Seedling recruitment failure following dipterocarp mast fruiting

Abstract

Many rain-forest trees in South-East Asia, including the dominant canopy family Dipterocarpaceae, reproduce in gregarious mast-fruiting events once every 2–11 y (Ashton et al. 1988). The dominant hypothesis for the evolution of masting is that predators are incapable of consuming mast seed crops, so that natural selection has favoured parent trees that fruit in synchrony (Janzen 1974, 1976). Mast flowering and fruiting are visually spectacular and quantified in harvest records for dipterocarp species producing large, oil-rich tengkawang seeds (Curran et al. 1999). Seedling recruitment following a mast is less obvious and has no immediate commercial value. However, a number of pulses of recruitment have been documented (Ashton et al. 1988, Chan 1980, Fox 1972, Liew & Wong 1973). These, together with general acceptance of the satiation hypothesis, have led to the widespread assumption that masts reliably increase seedling density and generate distinct seedling cohorts (Whitmore 1998). Indeed, foresters in Malaysia and Indonesia often recommend harvesting only after a mast, to ensure high densities of seedling regeneration.