Caracterização do meio físico da Bacia Hidrográfica do Alto Taquari utilizando o sistema de informações geográficas SGI/INPE.

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Structure, composition and state of conservation of the woody-plant community of the otres quebrachosp forests in the Subhumid Central Chaco

El bosque de tres quebrachos en el SO de la Provincia de Chaco es un tipo de bosque poco estudiado y muy afectado por la expansión agropecuaria. Se estudió la composición, la estructura y el estado de conservación de la comunidad de plantas leñosas de los fragmentos remanentes. A partir de 60 parcelas distribuidas en 16 fragmentos (entre 5 y >1000 ha) se determinó la riqueza y la composición especíºca de la comunidad y el área basal y la densidad de cada una de las especies. Se detectaron 36 especies leñosas, todas ellas nativas, con un área basal de 24.73 m2/ha y una densidad de 13459 individuos/ha. Entre las especies del estrato superior se encontró una codominancia entre Schinopsis balansae y Aspidosperma quebracho blanco. Para evaluar el estado de conservación se compararon los resultados obtenidos con datos publicados para quebrachales en áreas protegidas de otras subregiones del Chaco argentino. Se encontró una notable similitud tanto en la riqueza como en los parámetros estructurales. El análisis de los tocones sugiere que la extracción selectiva no es de gran intensidad. Estas observaciones reflejarían un estado de conservación del bosque de tres quebrachos que resulta sorprendentemente bueno si se tiene en cuenta su alto grado de fragmentación.The otres quebrachosp forests in the SW Province of Chaco was scantily studied and strongly affected by the advance of the agricultural frontier. We studied the composition, structure and state of conservation of the woody plant community in remnants fragments. We determined the species richness and the community composition, and basal area and density of each woody species sampling 60 plots distributed in 16 forest fragments (between 5 and >1000 ha). We detected 36 species (trees and shrubs), all of them native. Considering all species together, the mean basal area for all sites was of 24.73 m2/ha, and the density of 13459 individuals/ha. We found a codominance between Schinopsis balansae and Aspidosperma quebracho-blanco among the species of the upper strata. The stumpms analysis showed that selective extraction is limited and it does not imply a strong alteration of the forest structure. To assess the conservation status of these forests, results were compared with published data for other quebracho forests of protected areas from other subregions of the Argentine Chaco. We found a remarkable similarity in the richness and structural parameters of the community. Considering the severe fragmentation of otres quebrachosp forests, our results reflect a surprisingly satisfactory state of conservation. It is necessary to design and implement management strategies to ensure the conservation of this environment

Neutralising antibodies for West Nile virus in horses from Brazilian Pantanal

Despite evidence of West Nile virus (WNV) activity in Colombia, Venezuela and Argentina, this virus has not been reported in most South American countries. In February 2009, we commenced an investigation for WNV in mosquitoes, horses and caimans from the Pantanal, Central-West Brazil. The sera of 168 horses and 30 caimans were initially tested using a flaviviruses-specific epitope-blocking enzyme-linked immunosorbent assay (blocking ELISA) for the detection of flavivirus-reactive antibodies. The seropositive samples were further tested using a plaque-reduction neutralisation test (PRNT90) for WNV and its most closely-related flaviviruses that circulate in Brazil to confirm the detection of specific virus-neutralising antibodies. Of the 93 (55.4%) blocking ELISA-seropositive horse serum samples, five (3%) were seropositive for WNV, nine (5.4%) were seropositive for St. Louis encephalitis virus, 18 (10.7%) were seropositive for Ilheus virus, three (1.8%) were seropositive for Cacipacore virus and none were seropositive for Rocio virus using PRNT90, with a criteria of > four-fold antibody titre difference. All caimans were negative for flaviviruses-specific antibodies using the blocking ELISA. No virus genome was detected from caiman blood or mosquito samples. The present study is the first report of confirmed serological evidence of WNV activity in Brazil