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• Carbon harvested in cork represent less than 1.5% of annual net primary production. • Cork is a very low nutrient demanding tissue compared to leaf canopy. • Trunk water losses following cork stripping are negligible. • Cork stripping induced a 46% decrease on sap flow in a dry year. • Cork harvesting practice should be avoided in severe dry years. Cork is a high value periodical forest product which ensures the economic, social and ecological sustainability of cork oak woodlands. Abiotic and biotic stresses lead to tree decline which is endangering the productivity and sustainability of these ecosystems. It is therefore critical to find and implement management practices that minimize the impact of these stresses. The current study was conducted in a certified evergreen cork oak woodland of central Portugal under Mediterranean climate. The main aims of the study were to assess the effects of cork stripping in tree water and carbon fluxes. Results are based on the monitoring of cork stripped and unstripped (control) trees. The experiment was repeated with different sets of trees during two contrasting summers (2014 and 2015). 2014 was a wet year (924 mm) with a typical summer drought pattern and 2015 a dry year (440 mm) with a 31% reduction in annual average precipitation. In 2015 the experimental site was entirely cork harvested and effects on ecosystem CO 2 fluxes were evaluated. Results showed that the amount of carbon in harvested cork represents less than 1.5% of net primary production on a yearly basis. In addition, cork tissue is very low demanding in nutrients: primary macronutrients content in cork represents approximately 2% of the yearly nutrient needs of leaf canopy. Regardless of the climatic year, trunk water losses following cork stripping amounted to only 2% of canopy transpiration not affecting significantly summer tree water balance. However, cork stripping induced a 46% decrease on sap flow in the dry year suggesting that cork stripping triggered an increase in stomatal closure through an interaction between stripping traumatic effects and soil water scarcity. Although the effects of summer drought on carbon sequestration are more prominent than cork stripping effects, this superimposed stress led to a significant reduction of summer net carbon ecosystem exchange (ca. 32%). Our results suggest that cork stripping detrimental effects can be especially critical in more vulnerable trees growing near their vitality breakdown threshold. Therefore, and concerning cork oak woodland management, the cork stripping practice should be avoided in severe dry years and in the more stress-prone trees. [ABSTRACT FROM AUTHOR]

Abstract: 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 from savanna-type woodland, whereby the ecosystem evaporation is derived by scaling up the evaporation from individual trees, rather than by considering a homogeneous forest cover. Interception loss from isolated trees was estimated by combining the aforementioned equation for water vapour flux with Gash''s analytical model. A new methodology, which avoids the subjectivity inherent in the Leyton method, was used for estimating the crown storage capacity. Modelling performance was evaluated against data from two Mediterranean savanna-type oak woodlands (montados) in southern Portugal. Interception loss estimates were in good agreement with observations in both sites. The proposed modelling approach is physically based, requires only a limited amount of data and should be suitable for the modelling of interception loss in isolated trees and savanna-type ecosystems. [Copyright &y& Elsevier]

The experiment took place at a sparse evergreen oak woodland in southern Portugal. Seasonal courses of sap flow, measured in eight points of the stem of a Quercus rotundifolia tree, were monitored during a 2-year period. Plant water relations (predawn and midday leaf water potential, canopy conductance and whole-plant hydraulic conductance) as well as meteorological variables were also measured during the experimental period (May 1996–August 1998). All evidence showed that the plants remained well watered throughout the observation period. The highest transpiration rates occurred during the summer, when only vestigial amounts of rain fell on the shallow soil with a low water storage capacity. This could only be explained by the direct access of the root system to a 13 m deep water table. Although there was no increase in water stress during the summer drought, the transpiration rates showed an upper limit well below the atmospheric evaporative demand. This was consistent with the occurrence of a maximum limit for the root water uptake capacity determined by the summer value of whole-plant hydraulic conductance and by stomatal control, which prevented leaf water potential from falling below a cavitation threshold. [Copyright &y& Elsevier]