Concluding remarks

My thesis has provided considerable insight into the transient versus multiyear effects of soil freezing on a grass-dominated old field ecosystem, and how projected increases in atmospheric N deposition may alter plant and soil responses. I found that soil freezing can increase losses of N currently in the system, but this only occurred during the winter, while summer N losses resulted from the inability of plants to retain N being added to the system (i.e. simulated N deposition). Furthermore, I found that while soil freezing and atmospheric N deposition can have a considerable impact on plant productivity over multiple years, in general, outside of very short term responses, changes in soil properties such as soil inorganic and organic N were minimal, and did not correspond with the aboveground changes observed over the longer term. However, it is possible that more drastic changes in plant relative species abundances in the future could lead to changes in soil responses beyond those observed over the time course of my experiments. Therefore, extreme soil freezing events can have short term impacts on soil N cycling with long term implications for plant productivity and species abundances.

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Appendices

Dec Jan Feb Mar

T e m p e ra tu re ( ο C ) -30 -20 -10 0 10 20 30 Control Air temp SR SR completed SR = snow removal

Appendix A: Mean air temperature and soil temperature under ambient snow and snow removal plots from early December 2011 to mid-March 2012 at 5 cm soil depth (nitrogen treatments had no effect on winter soil temperature and thus were pooled).

Appendix B: Gravimetric soil moisture (g water/g soil dw-1) for each treatment combination during the first (2011) and second (2012) year in the snow removal experiment. Means within columns for each year are not significantly different if they share a common lowercase letter (Tukey's test, P <0.05).Parentheses indicates standard error (n=6).

February Snowmelt May June October

First year Ambient 0.31b (0.03) 0.33a (0.02) 0.40a (0.03) 0.26a (0.02) 0.33a (0.03) Ambient +N 0.34b (0.03) 0.38a (0.02) 0.36a (0.03) 0.30a (0.03) 0.31a (0.03) Snow removal 0.67a (0.08) 0.34a (0.03) 0.46a (0.07) 0.27a (0.01) 0.34a (0.01) Snow removal + N 0.73a (0.04) 0.35a (0.02) 0.41a (0.02) 0.23a (0.01) 0.31a (0.01) Second year Ambient 0.37a (0.02) 0.35a (0.02) 0.29a (0.02) 0.20a (0.01) 0.27a (0.01) Ambient +N 0.37a (0.02) 0.34a (0.02) 0.34a (0.02) 0.18a (0.01) 0.28a (0.01) Snow removal 0.41a (0.04) 0.35a (0.01) 0.32a (0.01) 0.20a (0.01) 0.28a (0.01) Snow removal + N 0.38a (0.02) 0.34a (0.01) 0.31a (0.02) 0.19a (0.01) 0.31a (0.04)

Appendix C: Permission to reproduce published material

A version of Chapter 2 was published in Ecosystems. As per Springer-Verlag copyright policy, manuscript reproduction for the purpose of thesis publication was obtained by acquiring an electronic republishing permit, license ID 3215381155731

Curriculum Vitae

Name: Mat Vankoughnett

Post-secondary Trent University

Education and Peterborough, Ontario, Canada

Degrees: 2005-2007 B.Sc. Environmental Science Queen’s University

Kingston, Ontario, Canada 2007-2009 M.Sc. Biology.

The University of Western Ontario London, Ontario, Canada

2009- current Ph.D. Biology

Honours and Karl Ivarson Soil Science Scholarship

Awards: 2010

University of Western Ontario Biology Department Travel Award, 2013

Society of Biology Graduate Students Member of the Year, 2013

Arthur D. Latornell Award of Merit, 2012

Graduate Student Teaching Award, 2011, 2012*, 2013* (*=nominated) Queen’s University Travel Award, 2009

Northern Scientific Training Program 2008, 2009

Related Work Experience

Guest Lecture:

The University of Western Ontario

Bio 2485 (Environmental Biology): Climate change, 2013 Bio 3445 (Community Ecology): Ecosystem stability, 2012

Teaching Assistant:

The University of Western Ontario Bio 3445 (Community Ecology), 2011-12 Bio 2485 (Environmental Biology), 2010-12 Bio 2483 (Ecology), 2009-10

Queen’s University

Bio 303 (Community and Ecosystem Ecology), 2008-09 Bio 243 (Statistics in Biology), 2007-08

Publications:

Vankoughnett, M.R., and H.A.L. Henry. Combined effects of soil freezing and N addition on losses and interception of N over winter and summer. Ecosystems (2013): 1- 10.

Vankoughnett M.R. and P. Grogan (in press). Plant nitrogen acquisition in low and tall birch tundra communities: A test of the snow-shrub hypothesis. Biogeochemistry.