<?xml version="1.0" encoding="UTF-8"?><xml><records><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Gouveia, António C</style></author><author><style face="normal" font="default" size="100%">Freitas, Helena</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Intraspecific competition and water use efficiency in Quercus suber: evidence of an optimum tree density?</style></title><secondary-title><style face="normal" font="default" size="100%">Trees</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">carbon isotope discrimination</style></keyword><keyword><style  face="normal" font="default" size="100%">evergreen oak</style></keyword><keyword><style  face="normal" font="default" size="100%">montado</style></keyword><keyword><style  face="normal" font="default" size="100%">Specific leaf area</style></keyword><keyword><style  face="normal" font="default" size="100%">stand density</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2008</style></year></dates><volume><style face="normal" font="default" size="100%">22</style></volume><pages><style face="normal" font="default" size="100%">521-530</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The dehesa and montado agroecosystems seem to be water-stress induced structures and some authors have found evidence of a relationship between stand tree density and mean annual precipitation. In order to assess the ecophysiological responses of Quercus suber to increasing tree density and to evaluate if there was evidence of an ‘‘optimum tree density’’ with respect to mean annual rainfall in our study area, we established a tree-density gradient of 20, 40, and 60 trees ha -1 , coded D20, D40, and D60, respectively. Trees in D40 plots had higher speciﬁc leaf area (SLA) values and the highest water content. Both D20 and D60 trees had leaves with higher dry matter content (LDMC). The trade-off between SLA and LDMC was very strong and placed D40 trees as the least stressed, in terms of leaf anatomy. We also found differences in mean carbon isotope discrimination (D), between different density plots, as big as 1.25%. Again, D40 trees discriminated more against 13 C than the trees from D20 and D60 plots, which suggests a less conservative water use strategy, possibly deriving from greater water availability. The lower water retention in the D20 areas and the increased competition for water resources in D60 plots placed trees, in both areas, in a more stressful situation, regarding water availability. The D40 areas thus seemed to represent a more favourable environment for Q. suber in our montado. Therefore, the areas with 40 trees ha -1 suggest the existence of an optimum tree density with respect to annual rainfall in our site, and may represent a compromise between an increased retention of water resources and intraspeciﬁc competition.</style></abstract></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Gouveia, António C.</style></author><author><style face="normal" font="default" size="100%">Freitas, Helena</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Modulation of leaf attributes and water use efficiency in Quercus suber along a rainfall gradient</style></title><secondary-title><style face="normal" font="default" size="100%">Trees</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">carbon isotope discrimination</style></keyword><keyword><style  face="normal" font="default" size="100%">carbon isotope discrimination á</style></keyword><keyword><style  face="normal" font="default" size="100%">evergreen tree</style></keyword><keyword><style  face="normal" font="default" size="100%">evergreen tree á</style></keyword><keyword><style  face="normal" font="default" size="100%">leaf plasticity</style></keyword><keyword><style  face="normal" font="default" size="100%">leaf plasticity á</style></keyword><keyword><style  face="normal" font="default" size="100%">rainfall gradient</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2008</style></year></dates><volume><style face="normal" font="default" size="100%">23</style></volume><pages><style face="normal" font="default" size="100%">267-275</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The aim of our study was to assess the intraspeciﬁc variation of a range of leaf attributes and carbon isotope discrimination (D), in Quercus suber, along an 800 mm rainfall gradient in Portugal. We measured speciﬁc leaf area (SLA), leaf thickness (LT) and density, and used leaf carbon isotope content as an integrated record of water use efﬁciency. The values of SLA of Q. suber were strongly, positively correlated with rainfall, decreasing as rainfall decreased. This reduction was mainly driven by LT, which was tightly correlated with SLA (R = -0.80, P\0.001), and steadily increased with declining rainfall. The signiﬁcant increase in carbon isotope discrimination towards the wetter end of the gradient, with a difference of 4.2% in D between the two extremes, suggests a strong adjustment of leaf gas exchange to water availability. Leaf changes associated with precipitation in Q. suber thus seem to inﬂuence water economy, since reduction of SLA with the increase of LT with aridity improves water use efﬁ- ciency. These data suggest that this evergreen tree species relies on its foliage plasticity and physiology to overcome water shortage.