Tuesday, November 6, 2007 - 10:30 AM
180-5
A Conceptual Model to Quantify Plant Root Induced Changes in Soil Hydraulic Conductivity and Water Retention.
Craig Scanlan, 35 Stirling Highway, University of Western Australia, U. of Western Australia, MO87, Crawley, WA 6009, AUSTRALIA and Christoph Hinz, 35 Stirling Highway, AUSTRALIA, Univ. of W. Australia, U. of Western Australia, MO87, Crawley, WA 6009, AUSTRALIA.
The root systems of plants modify the physical properties of the soil they occupy, which can lead to a change in soil hydraulic conductivity and water retention (hydraulic properties). Changes in hydraulic properties have not been modeled explicitly in response to the temporal growth and or decay of root systems. We developed a conceptual model that partitions the soil volume into either soil with or soil without roots, and use the capillary bundle approach to model the hydraulic properties of these partitions. In soil where roots are present we maintain the assumption that pores are cylindrical, however, we assume that roots are also cylinders that lie concentrically within these pore cylinders. We used the volume, capillary pressure and flow rate within an annulus to model the hydraulic properties of soil with roots present. The hydraulic properties of the combination of soil with and soil without roots present were found by summing the two.
Preliminary results show that the greatest effect of plant roots on the hydraulic properties of soil is in the near- to saturated range. In this range hydraulic conductivity and water content both decrease as the amount of live root mass increased, and vice versa. Other preliminary results show that amount of change in the modeled hydraulic properties is sensitive to root radii distribution, which suggests different temporal trends may be observed for different vegetation types. We will discuss the implications of these changes in soil hydraulic properties on water fluxes in the root zone.