A field guide to Kenyan mangroves

 

Rhizophora mucronata Lamk. 1804

Family: Rhizophoraceae

Distribution
Rhizophora mucronata occurs on the coasts of the Indian Ocean and the West-Pacific. In East-Africa, R. mucronata is the only representative of the genus.

Tree Structure
In Kenya, R. mucronata trees grow up to 20-25 m height in riverine mangroves and up to 15 m, but more commonly around 10m height in fringing mangroves. Lives up to about 100 years in Kenya (Verheyden et al., 2004a). The trees usually occur in a large zone, adjacent to the water. The height of the trees decrease gradually as you go landwards. Stem contains annual growth rings offereing the potentail for mangrove dendrochonology (Verheyden et al., 2004a; Verheyden et al., 2005a) and dendrochemistry (Verheyden et al., 2004b; Verheyden et al., 2005b).

Read AOB Snapshot Growth rings in R. mucronata - See Verheyden et al. 2004a

Leaves
Elliptical leaves up to 25 cm in length and 10 cm wide, but more commonly around 12 cm x 6 cm. Presence of a long mucron at the end of the leaves up to 0.8 cm, but usually broken off. Leaves on the forest floor can be identified by the presence of cork warts on the underside of the leaves (see photo on right), however these warts are sometimes only visible in older or dried material. Leaves of this trees are a favorite of many crabs (e.g., Gillikin et al., 2004).

Root-system
Well developed aerial stilt roots, which allow easy recognition of this species in the field, since it is the only representative of the genus in Kenya.

Flowers
Flowers occur as axillary inflorescences and open within the leafy crown hanging downwards from a long peduncle. Flowers have a yellow-white calyx with 4 thick and hard lobes. When the flower opens the 4 white, and hairy petals appear alternated with the calyx lobes.

Seeds
The seeds of the mangrove Rhizophoraceae are all viviparous. The hypocotyl in R. mucronata is very long, and narower at the top end.

References:

Tomlinson, P.B., 1986. The Botany of Mangroves. Cambridge University Press. Cambride Tropical Biology Series. 413 pp.

Gillikin, D.P., B. De Wachter and J.F. Tack, 2004. Physiological responses of two ecologically important Kenyan mangrove crabs exposed to altered salinity regimes. Journal of Experimental Marine Biology and Ecology 301(1):93-109. (Reprint).

Verheyden, A., F. De Ridder, N. Schmitz, H. Beeckman and N. Koedam, 2005a. High-resolution time series of vessel density in Kenyan mangrove trees reveal link with climate. New Phytologist 167: 425-435. (Reprint).

Verheyden A., M. Roggeman, S. Bouillon, M. Elskens, H. Beeckman and N. Koedam, 2005b. Comparison between d13C of a-cellulose and bulk wood in the mangrove tree Rhizophora mucronata: implications for dendrochemistry. Chemical Geology. 219: 275-282. (Reprint).

Verheyden, Anouk , James Gitundu Kairo, Hans Beeckman, and Nico Koedam, 2004a. Growth rings, growth ring formation and age determination in the mangrove Rhizophora mucronata. Annals of Botany 94: 59-66 (Reprint).

Verheyden, A., G. Helle, G. H. Schleser, F. Dehairs, H. Beeckman & N. Koedam, 2004b. Annual cyclicity in high-resolution stable carbon and oxygen isotope ratios in the wood of the mangrove tree Rhizophora mucronata. Plant, Cell and Environment 27, 1525–1536.. (Reprint).

 

 

 

 

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all text copyright© 2003 David Gillikin and Anouk Verheyden
Created 13 April 2002

updated: December 5, 2005
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