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By Jeffrey R. Bacon
Although oaks (Fagaceae, Quercus spp.) Are the predominant trees and shrubs in much of the Latin American temperate mountain ranges, they have been misunderstood since the conquest of the New World by Europeans. Only recently have they recognized the value of this important group of plants for their economic potential and ecological role.
The oaks of the Ancient World and the higher latitudes of North America have been appreciated and exploited as high value resources for centuries. Encino and oak are known in Europe, the USA and Canada as trees that provide important timber products to the economies of both continents. Furthermore, due to their abundance and predominance in temperate forests, they have been extensively studied and are recognized as important elements of biodiversity and important functionaries in ecosystems.
Europe, by the time New World explorers returned with news of the abundant resources available in the Americas, had established a major oak wood industry. Several generations of European craftswomen had already perfected the production of quality products such as furniture, tool handles, corks, building boards and others. However, the oaks of Latin America challenged the conquerors of the New World with their dense, hard and resistant wood.
So the new civilization attacked the oak, quickly wiping out much of the better quality trees in the production of beams, railroad ties, construction, firewood, charcoal, and miscellaneous products. The remains of Latin American oaks, mainly trees too deformed or small for commercial use, soon gained a bad name for being difficult to use. The oak in this culture fell in status to a second class wood, suitable mainly for use as firewood, charcoal or cellulose.
Oak trees, whose habitat is mainly shared with pine trees in temperate forests, have a reproductive advantage next to conifers. Almost all species can reproduce by both sexual and asexual means. In addition, they grow slowly in the shade for years until a fire, a fallen tree, or a logging results in a perforation of the forest canopy, opening it and releasing the seedling allowing it to grow to its maximum potential.
After the intensive exploitation of the colonization and industrialization of the New World, the genetic batch that was deteriorated by the lack of adequate management of the oaks, left mainly parent trees of poor economic and genetic quality. This, along with the high reproductive capacity of oaks compared to commercial pines, quickly earned them a reputation as a pest. In the middle of the century, foresters were more concerned with the elimination of their oaks than with their propagation, and they were cinched and felled to make room for pine reproduction.
Now the forest service providers in Latin American countries, especially in Mexico, are faced with a pineapple resource (Pinaceae, Pinus spp.) At its harvest tolerance limits. As a result, they are looking at the oak resource as an alternative to relieve pressure on pine and open new doors to previously untapped markets (1). Consequently, oak, as a natural resource, is once again feeling the pressure of increases in harvest rates in many regions of Latin America. Again, its genetic composition is at risk of changes that will affect the quality and evolution of the species of this genus.
However, modern knowledge about genetic improvement and the importance of the conservation of genetic and biological diversity can, if applied by stakeholders, can be the lifesavers of this resource for the future.
In Latin America, oaks are found mainly in the northern countries. Most of the American species develop in Mexico, where approximately 135 species are found (2). The exact number is not yet known because there is much confusion about the taxonomy of the oaks in this region. The same confusion has contributed to the problem of the intelligent use of these species because the forest industry has struggled to determine the characteristics of different species, and to date they do not take into account the silvicultural differences between the species in their management for the same reason.
Oak trees in general tend to develop mainly in temperate forests. However, some Latin American species develop in tropical and semi-tropical forests and jungles and others on grasslands in the interior of the Republic. Although the first oaks in the Americas are thought to have been species from the arid tropics (3), most species currently develop in temperate zones.
Being a genus with many commercial or commercial potential species, the importance of conserving genetic diversity in the group is understood. Even species with no apparent utility to humans are considered important contributors to the genetic batch of commercial species. Introgressive hybridization, a species of forming reproductive bridges between different species, is an important mechanism of gene migration from one species to another in oaks. It is considered that cyclical hybridization may be a mechanism used by groups of perennial plants to adapt to long-term cyclical climatic changes, and in areas of the Americas where the climate alternates from one extreme to another over geological time, this phenomenon may be important. in the evolution of Quercus.
Forest management supervisors know the importance of artificial selection in managing tree stands. In fact, the poor quality of many stands in the Sierra Madre Occidental of Mexico has been attributed to artificial selection against trees of better quality and economic value (4). The application of genetic improvement techniques is a technique that can be used to increase the quality of oak populations, taking advantage of existing genes in them.
Apart from their own genetic diversity, oaks contribute to biodiversity in the forests, jungles and grasslands where they develop, oaks are important elements of biodiversity. They are habitat and food for many species of wildlife. Some species, such as certain squirrels, turkeys and deer, depend on the acorns of oaks in certain seasons. In general, oak forests have been identified as important elements for the conservation of migratory bird species.
Oak trees are also important for wild flora. They generate a lot of organic matter, sometimes they are one of the few species that develop in places with thin soils and little organic matter. The branches act as a substrate for the development of various epiphytes, such as orchids (Orchidaceae), bromeliaceae (Bromeliaceae), and mistletoe (Viscaceae). Also many species of insects and other invertebrates inhabit the foliage, fruits, branches and roots of oaks. Among fungi, some species depend on oaks, such as mycorrhizae, and others have a different symbiotic relationship with plants of this genus.
So the oak, despite being a tough and resistant plant with high reproductive potential, has been the victim of intensive exploitation at different stages of the colonization of the Americas. Its mistreatment has had a high cost to the same industry that takes advantage of it and today the forest industry is looking for solutions for a recovery and better use of the renewable resource. Despite the current poor state of the resource, in economic terms, oaks are very important due to their ecological roles and have potential with genetic improvement techniques and intelligent use, contributing to a sustainable economy in Latin America.
The revision of the writing by C. Socorro Mora Cabrales (ISIMA-UJED) is appreciated. S. I. Díaz Reyes and A. Martínez from the School of Chemical Sciences of the UJED provided transportation for taking pictures related to this article. Research was funded by FOSIVILLA XX, FOSIVILLA XX and FMCN XX.
(1) Bacon, J. R. 1997. Diagnosis of the Encio and its Industrialization in the State of Durango, Mexico: Part I: Problems from the Biological Point of View. University Research Products Collection, Forest Ecology Series Number 1, Universidad Juárez del Estado de Durango, Cd. Durango, Dgo., Mexico.
(2) Nixon, K. C. 1993. The genus Quercus in Mexico. In T. P. Ramamoorthy, R. Bye, A. Lot, and J. Fa. (eds.). Biological Diversity of Mexico: Origins and Distribution. Oxford University Press, New York, E. U. A.
(3) Axelrod D. L. 1983. Biogeography of oaks in the arcto-tertiary province. Annals of Missouri Botanical Garden 70: 629-657.
(4) Bacon, J. 1999. The genetic quality of oaks (Quercus spp.) In the Sierra Madre Occidental of Mexico and implications for its forest management. Ubamari 15 (45).
* Jeffrey R. Bacon
Forest Ecology Area
Institute of Forestry and Wood Industry
Durango State Juárez University
Calle Constitución 404 Sur, Downtown Area, Cd. Durango, Dgo., Mexico.