An intricate cycle of geological and chemical interactions accounts for the highly acidic soils of mysterious barren areas in the Klamath Mountains of Northern California, according to a study by a UC Davis researcher. Nitrogen, released by the weathering of rock, increases soil acidity, leaches out critical soil nutrients and mobilizes aluminum into its toxic form, preventing revegetation of areas apparently left barren by lightning fires, reports biogeochemist Randy A. Dahlgren in a recent issue of the scientific journal Nature. The findings suggest important implications for dealing with ecosystems affected by acid rain, excessive use of nitrogen fertilizers and timber harvesting, according to Dahlgren, an assistant professor in the UC Davis land, air and water resources department. "Although these barren areas created by acidification from geologic nitrogen are probably quite rare, they present an important analogy to acid rain, which has affected the soils of some parts of Europe and the Northeastern United States," says Dahlgren. "In the case of acid rain, humans have created a nitrogen-saturated ecosystem. If those areas are clear-cut in timber harvest and the nutrient-rich soil surface eroded, we would likely see the same type of barrenness. As long as the organic material of the forest floor is maintained, this can be prevented."