Usually, tropical research in plant ecology is based on trees. Non tree species are rarely considered. The reasons are various, poor knowledge on the non tree species composition, difficulties to gather large data, lack of financial support for non tree species, etc. 

In this study we considered the non tree species in Papua New Guinea along an altitudinal gradient. Specifically we assess the ferns, herbs, liana, palms and shrubs richness. Yes, some of them are woody as liana and shrubs but they are not trees therefore they still belong, according to our classification, within the category of non tree species. We found an incredible number of 463 species. The study shows that the species richness increases with the elevation.

In other words, the higher you go the more species you have. However, this is valid if we combine all the species together. If we divide each group we can observe that palm and liana are more abundant in the lowland and nearly absent at higher elevation. Whereas ferns and shrubs are richer at higher elevation. Papua New Guinea is still the frontier of tropical ecology and our knowledge of this island’s richness, composition and distribution is still far to be completed. This project has contributed a bit to a group of plants poorly considered.