Nitrogen cycling in s subarctic Alaskan watershed: the role of lichens and the potential effects of acid deposition

Thesis/Dissertation · Thu Jan 01 04:00:00 EST 1987

OSTI ID:6830613

Gunther, A J

It has been hypothesized that the loss of nitrogen-fixing lichens due to stress from air pollution could have adverse effects upon nitrogen availability, and thus primary productivity, in some ecosystems. There is general agreement, however, that the ecological role of these lichens has not been sufficiently well defined to determine whether they are keystone species. The objectives of this study were: (1) to examine the importance of nitrogen-fixing lichens to the nitrogen cycle in the drainage of Brooks Lake, Alaska, a nitrogen-limited nursery lake for the commercially important sockeye salmon (Oncorhychus nerka); and (2) to investigate the sensitivity of nitrogen fixation by lichens in this ecosystem to acid deposition. Biological nitrogen fixation was found to be the major source of new nitrogen to the Brooks Lake drainage. The rate of fixation is approximately 3 kg N/ha-yr, which compares to 0.3 kg N/ha-yr in precipitation and only 0.02 kg N/ha-yr in returning adult salmon. Cyanophillic lichens contribute about 0.21 kg N/ha-yr. The low levels of nitrogen in precipitation, combined with a lack of nitrogen-fixation activity in open lake waters, indicates that nitrogen in tributary streams is the major source of new nitrogen for Brooks Lake. The measurements of nitrogen inputs, along with estimates of other stocks and flows of nitrogen, were used to construct a steady-state box model of the nitrogen cycle in the drainage.

• Research Organization: California Univ., Berkeley (USA)
• OSTI ID: 6830613
• Country of Publication: United States
• Language: English

Related Subjects

500200* -- Environment
Atmospheric-- Chemicals Monitoring & Transport-- (-1989)
520200 -- Environment
Aquatic-- Chemicals Monitoring & Transport-- (-1989)
54 ENVIRONMENTAL SCIENCES
ACID RAIN
ALASKA
ALGAE
AQUATIC ECOSYSTEMS
ATMOSPHERIC PRECIPITATIONS
BIOLOGICAL EFFECTS
ECOSYSTEMS
ENVIRONMENTAL IMPACTS
FEDERAL REGION X
FUNGI
LICHENS
NITROGEN FIXATION
NORTH AMERICA
PLANTS
RAIN
USA
WATERSHEDS