Nitrogen fixation by lichens in a subarctic Alaskan watershed

Journal Article · · Bryologist; (USA)

DOI:https://doi.org/10.2307/3243946· OSTI ID:6710398

Gunter, A J ^[1]

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1. Aquatic Habitat Institute, Richmond, CA (USA)

It has been postulated that Arctic haze or acid deposition could disrupt the nitrogen cycle of ecosystems by affecting lichens, which are known to be sensitive to air pollutants. Recent research indicates, however, that nitrogen fixation by lichens may be less sensitive to acid deposition than previously supposed. Measurements of lichen biomass and nitrogenase activity were used to estimate the annual nitrogen fixation by lichens in the watershed of nitrogen-limited Brooks Lake, Alaska. These measurements, when combined with the areal extent of different habitats as determined from satellite photos and conversation ratios relating short-term acetylene reduction measurements to long-term nitrogen fixation rates, produced a best estimate for nitrogen fixed by lichens of 0.1 kg N ha{sup {minus}1} yr{sup {minus}1}. The uncertainty in this calculation, however, suggests a more reasonable estimate of nitrogen fixation by lichens to be a range of 0.04-0.21 kg N ha{sup {minus}1} yr{sup {minus}1}, although in a moist habitat where nitrogen-fixing lichens are abundant they may contribute up to 0.94 kg N ha{sup {minus}1} yr{sup {minus}1}. Even in this ecosystem remote from anthropogenic influences, the contribution of fixed nitrogen by lichens is less than that from precipitation and an order of magnitude below nitrogen fixed by Alnus trees, implying that at the watershed level lichens will only be important contributors of fixed nitrogen in moist, remote ecosystems where the abundance of nodulated plants is simple.

• OSTI ID: 6710398
• Journal Information: Bryologist; (USA), Journal Name: Bryologist; (USA) Vol. 92:2; ISSN 0007-2745; ISSN BRYOA
• Country of Publication: United States
• Language: English

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