Meeting Abstract
88.3 Monday, Jan. 6 14:00 Boundary layer turbulence induces penetration of eddies into rodent burrows PINSHOW, B*; ZUCKER, D; BRICKNER-BRAUN, I; TURNER, JS; BERLINER, P; Ben-Gurion University of the Negev; Ben-Gurion University of the Negev; Ben-Gurion University of the Negev; SUNY-ESF, Syracuse; Ben-Gurion University of the Negev pinshow@bgu.ac.il
Gas exchange between burrows and the atmosphere occur by its convection through the burrow and diffusion through burrow and soil. Wind-induced convection is most commonly thought of as unidirectional and caused by pressure gradients; air flowing at the surface enters a burrow through one entrance and leaves it through another. This model is based on the notion of laminar air flow at the surface, while in reality the surface is rough, inducing random vertical and horizontal velocity components resulting in turbulent flow and irregular gusts called eddies. Initially, we investigated the pattern of air movements through a two-entranced artificial burrow by a pulse-chase experiment using butane as a tracer and found that the gas left the burrow, alternating between entrances. We then tested the hypothesis that the underlying mechanism for the ventilation of burrows is by penetration of eddies that convey atmospheric air to the depths of the burrow from both entrances. We found that burrow ventilation occurs by several mechanisms, the importance of which varies depending on ambient conditions, especially wind speed (u). At u > 2 m/s, burrows are likely to be well ventilated by eddies. Although eddies do not penetrate directly into parts of the burrow that branch out from the main tunnels, such as a nest chamber, we suggest that these parts are also well ventilated due to the gas concentration gradients maintained between them and main tunnel. This gradient facilitates the diffusion of CO2 into the main tunnel where it is removed by eddies. At low wind speeds gas diffusion through the burrow and into the soil may become an important mechanism for ventilation.
