Consequences of potassium deficiency and throughfall exclusion on fine root distributions down to 17 m depth in Brazilian Eucalyptus grandis plantations

Bordron Bruno, Asensio Verónica, Christina Mathias, Abreu-Junior Cassio Hamilton, Germon Amandine, Bouillet Jean-Pierre, Gonçalves José Leonardo M., Laclau Jean-Paul. 2018. Consequences of potassium deficiency and throughfall exclusion on fine root distributions down to 17 m depth in Brazilian Eucalyptus grandis plantations. In : Eucalyptus 2018: Managing Eucalyptus plantation under global changes. Abstracts book. CIRAD, IUFRO, MUSE. Montpellier : CIRAD, Résumé, pp. 128-129. ISBN 978-2-87614-743-0 Eucalyptus 2018, Montpellier, France, 17 September 2018/21 September 2018.

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Abstract : In many tropical regions, climates changes are expected to cause longer drought periods. Potassium fertilization (K) can have a positive effect on plant water use efficiency. Important morphological and physiological traits are modified by K availability and water supply regimes. Our study aimed to assess the combined effect of K fertilization and soil water availability on deep roots exploration of Eucalyptus grandis trees. A throughfall exclusion experiment was used to compare stands with 37% of throughfall excluded (-W) and stands without rain exclusion (+W), with and without K fertilization (+K and {K, respectively). Eucalypt fine roots (diameter < 2mm) were collected along the soil profile down to the water table (17 m depth) in 12 plots (4 treatments x 3 blocks), at 2 and 3 years after planting. Total fine root biomass was twice as high in +K+W than in -K+W (507.5 and 253.2 g m-2 respectively) and 62% higher in +K-W than in -K-W (501.4 and 308.7 g m-2 respectively), 2 years after planting. The same patterns were observed at 3 years of age. The total fine root biomass almost doubled for all treatments between the second and third year of growth. At 2 years of age, the root front for all treatment was found from 7 meters depth for {K+W to 10.6 meters depth for +K-W. At 3 years, Eucalyptus trees in +K-W reached the water table at 17 m depth while no fine roots were found down 15 m depth in the other treatments. Potassium fertilization increased total fine root biomass and allowed Eucalyptus trees to reach the water table earlier when 37% of throughfall was excluded from the stand. Our study suggests that K fertilization increases the exploration of deep soil layers by fine roots, which is likely to improve tree tolerance to drought over the early growth of Eucalyptus grandis plantations, providing a fast access to water stored in deep soil layers.

Mots-clés libres : Eucalyptus, Sustainability, Ecosystem services, Abiotic stresses, Biotic stresses, Plantation project

Auteurs et affiliations

  • Bordron Bruno, ESALQ (BRA)
  • Asensio Verónica, Universidade de São Paulo (BRA)
  • Christina Mathias, CIRAD-PERSYST-UPR AIDA (REU) ORCID: 0000-0003-3618-756X
  • Abreu-Junior Cassio Hamilton, CENA (BRA)
  • Germon Amandine, CIRAD-PERSYST-UMR Eco&Sols (FRA)
  • Bouillet Jean-Pierre, CIRAD-PERSYST-UMR Eco&Sols (MDG)
  • Gonçalves José Leonardo M., ESALQ (BRA)
  • Laclau Jean-Paul, CIRAD-PERSYST-UMR Eco&Sols (FRA) ORCID: 0000-0002-2506-214X

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