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

Made available in DSpace on 2018-12-11T16:39:11Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-12-01 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 δ15N 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. USP-ESALQ Departamento de Ciências Florestais, Av. Pádua Dias, 11 CIRAD UMR Eco andSols Écologie Fonctionnelle and oBiogéochimie des Sols and Agroécosystèmes, 2 Place Viala USP-CENA Divisão de Desenvolvimento de Técnicas Analíticas e Nucleares, Av. Centenário, 303 INRA UR 1138 Biogéochimie des Ecosystèmes Forestiers CIRAD UMR AGAP, Avenue Agropolis INRA UMR Eco andSols Écologie Fonctionnelle and Biogéochimie des Sols and Agroécosystèmes, 2 Place Viala UNESP Departamento de Ciência Florestal Julio de Mesquita Filho UNESP Departamento de Ciência Florestal Julio de Mesquita Filho