Protium (PROSEA)
Introduction |
Protium Burm. f.
- Protologue: Fl. indica: 88 (1768).
- Family: Burseraceae
- Chromosome number: x= unknown;P. serratum(Colebr.) Engl.:n= 11
Vernacular names
- Kedondong (trade name)
- Indonesia: ketos
- Papua New Guinea: protium (En).
Origin and geographic distribution
Protium comprises about 85 species, most of which are found in tropical America, furthermore in Madagascar, the Mascarenes, and from India to Indo-China, Thailand, Java, the Philippines (Palawan), the Lesser Sunda Islands and Papua New Guinea. There are 3 species within the Malesian region and only 1 in continental Asia.
Uses
The wood of Protium is used for posts, pulley-blocks, tool handles and wooden hammers. It yields a good-quality charcoal. The wood of the continental Asian species P. serratum is much esteemed and used for furniture.
The young leaves and fruits are edible. The leaves, young twigs and the rind of fruits are used as a flavouring in cooking. A decoction of the leaves has been used medicinally in Java against stomach-ache and coughs. The rind of the fruit contains an aromatic essential oil used as a substitute for e.g. turpentine. P. javanicum has been used as a cover crop in teak ( Tectona grandis L. f.) plantations. P. macgregorii is also planted as a shade tree in Papua New Guinea.
Production and international trade
Protium timber is traded together with that of many other Burseraceae genera as "kedondong", but comprises only a very small proportion of the total amount traded. In 1996 Papua New Guinea exported only 67 m3of Protium logs at an average free-on-board (FOB) price of US$ 104/m3.
Properties
Protium yields a medium-weight to heavy hardwood with a density of 750-1060 kg/m3at 15% moisture content. Heartwood reddish-brown to dark brown, not clearly differentiated from the sapwood; grain interlocked; texture very fine to moderately fine and even; wood with ray flecks on longitudinal surface. Growth rings indistinct, tending to semi-ring porous; vessels moderately small; solitary or in radial multiples of 2-3, tyloses abundant ( P. javanicum ) or sparse ( P. connarifolium ); parenchyma sparse to absent, scanty paratracheal to vasicentric barely evident with a hand lens; rays very fine to moderately fine, inconspicuous; ripple marks absent.
The wood is hard to very hard but only of moderate strength. Some species are difficult to saw due to the high silica content. Splitting is difficult due to grain irregularities. It should be treated with anti-stain chemicals immediately after sawing. The wood is moderately durable. The sapwood is susceptible to Lyctus .
The gross energy value is about 20 360 kJ/kg for sapwood and 21 840 kJ/kg for heartwood of P. javanicum .
See also the table on microscopic wood anatomy.
Botany
Monoecious, small to medium-sized trees up to 30 m tall; bole often short and crooked, up to 115 cm in diameter, spurred; bark surface peeling off in large thin scales and slightly pustular, light-grey to brown, inner bark reddish or pink turning red-brown upon exposure, with sticky exudate. Twigs sometimes spiny. Leaves arranged spirally, imparipinnate, exstipulate; leaflets 1-11, opposite, entire, often mucronulate. Flowers in an axillary or sometimes pseudoterminal inflorescence, generally unisexual, 4-5-merous; sepals connate, forming a saucer-shaped receptacle; petals with inflexed tips; disk intrastaminal, annular. Male flower with stamens free, twice as many as the petals; pistil only slightly reduced. Female flower with a superior, 4-5-locular ovary with 2 ovules in each cell, stigma sessile, lobed; stamens only slightly reduced, occasionally even fertile. Fruit a globose to ovoid drupe with 1-5 1-seeded pyrenes; pericarp fleshy; calyx persistent. Seedling with epigeal germination; cotyledons emergent, lobed; hypocotyl elongated; first pair of leaves opposite, simple, subsequent ones arranged spirally and compound, leaflets serrate.
The mean annual increment of 7.5-year-old P. javanicum trees planted at 2 m × 1 m on moderately fertile soil in East Java was 1.0 cm in diameter and 1.1 m in height. Protium species are reputed to flower and fruit almost throughout the year, though flowers seem to be most abundant in the dry season and fruits in the wet season. Fruits are eaten by monkeys.
Protium resembles Scutinanthe but the latter differs in its cup-shaped receptacle, 3-locular ovary and 1-seeded fruit. The Asiatic species of Protium are grouped into the section Protium .
Ecology
Protium is found in evergreen or semi-deciduous, lowland, primary or secondary forests, up to 800(-1100) m altitude. P. javanicum prefers a periodically dry climate and is often associated with teak. It is also found in more open land, along the inner border of tidal forest and sometimes on the beach. P. macgregorii may also be found in swamps.
Silviculture Protium can be propagated by seed. Care should be taken to collect mature seeds only. The only available seed count is for P. javanicum which has about 19 500 dry seeds/kg. Seeds of P. javanicum gave about 70% germination and germination started 3-4 weeks after sowing; they should not be sown deeper than 2.5 cm. Seeds stored for 4.5 months are no longer viable. Seedlings of P. javanicum can be made successfully into stumps before being planted. P. javanicum has been extensively tested in Java to be planted as cover crop in teak plantations at 1 m × 1 m. On poor soils it performed unsatisfactorily, on fertile soils, however, it did fairly well when enough light was available, but wood production was minimal due to the bad stem form. When planted in pure stands at 1 m × 2 m on moderately fertile soils the first thinning was necessary 7 years after planting but the formation of low and heavy branches again proved to be a disadvantage. Pruning, however, is very well tolerated but the abundance of spines on the branches makes this operation difficult. P. javanicum also coppices easily; it is not resistant to fire.
Genetic resources and breeding
As Protium species have a narrow geographical distribution, destruction of the habitat may increase the risk of genetic erosion.
Prospects
Plantation experiments as conducted in Java indicate that P. javanicum can not be recommended for forestry plantations due to its poor stem form and very modest growth rate even on fertile soils.
Literature
70, 80, 161, 260, 308, 330, 341, 405, 408, 409, 423, 436, 442, 488, 680, 740, 780, 861, 934, 947, 1080.