ABSTRACT
ABSTRACT Currently, there is a lack of studies on the correct utilization of continuous distributions for dry tropical forests. Therefore, this work aims to investigate the diameter structure of a brazilian tropical dry forest and to select suitable continuous distributions by means of statistic tools for the stand and the main species. Two subsets were randomly selected from 40 plots. Diameter at base height was obtained. The following functions were tested: log-normal; gamma; Weibull 2P and Burr. The best fits were selected by Akaike's information validation criterion. Overall, the diameter distribution of the dry tropical forest was better described by negative exponential curves and positive skewness. The forest studied showed diameter distributions with decreasing probability for larger trees. This behavior was observed for both the main species and the stand. The generalization of the function fitted for the main species show that the development of individual models is needed. The Burr function showed good flexibility to describe the diameter structure of the stand and the behavior of Mimosa ophthalmocentra and Bauhinia cheilantha species. For Poincianella bracteosa, Aspidosperma pyrifolium and Myracrodum urundeuva better fitting was obtained with the log-normal function.
Subject(s)
Trees/growth & development , Tropical Climate , Forests , Plant Dispersal/physiology , Reference Values , Trees/classification , Brazil , Statistics, Nonparametric , Anacardiaceae/growth & development , Aspidosperma/growth & development , Caesalpinia/growth & development , Bauhinia/growth & development , Mimosa/growth & development , Biodiversity , Geographic MappingABSTRACT
Conservation and restoration projects involving abandoned cattle pastures pose several challenges. Restoration ecologists recognize that natural restoration is possible, but few species can successfully colonize degraded pastures. The aim of the present study was to evaluate whether land colonized by the tree Myracrodruon urundeuva increase the amount of habitat available for bird communities in Southeastern Brazil. We used fixed point counts within a 50m radius to compare the richness and composition of the bird community inhabiting naturally regenerated M. urundeuva with that an adjacent native forest remnant and a forest restored with planted Acacia spp. We recorded a total of 68 bird species. The M. urundeuva forest was able to provide valuable habitat for bird species, including more forest species, in comparison with the Acacia planting. These results indicate that M. urundeuva is a useful species for the ecological restoration of degraded pasture land.
La conservación y restauración de pastizales abandonados representan diversos retos. Los ecologistas reconocen que la restauración natural es posible, pero algunas especies pueden colonizar con éxito los pastizales degradados. El objetivo de este estudio fue evaluar si una zona de pastos colonizada por M. urundeuva puede aumentar la cantidad de hábitat disponible para las comunidades de aves en el sureste de Brasil. La metodología utilizada fue la de conteo de puntos en un radio de 50m para comparar la riqueza y composición de comunidades de aves en un pastizal regenerado por M. urundeuva con un remanente de bosque nativo y bosque restaurado mediante la plantación de Acacia spp. Se registró un total de 68 especies de aves. El área colonizada por M. urundeuva representa un hábitat importante para las aves, incluyendo especies forestales, en comparación con la plantación de Acacia spp. Estos resultados indican que M. urundeuva es una especie útil para la restauración ecológica de los pastizales degradados.
Subject(s)
Animals , Cattle , Birds/classification , Conservation of Natural Resources , Trees , Anacardiaceae/classification , Anacardiaceae/growth & development , Brazil , Seedlings/growth & development , Seeds/growth & development , Trees/growth & developmentABSTRACT
Pollen dispersion and reproductive success of four tree species of a xerophytic forest from Argentina. The "talares" in eastern Buenos Aires province, Argentina, are coastal xerophitic forests structured by few arboreal species surrounded by a lower and moister soil matrix. We studied the reproductive parameters of the most representative arboreal species (Celtis tala, Scutia buxifolia, Jodina rhombifolia,and Schinus longifolia). Pollen dispersion was studied through floral visitor traps (biotic dispersion) and using gravimetric pollen collectors (abiotic dispersion). The reproductive success (fruit formation rate) of the focal species was studied by enclosing flowers with different mesh bags. The reproductive system varied among the different species. C. tala was anemophilous and selfcompatible. S. buxifolia was entomophilous and floral visitors dependant. J. rhombifolia was entomophylous, although spontaneous autogamy could favor reproduction in the absence of pollinators. Lastly, S. longifolia could be an ambophilous species (pollinated by insects and by the wind). This dual system may be the result of system flexibility mechanism or an evolutionary transition. Rev. Biol. Trop. 57 (1-2): 283-292. Epub 2009 June 30.
Los "talares" del E de la provincia de Buenos Aires son bosques xerófitos costeros estructurados por pocas especies arbóreas rodeados de una matriz de suelos más bajos y húmedos. Estudiamos los parámetros reproductivos de las especies arbóreas más representativas (Celtis tala, Scutia buxifolia, Jodina rhombifolia y Schinus longifolia). La dispersión polínica fue estudiada a través de trampas para visitantes florales (dispersión biótica) y utilizando recolectores gravimétricos de polen (dispersión abiótica). El éxito reproductivo (tasa de formación de frutos) de las especies focales fue estudiado a través de embolsado de flores con bolsas de distintos tipos de malla. El sistema reproductivo varió entre las especies. C. tala resultó anemófila y autocompatible, S. buxifolia fue entomófila y dependiente de los visitantes florales. J. rhombifolia fue una especie entomófila, aunque la autogamia espontánea podría favorecer al aseguramiento reproductivo en caso de falta de polinizadores. Finalmente, S. longifolia podría ser una especie ambófila (polinizada por insectos y por el viento). Este sistema dual podría ser el resultado de un mecanismo de flexibilidad del sistema de polinización o una transición evolutiva.