<?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%">Rodriguez-Calcerrada, Jesus</style></author><author><style face="normal" font="default" size="100%">Limousin, Jean-Marc</style></author><author><style face="normal" font="default" size="100%">Martin-StPaul, Nicolas K</style></author><author><style face="normal" font="default" size="100%">Jaeger, Carsten</style></author><author><style face="normal" font="default" size="100%">Rambal, Serge</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Gas exchange and leaf aging in an evergreen oak: causes and consequences for leaf carbon balance and canopy respiration</style></title><secondary-title><style face="normal" font="default" size="100%">Tree Physiology</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">carbon budget</style></keyword><keyword><style  face="normal" font="default" size="100%">ecosystem respiration</style></keyword><keyword><style  face="normal" font="default" size="100%">leaf life span</style></keyword><keyword><style  face="normal" font="default" size="100%">resource remobilization</style></keyword><keyword><style  face="normal" font="default" size="100%">soluble sugars</style></keyword><keyword><style  face="normal" font="default" size="100%">temperature sensitivity</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2012</style></year></dates><volume><style face="normal" font="default" size="100%">32</style></volume><pages><style face="normal" font="default" size="100%">464-477</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Leaves of Mediterranean evergreens experience large variations in gas exchange rates over their life span due to aging and seasonally changing environmental conditions. Accounting for the changing respiratory physiology of leaves over time will help improve estimations of leaf and whole-plant carbon balances. Here we examined seasonal variations in light-saturated net CO2 assimilation (Amax), dark respiration (Rd) and the proportional change in Rd per 10 °C change in temperature (Q10 of Rd) in previous-year (PY) and current-year (CY) leaves of the broadleaved evergreen tree Quercus ilex L. Amax and Rd were lower in PY than in CY leaves. Differences in nitrogen between cohorts only partly explained such differences, and rates of Amax and Rd expressed per unit of leaf nitrogen were still significantly different between cohorts. The decline in Amax in PY leaves did not result in the depletion of total non-structural carbohydrates, whose concentration was in fact higher in PY than CY leaves. Leaf-level carbon balance modeled from gas exchange data was positive at all ages. Q10 of Rd did not differ significantly between leaf cohorts; however, failure to account for distinct Rd between cohorts misestimated canopy leaf respiration by 13% across dates when scaling up leaf measurements to the canopy. In conclusion, the decline in Amax in old leaves that are close to or exceed their mean life span does not limit the availability of carbohydrates, which are probably needed to sustain new growth, as well as Rd and nutrient resorption during senescence. Accounting for leaf age as a source of variation of Rd improves the estimation of foliar respiratory carbon release at the stand scale.</style></abstract><notes><style face="normal" font="default" size="100%">10.1093/treephys/tps020</style></notes><research-notes><style face="normal" font="default" size="100%">10.1093/treephys/tps020</style></research-notes></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%">Hemming, Deborah</style></author><author><style face="normal" font="default" size="100%">Yakir, Dan</style></author><author><style face="normal" font="default" size="100%">Ambus, Per</style></author><author><style face="normal" font="default" size="100%">Aurela, Mika</style></author><author><style face="normal" font="default" size="100%">Besson, Cathy</style></author><author><style face="normal" font="default" size="100%">Black, Kevin</style></author><author><style face="normal" font="default" size="100%">Buchmann, Nina</style></author><author><style face="normal" font="default" size="100%">Burlett, Regis</style></author><author><style face="normal" font="default" size="100%">CESCATTI, ALESSANDRO</style></author><author><style face="normal" font="default" size="100%">Clement, Robert</style></author><author><style face="normal" font="default" size="100%">Gross, Patrick</style></author><author><style face="normal" font="default" size="100%">Granier, André</style></author><author><style face="normal" font="default" size="100%">Grünwald, Thomas</style></author><author><style