Piezometer Sampling. More images available at http://mnspruce.ornl.gov/.
Credit or Source: Office of Biological and Environmental Research of the U.S. Department of Energy Office of Science. science.energy.gov/ber/
U.S. DOE. July 2015. Spruce and Peatland Responses Under Climatic and Environmental Change. U.S. Department of Energy Office of Science. (PDF)