Encontrados 9 documentos, a visualizar página 1 de 1
Drought-induced photosynthetic inhibition and autumn recovery in two Mediterran...
Vaz, M.; Pereira, J.S.; Gazarini, L.C.; David, T.S.; David, J.S.; Rodrigues, A; Maroco, J; Chaves, M.M.Responses of leaf water relations and photosynthesis to summer drought and autumn rewetting were studied in two evergreen Mediterranean oak species, Quercus ilex spp. rotundifolia and Quercus suber. The predawn leaf water potential (ΨlPD), stomatal conductance (gs) and photosynthetic rate (A) at ambient conditions were measured seasonally over a 3-year period. We also measured the photosynthetic response to lig...
A tree-based approach for modelling interception loss from evergreen oak medite...
Pereira, F.L.; Gasch, J.H.C.; David, J.S.; David, T.S.; Monteiro, P.R.; Valente, F.Evaporation of rainfall intercepted by tree canopies is usually an important part of the overall water balance of forested catchments and there have been many studies dedicated to measuring and modelling rainfall interception loss. These studies have mainly been conducted in dense forests; there have been few studies on the very sparse forests which are common in dry and semi-arid areas. Water resources are sca...
Modelling interception loss from evergreen oak Mediterranean savannas: applicat...
Pereira, F.L.; Gash, J.H.C.; David, J.S.; David, T.S.; Monteiro, P.R.; Valente, F.In a previous study, it was shown that an isolated, fully saturated tree-crown behaves like a wet bulb, allowing evaporation of intercepted rainfall to be estimated by a simple diffusion equation for water vapour. This observation was taken as the basis for a new approach in modelling interception loss fromsavanna-type woodland, whereby the ecosystem evaporation is derived by scaling up the evaporation from ind...
Selective feeding behaviour of key free-living protists: avenues for continued ...
Montagnes, David J. S.; Barbosa, Ana B.; Boenigk, Jens; Davidson, Keith; Jurgens, Klaus; Macek, Miroslav; Parry, Jacqueline D.; Roberts, Emily C.Phagotrophic protists are diverse and abundant in aquatic and terrestrial environments, making them fundamental to the transfer of matter/energy within their respective food webs. Recognising their grazing impact is essential to evaluate the role of protists in ecosystems, and this includes appreciating prey selectivity. Efforts have been made by groups and individuals to understand selective grazing behaviour ...
Water-use strategies in two co-occurring Mediterranean evergreen oaks: survivin...
David, T.S.; Henriques, M.O.; Kurz-Besson, C.; Nunes, J.; Valente, F.; Vaz, M,; Pereira, J.S.; Siegwolf, R.; Chaves, M.M.; Gazarini, L.C.; David, J,S.In the Mediterranean evergreen oakwoodlands of southern Portugal, the main tree species are Quercus ilex ssp. rotundifolia Lam. (holm oak) and Quercus suber L. (cork oak). We studied a savannah-type woodland where these species coexist, with the aim of better understanding the mechanisms of tree adaptation to seasonal drought. In both species, seasonal variations in transpiration and predawn leaf water potentia...
Aerodynamic conductances in a sparse mixed oak woodland (Quercus rotundifolia L...
Pereira, F.L.; Valente, F.; Gazarini, L.C.; David, J.S.The study of heat and mass exchange between the vegetation and its local environment plays a central role in the analysis of plant-atmosphere interactions. These studies can be undertaken at different scales, ranging from individual leaves to isolated trees or even the canopy scale. In each of these cases, heat and mass fluxes depend on the use of adequate values of transfer conductances. Within a broader study...
Radiation balance of an isolated holm oak tree (Quercus rotundifolia Lam.) in a...
Pereira, F.L.; Valente, F.; David, J.S.In closed canopy forests the energy absorbed by the trees can be adequately estimated solely from the vertical radiation fluxes. However, in isolated or widely spaced trees this approach is no longer valid and radiation fluxes in all directions must be accounted for. An adequate estimate of the tree available energy is critical to model and calculate both interception losses and transpiration. Within a study wh...
Transpiração em povoamentos adultos de eucalipto e de pinheiro bravo
Pereira, F.L.; David, J.S.; Madeira, M.V.Foi realizado um estudo com o objectivo de quantificar os consumos de água por transpirarão em dois povoamentos adultos de eucalipto (Eucalyptus globulus Labbill) e de pinheiro bravo (Pinus pinaster Aiton), respectivamente. A estimativa destes consumos foi feita recorrendo a dois métodos distintos: o balanço de água no solo e o modelo de Penman-Monteith (aplicado numa versão unilaminar). Os resultados obtidos i...
Leaf area estimation from tree allometrics in Eucalyptus globulus plantations
Fabião, António; Pereira, J.M.C.; Tomé, Margarida; Carreiras, J.M.B.; Tomé, José; Pereira, J.S.; David, J.S.Data from five studies on the relationships between dendrometric measurements and leaf area of Eucalyptus globulus Labill. plantations were pooled and analyzed to develop regression models for the estimation of leaf area of individual trees. The data, collected at two sites in west-central and southwestern Portugal, varied in age from 2 to 19 years and in plant density from 481 to 1560 trees/ha and included bot...
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