Amanda Young

Université de Sherbrooke
Postdoctoral fellow candidate

Supervisor: Mark Vellend
Start: 2017-03-06
End: 2019-03-07
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Between snow and shade: the importance of the timing of the high light period on the forest floor
The timing of spring snowmelt and canopy leaf out, from bud burst to canopy filling, has an important role on understory plant communities. The timing of full canopy expansion over the past 50 years in the northeastern forest has increased by 1.1 days per decade, while date of snow melt has occurred 2.6 days per decade. Increased temps cause an earlier onset of canopy leaf out thus reducing the spring high light period that ephemerals and summer green plants typically rely on for a substantial portion of their carbon accumulation. Post canopy leaf out only a small portion of light (<10%) reaches the forest floor, the reduction in light induces earlier leaf senescence of many ephemeral species. This comes in part due ephemerals inability to adjust to the new environment; instead they maintain high photosynthetic demands. Summer green species and tree seedlings typically emerge during the spring light phase but are able to adapt to the low irradiance conditions under the canopy. This research aims at examining the importance of the high light period on understory vegetation through observations and experimentation. The typical length of the period of high light will be examined using satellite imagery to classify when snow melts and the canopy trees leaf out. The timing of snow melt will be examined through a snow manipulation study where snow will be added and removed from locations where we planted ephemerals. Lastly, an experiment manipulating the timing of canopy leaf out will be conducted on spring ephemerals, summer green and tree seedlings across an elevation gradient. Collectively, this research will help understand the impacts of climate change on the forest understory through understanding the impacts of the timing of snow melt and canopy expansion in the spring.


light environment, spring ephemeral, range limits


1- Species and site differences influence climate-shrub growth responses in West Greenland
Young, Amanda B., David A. Watts, Alan H. Taylor, Eric Post
2016 Dendrochronologia

2- Geometrid Moth Outbreaks and their Climatic Relations in Northern Sweden
Young, Amanda B., David M. Cairns, Charles W. Lafon, Jon Moen
2014 Arctic, Antarctic, and Alpine Research

3- Landscape-scale modeling of reference period forest conditions and fire behavior on heavily logged lands
Maxwell, R. Stockton, Alan H. Taylor, Carl N. Skinner, Hugh D. Safford, Rachel E. Isaacs, Catherine Airey, Amanda B. Young
2014 Ecosphere

4- Comparing two methods for aging trees with suppressed, diffuse-porous rings (Betula pubescens ssp. czerepanovii)
Cairns, David M., Charles W. Lafon, Michelle F. Mouton, Rachel L. Stuteville, Amanda B. Young, Jon Moen
2012 Dendrochronologia

5- Dendroclimatic relationships and possible implications for mountain birch and Scots pine at treeline in northern Sweden through the 21st centuryThis article is a contribution to the series Tree recruitment, growth, and distribution at the circumpolar forest–tundra transition.
Young, Amanda B., David M. Cairns, Charles W. Lafon, Jon Moen, Laura E. Martin
2011 Canadian Journal of Forest Research

6- Dendrochronological dating of coal mine workings at the Joggins Fossil Cliffs, Nova Scotia, Canada
Quann, Sarah L., Amanda B. Young, Colin P. Laroque, Howard J. Falcon-Lang, Gibling R. Martin
2010 Atlantic Geology

7- Influences of Animal Activity on Treeline Position and Pattern: Implications for Treeline Responses to Climate Change
Young, Amanda, Jon Moen, Charles Lafon, David M. Cairns
2007 Physical Geography