</style></abstract></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Gouveia, António C.</style></author><author><style face="normal" font="default" size="100%">Freitas, Helena</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Modulation of leaf attributes and water use efficiency in Quercus suber along a rainfall gradient</style></title><secondary-title><style face="normal" font="default" size="100%">Trees</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">carbon isotope discrimination</style></keyword><keyword><style  face="normal" font="default" size="100%">carbon isotope discrimination á</style></keyword><keyword><style  face="normal" font="default" size="100%">evergreen tree</style></keyword><keyword><style  face="normal" font="default" size="100%">evergreen tree á</style></keyword><keyword><style  face="normal" font="default" size="100%">leaf plasticity</style></keyword><keyword><style  face="normal" font="default" size="100%">leaf plasticity á</style></keyword><keyword><style  face="normal" font="default" size="100%">rainfall gradient</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2008</style></year><pub-dates><date><style  face="normal" font="default" size="100%">2008///</style></date></pub-dates></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://www.springerlink.com/index/10.1007/s00468-008-0274-zhttp://link.springer.com/10.1007/s00468-008-0274-z</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">23</style></volume><pages><style face="normal" font="default" size="100%">267 - 275</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The aim of our study was to assess the intraspeciﬁc variation of a range of leaf attributes and carbon isotope discrimination (D), in Quercus suber, along an 800 mm rainfall gradient in Portugal. We measured speciﬁc leaf area (SLA), leaf thickness (LT) and density, and used leaf carbon isotope content as an integrated record of water use efﬁciency. The values of SLA of Q. suber were strongly, positively correlated with rainfall, decreasing as rainfall decreased. This reduction was mainly driven by LT, which was tightly correlated with SLA (R = -0.80, P\0.001), and steadily increased with declining rainfall. The signiﬁcant increase in carbon isotope discrimination towards the wetter end of the gradient, with a difference of 4.2% in D between the two extremes, suggests a strong adjustment of leaf gas exchange to water availability. Leaf changes associated with precipitation in Q. suber thus seem to inﬂuence water economy, since reduction of SLA with the increase of LT with aridity improves water use efﬁ- ciency. These data suggest that this evergreen tree species relies on its foliage plasticity and physiology to overcome water shortage.</style></abstract><issue><style face="normal" font="default" size="100%">2</style></issue></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Fleck, Isabel</style></author><author><style face="normal" font="default" size="100%">Grau, Daniel</style></author><author><style face="normal" font="default" size="100%">Sanjosé, M</style></author><author><style face="normal" font="default" size="100%">Vidal, D</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Carbon isotope discrimination in Quercus ilex resprouts after fire and tree-fell</style></title><secondary-title><style face="normal" font="default" size="100%">Oecologia</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">carbon isotope discrimination</style></keyword><keyword><style  face="normal" font="default" size="100%">Fire and tree-fell resprouts</style></keyword><keyword><style  face="normal" font="default" size="100%">Gas exchange</style></keyword><keyword><style  face="normal" font="default" size="100%">RuBPCase activity</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1996</style></year></dates><pages><style face="normal" font="default" size="100%">286-292</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Ecophysiological differences related to photo- synthesis were compared in holm oak Quercus ilex leaves from undisturbed holm-oak vegetation, resprouts after fire and resprouts after tree-fell. No significant dif- ferences in any parameter measured were observed be- tween the two kinds of resprout throughout the first growing season following disturbance. Resprouting leaves showed lower carbon isotope discrimination (A) and intercellular CO 2 concentration (Pi), and higher pho- tosynthesis, leaf conductance and transpiration rates than leaves from undisturbed stands. Nitrogen, soluble protein content and ribulose bisphosphate carboxylase (RuBP- Case) activity were 88%, 96% and 45% higher respec- tively, in both kinds of resprout. The results indicate that photosynthetic capacity, rather than stomatal conduc- tance, is the limiting factor in photosynthesis in re- sprouts. Chlorophyll content and chlorophyll a/b ratio did not differ between resprouts and undisturbed leaves, indicating that the observed differences were not a result of differences in light environment during leaf develop- ment. Leaf mass per area (LMA), was 80% higher in the resprouts, and was negatively related (r= -0,86) to A and positively related (r=0.87) to N content. Enhanced car- bon assimilation after disturbances resulted in higher wa- ter use efficiency, as indicated by lower A values in the resprouts. We conclude that the cause of defoliation was not relevant in the physiology of the resprouts, suggest- ing the importance of underground organs.