face="normal" font="default" size="100%">Havrankova, Katarina</style></author><author><style face="normal" font="default" size="100%">Janous, Dalibor</style></author><author><style face="normal" font="default" size="100%">Janssens, Ivan A</style></author><author><style face="normal" font="default" size="100%">Knohl, Alexander</style></author><author><style face="normal" font="default" size="100%">Östner, Barbara K</style></author><author><style face="normal" font="default" size="100%">Kowalski, Andrew</style></author><author><style face="normal" font="default" size="100%">Laurila, Tuomas</style></author><author><style face="normal" font="default" size="100%">Mata, Catarina</style></author><author><style face="normal" font="default" size="100%">Marcolla, Barbara</style></author><author><style face="normal" font="default" size="100%">Matteucci, Giorgio</style></author><author><style face="normal" font="default" size="100%">Moncrieff, John</style></author><author><style face="normal" font="default" size="100%">Moors, Eddy J</style></author><author><style face="normal" font="default" size="100%">Osborne, Bruce</style></author><author><style face="normal" font="default" size="100%">Pereira, João Santos</style></author><author><style face="normal" font="default" size="100%">Pihlatie, Mari</style></author><author><style face="normal" font="default" size="100%">Pilegaard, Kim</style></author><author><style face="normal" font="default" size="100%">Ponti, Francesca</style></author><author><style face="normal" font="default" size="100%">Rosova, Zuzana</style></author><author><style face="normal" font="default" size="100%">Rossi, Federica</style></author><author><style face="normal" font="default" size="100%">Scartazza, Andrea</style></author><author><style face="normal" font="default" size="100%">Vesala, Timo</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Pan-European δ13C values of air and organic matter from forest ecosystems</style></title><secondary-title><style face="normal" font="default" size="100%">Global Change Biology</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">carboeuroflux</style></keyword><keyword><style  face="normal" font="default" size="100%">CO2 fluxes</style></keyword><keyword><style  face="normal" font="default" size="100%">ecosystem carbon budget</style></keyword><keyword><style  face="normal" font="default" size="100%">ecosystem respiration</style></keyword><keyword><style  face="normal" font="default" size="100%">isotopic discrimination</style></keyword><keyword><style  face="normal" font="default" size="100%">Stable isotopes</style></keyword><keyword><style  face="normal" font="default" size="100%">δ13C</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2005</style></year></dates><publisher><style face="normal" font="default" size="100%">Blackwell Science Ltd</style></publisher><volume><style face="normal" font="default" size="100%">11</style></volume><pages><style face="normal" font="default" size="100%">1065-1093</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">We present carbon stable isotope, δ13C, results from air and organic matter samples collected during 98 individual field campaigns across a network of Carboeuroflux forest sites in 2001 (14 sites) and 2002 (16 sites). Using these data, we tested the hypothesis that δ13C values derived from large-scale atmospheric measurements and models, which are routinely used to partition carbon fluxes between land and ocean, and potentially between respiration and photosynthesis on land, are consistent with directly measured ecosystem-scale δ13C values. In this framework, we also tested the potential of δ13C in canopy air and plant organic matter to record regional-scale ecophysiological patterns. Our network estimates for the mean δ13C of ecosystem respired CO2 and the related ‘discrimination’ of ecosystem respiration, δer and Δer, respectively, were −25.6±1.9‰ and 17.8 ±2.0‰ in 2001 and −26.6±1.5‰ and 19.0±1.6‰ in 2002. The results were in close agreement with δ13C values derived from regional-scale atmospheric measurement programs for 2001, but less so in 2002, which had an unusual precipitation pattern. This suggests that regional-scale atmospheric sampling programs generally capture ecosystem δ13C signals over Europe, but may be limited in capturing some of the interannual variations. In 2001, but less so in 2002, there were discernable longitudinal and seasonal trends in δer. From west to east, across the network, there was a general enrichment in 13C (∼3‰ and ∼1‰ for the 2 years, respectively) consistent with increasing Gorczynski continentality index for warmer and drier conditions. In 2001 only, seasonal 13C