General flowering and fruiting in Kemena and Tatau River areas
Hiromitsu Samejima (CSEAS, Kyoto University)
Most lowland and hill areas of Borneo are covered by Mixed Dipterocarp Forest (MDF), in which large Dipterocarpaceae trees (ex. Shorea, Dipterocarpus and Dryobalanops spp.) dominate the canopy layer. In these forests, trees don’t flower and fruit every year. Once every one to five years, various taxa of trees synchronously blossom and fructify. These phenomena are called “general flowering” and “general fruiting” (Sakai et al., 1999). During the period of general flowering, a swarm of giant honey bees (Apis dorsta) appears, followed by a pack of wild boars in the time of general fruiting. Both species come and go enjoying nature’s blessings and during this period of time, local people collect honey, catch wild boars and gather Illipe nuts (fruit of “Engkabang”: Shorea stenoptera and several other species for food oil). During this period, collecting honey or gathering Illipe nuts are no longer common activities of locals, while wild boars are still their important source of protein. Many villagers well remember a recent time when wild boar was extremely abundant.
A wild boar captured on Camera trap
This general flowering and fruiting is considered to be triggered by dry conditions (Sakai et al., 2006). When precipitation was low for a certain amount of time (more or less one month?), most trees in the area began to bloom and produce fruit synchronically. The special extent of this phenomenon is sometimes limited only to valley areas but when it occurs on a grand scale, it occurs from the Malay Peninsula to the whole of Borneo.
During this joint-research, in each village we visited we intensively investigated when the last time they witnessed many wild boars was. Because massive general flowering and fruiting occurred twice in 2009 that covered western Kalimantan, the whole area of Sarawak, and the west coast of Sabah, I had presumed that in this confined geographical area¹, the answers would coincide with this period of general flowering and fruiting. However, the answers were different among each area (Fig.-1). This unevenness is explained by the following two presumptions:
1) The start of the dry period varied from region to region, as did the period of general flowering.
2 )The difference of location situations such as plantations of both acacia or oil palm and swampy forests created different landscape compositions.
Details of this issue will be revealed in my future research.
The fruit of “Engkabang” is a well-known non-timber forest product (NTFP) in Borneo which is exported even today. Along the Baram River areas, where I had been working, many Engkabang trees, planted in the past can still be seen. The business, however, is already obsolete. But in one village on the Anap River, I was informed people still collect Engkabang fruit and a Chinese trader in Sangan town buys it, although many villagers complain about its low trading price. During my visit, I was also informed about an Iban man who still collects wild honey from the giant bees. I expect these persons possess a certain amount of information on the history of general flowering and fruiting in the area and the geographical pattern of the event. I am planning to make contact with them in the future.
¹this confined geographical area: the total of Sebauh subdistrict, Tatau District（≒Kemena, Tatau river areas）is no more than 10,000Km square meters.