The Nitrogen Balance of Arctic Tundra: Pathways, Rates, and Environmental Implications

Abstract

The magnitude of the inputs and exports of nitrogen was estimated for the tundra ecosystem at Barrow, Alaska. Based on new data and on previous investigations, annual input of nitrogen from all sources was 92.4 mg N/m2 per year, with the most important sources being nitrogen fixation (75%) and ammonia in summer rain (18%). The low input of nitrogen by rain and snow results from both low annual precipitation and extremely low concentrations of nitrogen compounds in precipitation. Despite the meager nitrogen supply, the estimated retention is over 80% of the input, reflecting insignificant leaching due to the impermeable permafrost substrate, low precipitation, and restricted lateral movement of water over and through the nonfrozen soils. Denitrification also is low, at least partially due to nutrient deficiency.Interpretations of these data in respect to the sensitivity of the environment to perturbations, suggest that resource development or other activities which would have minor or negligible effects in temperate latitudes, could alter substantially the nitrogen balance of this arctic ecosystem.

Sources, fates, and impacts of nitrogen inputs to terrestrial ecosystems: review and synthesis

“…Van Cleve & Alexander (1981) suggest that low precipitation, cold temperatures, and restricted biological activity contribute to low annual nonsymbiotic N inputs in tundra and boreal environments. However, fixation rates may be quite high during the short tundra growing season (Barsdate & Alexander 1975), and some productive deciduous forests in the boreal zone may exhibit substantial N-fixing activity (Van Cleve et al 1971;Van Cleve & Alexander 1981). In deserts, reduced temperatures and light intensity together with favorable soil moisture conditions have resulted in some of the highest measured rates of nonsymbiotic nitrogen fixation (Skujins 1981).…”

“…In tundra, fixation is restricted to the short growing season (Barsdate & alexander 1975). Moisture availability, as regulated by microtopography, has also been shown to influence nitrogen-fixing activity (Barsdate & Alexander 1975;Van Cleve & Alexander 1981;Karagatzides et al 1985).…”

“…Moisture availability, as regulated by microtopography, has also been shown to influence nitrogen-fixing activity (Barsdate & Alexander 1975;Van Cleve & Alexander 1981;Karagatzides et al 1985). Activity generally increases from dry to wet sites and is associated with a shift from blue-green algae in lichen associations (dry sites) to free-living blue-greens associated with mosses (wet sites).…”

Nitrogen fixation by associative cyanobacteria in the Canadian Arctic.

“…Previous estimates of arctic ^-fixation inputs range from 0.06 to 3 kg N ha'yr" 1 , with the majority of estimates ranging from 0.10 to 1.20 kg N ha"'yr ' Barsdate & Alexander, 1975;Chapin & Bledsoe, 1992;Hobara, 2006 . Together, these numbers suggest that total biological N2-fixation input for the landscape study area at Daring Lake is approximately twice the amount of N deposited via atmospheric deposition.…”

Ecological Dynamics II: The Influences of Vertebrate Herbivory on Ecological Dynamics in Wetland Ecosystems

“…As a result of the extra N and the induced re-growth, Puccinellia had much higher N concentrations in its tissues throughout the grazing season and thus better foraging quality, and more N was taken up by the grazed compared with the ungrazed vegetation (Cargill and Jefferies 1984). Additionally, the grazed swards stayed short and more open, leaving space for mats of N-fi xing cyanobacteria, an important N source in Nordic environments (Barsdate and Alexander 1975). This extra nitrogen input into the system might partly compensate for N lost through volatilisation, incorporation into the growing goslings, or through export of faecal material after fl ooding in August Jefferies 1985, 1989).…”