Assessment of nutrient returns in a tropical dry forest after clear-cut without burning.

Tropical dry forests (TDFs) are being deforested at unprecedented rates. The slash/burn/ agriculture/fallow-extensive livestock sequence causes significant nutrient losses and soil degradation. Our aim is to assess nutrient inputs and outputs in a TDF area under an alternative management system, for exclusive wood production. The study involved clear-cutting a preserved caatinga TDF site without burning, quantifying nutrients exported in firewood/ timber and nutrients returned to the soil from the litter layer plus the slash debris, left to decompose unburned on the soil surface. Before clear-cut, the litter layer on the forest floor contained 6.1 t ha of dry matter (DM). After clear-cut, the aboveground biomass was 61.9 t DM ha-1 (consisting of 21.5 t DM ha-1 of commercial wood and 40.4 t DM ha-1 of clear-cut debris that did not include the underlying litter layer). The litter layer was composed of fine and coarse litter, with turnovers of 0.86 and 0.31 year-1, respectively, separately measured in uncut control plots during two rainy seasons (Dec-2007/June-2008 and Dec-2008/ June-2009). In a single season, its decomposition returned to the soil 48.4, 1.16 and 12.3 kg ha-1 of N, P and K. The clear-cut debris was mainly composed of branches, 33.4 t ha-1, bromeliads, 5.63 t ha-1 and green leaves, 1.32 t ha-1. In-situ decomposition rates for branches and bromeliads were 0.24 and 1.47 year-1, respectively. After two rainy seasons the clear-cut debris released 206, 6.5 and 106 kg ha-1 of N, P and K respectively. This input plus that of the underlying litter layer exceeded exports in the commercial wood, and replenished a soil nutrient stock (0?30 cm) of approximately the same magnitude

Effects of the rainy season on growth of Mimosa tenuiflora in dry tropical forest, Brazil.

Resumo

Madeireiras.

A situação madeireira no Nordeste; Diferenças na exploração madeireira entre formações vegetacionais do Nordeste; A situação do reflorestamento na região Nordeste; Espécies de elevado potencial madeireiro no Nordeste; Características das espécies madeireiras ocorrentes na caatinga; Indicativo das espécies de valor madeireiro ocorrente na mata atlântica

The influence of clear-cut area size on forest regrowth: a case study in the dry tropical forests of Pernambuco, Brazil.

Managed Caatinga forests in Northeast Brazil are an important source of wood products, however, successful regeneration and regrowth is important to guarantee sustainability in these forests. The main objective of this study was to evaluate the natural regeneration and forest regrowth ability of a Caatinga forest under varying clear-cut treatments, as well as to estimate the recovery time of stand parameters

La longue séquence pliocène de Marchésieux - Résultats analytiques et premiers résultats

National audienceLe sondage intégralement carotté de Marchésieux a permis d'atteindre l'objectif fixé dans le projet AR42 du BRGM : l'analyse paléoclimatique du premier épisode glaciaire de l'hémisphère nord (Prétiglien, -2,4 Ma) et probablement le premier rafraîchissement de -3,1 Ma. Les 159,3 m de sédiments datés du Reuvérien et du Prétiglien ont déjà livré une quantité importante d'informations aussi bien climatiques que paléoenvironnementales. De par sa position géographique privilégiée et de par son environnement côtier, la "Longue sequence" de Marchésieux a précisé les modalités de la séquence de dégradation climatique en milieu continental et marin à nos latitudes moyennes. La méthodologie fortement pluridisciplinaire, le plus souvent il très haute résolution, permet d'affiner notablement les modalités de la réponse de chaque environnement au changement climatique, et apparaît, en ce sens, beaucoup plus riche que les études monodisciplinaires classiques. Ainsi, les réponses zoologiques, phytosociologiques, sedimentologiques et géochimiques au stimulus climatique externe peuvent être comparées et calibrées

Poudingues calcareo-siliceux du permo-trias

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Galets et sables du pliocène étagés sur le plateau de la Pernelle (Manche)

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Sur le trias silicifié et barytinifère de La Pernelle (Manche)

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