Date of Award


Degree Type


Degree Name

Master of Science




Dr. Hugh Henry


In northern temperate regions, climate warming is predicted to increase the

frequency of soil freeze-thaw cycles (FTC) and reduce plant cold acclimation in late fall and early spring. To test if FTC inhibit plant nitrogen (N) uptake, I exposed Poa

pratensis tillers to FTC in late fall, mid winter, and early spring, then used a 15N tracer to assess N uptake from a hydroponic solution. To assess the direct effects of FTC on plant growth, I exposed P. pratensis tillers to FTC on the same dates, then measured plant biomass the following summer. Freezing of short duration at -10 °C and longer freezing a t - 5 °C in fall and spring decreased N uptake significantly. Plant growth decreased the most after spring FTC. Reduced plant cold acclimation in fall and spring must thus be coupled with extreme soil freezing to hinder plant N acquisition and growth.



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