This thesis consists of three manuscripts describing ecophysiological research on
the cyanolichen Lobaria oregana. The first manuscript includes a re-evaluation of
the assumptions underlying past estimates of N fixation by this species and
provides an estimate of annual N fixation at the Wind River Canopy Crane
(WRCC). Based upon litterfall data, canopy biomass data, N content of lichen
tissue, and published growth rates, L. oregana fixes 0.4-1.6 kg N₂ ha⁻¹ yr⁻¹. The
second manuscript presents a series of physiological response curves and a model
of N fixation by L. oregana. Temperature is the most important parameter
controlling nitrogenase activity in hydrated thalli. The model is used to predict
annual N fixation at the WRCC and at the H.J. Andrews (HJA) Experimental
Forest. Lobaria oregana fixes 1.4-1.8 kg N₂ ha⁻¹ yr⁻¹ at the WRCC, and low winter
temperatures often inhibit nitrogenase activity. Temperatures at the HJA are
slightly warmer during the winter, and L. oregana fixes 2.6-16.5 kg N₂ ha⁻¹ yr⁻¹
depending on its stand-level biomass. The third manuscript investigates the effects
of thallus water content, light, and temperature on CO₂ exchange in L. oregana.
This species shows a typical photosynthetic response upon rehydration, and like
other lichens it becomes light-saturated at low PAR levels. Positive net
photosynthesis in L. oregana occurs only between 1-12°C. High respiration rates
prevent carbon gain at warmer temperatures. The temperature constraints on carbon
gain and nitrogen fixation may explain some of the landscape distribution patterns
of L. oregana. / Graduation date: 2002
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/29326 |
| Date | 30 October 2001 |
| Creators | Antoine, Marie E. |
| Contributors | Winner, William E. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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