623 research outputs found
Biomass allometry and carbon factors for a Mediterranean pine (Pinus pinea L.) in Portugal
Forests play an important role in the global carbon balance because they offset a large portion of the carbon dioxide
emitted through human activities. Accurate estimates are necessary for national reporting of greenhouse gas inventories,
carbon credit trading and forest carbon management but in Portugal reliable and accessible forest carbon
measurement methodologies are still lacking for some species. The objective of this study was to provide forest managers
with a comprehensive database of carbon factors and equations that allows estimating stand-level carbon
stocks in Pinus pinea L. (P. pinea), regardless of the tree inventory information available. We produced aboveground
biomass and stem volume equations, biomass expansion factors (BEF) by component as well as wood basic density
(WBD) and component carbon fraction in biomass. A root-to-shoot ratio is also presented using data from trees in
which the root system was completely excavated. We harvested 53 trees in centre and south Portugal covering different
sizes (6.5 to 56.3 cm), ages (10 to 45 years) and stand densities (20 to 580 trees ha–1). The results indicate that
aboveground allometry in P. pinea is not comparable with other pines and varies considerably with stand characteristics,
highlighting the need to develop stand-dependent factors and equations for local or regional carbon calculations.
BEFaboveground decreases from open (1.33 ± 0.03 Mg m–3) to closed stands (1.07 ± 0.01 Mg m–3) due to a change
in biomass allocation pattern from stem to branches. Average WBD was 0.50 ± 0.01 Mg m–3 but varies with tree dimensions
and the root-to-shoot ratio found was 0.30 ± 0.03. The carbon fraction was statistically different from the
commonly used 0.5 factor for some biomass components. The equations and factors produced allow evaluating carbon
stocks in P. pinea stands in Portugal, contributing to a more accurate estimation of carbon sequestered by this
forest type
Water stress indicators during one stress cycle in an intensive olive orchard
The identification of a reliable and practical water stress indicator and the
corresponding threshold value, for irrigation scheduling, is a classical concern in water
management in agriculture. This is not well solved for woody crops, especially those
not traditionally irrigated, usually with large roots systems. Aiming to contribute to
these studies, we measured water fluxes and some water stress indicators in an olive
grove in south Portugal, during successive stress cycles. We report the first preliminary
results during a stress cycle in August-September 2011, using sap flow, leaf water
potential at predawn, stem diameter variations and soil water content, from which
some indicators were derived. From the preliminary information obtained we could
not identify a threshold value but very good relationships were found, between the
selected automated and not automated variables, useful for farmers and engineering
applications. These first encouraging results need confirmation and further analysi
Financial indicators to evaluate the economic performance of feedlot steers with different slaughter weights
A utilização do ELISA empregando antígenos homólogos e heterólogos para a detecção de IgG e subclasses (IgG1 e IgG2) no diagnóstico de Leishmaniose visceral canina
Indirect immunofluorescence is the method recommended for the diagnosis of visceral leishmanisis in dogs, however, the accuracy of this technique is low and its use on a large scale is limited. Since ELISA does not present these limitations, this technique might be an option for the detection of IgG or specific IgG1 and IgG2 subclasses. Canine ehrlichiosis is an important differential diagnosis of American Visceral Leishmaniasis (AVL). The present study compared ELISA using Leishmania chagasi and Leishmania braziliensis antigen for the detection of anti-Leishmania IgG and subclasses in serum samples from 37 dogs naturally infected with L. chagasi (AVL) and in samples from four dogs co-infected with L. braziliensis and L. chagasi (CI). The occurrence of cross-reactivity was investigated in control serum samples of 17 healthy dogs (HC) and 35 infected with Ehrlichia canis (EC). The mean optical density obtained for the detection of IgG was significantly higher when L. chagasi antigen was used, and was also higher in subgroup VLs (symptomatic) compared to subgroup Vla (asymptomatic). The correlation between IgG and IgG1 was low. The present results suggest that IgG ELISA using homologous antigen yields the best results, permitting the diagnosis of asymptomatic L. chagasi infection and the discrimination between cases of AVL and ehrlichiosis in dogs.A imunofluorescência indireta é o método recomendado para o diagnóstico de leishmaniose visceral em cães, entretanto, a acurácia dessa técnica é baixa e seu uso em grande escala é limitado. Uma vez que o ELISA não apresenta essas limitações, essa técnica poderia ser uma opção para a detecção de IgG ou subclasses IgG1 e IgG2 específicas. A ehrlichiose canina é um importante diagnóstico diferencial de Leishmaniose Visceral Americana (LVA). O presente estudo comparou o ELISA usando antígenos de Leishmania chagasi e Leishmania braziliensis para a detecção de IgG e subclasses anti-Leishmania em amostras de soro de 37 cães naturalmente infectados com L. chagasi (LVA) e em amostras de quatro cães co-infectados (CI). A ocorrência de reatividade cruzada foi investigada em amostras de soro controle de 17 animais saudáveis (HC) e 35 de infectados por Ehrlichia canis (EC). A média de densidade óptica obtida para a detecção de IgG foi significantemente maior quando o antígeno de L. chagasi foi usado e também mais elevada no subgrupo LVs (sintomático) quando comparado ao subgrupo LVa (assintomático). A correlação entre IgG e IgG1 foi baixa. O presente resultado sugere que ELISA IgG empregando antígeno homólogo, produz os melhores resultados, permitindo o diagnóstico de infecção assintomática por L. chagasi e a discriminação entre casos de LVA e ehrlichiose em cães
Ammonium and nitrate in soil and upland rice yield as affected by cover crops and their desiccation time
Decomposição da palhada de forrageiras em função da adubação nitrogenada após o consórcio com milho e produtividade da soja em sucessão
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