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

Abstract

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.

Carbon Storage and Allocation Pattern in Plant Biomass among Different Forest Plantation Stands in Guangdong, China

“…Second, belowground competition for nutrients varied with plant age [42]. For example, the fertilization of potassium (K) and sodium (Na) changed the fraction of carbon allocated belowground [43]. At different stand ages, the nutrient requirements of different tree species were different.…”

FERTILIZACIÓN CON BORO EN PLANTACIONES DE Eucalyptus urophylla S. T. Blake en TABASCO

“…For example, the application of K-based fertilizers has more influence on the distribution of biomass in eucalyptus components than the application of micronutrients. This is because K helps prolong the useful life of foliage by channeling more C to the bole and to the aerial biomass in general (Epron et al, 2012).…”

“…Por ejemplo, la aplicación de fertilizantes a base de K tiene más influencia en la distribución de biomasa en los componentes de eucalipto que la aplicación de micronutrientes. Lo anterior debido a que el K ayuda a prolongar la vida útil del follaje canalizando más C al fuste y a la biomasa aérea en general (Epron et al, 2012).…”

Potassium fertilization affects the distribution of fine roots but does not change ectomycorrhizal community structure

“…In Eucalyptus, fertilization with K doubled CO 2 assimilation rates (Battie- Laclau et al 2014). In an adjacent experiment, the K addition lead to an increase in the amount of gross primary production allocated to stem wood production (Epron et al 2011). The increase growth under elevated CO 2 was also a direct consequence of increased rates of photosynthesis.…”

“…photosynthesis rates (Linder and Troeng 1980). For example, in eucalyptus, K-fertilization increased photosynthesis (BattieLaclau et al 2014) and increased aboveground biomass (Laclau et al 2009;Epron et al 2011). In addition, K also has an important role in the movement of sucrose in and out of phloem vessels (Hermans et al 2006); thus, K deficiency can strongly influence tree carbon (C) allocation (Epron et al 2011).…”