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Ecophysiology of the cyanolichen Lobaria oreganaAntoine, Marie E. 30 October 2001 (has links)
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
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