Ecology and distribution of bago (Gnetum gnemon L.) in Mount Maculot, Batangas, Philippines

Gnetum gnemon L. is an extant gymnosperm species that is morphologically related to angiosperms. Populations of G. gnemon have become naturalized in Mount Maculot, Batangas after decades of introduction by local farmers. This study determined the distribution, investigated the abiotic habitat and associated species in plant communities, and described the morphological variations of G. gnemon in relation to environmental variables in Mount Maculot. Populations of G. gnemon individuals were found to be present only along the eastern aspect based on the result of reconnaissance survey. Results showed that 68 G. gnemon individuals occur in clumps within agricultural, agroforestry and secondary forest areas from 300 masl to 600 masl elevation levels and were not present at elevations greater that 600 mas where forest zone changed from lowland secondary to montane and mossy forests. The clumps of G. gnemon formed six clusters, each with a potential mother tree and recruits based on the dbh class size and the proximity and location of smalle-sized dbh class individuals. This pattern suggests that G. gnemon reproduced with the assistance of animal seed dispersers. The associated plant communities were composed of 52 species representing 30 families in the canopy layer and 96 species from 46 families in the understorey layer showing higher species diversity in the understorey layer. The G. gnemon habitat exhibited similarities along 400 masl and 500 masl elevation levels. G. gnemon also had strong association with agroforestry species Artocarpus heterophylla, Coffea sp., and Lansium domesticum. Results of the cluster analysis of the associated habitat revealed 6 clusters where G. gnemon grouped with the initially identified agroforestry fruit trees. Soil chemical properties including soil pH, OM, N, and P increased with increasing elevation while K decreased with increasing elevation. A contrasting relationship was observed for leaf morphological traits and stem dbh and height of G. gnemon with increase in elevation. A direct relationship was observed between leaf morphological characters while inverse relationship was observed for stem dbh and height. G. gnemon exhibited increased leaf length, width and leaf area with increasing elevation. In contrast, decreased height and stem dbh of G. gnemon was observed with increase in elevation. The information on the G. gnemon occurrence, pattern of distribution and reproductive success, association with other species in the community, variation in morphological traits along elevational levels and relationship with soil chemical properties provided an indication of the possible extent of its niche within a forest or agroforest ecosystem and science-based assessment of is population for management and conservation.