SignificanceIdentifying and explaining regional differences in tropical forest dynamics, structure, diversity, and composition are critical for anticipating region-specific responses to global environmental change. Floristic classifications are of fundamental importance for these efforts. Here we provide a global tropical forest classification that is explicitly based on community evolutionary similarity, resulting in identification of five major tropical forest regions and their relationships: (i) Indo-Pacific, (ii) Subtropical, (iii) African, (iv) American, and (v) Dry forests. African and American forests are grouped, reflecting their former western Gondwanan connection, while Indo-Pacific forests range from eastern Africa and Madagascar to Australia and the Pacific. The connection between northern-hemisphere Asian and American forests is confirmed, while Dry forests are identified as a single tropical biome.

Bornean heath (Kerangas) forests are a unique and increasingly rare tropical forest ecosystem that remains little studied. We quantified tree floristic diversity in Kerangas forests in the Tutong White Sands, Brunei Darussalam, and investigated the influence of soil and environmental variables on community composition. Six 20 m × 20 m plots were established, where all trees of ≥5 cm diameter at breast height (DBH) were identified and measured to determine stem diameter and basal area. We determined pH, gravimetric water content, and concentrations of total nitrogen (N) and phosphorus (P) in topsoil, as well as litter depth and percentage canopy openness. A total of 296 trees were recorded, representing 78 species in 59 genera and 38 families. Stem diameter, basal area, species richness, and species diversity differed significantly among the six plots. The NMDS ordination revealed that differences in tree community compositions were significantly associated with total N concentrations and percentage canopy openness. Despite the small sampling area, we recorded several Bornean endemic tree species (16/78 tree species; 20.5%), including several IUCN Red List endangered and vulnerable species. Our results illustrate the potentially high conservation value of the Kerangas forests in the Tutong White Sands and highlight the urgent need to protect and conserve this area.

Dryobalanops rappaBecc. and Shorea albida Sym. are Bornean endemics of high conservation value and increasingly threatened by anthropogenic disturbances. In-situ study of seedling abundance and growth performance of these Dipterocarp species was conducted in two selected peat swamp forests of Brunei Darussalam, following a mast fruiting event in March-May 2014. Within six 6 x 6 m plots at each forest site, D. rappa seedlings at the Anduki peat swamp forest and S. albida seedlings at the Badas peat swamp forest were measured for abundance at the initial census in September 2014, as well as survival and relative growth rates (RGR) after a period of 5 months, with the final census in February 2015. We found significantly higher seedling abundance for D. rappa (1885 ± 208) than S. albida (160 ± 71). Significantly higher percentage survival was recorded for D. rappa seedlings (90.8 ± 2.2%) in comparison to S. albida -1 -1 seedlings (81.7 ± 2.2%). S. albida seedlings (0.24 ± 0.02 mm mm month ) showed significantly greater RGR in stem -1 -1 diameter than D. rappa seedlings (0.18 ± 0.02 mm mm month ), however, there were no significant differences in the RGRs based on seedling height, leaf number and biomass between D. rappa and S. albida seedlings. In terms of seedling abundance and percentage survival, D. rappa seedlings appeared to be more successful in regeneration and may potentially be used for rehabilitation of degraded tropical peat swamps and other forest types. Our results suggested that greater conservation efforts of peat swamps must be made to protect the Bornean endemic plant species, in particular S. albida.