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

Abstract. Potassium (K) availability constrains forest productivity. Brazilian eucalypt plantations are a good example of the K limitation wood production. Here, we built upon previously described model (CASTANEA-MAESPA-K) and used it to understand whether simulated decline in C source under deficiency was sufficient explain productivity plantations. We developed allocation schemes for both included these CASTANEA-MAESPA-K. Neither direct limitations C-sink activity nor modifications by were model. Simulation results show that successful replicating observed patterns deficiency. Simulations also response net primary (NPP) is not linear with increasing fertilisation. Simulated stem carbon use water efficiencies decreased decreasing levels availability. Simulating stoichiometric NPP or growth necessary reproduce limitation, suggesting plasticity could be different N P. Confirming previous from literature, an intense recirculation trees, retranslocation processes essential tree functioning. Optimal fertilisation calculated similar nutritional recommendations currently applied plantations, paving way validation at larger scale this approach developing decision-making tools improve practices.