HR: 15:30h
AN: NS44A-01    [Abstracts]
TI: Electrical Imaging of Roots and Trunks
AU: * al Hagrey, S
EM: sattia@geophysik.uni-kiel.de
AF: University of Kiel, Institute of Geosciences, Otto-Hahn-Platz 1, Kiel, 24118 Germany
AU: Werban, U
AF: University of Kiel, Institute of Geosciences, Otto-Hahn-Platz 1, Kiel, 24118 Germany
AU: Meissner, R
AF: University of Kiel, Institute of Geosciences, Otto-Hahn-Platz 1, Kiel, 24118 Germany
AU: Ismaeil, A
AF: University of Kiel, Institute of Geosciences, Otto-Hahn-Platz 1, Kiel, 24118 Germany
AU: Rabbel, W
AF: University of Kiel, Institute of Geosciences, Otto-Hahn-Platz 1, Kiel, 24118 Germany
AB: We applied geoelectric and GPR techniques to analyze problems of botanical structures and even processes, e.g., mapping root zones, internal structure of trunks, and water uptake by roots.
The dielectric nature of root zones and trunks is generally a consequence of relatively high moisture content. The electric method, applied to root zones, can discriminate between old, thick, isolated roots (high resistivity) and the network of young, active, and hydraulically conductive zones (low resistivity). Both types of roots show low radar velocity and a strong attenuation caused by the dominant effect of moisture (high dielectric constant) on the electromagnetic wave propagation. Single root branches could be observed in radargrams by their reflection and diffraction parabolas.
We have perfected the inversion method for perfect and imperfect cylindrical objects, such as trunks, and developed a new multielectrodes (needle or gel) ring array for fast applications on living trees and discs. Using synthetic models we tested the technique successfully and analyzed it as a function of total electrode number and configuration. Measurements at a trunk show a well established inverse relationship between the imaged resistivity and the moisture content determined from cores. The central resistivity maximum of healthy trees strongly decreases toward the rim. This agrees with the moisture decrease to the outside where active sap flow processes take place. Branching, growth anomalies (new or old shoots) and meteorological effects (sunshine and wind direction) lead to deviations of the concentric electric structure. The strongest anomalies are related to infections causing wet, rotting spots or cavities. The heartwood resistivity is highest in olive and oak trunks, intermediate in young fruit trees and lowest in cork oak trunks that are considered to be anomalously wet.
Compared to acoustic tomography our electric technique shows a better resolution in imaging internal ring structures where moisture is the most dominating factor. We conclude that our imaging resistivity technique is applicable for investigating or controlling the botanical and physical conditions of endangered trees (health inspection) and capable to monitor dynamic processes of sap flow if adequate tracers are used.
DE: 0400 Biogeosciences
DE: 0925 Magnetic and electrical methods
DE: 1875 Unsaturated zone
DE: 1894 Instruments and techniques
SC: Near-Surface Geophysics [NS]
MN: 2005 Joint Assembly