James A. Danoff-Burg, Columbia University, [email protected] Mangrove Forests Dr. James A....

James A. Danoff-Burg, Columbia University, [email protected]

Mangrove Forests

Dr. James A. Danoff-BurgColumbia University


Mangrove Forests

• Found in coastal areas all over the tropics

• Primarily in brackish water– salty and fresh mix

• Cover approximately 22 million hectares in tropical and subtropical coasts


Ecosystem Functions & Threats

• Serve as an important buffer between sea and land– Lessen impact of intense storms– Reduce erosion and increase sedimentation– Important coastal pioneer species– Act as basis for a complex, biologically diverse,

and productive ecosystem

• Increasingly threatened– Human development is most intense along

coasts


Mangroves

• Not a natural taxonomic group– Convergence among several groups

• Possibly 16 convergent events

– Based on physiological attributes– 54 species total world-wide

• 16 Families– Principally: Avicenniaceae & Rhizophoraceae– These two families include 25 spp.

• 20 Genera


Mangrove Location

• Found in tropical areas only– Within the 20ºC isocline– More southern on East side of continents

• Due to southward moving warm Equatorial currents there


Terminology

• Mangal– Community of organisms in the mangrove

habitat

• Mangrove– Trees that flourish in the mangal

• Pneumatophore– Vertical root structures for air exchange– Lenticels - tiny pores for air exchange– Aerenchyma – tissue for air storage


Characteristics of Mangal

• Inundation with tides• Increasing salinity towards ocean• Sandy clay soil

– Nutrient poor

• Nitrogen & Phosphorus are limiting– Limiting mangrove growth only

• Organic nutrients deposited via siltation– Fresh water streams & down-shore currents– Most all are of terrestrial origin

• In sum: Mangal is a harsh place to live


Mangrove Adaptations

• Salt tolerance – Sequester in tissue (bark, stem, root)– Secrete through leaves– Exclusion by negative hydrostatic pressure

• Frequent inundation– Aerenchyma tissue & aerial roots

• Tolerant of soils low in oxygen– Hypoxic or anoxic


Mangrove Consequences of Adaptations

• Greater root mass– Relative to rest of plant & relative to non-mangrove

species– For water exchange & air exchange

• Lower growth rates– Consequence of salt & air exchange

• Tradeoff between salt tolerance & frequent inundation – Can adapt for one or other– Not both


Mangrove Pollination

• Pollination method varies by species– Wind (Rhizophora)– bat or hawk moth (Sonneratia)– birds and butterflies (Bruguiera)– bees (Acanthus, Aegiceras, Avicennia,

Excoecaria, Xylocarpus)– fruit flies (Nypa)– other small insects (Ceriops, Kandelia)


Mangrove Reproduction

• Vivipary normal– Reproduction and growth while still attached to

plant• Flowering• Fertilization• Propagule growth

Young propagule a.k.a. HypocotylHypocotyl

Mature propagule

http://fmel.ifas.ufl.edu/online/imgs/propagule1.jpg


Mangrove Dispersal

• Maturity -> Drop off maternal plant• Float horizontally initially

– Dispersal to novel environments ideally

• Float vertically with appropriate environmental conditions

• Rooting and growth


Mangal Habitat Types (from inland to oceanfront)

• Riverine– Often found in river deltas– Constant influx of freshwater– Great changes in salinity levels

• Basin Mangroves– Inland, behind coastal mangroves– Little change in tides, no wave action– Often higher salinity than others (evaporation)

• Tide-Dominated– Coastal front habitats– Frequent sedimentation– Unstable morphology due to coastal erosion


Intraspecific Differences in Environmental Tolerances

• Salinity variations and adaptations for excreting salt– Varies within and between species– Through growth stages

• Tidal Inundation and adaptations for gas exchange– Pneumatophores and other aerial root extensions

• Low soil stability, Shore morphology, and adaptations for rooting– Prop Roots

• Sedimentation rates and types


Mangrove Species Zonation

Bruguiera gymnorrhiza

Ceriops australis

Avicennia marina

Rhizophora stylosa

SalinitySalinityInundationInundation

Decreasing Soil StabilityDecreasing Soil StabilitySedimentation RateSedimentation Rate

All increase toward shoreAll increase toward shore


Most Common Species

• Red Mangrove (Rhizophora mangle)

• Black Mangrove (Avicennia germinans)

• White Mangrove(Laguncularia racemosa)

– All are found throughout tropics


Bark Identification


Tree Characters


Pneumatophores


Epiphytes


For more information

• Go to http://www.earthisland.org/map/mngec.htm and read the ecology link

• A clearinghouse on information on mangrove ecology is available at http://www.ncl.ac.uk/tcmweb/tcm/mglinks.htm

http://www.earthisland.org/map/mngec.htm

http://www.ncl.ac.uk/tcmweb/tcm/mglinks.htm

http://www.ncl.ac.uk/tcmweb/tcm/mglinks.htm


Mangroves of Australia

• The mangrove plants of Queensland (from http://www.aims.gov.au/pages/reflib/fg-mangroves/pages/fgm-qld-15.html) – Listed below are the true mangrove species that grow in Queensland. Hybrid plants are indicated by the use of an x in the scientific name (e.g.

Lumnitzera x rosea).

• AcanthaceaeAcanthus ebracteatus Acanthus ilicifolius • ArecaceaeNypa fruticans • AvicenniaceaeAvicennia marina • BignoniaceaeDolichandrone spathacea • BombaceaeCamptostemum schultzii • CaesalpiniaceaeCynometra iripa • CombretaceaeLumnitzera racemosa, Lumnitzera x rosea, Lumnitzera littorea • EbenaceaeDiospyros ferrea • EuphorbiaceaeExcoecaria agallocha • LythraceaePemphis acidula • MeliaceaeXylocarpus granatum • MyrsinaceaeXylocarpus mekongensis, Aegiceras corniculatum • MyrtaceaeOsbornia octodonta • PlumbaginaceaeAegialitis annulata • PteridaceaeAcrostichum speciosum • RhizophoraceaeBruguiera gymnorrhiza,Bruguiera sexangula, Bruguiera exaristata, Bruguiera parviflora, Bruguiera cylindrica,

Ceriops australis, Ceriops decandra, Ceriops tagal, Rhizophora apiculata, Rhizophora x lamarckii, Rhizophora stylosa, Rhizophora mucronata

• RubiaceaeScyphiphora hydrophyllacea • SonneratiaceaeSonneratia alba, Sonneratia x gulngai, Sonneratia caseolaris, Sonneratia lanceolata• SterculaceaeHeritiera littoralis

http://www.aims.gov.au/pages/reflib/fg-mangroves/pages/fgm-qld-15.html

James A. Danoff-Burg, Columbia University, [email protected] Mangrove Forests Dr. James A....

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