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Effects of competition control and annual nitrogen fertilization on gas exchange of different-aged Pinus taeda

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Abstract:

To determine the importance of competition control and annual fertilization on leaf gas exchange, light-saturated net photosynthesis (Asat), stomatal conductance (gs), and internal CO2 concentration (Ci) were measured multiple times in different-aged loblolly pine (Pinus taeda L.) stands growing at a Piedmont (BF Grant) and Coastal Plain (Waycross) location in Georgia, U.S.A. At both locations, competition control decreased Asat and gs (Asat from 4.53 to 4.12 µmol·m–2·s–1, gs from 0.058 to 0.050 mol·m–2·s–1 at BF Grant; Asat from 4.22 to 4.01 µmol·m–2·s–1, gs from 0.054 to 0.049 mol·m–2·s–1 at Waycross). Overall, fertilization did not have a positive impact on Asat, even though fertilization significantly increased foliar nitrogen concentration. At BF Grant, fertilization significantly decreased gs from 0.057 to 0.051 mol·m–2·s–1 and Ci from 217 to 205 µmol·mol–1. In addition, the decrease in Ci associated with fertilization became larger with stand age. At Waycross, fertilization decreased Ci from 211 to 203 µmol·mol–1 and the interaction between fertilization and stand age was significant for gs and Ci. These results indicate that silivcultural practices that increase resource availability and stand growth did not enhance leaf gas exchange.

Pour déterminer l'importance du contrôle de la compétition et de la fertilisation annuelle sur les échanges gazeux du feuillage, la photosynthèse nette en condition de lumière saturée (Asat), la conductance stomatale (gs) et la concentration interne en CO2 (Ci) ont été mesurées plusieurs fois dans des peuplements de pin à encens (Pinus taeda L.) d'âges différents croissant dans le Piedmont (BF Grant) et la Plaine côtière (Waycross) en Géorgie, aux États-Unis. Aux deux endroits, le contrôle de la compétition a diminué Asat et gs (Asat de 4,53 à 4,12 µmol·m–2·s–1, gs de 0,058 à 0,050 µmol·m–2·s–1 à BF Grant; Asat de 4,22 à 4,01 µmol·m–2·s–1, gs de 0,054 à 0,049 µmol·m–2·s–1 à Waycross). Dans l'ensemble, la fertilisation n'a pas eu d'impact positif sur Asat, même si elle a significativement accrue la concentration en azote du feuillage. À BF Grant, la fertilisation a significativement réduit gs de 0,057 à 0,051 µmol·m–2·s–1 et Ci de 217 à 205 µmol·mol–1. De plus, la diminution de Ci associée à la fertilisation a augmenté avec l'âge du peuplement. À Waycross, la fertilisation a diminué Ci de 211 à 203 µmol·mol–1 et l'interaction entre la fertilisation et l'âge du peuplement était significative pour gs et Ci. Ces résultats indiquent que les pratiques sylvicoles qui accroissent la disponibilité de la ressource et la croissance du peuplement n'améliorent pas les échanges gazeux du feuillage.[Traduit par la Rédaction]

Document Type: Research Article

Publication date: 2003-06-01

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