Tree diversity and phytogeographical patterns of tropical high mountain rain forests in Central Sulawesi, Indonesia

Tropical high mountain forests in Lore Lindu National Park, Sulawesi, Indonesia, were described by their floristic composition and the importance of tree families (Family importance values, FIV), based on tree inventories conducted on 4 plots (each 0.24 ha) in old-growth forest stands at c. 1800 and 2400 m a.s.l. (mid- and upper montane elevations). To identify general patterns and regional peculiarities of the forests in the SE Asian and SW Pacific context, the biogeography of the tree species was analysed using distribution records. Out of the total of 87 tree species, only 18 species were found at both elevational zones. The discovery of new species and new distribution records (28% of the data set) highlights the deficiencies in the taxonomic and distribution data for Sulawesi. Sulawesi endemism rate was 20%. In the mid-montane Fagaceae–Myrtaceae forests, Lithocarpus spp. (Fagaceae) were overall important (4 spp. occupying around half of the total basal area) and the Myrtaceae the most species rich (8 spp.), thus showing typical features of Malesian montane forests. The upper montane conifer-Myrtaceae forest contained several high mountain tree taxa and showed affinity to the forests of New Guinea. The mountain flora comprised both eastern and western Malesian elements, with the nearest neighbouring islands Borneo and Maluku both sharing species with Sulawesi, reflecting the complex palaeogeography of the island. A separate analysis showed the mid-montane forest to possess greatest biogeographical affinity to Borneo/western Malesia, and the upper montane forest had a number of typical elements of Papuasia/eastern Malesia and the Phillipines, which may be a result of historical patterns in land connection and the emergence of mountain ranges.