Multi-year data-model evaluation reveals the importance of nutrient availability over climate in arctic ecosystem C dynamics

Summary, in English

Arctic tundra is a globally important store for carbon (C). However, there is a lack of reference sites characterising C exchange dynamics across annual cycles. Based on the Greenland Ecosystem Monitoring (GEM) programme, here we present 9-11 years of flux and ecosystem data across the period 2008-2018 from two wetland sites in Greenland: Zackenberg (74°N) and Kobbefjord (64°N). The Zackenberg fen was a strong C sink despite its higher latitude and shorter growing seasons compared to the Kobbefjord fen. On average the ecosystem in Zackenberg took up ∼-50 g C m-2 yr-1 (range of +21 to-90 g C m-2 yr-1), more than twice that of Kobbefjord (mean ∼-18 g C m-2 yr-1, and range of +41 to-41 g C m-2 yr-1). The larger net carbon sequestration in Zackenberg fen was associated with higher leaf nitrogen (71%), leaf area index (140%), and plant quality (i.e. C:N ratio; 36%). Additional evidence from in-situ measurements includes 3 times higher levels of dissolved organic carbon in soils and 5 times more available plant nutrients, including dissolved organic nitrogen (N) and nitrates, in Zackenberg. Simulations using the soil-plant-atmosphere ecosystem model showed that Zackenberg's stronger CO2 sink could be related to measured differences in plant nutrients, and their effects on photosynthesis and respiration. The model explained 69% of the variability of net ecosystem exchange of CO2, 80% for photosynthesis and 71% for respiration over 11 years at Zackenberg, similar to previous results at Kobbefjord (73%, 73%, and 50%, respectively, over 8 years). We conclude that growing season limitations of plant phenology on net C uptake have been more than counterbalanced by the increased leaf nutrient content at the Zackenberg site.

• Författare: Efrén López-Blanco; Marcin Jackowicz-Korczynski; Mikhail Mastepanov; Kirstine Skov; Andreas Westergaard-Nielsen; Mathew Williams; Torben R. Christensen
• Avdelning/ar: Institutionen för naturgeografi och ekosystemvetenskap; BECC: Biodiversity and Ecosystem services in a Changing Climate; MERGE: ModElling the Regional and Global Earth system
• Publiceringsår: 2020-09-01
• Språk: Engelska
• Publikation/Tidskrift/Serie: Environmental Research Letters
• Volym: 15
• Issue: 9
• Länkar: http://dx.doi.org/10.1088/1748-9326/ab865b
• Dokumenttyp: Artikel i tidskrift
• Förlag: IOP Publishing
• Ämne: Physical Geography; Climate Research
• Nyckelord: Arctic tundra; Ecosystem respiration; Greenland; Net ecosystem exchange; Nutrient availability; Photosynthesis
• Aktiv: Published
• ISBN/ISSN/Övrigt: ISSN: 1748-9318