FLORISTIC DIVERSITY AND STRUCTURAL CHARACTERISTICS OF MANGROVE FOREST OF RAJA AMPAT, WEST PAPUA, INDONESIA
ABSTRACT: We studied the
floristic composition and structure of mangrove forests and mangrove species
distribution at the Raja Ampat Regency, West Papua. We sampled the forests
using (10×10 m) quadrats to record trees and saplings laid out contiguously
along 9 transects of 60 – 450 m long, stretching perpendicularly from the
coastlines or riverbanks to the landward borders. Seedlings were sampled using
a 1×1 m subplot nested in each quadrat. The transects were established on the
islands of Batanta (6), Salawati (2) and Waigeo (1). Within quadrats and
transects we recorded 17 mangrove species of trees with density of 768 stems/ha
and basal area of 37.82 m 2 /ha and tree height of 10 – 30 m. Two species possessed
the highest importance value (IV) , frequency, density and basal area i.e.
Rhizophora apiculata (IV = 168.06%) and Bruguiera gymnorrhiza (IV = 67.18%).
They also showed the highest similarity in their distribution, indicating
highest degree of association. The mangrove at Raja Ampat may, therefore, be
designated as the Rhizophora apiculata – Bruguiera gymnorrhiza association.
Other species with highest degree of distributional similarities but withlow
densities, basal areas and importance values were Barringtonia racemosa,
Excoecaria agallocha, Hibiscus tiliaceus, Inocarpus fagifera, Lumnitzera
littorea and Sterculia shillinglawii, of which four of them are not true mangrove
species, usually growing on less saline and more solid soils. The floristic
composition of the transects in the three islands showed relatively high
similarities of about 70% and at higher similarities the transects in Batanta
Island formed four groups, Salawati Island two groups and Waigeo Island one
group. The Bray-Curtis polar ordination resulted in four groups of transects,
which were related to the habitat conditions and the length of the transects.
Species diversity in the islands was very low, where the Shannon diversity
index ranged from 0.19 to 0.64 giving the average of 0.42. Rhizophora apiculata
and Bruguiera gymnorrhiza were gregenerating well and in the future they will
remain dominant. The mangrove forests of the Raja Ampat Islands by any means
should be maintained as green belts and protected from all kinds of destruction
and should be made into conservation areas in order to sustain its ability to provide
ecological services and non-destructive economic benefits.
Key words: Rhizophora
apiculata – Bruguiera gymnorrhiza association, mangrove,
Raja Ampat Islands, West Papua
Author: SUHARDJONO
PRAWIROATMODJO, KUSWATA KARTAWINATA
Journal Code: jpbiologigg140027
