2.1 Study area
We conducted field sampling during April and May 2002 in primary lowland dipterocarp rain forest, part of a Class I forest reserve gazettement for Ulu Segama, near Danum Valley Field Centre, Sabah, Malaysian Borneo (4°57’N, 117°48’E) (Dial et al. 2004b; Dial et al. 2006) (Fig. 1). Mean temperature is 26.7˚C ± 1.9˚C, relative humidity ranges from 72%-100% (saturation) daily and mean annual rainfall is 2,669 mm (range: 1,918 - 3,294 mm) (Walsh and Newbery 1999). Rainfall is high in May-June and October-January, and is low in March-April and August-September (Walsh and Newbery 1999).
Our sampling was conducted over a 160 m × 70 m (vertical section) primary forest plot 150 m a.s.l., spanning a small tributary stream of the Segama River (Fig. 1). The ground was relatively level within the plot without steep hillsides or ridges (Dial et al. 2004a). The forest trees of the plot consisted of 11 trees from four families, with nine individuals in the Dipterocarpaceae and Fabaceae families. These trees ranged from 40.8 m to 75.0 m in height (see Table S1 and Table 1 in Dial et al. 2004a for details of tree species), and stood over an overstory of unidentified trees.