Pinus tropicalis (pino blanco, tropical pine) description

Pinus tropicalis

Morelet 1851

Common names

Pino blanco, pino hembra [Spanish]; tropical pine.

Taxonomic notes

This predominantly 2-needled pine was originally assigned to subsection Sylvestres and regarded as closely related to P. resinosa (Farjon and Styles 1997), but it does not hybridize with P. resinosa (Hall et al. 1975) and more recent molecular studies (see discussion for Pinus) place it closest to three sub/tropical pines of east Asia: P. massoniana, P. merkusii, and P. latteri. This begs the question of how P. tropicalis got to the Caribbean.

Morelet (1851) recognized this species in western Cuba, including the Isla de la Juventud (then known as the Isla de Pinos), but his original collections are lost. Farjon and Styles (1997) have designated as neotype a 1916 collection by Britton from La Cañada on the Isla de la Juventud. The species was later (c. 1865) described by C. Wright under the name of P. terthrocarpa, which was first published as P. cubensis var. terthrocarpa by Grisebach 1866, and restored to species rank by Shaw as P. terthrocarpa (Grisebach) Shaw 1903. Shaw later (1914) synonymized it under P. tropicalis Morelet, where it has since remained (Farjon and Styles 1997).

Description

Trees up to 30 m tall and 180 cm dbh, with a slender, round trunk and a crown depth of 25% to 33%. Branches thick, spreading to ascending, forming an irregular, open crown. Bark on young trees and branches scaly, flaking, red-brown weathering to grey; with age becoming thick, rough, scaly, and breaking into irregular polygonal plates divided by deep longitudinal fissures. Shoots producing one node per year, thick, rough with large, persistent, decurrent pulvini, orange-brown in 1st and 2nd year, then grey, scaly with flat bases of pulvini. Fascicle sheaths initially 20 mm long, papery yellow-brown with whitish margins, persistent but only about 10 mm long on older fascicles. Needles in fascicles of 2 (rarely 3), straight and rigid, (15-)20-30 cm × 1.5 mm, with serrulate margins, acute, light or yellow-green, persisting 2 years. Stomata in 6-8 lines on all sides of needles. Pollen cones crowded near the basal end of shoots, oblong to cylindrical, 20-30 × 5 mm, pink turning yellow turning brown. Seed cones subterminal, erect on short, thick peduncles, solitary, in pairs or whorls of up to 6. Immature cones narrowly ovoid, 10 × 5-7 mm, purple-red, maturing in two seasons. Mature cones ovoid with a flattened base, then 5-8 × 4-5.5 cm when open, persisting several years, falling with the peduncle attached. Seed scales ca. 100-120, straight or strongly recurved, dark brown. Apophysis flat or slightly raised, up to 12 mm wide. Umbo dorsal, flat or slightly raised, rhombic, ca. 3 mm wide, without a prickle, greyish brown to grey. Seeds obliquely ovoid, slightly flattened, 5 × 4 mm, light grey-brown. Seed wings articulate, held to the seed by two claws, obovate-oblong, 12-15 × 5-6 mm, yellow with a grey or black tinge. Suppressed terminal growth and a thick radicle produce a "grass stage" seedling. Time of pollen dispersal not recorded; presumably later than P. caribaea (Farjon and Styles 1997).

Distribution and Ecology

W Cuba: Pinar del Rio and the Isla de la Juventud, on coastal plains and in foothills at elevations of 1-150(-300) m. It is found on very well-drained, nutrient-poor sandy or gravelly alluvial soils. The climate is tropical, with annual precipitation of ca. 1200 mm and a prolonged dry season. The vegetation type, pine savanna, consists of frequently burned grass-dominated lowland areas. It commonly co-occurs with P. caribaea var. caribaea (which also grows at higher elevations), but seems to be somewhat better adapted to frequent fires. Like many other fire pines (e.g. P. palustris), it has a "grass stage" which enables older seedlings and young saplings to survive frequent low-intensity ground fires (Farjon and Styles 1997). See the "Remarks" section HERE for details on "grass stage" growth. The importance of fire in this system has been described by Heras et al (2005, 2006). Heras et al. (2005) describe vegetation dynamics after a fire, including increased floristic richness. Heras et al. (2006) show that seed exposure to high heat actually increases germination success.

Distribution data from USGS (1999).

