ANTOINE, MARIE E.* AND WILLIAM E. WINNER. Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR 97331. - Analysis of nitrogen, carbon, and water use by Lobaria oregana, a cephalodiate lichen at the Wind River Canopy Crane site.
Lobaria oregana is a nitrogen-fixing cephalodiate lichen that
is abundant in old-growth forests west of the Cascades. Although this
lichen is believed to be an important source of nitrogen input to the
old-growth ecosystem, few studies have measured in situ rates of
nitrogen-fixation for Lobaria oregana. In this project, we are
using the Wind River Canopy Crane Research Facility to sample
Lobaria oregana thalli growing in the canopy, thereby measuring
and linking instantaneous rates of nitrogen-fixation, photosynthesis,
and water content. We will assess these physiological processes at
regular intervals throughout the year. Additional samples are
collected and brought back to the lab for analysis of thallus nitrogen
content, and for rehydration experiments to determine the lichen's
capacity for recovering metabolism following desiccation. We are using
the Acetylene Reduction Assay as a surrogate measurement of
nitrogen-fixation capacity, and net photosynthesis is measured with a
Li-Cor 6400 Portable Photosynthetic Meter. Initial measurements made
in December, 1999 indicated levels of nitrogen-fixation and
photosynthesis for Lobaria oregana that were below detectable
thresholds. Using the physiological data derived from this project,
meteorological data from the WRCCRF, and lichen biomass data available
from earlier studies, we will determine seasonal trends of metabolic
activity in Lobaria oregana, and estimate its potential
contribution of fixed nitrogen to the forest.
Key words: cephalodiate lichen, Lobaria oregana, nitrogen fixation, Wind River Canopy Crane Research Facility