Old logging practices linked to high erosion rates today

University of Oregon: Clear-cut logging and related road-building in the 1950s and 1960s in southern Oregon's Siskiyou Mountains disrupted soil stability and led to unprecedented soil erosion made worse during heavy rainstorms, report University of Oregon researchers.

While logging practices have improved dramatically since then, the damaged landscape -- the removal of low vegetation that helps to protect hillsides during fires and rain -- continues to pose a threat into the foreseeable future, said Daniel G. Gavin, professor of geography, and postdoctoral doctoral researcher Daniele Colombaroli.

Their research -- funded by the Swiss National Science Foundation and the UO -- involved the analyses of charcoal, pollen and sediment taken from 30-foot-deep cores drilled below Upper Squaw Lake in the Rogue River-Siskiyou National Forest. Their findings, which provide a look at the impacts of fires over the last 2,000 years, appeared online Oct. 18 in the Early Edition of the Proceedings of the National Academy of Sciences. The data, which provided for greater scrutiny than that of tree-ring records, allowed the researchers to analyze conditions at different time periods and compare soil conditions during fire and flooding events over time.

"There is a legacy of poor logging practices conducted decades ago," Gavin said. "Road building during that period was done with little concern for subsequent erosion. The soils were much more heavily impacted by that development compared to the prehistoric fires of the past. Our study shows that at least four times more erosion occurred on the landscape after the logging and floods of the 1960s compared to the most severe prehistoric fire. So we are dealing with a more delicate, less-resistant ecosystem in the majority of areas that has seen this logging."…

Forests and mountains in Cascade-Siskiyou National Monument, Oregon, from a Bureau of Land Management photo