Greater soil carbon and nitrogen in a Mojave Desert ecosystem after 10 years exposure to elevated CO2

• Published in: Geoderma 2019-12, Vol.355 (C), p.113915, Article 113915
• Main Authors: Koyama, Akihiro, Harlow, Benjamin, Evans, R. Dave
• Format: Article
• Language: English
• Subjects: Biological soil crust; Free Air CO2 Enrichment (FACE); Mojave Desert; Soil organic carbon; Soil total nitrogen
• ISSN: 0016-7061; 1872-6259
• DOI: 10.1016/j.geoderma.2019.113915

We investigated patterns and possible mechanisms in the greater soil organic carbon (SOC) and total nitrogen (N) after 10 years exposure to elevated atmospheric CO2 concentration ([CO2]) at the Nevada Desert FACE Facility, USA, reported by Evans et al. (2014). Differences in SOC under elevated and ambient [CO2] depended on cover types, and most evident in soils under deciduous shrubs. Greater SOC was observed in soils close to the surface as well as 0.4 to 0.8 m suggesting elevated [CO2] stimulated production of aboveground litter, root litter, and rhizodeposition. Greater total N under elevated [CO2] was most evident under deciduous shrubs as well as plant interspace that had extensive coverage of biological soil crusts. Greater total N in the top soil profile under elevated [CO2] was accompanied with reduced δ15N by 0.4‰, suggesting elevated [CO2] stimulated N2-fixation and/or reduced N loss. We conclude that, in arid ecosystems under elevated [CO2], shrubs play a major role in determining C sink capacity in desert soils, and N limitation for vascular plants is unlikely to occur due to sustained net N supply. •Soil C and N were greater below deciduous shrubs under elevated than ambient CO2.•Soil N was also greater at plant interspace under elevated than ambient CO2.•Elevated CO2 stimulated N2-fixation and/or reduced N loss.