Pinus merkusii

Junghuhn et de Vriese ex de Vriese 1845

Common names

Thông nhua, Thông hai lá [Vietnamese]; Tusam Sumatera [Indonesian]; Sumatran pine.

Taxonomic notes

Syn: P. merkiana Gordon; P. sumatrana Junghuhn (Farjon 1984), P. finlaysoniana Wall. ex Blume 1847 (Farjon 1998). P. latteri Mason, previously considered conspecific, is now treated as a separate species (Farjon 1998). The two taxa have very similar appearance, but P. latteri seedlings have a grass stage and it occupies a different distribution within somewhat different habitat; as such it could reasonably be called either a sister species, or a subspecies of P. merkusii.

Description

Tree 30-50(70) m tall and 60-80 cm dbh with straight bole level to upcurved branches, the open crown changing from conical to rounded as the tree ages. Bark thick, rough, gray-brown or reddish-brown, deeply fissured, forming small rounded plates on the lower part of the trunk; thin and flaky in upper crown; all bark thin on trees from some areas at higher altitude (Tapanuli prov., Sumatra) where grass fires are infrequent. Branches mostly multinodal. First year branches brownish and glabrous. Leaves dark green, 2 per fascicle, 15-25 cm long, slender, rigid, persistent 2 years, sheaths persistent; dried leaves 60-90 mg per fascicle (c.f. over 100 mg in P. latteri). Cones singly or in pairs with short stalks, 4.5-9(11) cm long, with a rounded base, green ripening orange-brown, maturing after 2 years. Scales of the first year cone spineless. Mature cone cylindrical or long-ovate, with pedicel about 1cm long; scales rhomboid, with a thick, glossy, sometimes furrowed apophysis and a prominent transverse keel; umbo slightly concave. Seeds small, ovate, slightly flat, bearing a thin wing, 7.5 mm, 15-20 mm with wing (Cooling and Gaussen 1970, Farjon 1984, de Laubenfels 1988, FIPI 1996). See García Esteban et al. (2004) for a detailed characterization of the wood anatomy.

Distribution and Ecology

Vietnam, Cambodia, Philippines, Malaysia and Indonesia. In Malesia, found in N & C Sumatra, and in the Philippines, on Mindoro I. and Zambales prov., Luzon I. In Vietnam found in large stands or in small groups at Lai Chau, Son La, Lang Son, Bac Thai, Ha Bac, Quang Ninh, Thanh Hoa, Nghe An, Ha Tinh, Quang Binh and Thua Thien Hue provinces, but mainly in Kon Tum and Lam Dong provinces. It has the most southerly distribution of any pine and is the only pine occurring south of the Equator, to 2.10° S in the Barisian Range of Sumatra. It is found at elevations of (0)800-2000 m, usually in open, savannah-like areas that are frequently burned by native peoples, but also in tropical broadleaf forest. The best-developed forests are to be found around Lake Toba in northern Sumatra (Mirov 1967, Farjon 1984, de Laubenfels 1988, FIPI 1996).

In areas of frequent fire, seedlings of this species may develop a "grass stage." See the "Remarks" section HERE for details on "grass stage" growth.

This is a light-demanding, heat- and drought-tolerant tree, growing well on sandy and red soils. In north Vietnam, this species is one of the principal tree species planted on bare or bushy hills, having the function of protecting against erosion and land-deformation. Young trees are slow-growing during the first five years, later rather fast-growing. From 15 years onward, the resin can be harvested. Natural regeneration is good, especially on open lands. Flowers in May-June; cones mature in October-November of the following year (FIPI 1996). USDA hardiness zone 10.

Zone 10 (cold hardiness limit between -1°C and +4.4°C) (Bannister and Neuner 2001).

Remarkable Specimens

Trees have been reported to 70 m tall (de Laubenfels 1988), which would make it the tallest pine in the Old World.

A tree-ring chronology collected at Phu Kradung, Thailand, extended from 1616 to 1993 (ITRDB 2014). Phu Kradung is a national park, protected from logging since 1943, and all the cores ended at about the same time; so I expect the collection was performed in 1994 from living trees. In this case the trees were up to 378 years old.

Ethnobotany

The wood is heavy (density 0.88-0.96). It is used in construction, matches, paper pulp, common furniture, pit props, electronic poles, ships and vehicle-building. There is a high content of resin, each tree giving 3-4 kg of resin per year; this is a precious raw material used in medicine, paints, printing, and the perfume industry (FIPI 1996).

This species has been used in dendrochronology to reconstruct long-term trends in monsoonal precipitation (Cook et al. 2010).

Observations

Phu Kradung National Park, Thailand, looks like a good place to see Pinus merkusii in habitat. As noted above, the oldest known specimens occur at this site, a mountain plateau in the tropics.

Remarks

The epithet honors Henrik Merkus de Kock (1779-1845), an official in the Dutch East Indies who passed away shortly before this species was described. His work in the East Indies occurred well before Junghuhn and de Vriese worked there, so his connection to the species remains unclear.

Citations

Cook, E.R., K.J. Anchukaitis, B.M. Buckley, R.D. D'Arrigo, G.C. Jacoby, and W.E. Wright. 2010. Asian monsoon failure and megadrought during the last millennium. Science 328(5977):486-489.

Cooling, E.N.G. and H. Gaussen 1970. In Indochina Pinus merkusiana sp. nov. et non P. merkusii Jungh. et De Vriese. Trav. Lab. Forest. Toulouse T.1 V.8 Art. 7.

International Tree-Ring Data Bank [ITRDB]. 2014. Results for Selection of Site: Phu Kradung. http://hurricane.ncdc.noaa.gov/pls/paleox/f?p=519:1:0::::P1_STUDY_ID,P1_SITE_ID:12646,52804, accessed 2014.10.17, now defunct.

Vriese, W. H. de. 1845. Plantae novae et minus cognitae Indiae batavae orientalis. Nouvelles recherches sur la flore... II. Sur une nouvelle espèce de Pin de l'ile de Sumatra, pp 5-8, pl. 2.

See also

The species account at Threatened Conifers of the World.

Luu and Thomas 2004 provide a recent description, range map, conservation status, drawings and photos, and a wealth of additional information.