<?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%">Jardine, K</style></author><author><style face="normal" font="default" size="100%">Harley, P</style></author><author><style face="normal" font="default" size="100%">Karl, T</style></author><author><style face="normal" font="default" size="100%">Guenther, A</style></author><author><style face="normal" font="default" size="100%">Lerdau, M</style></author><author><style face="normal" font="default" size="100%">Mak, J E</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Plant physiological and environmental controls over the exchange of acetaldehyde between forest canopies and the atmosphere</style></title><secondary-title><style face="normal" font="default" size="100%">BIOGEOSCIENCES</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">acetaldehydes</style></keyword><keyword><style  face="normal" font="default" size="100%">emission</style></keyword><keyword><style  face="normal" font="default" size="100%">Populus deltoides</style></keyword><keyword><style  face="normal" font="default" size="100%">Quercus ilex</style></keyword><keyword><style  face="normal" font="default" size="100%">stomatal resistance</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2008</style></year></dates><publisher><style face="normal" font="default" size="100%">COPERNICUS GESELLSCHAFT MBH</style></publisher><pub-location><style face="normal" font="default" size="100%">BAHNHOFSALLEE 1E, GOTTINGEN, 37081, GERMANY</style></pub-location><volume><style face="normal" font="default" size="100%">5</style></volume><pages><style face="normal" font="default" size="100%">1559-1572</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">We quantified fine scale sources and sinks of gas phase acetaldehyde in two forested ecosystems in the US. During the daytime, the upper canopy behaved as a net source while at lower heights, reduced emission rates or net uptake were observed. At night, uptake generally predominated throughout the canopies. Net ecosystem emission rates were inversely related to foliar density due to the extinction of light in the canopy and a respective decrease of the acetaldehyde compensation point. This is supported by branch level studies revealing much higher compensation points in the light than in the dark for poplar (Populus deltoides) and holly oak (Quercus ilex) implying a higher light/temperature sensitivity for acetaldehyde production relative to consumption. The view of stomata as the major pathway for acetaldehyde exchange is supported by strong linear correlations between branch transpiration rates and acetaldehyde exchange velocities for both species. In addition, natural abundance carbon isotope analysis of gas-phase acetaldehyde during poplar branch fumigation experiments revealed a significant kinetic isotope effect of 5.1 +/- 0.3 parts per thousand associated with the uptake of acetaldehyde. Similar experiments with dry dead poplar leaves showed no fractionation or uptake of acetaldehyde, confirming that this is only a property of living leaves. We suggest that acetaldehyde belongs to a potentially large list of plant metabolites where stomatal resistance can exert long term control over both emission and uptake rates due to the presence of both source(s) and sink(s) within the leaf which strongly buffer large changes in concentrations in the substomatal airspace due to changes in stomatal resistance. We conclude that the exchange of acetaldehyde between plant canopies and the atmosphere is fundamentally controlled by ambient acetaldehyde concentrations, stomatal resistance, and the compensation point which is a function of light/temperature.</style></abstract><notes><style face="normal" font="default" size="100%">APS</style></notes><research-notes><style face="normal" font="default" size="100%">APS</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%">Lhomme, J. P.</style></author><author><style face="normal" font="default" size="100%">Rocheteau, A.</style></author><author><style face="normal" font="default" size="100%">OURCIVAL, J. M.</style></author><author><style face="normal" font="default" size="100%">Rambal, S.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Non-steady-state modelling of water transfer in a Mediterranean evergreen canopy</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%">Capacitance</style></keyword><keyword><style  face="normal" font="default" size="100%">Holm oak</style></keyword><keyword><style  face="normal" font="default" size="100%">Hydraulic resistance</style></keyword><keyword><style  face="normal" font="default" size="100%">Non-steady-state model</style></keyword><keyword><style  face="normal" font="default" size="100%">stomatal resistance</style></keyword><keyword><style  face="normal" font="default" size="100%">Transpiration</style></keyword><keyword><style  face="normal" font="default" size="100%">Water storage</style></keyword><keyword><style  face="normal" font="default" size="100%">Water uptake</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2001</style></year><pub-dates><date><style  face="normal" font="default" size="100%">2001///</style></date></pub-dates></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://linkinghub.elsevier.com/retrieve/pii/S0168192301002180</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">108</style></volume><pages><style face="normal" font="default" size="100%">67 - 83</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">A model simulating the diurnal pattern of water transfer within a Holm oak (Quercus ilex) canopy in Mediterranean conditions has been designed. It combines a non-steady-state hydraulic model with a transpiration model. The hydraulic model includes a reservoir represented by a capacitance, a soil–plant hydraulic resistance and a storage hydraulic resistance connected to the capacitance. It simulates the diurnal variation of water uptake and storage ﬂow from the diurnal course of transpiration used as input. The transpiration model is based upon the Penman–Monteith equation and a Jarvis-type representation of the stomatal resistance (i.e., a minimum stomatal resistance multiplied by the product of independent stress functions). Simultaneous measurements of canopy evaporation by an eddy covariance system and water uptake from the soil by sap ﬂow measurements have allowed one to calibrate and validate the model. The capacitance has been found to be equal to 0.17 mm MPa−1 (with a storage hydraulic resistance of about 2 MPa h mm−1 ), generating a time lag of about 1 h between the transpiration rate and the water uptake from the soil. The hydraulic model correctly represents the experimental data. The transpiration model provides reasonable estimates, but with a signiﬁcant scatter. The combined model simulates the diurnal variation of water uptake, storage ﬂow and transpiration rate directly from environmental variables, but in this latter case, the storage ﬂow is estimated with a rather poor accuracy</style></abstract><issue><style face="normal" font="default" size="100%">1</style></issue></record></records></xml>