“What These Numbers Actually Mean”

By Aleta Wiley
REU Summer Proctor

Yesterday, I tagged along with three students working on a collaborative project who were out, collecting data in the field, for the first time this summer without their research mentors. It is amazing how much they all have learned in less than two weeks here at Harvard Forest! For their project, they are studying changes in soil respiration under varying scenarios. Yesterday, they were working in the “dirt plots” – a series of 21 plots (each about 10 x 10 ft) in the Tom Swamp Tract of the Forest. The plots had been subjected to different treatments; for example, some had all of the detritus (dead, organic matter, such as leaves and branches) removed while others did not.

In addition to measuring soil temperature and moisture in each plot, Maya, Joanna, and Claudia are using a Portable Photosynthesis System (“the heavy machine”, as it is informally named) to record the soil respiration, or the rate that CO2 is released from the soil. Based on papers they have read in the last two weeks, they have learned that plots with detritus usually have higher rates of soil respiration since the detritus is actively decomposing.

Using GIS, these students already have determined 58 different combinations of soil type and tree stand in the Prospect Hill Tract at the Forest. Next week, they will be measuring soil respiration in each of these sites in order to learn more about how these different factors affect soil respiration. They are also learning how these questions relate to larger issues, such as climate change – both how global warming might affect soil respiration under warming conditions and also how soil might help mitigate climate change through carbon sequestration (holding CO2 in the soil without releasing it into the atmosphere).

After taking numerous biology, natural resource management, and ecology courses, these girls were finally seeing ecological processes happening right before their eyes. As Joanna said, “That’s what’s so great about using this machine out in the field and not just reading a paper with piles of data – I’m actually starting to understand what these numbers actually mean”.