HR: 0800h
AN: H31G-0741    [Abstracts]
TI: Long term adjustment of canopy root depth and strength: Implications catchment hydrology and slope stability
AU: * Hales, T C
EM: tristramhales@gmail.com
AF: Cardiff University, School of Earth, Ocean and Planetary Sciences, Main Building, Park Place, Cardiff, CF10 3YE, United Kingdom
AU: Taehee, H
EM: h7666@email.unc.edu
AF: University of North Carolina, Department of Geography, Saunders Hall, CB# 3220, Chapel Hill, NC 27599, United States
AU: Band, L
EM: lband@email.unc.edu
AF: University of North Carolina, Department of Geography, Saunders Hall, CB# 3220, Chapel Hill, NC 27599, United States
AU: Vose, J
EM: jvose@fs.fed.gov
AF: USDA- Forest Service, 3160 Coweeta Lab Road, Otto, NC 28763, United States
AB: The species composition of southern Appalachian forests is changing rapidly due to fire suppression, residential expansion and introduced parasites, such as the woody adelgid. Changes in the distribution and age of tree and understory species cause changes in rooting characteristics and therefore the stability of slopes. Roots increase soil cohesive strength and fail in tension during debris flows. The amount of root reinforcement to the soil mass is dependent on the number, size and tensile strength of the roots. We have characterized how changes in the composition of southern Appalachian forests, particularly the expansion of Rhododenron maximum due to fire suppression, may affect the potential for slope failure. We measured the vertical distribution and tensile strength of roots for fifteen individual trees and two mixed species locations in the Coweeta Hydrological Laboratory, North Carolina. The individual pits were chosen to capture variations in species (10 species total), topographic position (nose, side slope, hollow), and age (a range of DBH between 5 cm and 60 cm). Root tensile strengths from different hardwood species were very similar, while rhododendron, a woody shrub, has considerably weaker roots. Roots are concentrated close to the soil surface (at least 70% of biomass occurs within 50 cm of the surface) and variations in this pattern occur primarily as a function of age. R. maximum roots are shallower and weaker than tree roots, which when coupled with low transpiration rates, lowers the total cohesive strength and makes them susceptible to high pore pressure events. We have investigated the potential for mapping R. maximum based on the ratio of near-infrared to red within leaf-off color infrared images. When we combine the remotely-sensed distribution of R. maximum with the root cohesion data from individual pits, we can produce a realistic spatial distribution of root cohesion for southern Appalachian forests. The spatial distribution of root cohesion can be coupled with an eco-hydrological model (we use the Regional Hydro-Ecologic Simulation System (RHESSys)) to understand how coupled changes between hydrology and ecology affect the slope stability of southern Appalachian forests.
DE: 1803 Anthropogenic effects (4802, 4902)
DE: 1810 Debris flow and landslides
DE: 1813 Eco-hydrology
DE: 1816 Estimation and forecasting
SC: Hydrology [H]
MN: 2007 Fall Meeting