L. Liegel

Regional characteristics of land use in northeast and southern Blue Ridge province: Associations with acid-rain effects on surface-water chemistry

The Direct/Delayed Response Project (DDRP) is one of several studies being conducted by the United States Environmental Protection Agency to assess risk to surface waters from acidic deposition in the eastern United States. In one phase of DDRP, land use, wetland, and forest cover data were collected for statistical samples of 145 Northeast lake and 35 Southern Blue Ridge Province stream watersheds in the United States. Land-use and other data then were extrapolated from individual to target watershed populations. Project statistical design allows summarization of results for various subsets of the target population. This article discusses results and implications of the land-use and land-cover characterization for both regions.Forest cover was the primary land use in both regions. In the Northeast, developed (agriculture and urban) land was positively associated with surface-water chemistry values for acid neutralizing capacity, Ca plus Mg, pH, and sulfate in the Pocono/Catskill subregion. Extensive wetlands and beaver activity occur in parts of the Northeast region, whereas topography limits wetland and riparian development in the Southern Blue Ridge Province. Northeast soils have low sulfate adsorption capacity, most watersheds are near sulfur steady state, and lake sulfate concentrations are controlled principally by levels of sulfur deposition. Net annual sulfur retention in Northeast watersheds is positively correlated with occurrence of wetlands and beaver impoundments. In contrast, most Southern Blue Ridge Province soils have high sulfate adsorption capacities, resulting in high net watershed sulfur retention. At the present time, stream sulfate concentrations and percent sulfur retention are controlled principally by soil chemical properties related to adsorption rather than atmospheric deposition and land use.

Overstory mortality as an indicator of forest health in California

The interagency Forest Health Monitoring Program involves a network of about 4200 forest plots on a triangular grid across the United States. We present data on recent mortality of trees ≥27.9 cm diameter from the first three years of measurements in California (1992–1994). Three plot designs were used to collect data representative of a 1-ha stand at each site; the designs differed primarily in total area sampled (0.067, 0.4 and 1.0 ha). Approximately 50 sites were visited each year yielding a total of about 150. Field tallies showed few cases of recent mortality in the smallest plot size. Cumulative distribution functions of recent dead tree densities in the 0.067-ha plots differed significantly from those generated by tallies from entire 1-ha stands. We conclude that an area of 0.067 ha is unsuitable to assess and monitor overstory mortality in Pacific Coast forests.

Effect of dry‐heat sterilization on chemical properties of Puerto Rican soils

Abstract Few references explain the effects of dry‐heat sterilization on soil chemical properties. Yet dry heating at 121°C for 2 hours is the prescribed USDA Animal, Plant, and Health Inspection Service basic treatment for soils entering United States ports of entry. This study concerns the effects of air drying and dryheat sterilization on chemical properties of Puerto Rican soils, chiefly macronutrients and micronutrients, found after extracting with Mehlich‐1 and Olsen solutions. Results for dry heating are compared with reported results for other sterilization procedures. Dry heating did not significantly alter soil N, organic matter content, or soil bases. Depending on the extractant used, changes in P concentrations were significant. Results for micronutrient determinations were more variable and also depended on the extractant used after sterilization. Concentrations of Mn and Fe extracted from dry‐heated soils were significantly greater than concentrations extracted from air‐dried soils. Effects ...