Mediterranean evergreen oaks have to survive a long summer drought. Roots may play a relevant role under these conditions. We studied their structure and function in a mature Quercus suber L. tree in central Portugal. The root system was mapped till the lowest water table level (4.5 m depth). Xylem anatomy was analyzed in a vertical profile belowground. Sap flow was continuously monitored for 1.5 yrs in the stem and roots of this intensively studied tree (heat field deformation method) and in the stem of four trees (Granier method), in relation to environmental variables and predawn leaf water potential. The sources of water uptake were assessed by stable isotope analyses in summer. Results showed a dimorphic root system with a network of superficial roots linked to sinker roots, and a taproot diverting into tangles of deep fine roots submerged for long periods, with parenchyma aerenchyma. Transpiration was not restricted in summer due to root access to groundwater. The isotopic d 18 O signature of twig xylem water was similar to that of groundwater in the dry season. Two functional types of superficial roots were identified: shallow connected and deep connected roots. A modeling approach was built considering that each superficial root was linked to a sinker, with part of the root deep connected (between the stem and the sinker) and part shallow connected (between the sinker and topsoil). This conceptual framework simulated tree stem sap flow from root sap flow with a high efficiency (R 2 = 0.85) in four plot trees. On an annual basis, soil water and groundwater contributions were 69.5% and 30.5% of stem flow, respectively. Annual hydraulic lift and hydraulic descent were 0.9% and 37.0% of stem flow, respectively. The trees maximize the exploitation of the environmental resources by using the topsoil water during most of the year, and groundwater together with hydraulic lift (nutrient supply) in the dry summer. This study shows that a dimorphic root system, with roots reaching groundwater, is an efficient strategy of Q. suber trees to cope with seasonal drought. Knowledge of the functional behavior of Q. suber trees under shallow water table conditions may contribute to the definition of better adapted management practices and to anticipate their responses to climate change.

Eucalypt wood is known worldwide as a raw-material for pulping but only a few species are used by the industry. One of the important features for pulping is the wood structure and anatomy, including cell biometry and cell type proportion. This work makes a prospective study of nine eucalypt species aiming at a pulping use by an early assessment of wood anatomical features. Young 50-month-old trees grown in the same environment of Eucalyptus camaldulensis, Eucalyptus globulus, Eucalyptus maculata, Eucalyptus melliodora, Eucalyptus ovata, Eucalyptus propinqua, Eucalyptus sideroxylon, Eucalyptus tereticornis and Eucalyptus viminalis were studied in relation to wood anatomy, cell biometry and proportion, and morphological fibre ratios. The nine species are structurally similar with typical eucalypt wood features, e.g. diffuse porosity with predominantly solitary vessels and simple perforations plates, and most anatomical differences between species related to rays and axial parenchyma. The wood is in general uniform and the radial variation of cellular dimensions is of small magnitude. The species showed a higher diversity regarding proportion of fibres (15-50%) and morphological characteristics e.g. slenderness ratio (39-48) and flexibility coefficient (0.37-0.65). The eucalypt species position themselves differently as regards the combination of morphological parameters, therefore allowing species targeting for specific paper properties. By considering these indicators, and the relative species growth, it seems promising to further study E. maculata, E. ovata and E. sideroxylon as potential new paper making eucalypt species, in parallel to the prized E. globulus and the already used E. camaldulensis.

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Eucalyptus globulus trees, 15 years old, were sampled at different heights from commercial pulpwood plantations in two sites in Portugal. Bark thickness was higher in the site with better growth and always decreased from the tree base to the top. Bark content was site independent and on average 11% of stem dry weight, higher at the base and top, and lower at 35% height level.Tree mean wood basic density averaged 600 kg /m3 and 568 kg /m3 for best and worst site, respectively, and was not correlated with tree growth. Wood density increased from base to top of the tree. Between-tree variation was low with coefficients of variation of site mean below 10%. Bark density (374 kg /m3 and 454 kg /m3 for best and worst site, respectively) did not show significant within tree variation. Average tree wood density could not be predicted with reasonable accuracy using a breast height sampling and better results were obtained using a sampling as a percentage of total height (e.g. 15%).

Ten trees of Eucalyptus globulus Labill. from three different sites within Portugal were felled at 12–15 years, to study fibre length variation in bark and wood. The fibres of E. globulus were morphologically similar in bark and wood, but generally longer in the bark (on average, 0.97 mm in wood and 1.11 mm in bark). The axial variation was small and opposite in wood and bark; fibre lengths decreased in the wood and increased in the bark from the base to the top. Fibre length in wood increased significantly from pith to bark at all height levels. The measurement of fibre length at 1.3 m height level was representative for the tree average for both wood and bark.