|Halvorson, Jonathan - WASHINGTON STATE UNIV.|
|Gatto, Larry - DEPPARTMENT OF DEFENSE|
|Pannkuk, Chris - USDA FOREST SERVICE|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: April 1, 1999
Publication Date: N/A
Technical Abstract: Studies at Yakima Training Center (YTC), located in the cool, semi-arid shrub-steppe of central Washington, suggest freeze-thaw cycles (FT) reduce effects of soil compaction by military vehicles. However, we know little about the patterns of freezing or its effects over a single winter. We monitored soil freezing during winter 1997-1998 at YTC using electrical resistivity probes. We also measured bulk density, penetration resistance and steady-state runoff rates in recently tracked and untracked soils, before and after winter. Patterns of FT during winter of 1997-98 were similar in compacted and uncompacted soil near the surface. At greater depth, freezing did not occur in compacted soil, or occurred later than in uncompacted soil. The magnitude of diurnal cycles of FT was inversely correlated to soil depth, being most apparent at depths less than 13 cm. We observed no freezing below 30 cm. Surface bulk density was significantly higher in tank ruts than uncompacted soil but we observed no significant change during the winter. Similarly, soil penetration resistance was highest in compacted soil but decreased near the surface (4 cm) of tank ruts over winter. Steady-state runoff rates were greater in tank ruts than uncompacted soil and were slightly lower and more variable in May 1998 than during August 1997. Our data suggest compaction of surface soil is significantly ameliorated by FT cycles during the first winter after trafficking.