5558

5(3): Timber trees; Lesser-known timbers

Gyrocarpus Jacq.

Select. stirp. amer. hist.: 282 (1763).

HERNANDIACEAE

x = unknown; G. americanus: n = 15

Indonesia: bonak busuk (Timor), ganggangan, gedreg (Javanese), hambui (Alor). Philippines: gyrocarpus (general), lapo-lapo (Iloko), malasapsap (Nueva Ejica and Rizal). Burma (Myanmar): pinle-thikauk. Thailand: puu le (peninsular), sao (south-western).

Gyrocarpus is a pantropical genus comprising 3 species. The only Malesian species, Gyrocarpus americanus Jacq. (synonyms: Gyrocarpus acuminatus Meissn., Gyrocarpus asiaticus Willd., Gyrocarpus jacquinii Gaertn.), has a pantropical distribution and occurs from Mexico to northern South America, in the drier parts of tropical Africa and in Madagascar, India, Sri Lanka, Burma (Myanmar), Indo-China, Thailand, Peninsular Malaysia (Langkawi Islands), the Philippines, East Java, the Lesser Sunda Islands, Papua New Guinea, northern Australia and into the Pacific towards Tahiti.

The wood of G. americanus has been used for boat and canoe building in Java and the Lesser Sunda Islands, and also for low-quality boxes and crates. In the Philippines it is regarded as a suitable substitute for kiri wood (Paulownia spp.) which is prized for wooden clogs, light furniture and floats. In India it has been used for boxes, toys and trays and is preferred for catamaran construction.

G. americanus wood is seldom brought to the market and trade is on a local scale only.

G. americanus yields a lightweight hardwood with a density of 190-230 kg/m³ at 15% moisture content. The wood of Indian samples is recorded at 290-415 kg/m³. Heartwood cream to straw, darkening to a greyish-brown upon age, not clearly demarcated from the buff-coloured sapwood; grain straight with a tendency to be wavy; texture moderately coarse to coarse; wood very lustrous and with conspicuous silver grain. Growth rings often distinct, delimited by concentric rings of vessels, with a strong tendency to align tangentially, sometimes diffuse-porous; vessels moderately large to large, solitary and in multiples of 2-3, open; parenchyma paratracheal vasicentric, aliform and sometimes confluent; rays moderately broad; ripple marks absent.
The wood seasons well. It is soft, not strong and not tough. The wood is non-durable and susceptible to dry-wood termites and the sapwood is susceptible to Lyctus; its resistance to insect attacks is probably erroneously reported.
See also the table on microscopic wood anatomy.

A deciduous, small to medium-sized tree up to 25(-30) tall; bole up to 100 cm in diameter, without buttresses; bark surface smooth to moderately rough or occasionally scaly or flaky and/or finely and irregularly cracking, pale cream to greenish-brown or pale grey; slash exuding a cream to yellowish or orange sap. Leaves arranged spirally, clustered at the apex of fleshy twigs, simple, entire or 3(-5)-lobed, heart-shaped to attenuate and 3-veined at base, acuminate, exstipulate. Flowers in a corymbose cyme borne axillary, bisexual and male ones on the same individual; perianth lobes (6-)7(-8); stamens 4, opening by 2 valves and with 2 glands at base; ovary inferior, 1-locular with 1 ovule; style simple. Fruit a samara, nut with 2 large wings on the persistent calyx tube which surrounds it. Seed with spongy testa. Seedling with epigeal germination; cotyledons emergent, bilobed, conduplicate; first few leaves entire, subsequent ones 3-lobed, leaves of mature trees entire.
Fast growth is reported from Timor. Trees often flower while leafless. In East Java trees flower in April and May. In the monsoon area around Port Moresby, Papua New Guinea, trees flower in April and May and mature fruits are found in July and August. Trees in the Andaman Islands are leafless from January to March, new leaves appear in April, flowering takes place in December and January and the fruits are mature in April to May. Pollination is probably by wind. The winged fruits are an obvious adaptation for wind dispersal in the same manner as those of the Dipterocarpaceae: they rotate when falling. Dispersal may also be by water as the fruits can float for several months.
Hernandiaceae forms a small family of primitive Angiosperms showing affinities with both Lauraceae and Monimiaceae. Gyrocarpus is sometimes treated as a separate family, the Gyrocarpaceae. G. americanus has been subdivided into 8 subspecies. Within the Malesian region the subsp. americanus and subsp. sphenopterus (R. Br.) Kubitzki occur.

G. americanus is generally found scattered near the shore, on the beach, on rocky slopes and dune scrub. It also occurs in inland localities, on well-drained or rocky sites, in savanna, sclerophyll forest on calcareous soils, poor monsoon forest, stony crests and on river banks, up to 200 m altitude. It is confined to areas with a pronounced dry season.

In India G. americanus is propagated by seed and one kg contains about 2650 fruits without wings. Seeds remain viable for one year if stored properly and the viability of fruits having floated in water for 2 months was not affected. Seeds do not need any pretreatment, although improved germination is reported from Madagascar after soaking seed in water for 24 hours. Germination starts 10 days after sowing and attains about 60% of the seeds sown in full light, but in a trial in Peninsular Malaysia seeds germinated much later: about 70% germination was achieved from 11 months to almost 3 years. In India germination decreased when seeds were sown under shade. Seedlings attain 40 cm and more in a year and seedlings over 30 cm tall tolerate planting out best (about 60% survival) either as containerized plants or as bare-rooted stock. Stumping of seedlings failed completely. For Indonesia G. americanus is recommended for planting in areas with an annual rainfall of 1000-1200 mm. It is not fire resistant, does not tolerate periodic waterlogging and easily regenerates naturally in the degraded woodland of Timor, provided heavy grazing is absent.

Since G. americanus is little exploited its genetic resource base is not at risk.

Commercial interest in G. americanus is unlikely to increase as the wood quality is insufficiently known. Its utilization for carving in cottage industry may attract interest in the future.

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E. Boer & M.S.M. Sosef

Boer, E. & Sosef, M.S.M., 1998. Gyrocarpus Jacq.. In: Sosef, M.S.M., Hong, L.T. and Prawirohatmodjo, S. (Editors): Plant Resources of South-East Asia No 5(3): Timber trees; Lesser-known timbers. PROSEA Foundation, Bogor, Indonesia. Database record: prota4u.org/prosea