Thursday, August 14, 2014

Warmer Summers Benefit Red Spruce Trees



Despite having spent only a couple of seasons as a Field Instructor at Spruce nearly a decade ago, the spirit and ideals embodied in the place have been with me ever since. As a geographer I am particularly sensitive to the importance of place. In the years since my time at Spruce I have been fortunate enough to spend time in a number of spectacular places in the world, but West Virginia, and Spruce, remain solidly atop my list of favorites. This past spring I was happy to share this place with students from the biogeography course that I teach at Colgate University. 

 One of my favorite things to do as a science educator is to actually do science with my students. By this I mean that we use science to address questions that none of us, including me, know the answer to, as opposed to me simply explaining processes and concepts, or having the students completing a laboratory assignment that I know the answer to. In biogeography we focused on the distribution of life on earth (i.e. plants and animals). Perhaps more importantly, we try to understand how physical and biological things like temperature, precipitation, or the availability of food, impact where different kinds of plants and animals are located. The red spruce forests that adorn Spruce Knob and other mountaintops throughout Appalachia have a geographic distribution that is interesting to biogeographers, and we humans are in the midst of a large experiment involving global climate.

This has led me to wonder how these red spruce ecosystems might respond to climate change. Red spruce forests are restricted to mountaintops in Appalachia because they like relatively cool and moist conditions. Further north, in places like New England and eastern Canada you can find such forests at lower elevations. My initial hypothesis was that more southerly red spruce forests, in places like West Virginia or North Carolina, will not fare well as the climate warms. We intended to test this hypothesis on our visit by taking tree cores from the red spruce stand just next to the yurts to look at changes in growth over time. Most people have probably seen the annual growth rings that trees produce on a piece of firewood or a recently cut stump. Tree coring involves using what is essentially a hollowed out drill bit to extract a ‘tree core’ in order to be able to count the rings without damaging the tree. By measuring the width of the rings, and then comparing the widths to things like average summer temperature it is possible to figure out if trees are growing more or less in warm years.

We collected thirty cores from fifteen trees while at Spruce. The largest trees were between 95 – 100 years old. By comparing the widths of the tree rings with climate data we found that the trees have been growing more during warmer summers. This suggests that changes in climate have benefited these forests. In the forest we also noticed quite a few seedlings and saplings, indicating the trees are reproducing and germinating well. It is important to note that the apparent positive benefits of a warmer climate are not unlimited, that is continued warming may eventually be harmful to red spruce trees. But for the time being I am happy to say it appears that the forest at Spruce is doing well. I am also happy to report that, despite the long van ride, the students thoroughly enjoyed a weekend away from campus (and cell phone service!) doing science. I’m already looking forward to our next visit. 

Mike Loranty is an Assistant Professor of Geography at Colgate University and former TMI Field Instructor. For more information about his research, visit his site, http://mikeloranty.wordpress.com/.

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