Ibanez T. auteur aut IRD Blanchard E. auteur aut IRD Hequet Vanessa auteur aut IRD Keppel G. auteur aut IRD Laidlaw M. auteur aut IRD Pouteau Robin auteur aut IRD Vandrot H. auteur aut IRD Birnbaum P. auteur aut IRD text journalArticle eng text/pdf born digital access Background and Aims The biodiversity hotspot of New Caledonia is globally renowned for the diversity and endemism of its flora. New Caledonia's tropical rainforests have been reported to have higher stem densities, higher concentrations of relictual lineages and higher endemism than other rainforests. This study investigates whether these aspects differ in New Caledonian rainforests compared to other high-diversity rainforests in the Southwest Pacific. Methods Plants (with a diameter at breast height >= 10 cm) were surveyed in nine 1-ha rainforest plots across the main island of New Caledonia and compared with 14 1-ha plots in high-diversity rainforests of the Southwest Pacific (in Australia, Fiji, Papua New Guinea and the Solomon Islands). This facilitated a comparison of stem densities, taxonomic composition and diversity, and species turnover among plots and countries. Key Results The study inventoried 11 280 stems belonging to 335 species (93 species ha(-1) on average) in New Caledonia. In comparison with other rainforests in the Southwest Pacific, New Caledonian rainforests exhibited higher stem density (1253 stems ha(-1) on average) including abundant palms and tree ferns, with the high abundance of the latter being unparalleled outside New Caledonia. In all plots, the density of relictual species was >= 10 % for both stems and species, with no discernible differences among countries. Species endemism, reaching 89 % on average, was significantly higher in New Caledonia. Overall, species turnover increased with geographical distance, but not among New Caledonian plots. Conclusions High stem density, high endemism and a high abundance of tree ferns with stem diameters >= 10 cm are therefore unique characteristics of New Caledonian rainforests. High endemism and high spatial species turnover imply that the current system consisting of a few protected areas is inadequate, and that the spatial distribution of plant species needs to be considered to adequately protect the exceptional flora of New Caledonian rainforests. specialized Endemism hotspot New Caledonia island Oceania Pacific rainforests palms plot network relictual lineages species richness trees tree ferns tropical forest NOUVELLE CALEDONIE PACIFIQUE SUD OUEST 076 082 121 1 25-35 2018 0305-7364 https://www.documentation.ird.fr/hor/fdi:010072052 10.1093/aob/mcx107 0305-7364 [F B010072052] https://www.documentation.ird.fr/hor/fdi:010072052 https://www.documentation.ird.fr/intranet/publi/2018/02/010072052.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2018-03-05 2023-07-11 fdi:010072052 fre