SOIL CLIMATES OF THE SHENANDOAH VALLEY AND THE VIRGINIA PIEDMONT

From acid rain to global warming to sustaining agricultural yields from a shrinking arable landbase, many environmental geoscience issues will require a greater appreciation of soils and soil processes. Here, I describe a soils class exercise developed to give students practice in analyzing large datasets. Soil climates for the Shenandoah Agricultural Research and Extension Center (SAREC) and Northern Piedmont AREC in northern Virginia were quantified using >83,000 and ~50,000 hourly readings, respectively. Monthly data were first mined from the USDA Natural Resources Conservation Service Soil Climate Analysis Network website (www.wcc.nrcs.usda.gov/scan). PivotTable analyses were then performed to summarize yearly, monthly, and weekly averages for air temperature, precipitation, and 10 sets of soils data: temperatures as well as Hydraprobe moistures at 5 depths (5, 10, 20, 50, and 100 cm below the surface). The mean annual soil temperatures (at 50 cm below the surface) were similar (13.2 and 15.5 degrees C, respectively), but soil temperature regimes were mesic and thermic, respectively, because the dividing line is 15 degrees C. Soil moistures at 50 cm were very similar (~37%), but at 5 cm, the Shenandoah site (540 m) was slightly drier (22%) than the Piedmont site (160 m; 27%). Over the last several decades, air temperatures at the NPAREC have averaged 13.1˚C, while annual precipitation has averaged 106 cm (D. Starner, pers. comm.). Soils near the SAREC have been mapped as fine, mixed, semiactive, mesic Typic Paleudults, while the NPAREC soil has been mapped as fine, kaolinitic, thermic Rhodic Kandiudults. Although both suborder classifications are identical (Udults), implying leached soils, students were asked to contrast soil properties given their soil climate summaries and their general knowledge of parent materials for the two sites (limestone and greenstone, respectively). Finally, students were asked how the soil profiles might differ if the parent materials were switched. These types of soil climate data can be used to parameterize models, improve carbon balance and chemical weathering predictions, and define and track growing season length. They also provide a data-rich foundation for "real world" environmental geoscience questions.