Date of Award


Degree Type


Degree Name

Master of Science




Dr. Hugh Henry


Both climate warming and atmospheric nitrogen deposition are predicted to alter plant productivity and species composition over the next century; however, the extent to which their effects may interact is unclear. I measured plant productivity and species composition in response to warming (winter-only or year-round) and nitrogen in a temperate old field. I used shoot allometric relationships and spectral data to estimate productivity non-destructively, and sampled root biomass destructively, throughout two growing seasons. In 2007 there were no treatment effects on plant growth. However, in 2008, both warming and nitrogen addition increased aboveground productivity, and these effects were additive, resulting in an approximate doubling in aboveground plant biomass. Warming increased belowground biomass but no nitrogen effect was evident. Conversely, nitrogen addition increased plot greenness but greenness did not respond to warming. My results do not support the hypothesis that warming-induced changes to soil freezing dynamics over winter reduce plant productivity.



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