B31C-0560
Identifying nitrogen limitations to organic sediments accumulation in various vegetation types of arctic tundra (Hornsund, Svalbard)

Wednesday, 16 December 2015
Poster Hall (Moscone South)
Grzegorz Skrzypek1, Bronisław Wojtuń2, Quan Hua3, Dorota Richter4, Dariusz Jakubas5, Katarzyna Wojczulanis–Jakubas5 and Aleksandra Samecka–Cymerman2, (1)University of Western Australia, Crawley, WA, Australia, (2)The University of Wrocław, Department of Ecology, Biogeochemistry and Environmental Protection, Wrocław, Poland, (3)Australian Nuclear Science and Technology Organization, Kirrawee, Australia, (4)The Wrocław University of Environmental and Life Sciences, Department of Botany and Plant Ecology, Wrocław, Poland, (5)The University of Gdańsk, Department of Vertebrate Ecology and Zoology, Gdańsk, Poland
Abstract:
Arctic and subarctic regions play important roles in the global carbon balance. However, nitrogen (N) deficiency is a major constraint for organic carbon sequestration in the High Arctic. Hence, the identification of the relative contributions from different N-sources is critical for understanding the constraints that limit tundra growth.

The stable nitrogen composition of the three main N-sources and numerous plants were analyzed in ten tundra types in the Fuglebekken catchment (Hornsund Fjord, Svalbard, 77°N 15°E). The percentage of the total tundra N-pool provided by seabirds’ feces (colonially breeding, planktivorous Alle alle), ranged from 0–21% in Patterned-ground tundra to 100% in Ornithocoprophilous tundra. The total N-pool utilized by tundra plants in the studied catchment was built in 36% by birds, 38% by atmospheric deposition, and 26% by N2-fixation. The results clearly show that N-pool in the tundra is significantly supplemented by nesting seabirds. Thus, if they experienced substantial negative environmental pressure associated with climate change, it would adversely influence the tundra N-budget [1].

The growth rates and the sediment thickness (<15 cm) in different tundra types varied considerably but the tundra age was similar, <450 cal BP. The only exception was Ornithocoprophilous tundra with very diverse ages ranging from 235 to 2300 cal BP and thickness up to 110cm. The growth rates for this tundra (62 cm core, 18 AMS 14C dates) were high (1.5-3.0 mm/yr) between 1568 and 1804 AD and then substantially declined for the period between 1804 and 1929 AD (0.2 mm/yr). These findings deliver an additional argument, that the organic matter accumulation is driven not only directly by climatic conditions but also by birds’ contribution to the tundra N-pool.

[1] Skrzypek G, Wojtuń B, Richter D, Jakubas D, Wojczulanis–Jakubas K, Samecka–Cymerman A, 2015. Diversification of nitrogen sources in various tundra vegetation types in the high Arctic. PLoS ONE (in review).

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