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The Smallest of the Small, a Step into the Unknown

Thursday, July 13, 2017, by Colleen Smith
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[Recording data as my research partner Kalaina is taking measurements. Photo by Jill Fusco]7:00 am Snooze

7:10 am Snooze

7:30 am Wake up, pull on cargo pants, lace up boots

8:10 am Breakfast

9:00 am Walk onward into the lair of the mosquitos with my net on and trustee meter stick in hand

This is more or less how I’ve begun each of my days here at Harvard Forest. I have a schedule, I know what I have to get done, and I do it (gladly). I never in my life imagined that I would end up here, and when I got here I could have never imagined what I would spend my summer doing. I was initially hired on to study soil microbiology, but in a strange and fortuitous turn of events I ended up where I am now.  While I am endlessly fascinated by soil and all it has to offer, trees are my specialty. I’ve spent the past three years of my life as a forestry major on the Redwood Coast of Humboldt, CA surrounded by some of the world’s tallest trees. I knew when I joined this project that I would be working with trees relatively smaller than what I am used to, but what I didn’t know at the time was exactly how small these trees would be. To state it plainly, most of the trees I work with could easily be hidden beneath a fern. In fact, my work this summer has been entirely focused on seedlings under 1 cm in diameter.

[The majority of trees we measure are no larger than this small seedling. Photo shows tags used to track individual growth over time. Photo by Jill Fusco] While these seedlings are nowhere near the size of the looming giants I’m used to, they hold an incredible amount of research potential. When conducting censuses, researchers often only identify and measure trees over 1 cm in diameter. This leaves the most abundant size class of trees as one of the least researched. For the longest time I simply could not understand why no one had thoroughly conducted this research before, but it didn’t take too many days of field work for me to finally understand. Collecting the data is super tough! Merely locating each of these trees within our plots has proven to be a challenge at times, not to mention the fact that some plots can hold over 200 individuals. It’s our job to tag, measure, and locate each individual within our research area. This can sometimes take hours, and since each plot was selected randomly throughout the Harvard Forest Megaplot my research partner Kalaina and I often end up walking several miles per day. The Mega-plot is a 35-hectare (500m x 700m) plot that was established in 2014. Upon completion, each woody stem over 1 cm in diameter was tagged, GIS-mapped, and measured with measurements set to be taken every five years. The plot was created as a forest dynamics monitoring plot in the Smithsonian ForestGEO, and is one of the first temperate sites to be added to the observatory.  I’ve calculated it, and since beginning the field work I’ve personally walked over 200 miles and we’ve collectively measured well over 1,000 seedlings. We’re nearly finished censusing our plots, and my time crouching among the seedlings is almost over. While tedious at times, the work is exhilarating and incredibly rewarding. There is nothing quite like the feeling of collecting data that hasn’t been collected before. I feel like I’m actually contributing something to science, and that feels really cool!

[A beautiful Luna Moth that greeted us after a particularly long and difficult field day. Photo by Colleen Smith]If I had to name one truly great thing about crouching between ferns for hours at a time it would have to be the wildlife sightings. It has been incredible to watch nature come to life when it doesn’t think I’m there to see it. There are endless beauties to be seen deep within the understory of New England forests, and I am always going to cherish the perspective that I’ve gained by working at this level. 

At this point you’re probably wondering what exactly I’m doing with these incredibly small trees. Well, in the most general of terms I’m using our data to fill in gaps in the literature. We are focusing on two main relationships in nature that are fairly well understood; the relationship between size and abundance, and the relationship between size and energy. The first relationship asserts that as individuals increase in size, they decrease in abundance. This can be seen across all forms of life. There are more mice in the world than there are elephants, just as there are more seedlings in the world than there are large - trees. The second relationship describes the use of energy based on individual body size. If we were to take the example of mice and elephants again it would be easy to understand that the individual mouse consumes far less food than an elephant on any given day. We can think of food consumption as a form of energy consumption and from there we see that individuals with a larger body size require more energy to grow. These relationships inform various aspects of ecology and are the basis for a much more complex idea of energy equivalence. This idea essentially asserts that the product of these two relationships provides evidence that collectively small trees use the same amount of energy as larger trees. However, these relationships have been formed without taking into account trees that are under 1 cm in diameter. That’s where our data comes in to fill the gap.

[A visual explanation of the idea of energy equivalence. Photo by Colleen Smith]Our work at Harvard Forest in mainly focused on growth, and for the purpose of our study energy consumption can be measured as physical growth. But where are these seedlings getting their energy? What is their food? While numerous other biotic and abiotic factors contribute to the growth of plants we decided to focus on one limiting factor in particular – PAR: Photosynthetically Active Radiation, also known as good wholesome sunlight. With the size of trees we are working with we decided that light availability would be a strong limiting factor of growth. Using a hemispherical camera we are able to determine canopy openness and in turn the amount of sunlight reaching the seedlings. We hypothesize that if light is limited, then growth will decrease despite the assumption of energy equivalence. So, I’m currently spending my days running around with a camera in the Megaplot, lens pointed skyward, and crouching once again- this time to stay out of the photo.

Colleen Smith is a rising Senior at Humboldt State University where she majors in Forestry with an emphasis in Forest Soils and a minor in Geospatial Analysis. Colleen has many academic interests and wishes to pursue each of them if only she had the time.