Soil warming and fertilization altered rates of nitrogen transformation processes and selected for adapted ammonia-oxidizing archaea in sub-arctic grassland soil

• Published in: Soil Biology and Biochemistry
• Main Authors: Daebeler, Anne, Bodelier, Paul L.E., Hefting, Mariet M., Rütting, Tobias, Laanbroek, Hendrikus J.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2017
• Subjects: 15N-tracing; 15N-pool-dilution; Nitrogen cycle; Climate change; Ammonia-oxidizing archaea; Warming; N enrichment; international; Arctic; Iceland
• Online Access: https://pure.knaw.nl/portal/en/publications/bbaa12f0-380c-4890-982a-71cb27866938; https://doi.org/10.1016/j.soilbio.2016.12.013; https://hdl.handle.net/20.500.11755/bbaa12f0-380c-4890-982a-71cb27866938; http://mda.vliz.be/mda/directlink.php?fid=VLIZ_00000353_587355830e0cd; http://www.sciencedirect.com/science/article/pii/S0038071716307787

Abstract The balance of microbial nitrogen (N) transformation processes in sub-arctic terrestrial ecosystems is most likely affected by global change, with potential feedbacks to greenhouse gas emissions and eutrophication. Soil temperature and N availability – their global increases being two of the most pressing global change features - will be prime drivers of N dynamics and microbial community structure, but little is known about their interactive effects in these ecosystems. We utilized geothermally warmed soils from Iceland as a natural experiment for assessing fertilization and warming effects on gross soil N transformation processes. Experimental incubations of these soils at different temperatures coupled with a dual 15N-labelling/-tracing approach and pyrotag transcript-sequencing allowed for the analysis of independent and combined impacts of N fertilization and temperature shifts on gross N mineralisation, nitrification, and ammonium and nitrate immobilisation rates and archaeal ammonia-oxidizing (AOA) communities, being the key ammonia oxidizers in this soil. Gross nitrification in warmed soil was increased in relation to ambient temperature soil and exhibited a higher temperature optimum. Concomitantly, our results revealed a selection of AOA populations adapted to in situ soil temperatures. Phylogenetically distinct populations of actively ammonia-oxidizing archaea exhibited conserved temperature optima. N mineralization and nitrification showed higher sensitivities in response to short-term temperature changes if the soils had been warmed. In part, the influence of short-term temperature changes could however be neutralized by the effects of N fertilization. Long-term N fertilization alone affected only gross N mineralization. However, all gross N transformation rates were significantly altered by the interactive effects of N fertilization and soil warming. We conclude that in order to reliably predict effects of global change on sub-arctic soil N transformation processes we need to consider ...