Demographic response and life history of traditional forest resource tree species in a tropical mosaic landscape in Papua New Guinea

Abstract

Disturbance is well known to play an important structuring role in rainforest succession and in maintaining overall diversity. However, the ecological responses arising from changes in land use such as traditional and modified shifting cultivation practices are less well known. The distribution and dynamics of plant populations may be affected by such changes in land use and often their responses are compounded by a lack of life history data. The life history traits and demographic parameters important to successional species responses to disturbance remain poorly understood beyond broad generalisations, particularly in rainforests outside of the Neotropics. We examined the life history and demography of five rainforest tree species in Papua New Guinea to investigate the effect of shifting cultivation practices on their population dynamics. The demographic parameters most successful for continued population growth were medium to high recruitment, low seedling mortality and high seedling abundance, relatively low growth rates (compared to many pioneer species) and moderate to high abundance in all life stages. Successful life history traits were high seed mass, moderate shade-tolerance and high cultural value. In accordance with their demographies and life histories, Pterocarpus indicus, Vitex cofassus and Artocarpus altilis were classified as early successional species, while Pometia pinnata and Canarium indicum were considered mid-successional. The results suggest that the earlier successional species do not necessarily have an advantage in disturbed environments; persistence is more likely to rely on the response of inherent demographic processes to external influences.