For the past few weeks, the Geology of Soils class here has been attempting to characterize and describe the soils in the Arboretum. We have been digging (occasionally with frustratingly small shovels) our own little pits sometimes nearly 2 meters deep to view the various profiles around the arb. The experience has been continually surprising. A soil in one location can be entirely different than a soil a few hundred meters away!
The thick, dark layers of soil commonly seen in the arboretum are characteristic of prairie soils, or Mollisols, all over the world. These dark layers are built from thousands of years of accumulation and decomposition of prairie grasses and other plants. Unique to Mollisols is the incredibly high concentration of roots even down to depths of eight feet or more. Prairie grasses are the powerhouses of forming rich, fertile soil. The high organic matter concentrations forming the upper layers of a Mollisol are distinctly beneficial in their accumulation and retention of nutrients relevant to growing our food. As a short drive (or even walk) from campus will confirm for you, these soils are among the most agriculturally important in the world. All that said, by looking at the pits from our class, you might not necessarily see the similarities because of the enormous variation in thicknesses, material, color, etc. While we as humans strive to homogenize and label things such as soils the vegetation, topography and geology of the arboretum do little to fulfill our goals. But wouldn’t it be a boring world if all the soil was the same?
So get out in the arb and go on a scavenger hunt for our pits, there should be enough soil for everyone.
Griffin Williams ‘12
for the Cole Student Naturalists