Plant reproductive phenology over four years including an episode of general flowering in a lowland dipterocarp forest, Sarawak, Malaysia

The first systematic observation of a general flowering, a phenomenon uniqu e to lowland mixed-dipterocarp forests in Southeast Asia, is presented. Dur ing general flowering, which occurs at irregular intervals of 3-10 yr, near ly all dipterocarp species together with species of other families come hea vily into Bower. We monitored reproductive phenology of 576 individual plan ts representing 305 species in 56 families in Sarawak, Malaysia. Observatio ns continued for 53 mo from August 1992 and covered one episode of a genera l flowering cycle. Among 527 effective reproductive events during 43 mo, 57 % were concentrated in the general flowering period (GFP) of 10 mo in 1996. We classified 257 species into flowering types based on timing and frequen cy of flowering, The most abundant type was "general flowering" (35%), whic h flowered only during GFP. The others were '"supra-annual" (19%), "annual" (13%), and "sub-annual" (5%) types. General flowering type and temporal ag gregation in reproductive events were commonly found among species in vario us categories of taxonomic groups, life forms, pollination systems, and fru it types. Possible causes for general flowering, such as promotion of polli nation brought about by interspecific synchronization and paucity of climat ic cues suitable for flowering trigger, are proposed, in addition to the pr edator satiation hypothesis of Janzen (1974).