Split-root labelling to investigate 15 N rhizodeposition by Pinus sylvestris and Picea abies

• Published in: Isotopes in environmental and health studies 2018-03, Vol.54 (1), p.16-27
• Main Authors: Veerman, Liz, Kalbitz, Karsten, Schoorl, Jorien C, Tietema, Albert
• Format: Article
• Language: English
• Subjects: Environmental Monitoring - methods; Nitrogen Isotopes - metabolism; Picea - metabolism; Pinus sylvestris - metabolism; Plant Roots - metabolism
• ISSN: 1025-6016; 1477-2639
• DOI: 10.1080/10256016.2017.1352586

We investigated the transfer of N into the soil via N uptake and release by tree roots, which involves the principles of the split-root technique. One half of the root system received an injection of ( NH ) SO and the other half equivalent amounts of (NH ) SO at N natural abundance level. N was transferred from one side of the root system ( N side) to the other side ( N side) and released into the soil. The method was conducted with Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies [L.] Karst). Two concentration levels of (NH ) SO were used, corresponding with annual N deposition in the Netherlands (30 kg N ha ) and a twelfth of that (2.5 kg N ha ). Samples were taken 3 and 6 weeks after labelling and divided into needles + stem, roots, rhizosphere and bulk soil. Already 3 weeks after labelling, Scots pine took up 23.7 % of the low and 9.1 % of the high amounts of N, while Norway spruce took up 21.5 and 32.1 %, respectively. Both species transported proportions of N to the rhizosphere (0.1-0.2 %) and bulk soil (0.3-0.9 %). The method is a useful tool to investigate the fate of root-derived N in soils, for example, for the formation of stable forms of soil organic matter.