Free atmospheric CO2 enrichment increased above ground biomass but did not affect symbiotic N2-fixation and soil carbon dynamics in a mixed deciduous stand in Wales

Hoosbeek, M. R., Lukac, M. ORCID: https://orcid.org/0000-0002-8535-6334, Velhorst, E. J., Smith, A. R. and Godbold, D. L. (2011) Free atmospheric CO2 enrichment increased above ground biomass but did not affect symbiotic N2-fixation and soil carbon dynamics in a mixed deciduous stand in Wales. Biogeosciences, 8 (2). pp. 353-364. ISSN 1726-4170 doi: 10.5194/bg-8-353-2011

Abstract/Summary

Through increases in net primary production (NPP), elevated CO2 is hypothesizes to increase the amount of plant litter entering the soil. The fate of this extra carbon on the forest floor or in mineral soil is currently not clear. Moreover, increased rates of NPP can be maintained only if forests can escape nitrogen limitation. In a Free atmospheric CO2 Enrichment (FACE) experiment near Bangor, Wales, 4 ambient CO2 and 4 FACE plots were planted with patches of Betula pendula, Alnus glutinosa and Fagus sylvatica on a former arable field. Four years after establishment, only a shallow L forest floor litter layer had formed due to intensive bioturbation. Total soil C and N contents increased irrespective of treatment and species as a result of afforestation. We could not detect an additional C sink in the soil, nor were soil C stabilization processes affected by FACE. We observed a decrease of leaf N content in Betula and Alnus under FACE, while the soil C/N ratio decreased regardless of CO2 treatment. The ratio of N taken up from the soil and by N2-fixation in Alnus was not affected by FACE. We infer that increased nitrogen use efficiency is the mechanism by which increased NPP is sustained under elevated CO2 at this site.

Additional Information	The discussion paper for this item can be found in Biogeosciences Discussions, 7 (3), pp.4153-4180, doi:10.5194/bgd-7-4153-2010.
Item Type	Article
URI	https://reading-clone.eprints-hosting.org/id/eprint/18381
Identification Number/DOI	10.5194/bg-8-353-2011
Refereed	Yes
Divisions	Life Sciences > School of Agriculture, Policy and Development > Department of Crop Science Interdisciplinary centres and themes > Soil Research Centre
Additional Information	The discussion paper for this item can be found in Biogeosciences Discussions, 7 (3), pp.4153-4180, doi:10.5194/bgd-7-4153-2010.
Publisher	Copernicus Publications
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