One of the most important white pine species native to Central America and Mexico, Pinus ayacahuite Ehren occurs in a number of areas where human pressure for agricultural land has resulted in a reduction in forest cover (Dvorak and Donahue, 1992). The species is not frequently planted within the native range though there are forest reserves where attempts are being made at in situ conservation.
There are two known varieties: Pinus ayacahuite var. brachyptera Shaw which occurs primarily in northern Mexico and Pinus ayacahuite var. veitchii Shaw which occurs mainly in central Mexico. Typical P. ayacahuite, which is the most tropical, has a range from Guerrero, Mexico to Honduras and El Salvador. Even though the species is relatively abundant in the cloud forests of western Guatemala (Styles and Hughes, 1987), P. ayacahuite is under severe pressure from wood cutters in Chiapas, Mexico, eastern Guatemala and northwestern El Salvador (Dvorak and Donahue, 1992). The northern varieties of P. ayacahuite occur on both fertile and infertile sites. Typical P. ayacahuite generally is found on rich, deep soils at elevations of 1800-3200 meters (Donahue et al., 1991).
In 1983, CAMCORE (Central America and Mexico Coniferous Forest Resources Cooperative) made seed collections from 15 provenances and 365 mother trees in the native range to allow for ex situ conservation and to evaluate the commercial potential. The seed collection sampled many provenances that had never been sampled and was the first large scale mother tree collection ever undertaken. Smurfit Carton de Colombia (SCC) received three sets of P. ayacahuite provenances for trial establishment which form the basis for this paper. Previous reports from this series of trials have appeared (Endo, 1994; Osorio, 1993).
The three trials were planted in the Cauca Department at an altitude of 2600 meters and 2.25 0 North latitude. The annual rainfall is 1970 mm with a mean annual temperature of 15 0C. The site does experience high winds which affect growth and form of the trees. Climatic and geographic details for the P. ayacahuite provenances are in Table 1.
Table 1. Climatic and geographic conditions of the P. ayacahuite provenances established in trials in Colombia
Growth in the nursery to a height of 15-20 cm took one year which is longer than for other sub-tropical pines such as P. patula. The trial design was a randomized complete block with nine replications of six tree family row plots. In such a design, families from one provenance are grouped together in each replication, but their position within the replication is randomized.
Survival in the trials was above sixty per cent indicating a certain adaptability for the species. Initial growth, however, was exceedingly slow with average height of one meter at three years of age. One way to increase the growth rate in nursery and field plantings is to produce seedlings of P. ayacahuite in bags of one liter dimension (Dvorak, 1990). Average height of P. ayacahuite was six meters at eight years of age. At the age of eight years the trials were evaluated for height, diameter and form traits. Data were analyzed using general linear model (Table 2) and means were compared using the Duncan Waller test (Table 3).
Table 2. Analysis of variance and mean square values (MS) for volume per tree (VOL) in provenance trials of P. ayacahuite in Colombia. Values followed by *** differ at the 0.001 level
Provenances differed significantly in volume per tree. However, the P. patula control had five to ten times more volume than the provenances of P. ayacahuite. For the soil and climatic conditions of the test site the species P. ayacahuite can not be suggested for commercial plantation establishment.
Table 3. Volume per tree (VOL) for the P. ayacahuite provenances and controls planted in Colombia. Mean values followed by the same letter do not differ significantly (p=0.05) using the Duncan Waller comparison
EX SITU GENE CONSERVATION
Farmers and wood cutters use P. ayacahuite for low grade construction timber, furniture and wood carvings. Wood of the species is similar in quality to the other white pines such as P. chiapensis. Wood density is approximately 350 kg/m3 with little variation due to juvenile or mature wood. Therefore boards shrink and warp very little during drying.
Isolated stands of P. ayacahuite in Mexico and Central America make efforts at in situ conservation very difficult. Ex situ conservation is further complicated because land above 2500-3000 meters elevation near the equator needs to be found for the species to be planted successfully. However, initial efforts at ex situ conservation in Colombia have been promising.
In each family represented in the trials reported here there have been selected one or two trees that have exhibited the best growth and form. These trees have been grafted and will be established in two clone banks. Seed produced from these clone banks will then be used to establish an open pollinated trial and conservation bank in Colombia. There exists the possibility to send seed of P. ayacahuite to Mexico and Central America should the forest authorities of those countries want to reestablish this species in areas where it was once present. However, the implications of reintroduction of forest species in terms of gene contamination need to be considered before being undertaken.
CAMCORE membership would like to thank the Agency for International Development, Office of the Science Advisor, USA, for partially funding the seed collection in Mexico and Central America.
Donahue, J.K., Dvorak, W.S. and Gutierrez, E.A. 1991. The distribution, ecology and gene conservation of Pinus ayacahuite and P. chiapensis in Mexico and Central America. CACMORE Bulletin on Tropical Forestry No. 8, North Carolina State University, Raleigh, NC, USA, 28 p.
Dvorak, W.S. 1990. Genetic variation in root morphology of Pinus ayacahuite and Pinus chiapensis.
IN:Proceedings, XIX IUFRO World Forestry Congress, August, 1990, Montreal, Canada, Vol. 2:112-116.
Dvorak, W.S. and Donahue, J.K. 1992. The Central America and Mexico Coniferous Resources Cooperative, CAMCORE. Research Review 1980-1992. CAMCORE, North Carolina State University, Raleigh, NC, USA, 93 p.
Endo, M. 1994. CAMCORE: Twelve years of contribution to reforestation in the Andea region of Colombia. Forest Ecology and Management 63:219-233.
Osorio, L.F. (1993). Five year results of Pinus ayacahuite growth in the Colombian Andes. Proceedings, IUFRO Symposium, Resolving tropical forest resource concerns through tree improvement, gene conservation and domestication of new species. (eds. Lambeth, C.C. and Dvorak, W.). Cali and Cartagena, Colombia, October, 1992. CAMCORE, Raleigh, NC, USA. pp 57-62.
Styles, B.T. and Hughes, C.E. 1983. Studies of variation in Central American pines III. Notes on taxonomy and nomenclature of the pines and related gymnosperms in Honduras and the adjacent Latin American republics. Brensia 21:269-291.