enrichment between July and September, followed by depletion in November (from about −26.0‰ to −24.5‰ to −30.0‰), was also observed. In 2001, July and August δer values across the network were significantly related to average daytime vapor pressure deficit (VPD), relative humidity (RH), and, to a lesser degree, air temperature (Ta), but not significantly with monthly average precipitation (Pm). In contrast, in 2002 (a much wetter peak season), δer was significantly related with Ta, but not significantly with VPD and RH. The important role of plant physiological processes on δer in 2001 was emphasized by a relatively rapid turnover (between 1 and 6 days) of assimilated carbon inferred from time-lag analyses of δer vs. meteorological parameters. However, this was not evident in 2002. These analyses also noted corresponding diurnal cycles of δer and meteorological parameters in 2001, indicating a rapid transmission of daytime meteorology, via physiological responses, to the δer signal during this season. Organic matter δ13C results showed progressive 13C enrichment from leaves, through stems and roots to soil organic matter, which may be explained by 13C fractionation during respiration. This enrichment was species dependent and was prominent in angiosperms but not in gymnosperms. δ13C values of organic matter of any of the plant components did not well represent short-term δer values during the seasonal cycle, and could not be used to partition ecosystem respiration into autotrophic and heterotrophic components.</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%">Joffre, Richard</style></author><author><style face="normal" font="default" size="100%">OURCIVAL, JEAN-MARC</style></author><author><style face="normal" font="default" size="100%">Rambal, Serge</style></author><author><style face="normal" font="default" size="100%">ROCHETEAU, ALAIN</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">The key-role of topsoil moisture on CO$_2$ efflux from a Mediterranean Quercus ilex forest</style></title><secondary-title><style face="normal" font="default" size="100%">Ann. For. Sci.</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">CO2 efflux</style></keyword><keyword><style  face="normal" font="default" size="100%">ecosystem respiration</style></keyword><keyword><style  face="normal" font="default" size="100%">Mediterranean ecosystem</style></keyword><keyword><style  face="normal" font="default" size="100%">Quercus ilex</style></keyword><keyword><style  face="normal" font="default" size="100%">Soil temperature</style></keyword><keyword><style  face="normal" font="default" size="100%">Soil water content</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2003</style></year></dates><volume><style face="normal" font="default" size="100%">60</style></volume><pages><style face="normal" font="default" size="100%">519-526</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">CO2 respiratory losses partly determine net carbon ecosystem exchanges. The main objective of this paper was to understand regulation imposed by soil water content and temperature on soil and ecosystem CO2 efflux in a holm oak (Quercus ilex L.) Mediterranean forest. Soil CO2 efflux was monitored monthly during 1999 and 2001. Moreover, experimental water treatments were conducted in 1999 over 9 small plots (0.3 m2) during nine months. Results showed strong decreases of soil CO2 efflux for a relative soil water content below 0.7. Ecosystem respiration measured by eddy covariance over a 4-year period showed strong sensitivity to soil water content and temperature. Severe limitations of soil and ecosystem efflux imposed by low values of soil water content occurred on about 90 days per year. The best adjustments of soil and ecosystem CO2 efflux were obtained using regression models where the exponential effect of temperature is linearly related to soil water content ( r2 = 0.68 and 0.79 for soil and ecosystem respectively). Our results highlighted strong differences in respiration sensitivity to topsoil moisture between soil and ecosystem. When the relative water content (RWC) is low (0.4), an increase of 1 °C provokes an increase of soil respiration of 5.7% and an increase of ecosystem respiration of 8.6%. For nonlimiting soil water conditions, at RWC = 1, the increases of respiration caused by a 1 °C temperature increase are of 8.5% and 16.5% for soil and ecosystem respectively. These results emphasized the probable determinant influences of changes in soil water regime for respiratory fluxes and net carbon exchanges of Mediterranean forest ecosystems.</style></abstract></record></records></xml>