Measured and modeled interactive effects of potassium deficiency and water deficit on gross primary productivity and light‐use efficiency in Eucalyptus grandis plantations

• Published in: Global change biology 2015-05, Vol.21 (5), p.2022-2039
• Main Authors: Christina, Mathias, Le Maire, Guerric, Battie‐Laclau, Patricia, Nouvellon, Yann, Bouillet, Jean‐Pierre, Jourdan, Christophe, Moraes Gonçalves, José Leonardo, Laclau, Jean‐Paul
• Format: Article
• Language: English
• Subjects: Agricultural sciences; Biogeochemistry; Biomass; biomass production; Botany; Brazil; carbon; carbon assimilation; Climate Change; drought; Droughts; eucalypt; Eucalyptus - growth & development; Eucalyptus - metabolism; Eucalyptus grandis; fertilization; Forestry - methods; Forestry - statistics & numerical data; forests; leaf area index; Life Sciences; modeling; Models, Biological; nutrient shortage; nutrition; Photosynthesis; plant growth; plantations; planting; Potassium; Potassium - metabolism; primary productivity; radiation-use efficiency; Rain; roots; throughfall; tree traits; trees; tropical and subtropical crops; tropics; water supply; water uptake
• ISSN: 1354-1013; 1365-2486
• DOI: 10.1111/gcb.12817

Global climate change is expected to increase the length of drought periods in many tropical regions. Although large amounts of potassium (K) are applied in tropical crops and planted forests, little is known about the interaction between K nutrition and water deficit on the physiological mechanisms governing plant growth. A process‐based model (MAESPA) parameterized in a split‐plot experiment in Brazil was used to gain insight into the combined effects of K deficiency and water deficit on absorbed radiation (aPAR), gross primary productivity (GPP), and light‐use efficiency for carbon assimilation and stem biomass production (LUECand LUEₛ) in Eucalyptus grandis plantations. The main‐plot factor was the water supply (undisturbed rainfall vs. 37% of throughfall excluded) and the subplot factor was the K supply (with or without 0.45 mol K m⁻² K addition). Mean GPP was 28% lower without K addition over the first 3 years after planting whether throughfall was partly excluded or not. K deficiency reduced aPAR by 20% and LUECby 10% over the whole period of growth. With K addition, throughfall exclusion decreased GPP by 25%, resulting from a 21% decrease in LUECat the end of the study period. The effect of the combination of K deficiency and water deficit was less severe than the sum of the effects of K deficiency and water deficit individually, leading to a reduction in stem biomass production, gross primary productivity and LUE similar to K deficiency on its own. The modeling approach showed that K nutrition and water deficit influenced absorbed radiation essentially through changes in leaf area index and tree height. The changes in gross primary productivity and light‐use efficiency were, however, driven by a more complex set of tree parameters, especially those controlling water uptake by roots and leaf photosynthetic capacities.