Los paisajes físico-geográficos de los manglares de la laguna de La Mancha, Veracruz, México

Interciencia: Revista de ciencia y tecnología de América, ISSN 0378-1844, Vol. 31, Nº. 3, 2006, pags. 211-219
Source: OAI


Los manglares que rodean la laguna de La Mancha en Veracruz, México, en condiciones de adecuada conservación, se caracterizan por la complejidad físico-geográfica de sus paisajes. Este trabajo profundiza en la estructura y composición de los geocomplejos en ese territorio. El empleo de los principios estructuro-genético e histórico-evolutivo permitió el levantamiento, clasificación y cartografía de los paisajes de manglares a escala detallada (1: 25000). Se lograron diferenciar 28 unidades inferiores, 6 intermedias y 5 de orden superior. Los resultados sugieren que el enfoque físico-geográfico complejo puede ser de gran utilidad para el inventario, caracterización y cartografía de manglares a escala detallada, brindando información sobre el tipo genético del relieve, composición litológica, periodicidad de inundación de las superficies, cobertura vegetal y suelos, lo cual es de inestimable valor para el ordenamiento ecológico y la preservación de estos ecosistemas.


Available from: Jorge López-Portillo
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    ABSTRACT: The habitats of La Mancha Lagoon, located midway along the coast of Veracruz, Mexico, are responding to the change of sediment supply reaching its primary inlet at the Gulf of Mexico. Until several decades ago, an abundant alongshore supply of sediment created a periodic opening and closing of the La Mancha inlet. The hydrologic regime of the lagoon consisted of raised water level and lower salinity during the closures, whereas the open inlet favored lower water level, higher salinity, and sediment accumulation in the flood tidal delta. Currently, diminished alongshore sediment supply has affected the inlet morphology and the discharge regime. Associated with the reduced sediment supply, the inlet is open longer in its periodic cycle, the water level variation is reduced, the salinity contrasts are reduced, and the rate of sedimentation in the flood-tide delta is increased. This combination of alterations to the inlet area is changing the flooding regime and affecting the conditions in a very well-developed mangrove habitat at the lagoon margins as well as conditions within the aqueous portions of the lagoon. Management options produce a conflict between supporting the direction of change or preserving the existing habitats.
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    ABSTRACT: Key Message Morphological plasticity helps plants to cope to environmental conditions. Allometric responses of the mangrove Avicennia germinans to increasing salinity are easily detectable when focusing on the top height trees. Abstract Several studies show that mangrove trees possess high species- and site-related trait allometry, suggesting large morphological plasticity that might be related to environmental conditions, but the causes of such variation are not clearly understood and systematic quantification is still missing. Both aspects are essential for a mechanistic understanding of the development and functioning of forests. We analyzed the role of salinity in the allometric relations of the mangrove Avicennia germinans, using: (1) the top height trees (trees with the largest diameters at breast height, which reflect forest properties at the maximum use of resources); (2) the slenderness coefficient (which indicates competition and environmental conditions); and (3) the crown to DBH ratio. These standard tools for forest scientists dealing with terrestrial forests are suitable to analyze the plastic responses of mangroves to salinity. First, the top height trees help to recognize structural forest properties that are not detectable when studying the whole stand. Second, we found that at salinities above 55 ‰, trees are less slender and develop wider crowns in relation to DBH than when growing at lower salinities. Our results suggest a significant change in allometric traits in relation to salinity, and reflect the plastic responses of tree traits in response to environmental variation. Understanding the plastic responses of plants to their environment can help to better model, predict, and manage forests in changing environments.
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