Do changes in carbon allocation account for the growth response to potassium and sodium applications in tropical Eucalyptus plantations?
Understanding the underlying mechanisms that account for the impact of potassium (K) fertilization and its replacement by sodium (Na) on tree growth is key to improving the management of forest plantations that are expanding over weathered tropical soils with low amounts of exchangeable bases. A complete randomized block design was planted with Eucalyptus grandis (W. Hill ex Maiden) to quantify growth, carbon uptake and carbon partitioning using a carbon budget approach. A combination of approaches including the establishment of allometric relationships over the whole rotation and measurements of soil CO(2) efflux and aboveground litterfall at the end of the rotation were used to estimate aboveground net production (ANPP), total belowground carbon flux and gross primary production (GPP). The stable carbon isotope (δ(13)C) of stem wood α-cellulose produced every year was used as a proxy for stomatal limitation of photosynthesis. Potassium fertilization increased GPP and decreased the fraction of carbon allocated belowground. Aboveground net production was strongly enhanced, and because leaf lifespan increased, leaf biomass was enhanced without any change in leaf production, and wood production (P(W)) was dramatically increased. Sodium application decreased the fraction of carbon allocated belowground in a similar way, and enhanced GPP, ANPP and P(W), but to a lesser extent compared with K fertilization. Neither K nor Na affected δ(13)C of stem wood α-cellulose, suggesting that water-use efficiency was the same among the treatments and that the inferred increase in leaf photosynthesis was not only related to a higher stomatal conductance. We concluded that the response to K fertilization and Na addition on P(W) resulted from drastic changes in carbon allocation.
Université de Lorraine, UMR 1137, Ecologie et Ecophysiologie Forestières, Faculté des Sciences, F-54500 Vandoeuvre-les-Nancy, France. daniel.epron@scbiol.uhp-nancy.fr
Daniel
D
Epron
Jean-Paul
JP
Laclau
Julio C R
JC
Almeida
José Leonardo M
JL
Gonçalves
Stephane
S
Ponton
Carlos R
CR
Sette
Juan S
JS
Delgado-Rojas
Jean-Pierre
JP
Bouillet
Yann
Y
Nouvellon
D018533:Biomass; D002244:Carbon / Q000378:metabolism*; D002247:Carbon Isotopes / Q000378:metabolism; D002482:Cellulose / Q000378:metabolism; D005052:Eucalyptus / Q000254:growth & development* / Q000378:metabolism; D005308:Fertilizers; D016468:Forestry; D018515:Plant Leaves / Q000254:growth & development; D054046:Plant Stomata / Q000502:physiology; D011188:Potassium / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*; D014934:Wood / Q000378:metabolism
D002247:Carbon Isotopes; D005308:Fertilizers; D002244:Carbon; D002482:Cellulose; D012964:Sodium; D011188:Potassium