Beyond the trees. A comparison of nonwoody species, and their ecology, in Papua New Guinea elevational gradient forest

This study appraises the richness of nonwoody species (ferns, herbs, lianas, palms, and shrubs) in 31 sites across undisturbed and disturbed forests in the lowland of Papua New Guinea (PNG) and at montane forest sites at 2,700 m a.s.l. The assessment was conducted following the PNG National Forest Inventory protocol. The results indicate that with 463 nonwoody species, the tropical forest of PNG has remarkable species richness. No significant difference was observed in richness among lowland, logged and pristine, and montane forests. The study shows that the richness of nonwoody species increases with elevation, but this trend is different when considering the taxonomic group separately. Palms and lianas decrease along the elevation, whereas ferns, herbs, and shrubs are positively correlated with elevation. The species composition between lowland forest and mountain sites is different, with a tree fern and an Araliaceae as an indicator of the mountain forest. The findings demonstrate a high taxonomic richness of nonwoody species in PNG, supporting previous research but highlighting the significant contribution of nonwoody species to the overall plant richness in a tropical habitat.