −1 for the tallest stands and between 14 and 65 t ha −1 for shortest stands. Our estimates for litterfall are 7.4–8.5 t ha −1 yr −1 in the tallest stands and 5.1–6.9 t ha −1 yr −1 in the shortest stands. These values of biomass are intermediate between levels reported for the same species in New Zealand and in Australia and the estimate of litterfall is comparable with that obtained from stands in Australia. Thus, despite the harsh ecological conditions, A. marina forms highly productive stands. We have analyzed leaf cuticular hydrocarbon composition, by gas chromatography, as a marker of population differentiation. The dominant alkanes were C 33 and C 31, which are unusually long as compared with the other widespread species Avicennia. germinans. Since longer carbon chain lengths appear to offer an adaptation to minimize cuticular water loss, it would appear that A. marina has evolved under more arid conditions than A. germinans. Our sampled population from the Inner Gulf differed in quantitative cuticular wax composition from the Outer Gulf population, suggesting a possible genetic differentiation between the two populations. Our data indicate the need for more detailed analyses of the possible role of genetic adaptation in the productivity of mangrove ecosystems at the margins of their ecological range.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call