Nutrient supply modulates species interactions below ground: dynamics and traits of fine roots in mixed plantations of Eucalyptus and Acacia mangium

Bordron Bruno, Germon Amandine, Laclau Jean-Paul, Oliveira I.R., Robin Agnès, Jourdan Christophe, Paula Ranieri Ribeiro, Pinheiro R.C., Guillemot Joannès, Gonçalves José Leonardo M., Bouillet Jean-Pierre. 2021. Nutrient supply modulates species interactions below ground: dynamics and traits of fine roots in mixed plantations of Eucalyptus and Acacia mangium. Plant and Soil, 460 : 559-577.

https://doi.org/10.1007/s11104-020-04755-2

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Quartile : Q1, Sujet : AGRONOMY / Quartile : Q1, Sujet : PLANT SCIENCES / Quartile : Q2, Sujet : SOIL SCIENCE

Résumé : Aims: Belowground interactions are still poorly understood in mixed-species forests. We investigated the effects of soil fertility on belowground processes in mixed planted forests. Methods: The dynamics and traits of Eucalyptus and Acacia mangium fine roots (diameter < 2 mm) in plantations with 50% of each species were studied in a randomized block design established in a nutrient depleted soil. Stands with NPK fertilization applied at planting (F+) were compared to unfertilized stands (F-). Results: In the 0–15 cm soil layer, Eucalyptus root mass density (RMD) was higher than Acacia RMD by 50% in F+ and 10% in F-, considering both ages. At 34 months of age, Eucalyptus RMD was 94% higher near Acacia trees than near Eucalyptus trees in F-. In this layer, Eucalyptus specific root length (SRL) was 21% higher than Acacia SRL at 16 months of age and was 10% higher in F- than in F+ at 34 months of age. The cumulative Eucalyptus fine root length production between 16 and 34 months was 66% higher in F- than in F+ in the 0–1 m soil layer. Conclusions: Fertilization increased the competition between species and led to a partial exclusion of Acacia fine roots from the nutrient-rich topsoil. Soil exploration by Eucalyptus roots in the vicinity of Acacia trees was higher in F- than in F+, which suggests that unfertilized trees benefited from facilitation through higher soil N availability and direct N transfer from Acacia trees.

Mots-clés Agrovoc : fertilité du sol, culture en mélange, Eucalyptus, Acacia mangium, culture associée, forêt tropicale, sol de forêt, relation plante sol, interactions biologiques, taille des racines, système racinaire