Icelandic grasslands as long-term C sinks under elevated organic N inputs
Leblans, Niki I. W. (Universiteit Antwerpen. Departement Biologie)
Aerts, Rien (Vrije Universiteit Amsterdam)
Vicca, Sara (Universiteit Antwerpen. Departement Biologie)
Magnússon, Borgthór (Icelandic Institute of Natural History (Gardabaer, Islàndia))

Date:	2017
Abstract:	About 10% of the anthropogenic CO₂ emissions have been absorbed by northern terrestrial ecosystems during the past decades. It has been hypothesized that part of this increasing carbon (C) sink is caused by the alleviation of nitrogen (N) limitation by increasing anthropogenic N inputs. However, little is known about this N-dependent C sink. Here, we studied the effect of chronic seabird-derived N inputs (47-67 kg N ha⁻¹ year⁻¹) on the net soil organic C (SOC) storage rate of unmanaged Icelandic grasslands on the volcanic Vestmannaeyjar archipelago by using a stock change approach in combination with soil dating. We studied both early developmental (young) soils that had been receiving increased N inputs over a decadal timescale since an eruption in 1963, and well-developed soils, that had been receiving N inputs over a millennial timescale. For the latter, however, the effects on both decadal (topsoil; 40 years) and millennial (total soil profile; 1600 years) SOC storage could be studied, as the age of topsoil and the total soil profile could be determined from volcanic ash layers deposited in 1973 and 395 AD. We found that enhanced N availability-either from accumulation over time, or seabird derived-increased the net SOC storage rate. Under low N inputs, early developmental soils were weak decadal C sinks (0. 018 ton SOC ha−1 year−1), but this increased quickly under ca. 30 years of elevated N inputs to 0. 29 ton SOC ha⁻¹ year⁻¹, thereby equalling the decadal SOC storage rate of the unfertilized well-developed soils. Furthermore, for the well-developed soils, chronically elevated N inputs not only stimulated the decadal SOC storage rate in the topsoil, but also the total millennial SOC storage was consistently higher. Hence, our study suggests that Icelandic grasslands, if not disturbed, can remain C sinks for many centuries under current climatic conditions and that chronically elevated N inputs can induce a permanent strengthening of this sink.
Grants:	European Commission 610028
Rights:	Tots els drets reservats.
Language:	Anglès
Document:	Article ; recerca ; Versió acceptada per publicar
Subject:	Terrestrial C sink ; N inputs ; Long-term carbon storage ; Soil development ; Surtsey
Published in:	Biogeochemistry, Vol. 134, issue 3 (Aug. 2017) , p. 279-299, ISSN 1573-515X

DOI: 10.1007/s10533-017-0362-5

Post-print 36 p, 1.8 MB

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Research literature > UAB research groups literature > Research Centres and Groups (research output) > Experimental sciences > CREAF (Centre de Recerca Ecològica i d'Aplicacions Forestals) > Imbalance-P
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