We have been using the minirhizotron technique and other direct observational methods for studying root growth, turnover, and production. The minirhizotron method involves the use of a specialized video camera system for nondestructive observation of root dynamics at the interface between a buried clear plastic tube and the surrounding soil. The minirhizotron technique has many advantages as compared to traditional soil coring methods. The development of the minirhiozotron method has marked the new beginning of root research in ecology. The minirhizotron technique has been recommended to be the standard method for all long-term ecological research sites in the U.S.
Root demography including root density, growth rate, death rate, and age structure can be assessed by minirhizotron imaging. Minirhizotron tubes, made of 5-cm diameter clear polycarbonate plastic, are installed into the soil before measurements will take place. Images of a narrow strip (18 mm wide) of the upper soil-tube interface can be captured and digitized incrementally using an special video camera digitizing system with an indexing handle. All the image files obtained during one sampling period are transferred to CD-ROM disks for long-term storage and later analysis. The image changes through time at each exact tube position are recorded during a certain time period, and analyzed using the ARCOS computer software. ARCOS superimposes the images taken at different time steps and analyzes for changes. The software is able to recognize new roots, previously observed roots, and roots that have disappeared with respect to the previous image from the same position. The computer program includes a mouse-tracing module and an auto-comparison module with built in flexibility in parameter settings. Obtained images are analyzed for root density, growth rate, death rate, and age structure.
