Propagule Pages: Mmmmmangrove apples

Species: Sonneratia alba

Common names: Mangrove apple, Songery

Size: Generally up-to 25m tall; at Honko up-to approximately 7m.

Features: Large, ridged, conical pneumatophores, flowers of many extended white stamens.

Local uses: Masts for local vezo peoples’ boats (Pirogues)

Sonneratia alba tree growing in the mangrove stand at Ambondrolava

Sonneratia alba tree growing in the mangrove stand at Ambondrolava

The mangrove apple, Sonneratia alba, is a common species through-out the indo-pacific region and is found across most of the mangrove stands in Madagascar. The tree is typically dominant on the seaward side of forests and here at Ambondrolava is mostly found in the northern reaches of the wetland complex, however it does occur through-out the forest extent.

S.alba pneumatophore

S.alba pneumatophore

This species’ root adaptations are in the form of pneumatophores that protrude above the surface coming from a series of cable roots which run just below the surface of the substrate. In S.alba these rooting structures are large ridged conical projections that can reach up-to 1m tall! These structures, as with prop-roots of Rhizophora mucronata, act as ‘breathing straws’ and help bring oxygen into the root systems of the tree; that lives in anoxic sediments and experience regular immersion in salt-water. These root systems create areas of higher complexity which serve to drive diversity of various organisms.

Open flower of S.alba showing exerted white stamens.

Open flower of S.alba showing exerted white stamens.

During the months of October and November S.alba comes into flower at in the southwest of Madagascar creating a firework burst of white stamens from every bud.  These flowers add flashes of white lights to the typical uniform green canopy of the mangrove and also attracts various animals; such as bees and fruit bats who act as pollinators, or geckos (picture below,  Phelsuma mutabilis) who enjoy eating nectar from the depths of the flowers.

A gecko (Phelsuma mutabilis) is shown on an open flower of S.alba.

A gecko (Phelsuma mutabilis) is shown on an open flower of S.alba.

As the common name suggests this tree bears edible fruit – ‘apples’ – which in certain parts of the world is used to make a fruit juice. This strategy of fruit production impacts upon  the ability of the species to regenerate through low seed viability. At degraded sites as dropped fruit must remain in the environment as it first becomes compromised and then releases the seeds; during this time the fruit is exposed to tidal exportation; which is more pronounced due to decreased protection offered by intact forest stands. Lack of natural regeneration is displayed in the northern extent of the forest where large areas of the fringing S.alba have been cut down to provide masts for the pirogues of the vezo people, with no regeneration occurring and forest cover quickly shrinking.

S.alba fruit

S.alba fruit

This tree offers many services to both the ecosystem and the coastal communities alike, and could be described as the ‘prettiest’ species at the Ambondrolava forest complex with their white flowers and purple fruits. All of which contribute to the health of the ecosystem and maintain the good and services it provides.

Thanks for reading, we hope that you can now pick out the flash of white stamens that marks this tree. Watch out for the next Propagule Pages coming in December.

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