Haplolobus (PROSEA)

Plant Resources of South-East Asia
Introduction

Protologue: Ann. Jard. Bot. Buitenzorg 42: 25, 26 (1931).

Family: Burseraceae

Chromosome number: x= unknown; 2n= unknown

Origin and geographic distribution

Haplolobus comprises about 19 species occurring in Borneo, Sulawesi, the Moluccas, New Guinea, the Solomon Islands, and east towards Fiji and Samoa. Most species are found in New Guinea.

Uses

The wood of Haplolobus is used for general light construction and is probably suitable for the production of veneer and plywood. Wood of H. floribundus is suitable for the production of wood-wool board.

Production and international trade

Haplolobus wood is seldom used as supplies are generally very limited. Some of it may occasionally be mixed in consignments of "kedondong" timber comprising the wood of most Burseraceae genera.

Properties

Haplolobus usually yields a medium-weight hardwood with a density of 410-730 kg/m³at 15% moisture content, but H. floribundus shows an exceptionally wide density range of 340-1240 kg/m³at 15% moisture content. Heartwood pale brown to pink brown, denser material usually a little darker in colour, not clearly demarcated from the sapwood; grain straight to wavy alternating to produce coarse stripe figure; texture medium coarse to coarse and even. Growth rings indistinct; vessels medium-sized to large, solitary and in radial multiples of 2-3(-5), tyloses present, but not abundant; parenchyma absent to scanty paratracheal; rays fine, not visible to the naked eye; ripple marks absent.

The wood is fairly soft and weak. It is slightly durable to non-durable and should be treated with anti-stain chemicals immediately after sawing. The sapwood is susceptible to Lyctus .

See also the tables on microscopic wood anatomy and wood properties.

Botany

Dioecious, small to medium-sized trees up to 30(-45) m tall; bole straight, branchless for up to 20 m, up to 60(-80) cm in diameter, sometimes with small buttresses; bark surface scaly, greyish. Leaves arranged spirally, imparipinnate, exstipulate; leaflets 1-9(-13), opposite, entire, often with galls. Inflorescence axillary or rarely terminal, or borne on leafless twigs, paniculate. Flowers functionally unisexual, 3-merous, small; calyx cup-shaped, 3-dentate to subtruncate; petals free, with inflexed tips. Male flower with 6 or rarely 3 stamens; disk annular. Female flower with a superior, 3-locular ovary with 2 ovules in each cell, stigma sessile or subsessile, 3-lobed to subglobular. Fruit an ovoid to subglobular, 1(-2)-seeded drupe with dry, thin, smooth pericarp; stigmatic remains terminal. Seedling with hypogeal germination; cotyledons entire, not emergent; hypocotyl not elongated; first pair of leaves opposite, subsequent ones alternate, simple at first.

H. floribundus has been observed flowering throughout the year and fruiting in February-May and September-October.

Haplolobus species may be taken for those of Santiria which differ in their saucer-shaped calyx, the fruit having strongly excentric stigmatic remains, and the lobed cotyledons. H. floribundus is highly polymorphic with 4 recognized subspecies.

Ecology

Haplolobus is found scattered or occasionally gregariously (e.g. H. floribundus ) in primary or rarely secondary rain forest, from sea-level up to 1950 m altitude. The species are most common on hills and ridges and generally occur on well-drained, alluvial or clayey soils, but e.g. H. floribundus has also been reported from coral limestone. H. furfuraceus also grows in open forest or even open grassland.

Genetic resources and breeding

Most Haplolobus species are very rare and narrowly endemic. Most are also confined to primary forest and seem vulnerable to genetic erosion or extinction through destruction of their habitat.

Prospects

As a timber Haplolobus is poorly known and its increased use seems highly unlikely.

Literature

126, 341, 456, 582, 652, 685, 692, 740, 861, 1048, 1072, 1232.