Seed Dispersal and Predation in Forest on Doi Suthep

The study determined the relative importance of seed dispersal and predation, compared with other site environmental conditions, as factors that limit some tree species from colonizing gaps. Two sites: primary disturbed forest and a gap were selected in Doi Suthep-Pui National Park. Seed traps were used to determine which species are able to disperse their fruits/seeds from forest into gaps. Seed predation was assessed by using three selected species and live- trapping of potential mammalian seed predators was also done. 

Small, flat, light-weight and usually winged fruits/seeds disperses further into the gap, whilst bigger ones could disperse only a few metres from parent trees. Seeds of 70 tree species were found in the traps, of which 21 were found only in the gap and 17 only in the forest. The rest were found at both sites. Species diversity of fruits/seeds declined with increasing distance from forest edge, and with high seasonal variation. This knowledge could possibly be used to choose tree species, which cannot grow naturally, because of  lack of dispersal and different fruiting phenologies for forest regeneration in different places and seasons.

Seed predation rates were determined for Engelhardia spicata Lechen. ex Bl. var. spicata (Juglandaceae), Styrax benzoides Craib (Styracaceae), and Castanopsis acuminatissima (Bl.) A . DC. (Fagaceae). Seed predation rates in  gap and forest did not differ significantly (p> 0.05). Environmental conditions seemed to be more important than seed predation in limiting forest regeneration.

Live trapping of potential fruit/seed predators showed a much higher density of small mammals in the gap than in the forest, but the species found in both sites were not very different. Species common in both forest and gap were Rattus rattus, R. surifer, and R. bukit, but Mus cookii was found only in the gap.