Diversity and structural complexity of mangrove forest along Puerto Princesa Bay, Palawan Island, Philippines

The paper describes the diversity and structural complexity of mangrove forest along Puerto Princesa Bay, Palawan Island, Philippines. Occurrence of 28 mangrove species and 11 floral associates were found, which identifies the entire bay as one of the most diverse mangrove forests in the country. Of the six coastal barangays surveyed, San Pedro had the highest diversity index, H′ = 0.912 while Sta Monica had the lowest, H′ = 0.349. Mangrove stands are structurally simple with two types of vegetation, fringe and riverine that further constitute five distinct mangrove zones named according to dominating species, Rhizophora-Sonneratia; Rhizophora-Sonneratia-Lumnitzera; Rhizophora-Lumnitzera-Xylocarpus; Rhizophora-Xylocarpus; and Rhizophora-Avicennia. Commonality among these zones is obvious as revealed in Bray-Curtis cluster analysis. Structural features differed across zones. Trees of larger dbh, 104.5 cm and higher species richness, a total of 15 species, were found in zone 1 while those that comprised the highest basal area, 438 m−2 ha−1 and density, 8100 ha−1 from zones 2 and 4, respectively. Zones 1 and 4 are fringing mangrove forests. Degrees of perturbations greatly depend on human access to mangrove areas. Garbage dumping, occasional cutting of trees, soil erosion, and encroachment of human settlers were identified as potential threats to mangrove forest along the bay.