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Evidence of short-term belowground transfer of nitrogen from Acacia mangium to Eucalyptus grandi trees in a tropical planted forest

Ribeiro Paula R., Bouillet J.P., Trivelin P.C.O., Zeller B., De Moraes Gonçalves J.L., Nouvellon Y., Bouvet J.M., Plassard C., Laclau J.P.. 2015. Soil Biology and Biochemistry, 91 : p. 99-108.

The short-term belowground transfer of nitrogen from nitrogen-fixing trees to companion trees has never been studied in the field. A 15N pulse-labeling study was conducted in a mixed plantation of Acacia mangium and Eucalyptus grandis at the peak of leaf area, 26 months after planting. 15N¿NO3? was injected into the stem of one big Acacia tree in three plots. 15N was traced over 2 months in the labeled Acacia tree as well as in neighboring Eucalyptus trees. For both species, young leaves were sampled, as well as fine roots and the rhizosphere at a distance of 0.75 m and 2.25 m from the labeled tree. The 15N atom% was also determined in the wood, bark, branches and total foliage of the 3 labeled Acacia trees and 9 Eucalyptus trees, 60 days after labeling. Most of the leaves, fine roots and rhizosphere samples of both species were 15N enriched from 5 days after labeling. The ?15N values were higher at a distance of 0.75 m than at 2.25 m in Acacia roots, but were similar at both distances in Eucalyptus roots and the rhizospheres. The wood and bark of Eucalyptus trees sampled at a distance of 6.2 m from the labeled Acacia trees were 15N enriched. This shows belowground N transfer from Acacia to Eucalyptus trees in the field during the first few days after labeling. This facilitation process may provide a significant amount of the nitrogen requirements of trees close to N-fixing trees in mixed forests. (Résumé d'auteur)

Mots-clés : Écorce; bois; analyse de tissu foliaire; racine; espacement; mycorhization; rhizosphère; fixation de l'azote; injection d'arbres; arbre fixateur d'azote; eucalyptus grandis; acacia mangium; plantation forestière; forêt mélangée; brésil

Thématique : Production forestière; Physiologie végétale : nutrition; Biologie du sol

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