09 Sep 2022
09 Sep 2022
Status: this preprint is open for discussion.

Potassium-limitation of forest productivity, part 2: CASTANEA-MAESPA-K shows a reduction in photosynthesis rather than a stoichiometric limitation of tissue formation

Ivan Cornut1,2,5, Guerric le Maire2,5, Jean-Paul Laclau2,5, Joannès Guillemot2,4,5, Yann Nouvellon2,5, and Nicolas Delpierre1,3 Ivan Cornut et al.
  • 1Université Paris-Saclay, CNRS, AgroParisTech, Ecologie Systématique et Evolution, 91405, Orsay, France
  • 2CIRAD, UMR Eco&Sols, F-34398 Montpellier, France
  • 3Institut Universitaire de France (IUF)
  • 4Department of Forest Sciences ESALQ, University of São Paulo, Piracicaba, São Paulo, Brazil
  • 5Eco&Sols, Univ. Montpellier, CIRAD, INRAe, Institut Agro, IRD, Montpellier, France

Abstract. Potassium availability constrains forest productivity. Brazilian eucalypt plantations are a good example of the K-limitation of wood production. Here, we built upon a previously described model (CASTANEA-MAESPA-K) and used it to understand whether the simulated decline in C-source under K deficiency was sufficient to explain the K-limitation of wood productivity in Brazilian eucalypt plantations. We developed allocation schemes for both C and K and included into CASTANEA-MAESPA-K. No direct limitations of the C-sink activity, nor direct modifications of the C-allocation by K availability were included in the model. Simulation results show that the model was successful in replicating the observed patterns of wood productivity, growth, NPP limitation by K deficiency. Simulations also show that the response of NPP is not linear with increasing K fertilisation. Simulated stem carbon use and water use efficiencies decreased with decreasing levels of K availability. Simulating a direct stoichiometric limitation of wood productivity, growth, NPP was not necessary to reproduce the observed decline of productivity under K limitation, suggesting that K stoichiometric plasticity could be different than that of N and P. Confirming previous results from the literature, the model simulated an intense recirculation of K in the trees, suggesting that retranslocation processes were essential for tree functioning. Optimal K fertilisation levels calculated by the model were similar to nutritional recommendations currently applied in Brazilian eucalypt plantations, paving the way for validating the model at a larger scale and this approach to develop decision-making tools to improve fertilisation practices.

Ivan Cornut et al.

Status: open (until 21 Oct 2022)

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Ivan Cornut et al.


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Short summary
After simulating the effects of low levels of Potassium on the canopy of trees and the uptake of carbon dioxide from the atmosphere by leaves in part 1, here we tried to simulate the way the trees use the carbon they have acquired and the interaction with the potassium cycle in the tree. We show that the effect of low potassium on the efficiency of the trees to acquire carbon is enought to exlplain why they do not produce enough wood when they are in soils with low levels of potassium.