</style></abstract></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Fleck, Isabel</style></author><author><style face="normal" font="default" size="100%">Grau, Daniel</style></author><author><style face="normal" font="default" size="100%">Sanjose, M.</style></author><author><style face="normal" font="default" size="100%">Vidal, D.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Carbon isotope discrimination in Quercus ilex resprouts after fire and tree-fell</style></title><secondary-title><style face="normal" font="default" size="100%">Oecologia</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">carbon isotope discrimination</style></keyword><keyword><style  face="normal" font="default" size="100%">Fire and tree-fell resprouts</style></keyword><keyword><style  face="normal" font="default" size="100%">Gas exchange</style></keyword><keyword><style  face="normal" font="default" size="100%">RuBPCase activity</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1996</style></year><pub-dates><date><style  face="normal" font="default" size="100%">1996///</style></date></pub-dates></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://www.springerlink.com/index/g76r90270m4w0571.pdf</style></url></web-urls></urls><pages><style face="normal" font="default" size="100%">286 - 292</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Ecophysiological differences related to photo- synthesis were compared in holm oak Quercus ilex leaves from undisturbed holm-oak vegetation, resprouts after fire and resprouts after tree-fell. No significant dif- ferences in any parameter measured were observed be- tween the two kinds of resprout throughout the first growing season following disturbance. Resprouting leaves showed lower carbon isotope discrimination (A) and intercellular CO 2 concentration (Pi), and higher pho- tosynthesis, leaf conductance and transpiration rates than leaves from undisturbed stands. Nitrogen, soluble protein content and ribulose bisphosphate carboxylase (RuBP- Case) activity were 88%, 96% and 45% higher respec- tively, in both kinds of resprout. The results indicate that photosynthetic capacity, rather than stomatal conduc- tance, is the limiting factor in photosynthesis in re- sprouts. Chlorophyll content and chlorophyll a/b ratio did not differ between resprouts and undisturbed leaves, indicating that the observed differences were not a result of differences in light environment during leaf develop- ment. Leaf mass per area (LMA), was 80% higher in the resprouts, and was negatively related (r= -0,86) to A and positively related (r=0.87) to N content. Enhanced car- bon assimilation after disturbances resulted in higher wa- ter use efficiency, as indicated by lower A values in the resprouts. We conclude that the cause of defoliation was not relevant in the physiology of the resprouts, suggest- ing the importance of underground organs.</style></abstract></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Valentini, R</style></author><author><style face="normal" font="default" size="100%">Scarascia Mugnozza, G</style></author><author><style face="normal" font="default" size="100%">De Angelis, P</style></author><author><style face="normal" font="default" size="100%">Matteucci, G</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Coupling water sources and carbon metabolism of natural vegetation at integrated time and space scales</style></title><secondary-title><style face="normal" font="default" size="100%">Agricultural and Forest Meteorology</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">canopy conductance</style></keyword><keyword><style  face="normal" font="default" size="100%">canopy photosynthesis (voyant)</style></keyword><keyword><style  face="normal" font="default" size="100%">carbon isotope discrimination</style></keyword><keyword><style  face="normal" font="default" size="100%">water use</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1995</style></year></dates><volume><style face="normal" font="default" size="100%">73</style></volume><pages><style face="normal" font="default" size="100%">297-306</style></pages><isbn><style face="normal" font="default" size="100%">3976135739</style></isbn><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The linkage between water utilization and photosynthetic processes is investigated using stable isotopes and eddy covariance techniques, allowing integration of physiological pro- cesses both at time and space scales, respectively. Using the ratio of the stable isotopes of hydrogen (hydrogen vs. deuterium) and discrimination of 13C vs. ~2C, the relationship between water sources (rain water vs. ground water) utilization and intercellular carbon dioxide con- centration is analysed for various species of two different ecosystems: an alpine forest and a Mediterranean macchia. As an example of space scale integration of water-carbon coupling, the relationship between canopy carbon dioxide assimilation and bulk stomatal conductance, measured with eddy covariance, is presented for a macchia community and a low-productivity grassland.</style></abstract></record></records></xml>