Everardo Valadares de Sá Barretto Sampaio

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Despite the recognized importance of the process, estimates of the amount of nitrogen fixed by biological symbiosis in tropical dry forests are almost nonexistent. We estimated the nitrogen fixed annually by the leaves of trees and shrubs at sites regenerating for 16 and 38 years and in an old-growth dry forest using 15N abundance methodology. The total(More)
Our review focuses on the projections of climate change in the Brazilian semiarid region, the Caatinga, based on recent publications about global climate change and biology. We found several vulnerable points in the initial estimates, the main one being that the data were collected and analyzed without a multidisciplinary knowledge. This review discusses(More)
The phenology of tree species in environments that are subject to strong climatic seasonality is mainly determined by water availability, which may vary as a function of wood density. The relationship among phenology, water potential, wood density and the capacity of water storage in the stem were determined for woody species of caatinga vegetation (dry(More)
Root and shoot biomasses and their ratio (R:S) were determined for three stages of forest regeneration (18, 40 and > 60 years.), and for open and dense vegetation, in four soil classes in the semi-arid region of Northeast Brazil. Shoot biomasses were estimated by allometry and roots were collected in 0.7 × 0.7 × 1 m trenches. Root and shoot biomasses and(More)
The interpretation of ecosystem nitrogen isotopic patterns is subject to controversies since there are few surveys of signals along climate gradients within the same region. We determined the effects of a rainfall gradient, under high temperatures, on the soil and plant δ15N signals in Northeast Brazil. Nitrogen, carbon and δ15N signals were determined from(More)
Changes in physiognomy, species composition and structure, and dispersal mechanisms of canopy and subcanopy plant assemblages were investigated along a chronosequence of three ages: 12, 20, and 50+ years old (=old-growth), three replications in each, in an Atlantic Forest landscape in Northeastern Brazil. Our objective was to investigate whether there is(More)
Tropical dry forests have high diversity and plant abundance of potentially biologically nitrogen fixing (BNF) legume species, attributed to the ecological advantage of fixation. However, there are few estimates of N quantities annually fixed, hindering the understanding of factors that control BNF, like low phosphorus availability. The quantities of N(More)
Knowledge about litterfall and its nutrient fluxes is important for understanding ecosystem dynamics, especially in regards to vegetation at different succession stages. Regenerating vegetation represents a large proportion of tropical forests, such as the caatinga dry forest in NE Brazil, which is heavily used for fuel wood and slash-and-burn agriculture.(More)
Proper management of N applied in fertilizers is important to optimize crop production and to avoid negative environmental impacts. The best way to study N dynamics in the soil plant system is to use fertilizers labeled with 15N. Recoveries of nitrogen following fertilization with 15N-labeled goat (Capra hircus L.) manure and gliricidia (Gliricidia sepium(More)
Leaves are major components of mangrove productivity, but data on leaf dynamics are scarce. We marked the shoot tips of three species in four sites of a riverine mangrove and monitored leaf formation, senescence and abscission and flower formation. The leaf area and biomass in the mangrove were estimated using phytosociological data. Leaf size and formation(More)