Graduate Defense: 'Low photosynthesis of treeline white spruce is associated with limited soil nitrogen availablity in northwest Alaska,' June 5

Tuesday, June 5, 2 p.m.
ConocoPhillips Integrated Science Building, Room 105A

Robert McNown, biological sciences M.S. candidate, will defend his graduate thesis, based on research done near the Arctic treeline, on June 5. The graduate committee will be Bjartmar Sveinbjornsson, Andrew Kulmatiski and Patrick Sullivan. This event is open to the public.

About the thesis:
Trees at the Arctic treeline have long been used to reconstruct past climates because of strong positive correlations between temperature and main stem radial growth. To improve understanding of the relationships between temperature and treeline white spruce performance, measurements of needle gas exchange, needle nutrition and soil nutrient availability were made in three habitats near the Arctic treeline: Riverside Terrace, Hillslope Forest and Treeline.

Photosynthesis, needle nitrogen and soil nitrogen availability declined from the terrace to the forest to the treeline. Low nitrogen availability at the treeline was likely a consequence of cold soils that limit microbial activity. Soils at the treeline were colder than the terrace during the growing season and colder than the forest in winter, when the treeline maintains a shallow snowpack.

Results suggest effects of temperature on soil nitrogen availability may be more important than direct effects of temperature on tree growth at the Arctic treeline.

For more information, visit the Department of Biological Sciences website.