The relationships between microbiological attributes and soil and litter quality in pure and mixed stands of native tree species in southeastern Bahia, Brazil.

This study was conducted to link soil and litter microbial biomass and activity with soil and litter quality in the surface layer for different pure and mixed stands of native tree species in southeastern Bahia, Brazil. The purpose of the study was to see how strongly the differences among species and stands affect the microbiological attributes of the soil and to identify how microbial processes can be influenced by soil and litter quality. Soil and litter samples were collected from six pure and mixed stands of six hardwood species (Peltogyne angustifolia, Centrolobium robustum, Arapatiella psilophylla, Sclerolobium chrysophyllum, Cordia trichotoma, Macrolobium latifolium) native to the southeastern region of Bahia, Brazil. In plantations of native tree species in humid tropical regions, the immobilization efficiency of C and N by soil microbial biomass was strongly related to the chemical quality of the litter and to the organic matter quality of the soil. According to the variables analyzed, the mixed stand was similar to the natural forest and dissimilar to the pure stands. Litter microbial biomass represented a greater sink of C and N than soil microbial biomass and is an important contributor of resources to tropical soils having low C and N availability.

Influence of environmental variables on the shrub and tree species distribution in two Semideciduous Forest sites in Viçosa, Minas Gerais, Brazil

The floristic variations of shrub and tree components were studied in two sites of Semideciduous Forest, initial forest and mature forest, located in the Mata do Paraíso Forest Reserve, in Viçosa, State of Minas Gerais, Southeastern Brazil, in order to analyze the floristic similarity and the correlations between environmental variables and the distribution of tree species in these forests. Individual trees with a diameter at breast height (DBH) ≥ 4.8 cm were sampled in twenty 10 x 30 m plots (10 plots in each site). The plots were distributed systematically at 10 m intervals. The environmental variables analyzed were: the canopy openness and soil chemical and texture characteristics. The two forest sites showed clear differences in the levels of canopy openness and soil fertility, factors that reflect the floristic and successional differences of the shrub and tree component, revealed by the low similarity between these forests by cluster analysis. The canonical correspondence analysis (CCA) of environmental variables and species abundance indicated that the species in these forests studied are distributed under strong influence of canopy openness, moisture and soil fertility. Rev. Biol. Trop. 56 (3): 15571569. Epub 2008 September 30.

Estudiamos las variaciones florísticas de arbustos y árboles en dos sitios de un bosque semicaducifolio, bosque primario y bosque maduro, en la Reserva Forestal Mata do Paraíso, en Viçosa, Estado de Minas Gerais, Sudeste de Brasil, para analizar la similitud florística y las correlaciones entre las variables ambientales y la distribución de tres especies en estos bosques. Árboles individuales con diámetro a la altura del pecho (DAP) ≥ 4.8 cm. fueron muestreados en veinte parcelas de 10 x 30 m (10 parcelas en cada sitio). Las parcelas se distribuyeron sistemáticamente a intervalos de 10 m. Las variables ambientales fueron analizadas así: la abertura del dosel y características químicas y de textura del suelo. Los dos sitios de bosque mostraron diferencias evidentes en la abertura del dosel y fertilidad del suelo, factores que reflejan las diferencias florísticas y sucesionales de arbustos y árboles, revelado por la baja similitud entre estos bosques por medio de análisis de conglomerados. El análisis de correspondencia canónica (CCA) de variables ambientales y abundancia de especies indican que las especies en los bosques estudiados están distribuidas bajo una fuerte influencia de la abertura del dosel, humedad y fertilidad del suelo.

Influence of environmental variables on the shrub and tree species distribution in two Semideciduous Forest sites in Viçosa, Minas Gerais, Brazil.

The floristic variations of shrub and tree components were studied in two sites of Semideciduous Forest, initial forest and mature forest, located in the Mata do Paraíso Forest Reserve, in Viçosa, State of Minas Gerais, Southeastern Brazil, in order to analyze the floristic similarity and the correlations between environmental variables and the distribution of tree species in these forests. Individual trees with a diameter at breast height (DBH) > or = 4.8 cm were sampled in twenty 10 x 30 m plots (10 plots in each site). The plots were distributed systematically at 10 m intervals. The environmental variables analyzed were: the canopy openness and soil chemical and texture characteristics. The two forest sites showed clear differences in the levels of canopy openness and soil fertility, factors that reflect the floristic and successional differences of the shrub and tree component, revealed by the low similarity between these forests by cluster analysis. The canonical correspondence analysis (CCA) of environmental variables and species abundance indicated that the species in these forests studied are distributed under strong influence of canopy openness, moisture and soil fertility.