Woody plant species co-occurrence in the lowland forests of Puerto Princesa Subterranean River National Park, Palawan.

Abstract

The Puerto Princesa Subterranean River National Park (PPSRNP) hosts an interestingly rich floral diversity (CEFP, 2001) in its lowland forest. In this forest, plant assemblages exist that are possibly governed by co-occurrence. To test for this, a null model analysis was implemented. A 2 km transect line was laid along the jungle trail of PPSRNP, which was divided into 40 sampling plots with 50-m interval. In each point, the trees were surveyed using a modified Point Center-Quarter Method wherein the diameter at breast height (DBH) and the global positioning system (GPS) coordinates of each trees were obtained. A matrix of the presence or absence of species in each sampling site was constructed and was analyzed for species co-occurrence using EcoSim version 7 (Gotelli and Entsminger, 2004). The results from the C-score, Combo, Checker and V-ratio indices show that woody plant species in the lowland forest of PPSRNP exhibit a non-random, segregated pattern, which could not be attributed to competition. The segregated pattern observed could be accounted for the heterogeneous soil type along the trail which might suggest habitat preference or association. A distribution map was also generated using DIVA-GIS version 5.2 (Hijman et al., 2005). The map generated showed segregation pattern, as distinctly exhibited by Dimorphocalyx murinus and Casearia grewiifolia. The results of this research have implications on the in-situ conservation of the area, providing basic framework for ecological studies such as habitat preferences.