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)
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)
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)
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)
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)
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