The Nauclea, Tristaniopsis, and Terminalia forests: Exploring the lesser-known biotopes of Agusan Marsh, Philippines

Abstract

The peat swamp forest of Agusan Marsh is characterized by the dominance of a unique and conspicuous assemblage of tree species across different habitat types. Understanding the species richness, diversity, structural patterns, and distribution of these types of forests is crucial for maintaining ecosystem stability and conservation. This study describes three less-explored biotopes dominated by Bangkal (Nauclea orientalis L.), Dangilas (Tristaniopsis decorticata Merr.), and Lanipau (Terminalia copelandii Elmer), using a purposive random sampling method. Across the three sites, 22 tree species, belonging to 17 families and 21 genera, were recorded. Tree density was recorded as the maximum at the Tristaniopsis biotope (650 individuals ha-1) and the minimum at the Terminalia biotope (367 individuals ha-1). The maximum total basal area (162.93 m2 ha-1) was re-recorded in the Tristaniopsis biotope and the minimum area in the Nauclea biotope stand (17.3 m2 ha-1). The ANOVA results for stand DBH, tree density, species richness, species diversity, and species evenness varied significantly among biotope types. The Tristaniopsis biotope had the highest species richness and diversity among the three sites. All stands exhibited a high community dependence on forest resources, which may have increased the vulnerability of the forest to human interference, thus necessitating immediate attention to conservation. Site-specific management and conservation measures are proposed to provide opportunities for sustainable forest management.