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University of Michigan Biological Station

The University of Michigan Biological Station (UMBS) was founded in 1909.

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Quantifying inter-species differences in root hydraulic properties

Project Abstract: 
Root systems act as the gateway for water and nutrients to pass from the soil into the plant vascular system. Though the importance of below-ground water uptake processes has long been recognized, treatment of these processes in land surface models has been largely limited to empirical formulations based on biomass profiles. Recent model advances have improved the three-dimensional representation of root systems in hydrological models, but the parameterization of root hydraulic properties remains a source of significant uncertainty. This project focuses on measuring root hydraulic conductivity for dominant tree species and other relevant ecophysiological properties. These measurements will support modeling efforts and improve projections of forest hydrology under changing climate.
Investigator(s): 
Years Active: 
2017
Methods: 
For each study species, branching roots (5-10 cm deep) will be traced from the stem and excised. Fine roots (< 2 mm) will be dyed in methylene blue solution for 8-24 hours and then scanned for later image processing. Images will be analyzed using the IJRhizo extension for the ImageJ program for branching order, branching angles, interbranch distance, and root diameter distribution. Coarse roots will be used to determine xylem vessel length and xylem vessel density using optical microscopy. The xylem vessels will be stained by forcing dye through the segment. Small cross-sections will excised from the segment and fixed on plates for later imaging at our home lab. Unbranching or sealed root segments of 5-10 mm diameter will be selected from previously excised branches. Root axial hydraulic conductance will be measured by inducing a pressure differential across the segment and monitoring the flow of 0.1M KCl using a pressure differential sensor meter (Omega PX26-005GV). Conductance will be normalized by the branch dimensions to provide the root hydraulic conductivity. The response of conductivity to water stress will be determined by the pressure sleeve and bench dehydration methods. Measurements will be spread across the growing season to coordinate with collaborators who will be conducting research at the site
Funding agency: 
UMBS Student Research Funding