Nitrogen Inputs by Associative Cyanobacteria across a Low Arctic Tundra Landscape

作者：Stewart Katherine J^*; Coxson Darwyn; Grogan Paul

来源：Arctic Antarctic and Alpine Research, 2011, 43(2): 267-278.

DOI：10.1657/1938-4246-43.2.267

Available soil N is a key factor limiting plant productivity in most low arctic terrestrial ecosystems. Atmospheric N(2)-fixation by cyanobacteria is often the primary source of newly fixed N in these nutrient-poor environments. We examined temporal and spatial variation in N(2)-fixation by the principal cyanobacterial associations (biological soil crusts, Sphagnum spp. associations, and Stereocaulon paschale) in a wide range of ecosystems within a Canadian low arctic tundra landscape, and estimated N input via N(2)-fixation over the growing season using a microclimatically driven model. Moisture and temperature were the main environmental factors influencing N(2)-fixation. In general, N(2)-fixation rates were largest at the height of the growing season, although each N(2)-fixing association had distinct seasonal patterns due to ecosystem differences in microclimatic conditions. Ecosystem types differed strongly in N(2)-fixation rates with the highest N input (10.89 kg ha(-1) yr(-1)) occurring in low-lying Wet Sedge Meadow and the lowest N input (0.73 kg ha(-1) yr(-1)) in Xerophytic Herb Tundra on upper esker slopes. Total growing season (3 June-13 September) N(2)-fixation input from measured components across a carefully mapped landscape study area (26.7 km(2)) was estimated at 0.68 kg ha(-1) yr(-1), which is approximately twice the estimated average N input via wet deposition. Although biological N(2)-fixation input rates were small compared to internal soil N cycling rates, our data suggest that cyanobacterial associations may play an important role in determining patterns of plant productivity across low arctic tundra landscapes.

• 出版日期2011-5