Smog Nitrogen and the Rapid Acidification of Forest Soil, San Bernardino Mountains, Southern California

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 ~130 cm of soil where it accumulates and increases soil acidity

Small-Scale Rack Testing of Wood-Frame Shear Walls

A series of racking tests were performed with small-scale (1.2-m X 1.2-m) plywood and OSB assemblies as a means of assessing the potential of reduced assembly sizes in screening variables for subsequent full-size tests. The plywood materials and configurations included variations in stud spacing, nailing, panel thickness and number, and addition of gypsum board. OSB assemblies differed in panel orientation and nailing. The framing used was KD Select Structural to minimize variations in fastening. Both of the standard assemblies (400-mm stud spacing) were also exposed to high relative humidity and effects of green framing. There were clear statistical differences between most plywood configurations, but the most prominent were for center-stud framing, and 9-mm-thick panels. The addition of gypsum board gave higher maximum load and greater stiffness, but the increased variability precluded finding significant differences with the basecase. OSB was significantly lower than plywood in most results. Moisture effects were minimal except for a greater deformation of OSB to the maximum load. The effect of green framing for the bottom plate was minimal