Roots take up labeled nitrogen from a depth of 9 m in a wooded savanna in Brazil

Author(s)

Pinheiro, Rafael Costa ^[1] ; Bouillet, Jean-Pierre ^{[2, 3]} ; Pivello, Vania Regina ^[4] ; Alo, Livia Lanzi ^[1] ; Costa, Vladimir Eliodoro ^[5] ; Van den Meersche, Karel ^{[2, 3]} ; Guerrini, Irae Amaral ^[1] ; Laclau, Jean-Paul ^{[1, 2, 3]}

Affiliation

^[1] Sao Paulo State Univ UNESP, Sch Agr, Botucatu, SP - Brazil

^[2] CIRAD, UMR ECO & SOLS, F-34398 Montpellier - France

^[3] Univ Montpellier, Montpellier SupAgro, INRA, Eco & Sols, CIRAD, IRD, Montpellier - France

^[4] Univ Sao Paulo, Dept Ecol, Sao Paulo, SP - Brazil

^[5] Sao Paulo State Univ UNESP, Inst Biosci, Botucatu, SP - Brazil

• Document type: Journal article
• Source: SOIL BIOLOGY & BIOCHEMISTRY; v. 160, SEP 2021.
• Web of Science Citations: 0

Abstract

The savannas (called Cerrado) are the second-largest vegetation formation in Brazil after the Amazon rainforest, with about 2 million km(2). Roots have been found in very deep soil layers in Cerrado ecosystems, which suggests a crucial role of deep rooting in the supply of water and nutrients over dry periods. The aim of our study was to gain insight into the complementarity of common Cerrado woody species in taking up mobile nutrients throughout deep soil profiles. In a closed-canopy savanna with dense woody understory, labeled nitrate was injected into the soil at six soil depths (0.1, 1.5, 3.0, 6.0, 9.0, or 12.0 m) with three plots per depth, at two dates (in rainy and dry seasons). Five months after labeled nitrate injection, young leaves were sampled and foliar delta N-15 was determined in each plot in the three most common woody species (Coussarea hydrangeifolia, Miconia albicans and Xylopia aromatica). The maximum depth of N-15 uptake was dependent on the species. X. aromatica trees took up N-15 from a maximum depth of 9 m and exploited a much larger soil volume than the two other species, with the uptake of N-15 at a horizontal distance of up to 5 m between the trunk and the injection site. The behavior of M. albicans and C. hydrangeifolia was similar, with a strong uptake of N-15 only in the 0-1.5 m soil layer, within 2 m horizontally from the injection site. The depth of N-15 uptake over the dry season was not related to the diameter at breast height of the woody plants sampled. We show that roots can take up labeled nitrogen from a depth of 9 m in tropical wooded savannas, which suggests an important role of deep-rooted species in closing biogeochemical cycles on highly weathered tropical soils. (AU)

• FAPESP's process: 15/25946-0 - Maximum distance evaluation of nutrient uptake in tropical forest formations using 15N as tracer
• Grantee: Rafael Costa Pinheiro
• Support Opportunities: Scholarships in Brazil - Doctorate