title: Smog nitrogen and the rapid acidification of forest soil, San Bernardino Mountains, southern California.
abstract: We report the rapid acidification of forest soils in the San Bernardino Mountains of southern California. After 30 years, soil to a depth of 25 cm has decreased from a pH (measured in 0.01 M CaCl2) of 4.8 to 3.1. At the 50-cm depth, it has changed from a pH of 4.8 to 4.2. We attribute this rapid change in soil reactivity to very high rates of anthropogenic atmospheric nitrogen (N) added to the soil surface (72 kg ha(-1) year(-1)) from wet, dry, and fog deposition under a Mediterranean climate. Our research suggests that a soil textural discontinuity, related to a buried ancient landsurface, contributes to this rapid acidification by controlling the spatial and temporal movement of precipitation into the landsurface. As a result, the depth to which dissolved anthropogenic N as nitrate (NO3) is leached early in the winter wet season is limited to within the top approximately 130 cm of soil where it accumulates and increases soil acidity.
authors: Department of Environmental Sciences, University of California, Riverside, CA, USA. yvonne.wood@ucr.edu
authors: Yvonne A
authors: YA
authors: Wood
authors: Mark
authors: M
authors: Fenn
authors: Thomas
authors: T
authors: Meixner
authors: Peter J
authors: PJ
authors: Shouse
authors: Joan
authors: J
authors: Breiner
authors: Edith
authors: E
authors: Allen
authors: Laosheng
authors: L
authors: Wu
mesh_terms: D002140:California; D005843:Geography; D006863:Hydrogen-Ion Concentration; D009584:Nitrogen / Q000032:analysis*; D012905:Smog; D012987:Soil; D014197:Trees; D014867:Water / Q000737:chemistry
chemical_list: D012905:Smog; D012987:Soil; D014867:Water; D009584:Nitrogen