Journal Article

Do changes in carbon allocation account for the growth response to potassium and sodium applications in tropical <i>Eucalyptus</i> plantations?

Daniel Epron, Jean-Paul Laclau, Julio C.R. Almeida, José Leonardo M. Gonçalves, Stephane Ponton, Carlos R. Sette, Juan S. Delgado-Rojas, Jean-Pierre Bouillet and Yann Nouvellon

Edited by Michael Ryan

in Tree Physiology

Volume 32, issue 6, pages 667-679
Published in print June 2012 | ISSN: 0829-318X
Published online October 2011 | e-ISSN: 1758-4469 | DOI: http://dx.doi.org/10.1093/treephys/tpr107

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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 CO2 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 (δ13C) 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 (PW) was dramatically increased. Sodium application decreased the fraction of carbon allocated belowground in a similar way, and enhanced GPP, ANPP and PW, but to a lesser extent compared with K fertilization. Neither K nor Na affected δ13C 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 PW resulted from drastic changes in carbon allocation.

Keywords: carbon budget; Eucalyptus grandis; fertilization; soil CO2 efflux; stable carbon isotope

Journal Article.  8893 words.  Illustrated.

Subjects: Plant Sciences and Forestry

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