Méndez-Alonzo, Rodrigo , Hernández-Trejo, Humberto , Lopez-Portillo, Jorge .
Stress is the great equalizer for mangrove trees: size hierarchy and allometry of the mangrove Avicennia germinans in two landforms.
We explored the size inequality and height-diameter allometry of black mangrove (Avicennia germinans) trees growing in mudflats and interdistributary basins of a coastal lagoon in Veracruz, Mexico. Because mudflats consistently have higher pore water salinities (a surrogate for hydraulic stress) than the interdistributary basins, we hypothesized that there would be less size inequality in the more stressed landform. Size inequality indicators including Lorenz curves, Gini coefficients and Lorenz asymmetry coefficients were used to quantify the influence of the landform setting over size distributions. Regression analyses were performed between Gini coefficients and density, and linear as well as asymptotic height-diameter allometric equations were fitted to the census data obtained from 15 plots, each measuring 0.25 ha. Gini coefficients of the less saline landform were greater and positively correlated with density. The asymptotic allometry equation accounted for a greater amount of the total variability of the data in the interdistributary basin sites, and their determination coefficients were positive and highly correlated with the Gini coefficient, suggesting that the goodness of fit of the asymptotic allometric equation tends to increase with the inequality of size distribution. Under higher salinity stress conditions, size hierarchies are less pronounced and there is symmetric competition among trees. Contrariwise, under low salinity stress conditions some trees may grow taller and have larger, overlapping canopies, and understory trees will therefore be subject to asymmetric competition for light.
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1 - Instituto de Ecología, A. C, Departamento de Ecología Funcional, Km 2.5 Antigua Carretera a Coatepec 351, Xalapa, Veracruz, 91070, México
2 - Universidad Juárez Autónoma de Tabasco, División Académica de Ciencias Biológicas, Carretera Villahermosa-Cárdenas Km. 0.5 S/N Entronque a Bosques de Saloya, Villahermosa, Tabasco, 86150, México
Presentation Type: Oral Paper:Papers for BSA Sections
Location: Alpine B/Snowbird Center
Date: Tuesday, July 28th, 2009
Time: 9:00 AM