IUCN assesses this species as "Vulnerable". Most natural stands of P. tropicalis have been converted to P. caribaea var. caribaea plantations in recent decades (Figueroa Sierra 2002). Burkhard Witt (email, 2009.10.12) reports that, based on his travels to Cuba in 2004 and 2008, "in former times the frequently burned pine-savannahs were the home of P. tropicalis. On the 2 travels, I have seen only one very small spot of pine savanna, and even this has been reforested in the past few years. In order to not lose the pine-savannahs completely, the nature reserve Reserva Florística Manejada San Ubaldo-Sabanalamar was created. In 2004, I traveled to the pine-regions of western Cuba. Everywhere in these regions, I found plantations of P. caribaea var. caribaea. For two days, I looked only for P. tropicalis, but I only found a single tree on the edge of a Pinus caribaea var. caribaea plantation. In 2008, I traveled about 400 kilometers in these pine regions, entering as many forest trails as possible. The Cubans I asked in the countryside (three of them working in the forest service) were able to tell me where in former times had been pino hembra (P. tropicalis), but only two persons knew of existing stands in their surroundings. I mostly had to search on my own. At the end of four days of searching, I had found seven localities. Of these seven, five consisted of less than 20 trees (mostly natural regeneration on edges of P. caribaea var. caribaea plantations), and only four had adult trees. In some remote areas bigger stands of P. tropicalis still remain (Figueroa Sierra 2002). But the future for P. tropicalis doesn`t look good as many P. tropicalis stands after logging are still converted to P. caribaea var. caribaea plantations."

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

Remarkable Specimens

Diameters to 180 cm have been recorded in the wild (Wu and Raven 1999).

Ethnobotany

The wood of Tthis species is is dense, resinous, and thus durable. It is an important regional source of timber. It is used in plantation forestry, mainly in Cuba, but also in other countries (Farjon and Styles 1997).

Some dendrochronological research has been done on growth rates by Chernavskaya et al. (1999), who sampled upland trees (300-350 m elevations), and report that crossdating is difficult and sometimes impossible due to the year-round growth and frequent occurrence of false rings. Similar problems have been reported for P. caribaea var. caribaea.

Observations

A 52 km² reserve, the Reserva Florística Manejada San Ubaldo-Sabanalamar, has been set aside in Pinar del Rio at Sabana Lamar, located at 22.15902°N, 83.95315°W (see it on Google Maps).

Remarks

Citations

Chernavskaya, M. M., H. D. Grissino-Mayer, A. N. Krenke, and A. V. Pushin. 1999. Pinus tropicalis growth responses to seasonal precipitation changes in western Cuba. Pp. 185-190 in R. Wimmer and R. E. Vetter (eds.), Tree Ring Analysis: Biological, Methodological and Environmental Aspects. Wallingford, UK: CABI Publishing.

Grisebach, A. H. R. 1866. Catalogus plantarum cubensium, exhibens collectionem Wrightianam aliasque minorem ex insula Cuba missas. Leipzig: Engelmann. P.217.

Hall, R. B. Hall, D. F. Karnosky, and D. P. Fowler. 1975. Report on the cross Pinus resionsa [sic] X P. tropicalis. 12th Lake States Forest Tree Improvement Conference. Available: http://www.rngr.net/Publications/lake-states-improvement-conferences/, accessed 2009.10.15.

Figueroa Sierra, C. F. 2002. Ecología y conservación de Pinus tropicalis en bosques naturales de las alturas de pizarras. Dissertation, University Pinar del Río (Cuba) and University Alicante (Spain), 124 p.

de las Heras, J., M. Bonilla, and L. W. Martínez. 2005. Early vegetation dynamics of Pinus tropicalis Morelet forests after experimental fire (W Cuba). Annals of Forest Science 62:771-777.

de las Heras, J., M. Bonilla, and L. W. Martínez. 2006. Germination after heat treatments of Pinus tropicalis Morelet and Pinus caribaea Morelet var. caribaea seeds of west Cuban forests. Annals of Forest Science 63:469-475.

Morelet, A. 1851. Descriptions de deux novelle espèces de pins (Pinus tropicalis et P. caribaea). Rev. Hort. Côte d'Or 1: 105-107.

Shaw, G. R. 1903. Pinus terthrocarpa sp. nov. InC. S. Sargent, Trees and Shrubs, Illustrations of New or Little Known Ligneous Plants. Boston: Houghton Mifflin. Vol. 1, Part 3, p.149, t.75.

Shaw, G. R. 1914. The Genus Pinus. Publications of the Arnold Arboretum No. 5. Cambridge, MA: Harvard University.