Pacific Southwest Research Station

Kings River Experimental Watershed

SOIL CHARACTERIZATION

Characterizing the variation in soils that occur on KREW watersheds is important to understand watershed condition, changes in ecosystem processes, and changes that might be seen in stream conditions. The treatments that will be implemented on KREW are known to have impacts on soils and their structure. The use of heavy machinery and creation and/or maintenance of skid trails during logging operations can compact soils and increase erosion. Prescribed fire treatments alter the nutrient availability of soils, and have the potential to leave upper layers hydrophobic, which increases overland flow and erosion. Understanding how these treatments impact soils can contribute to the implementation, where necessary, of lower-impact management by the Forest Service and other agencies. For specifics concerning soil characterization see the KREW Study Plan (Hunsaker et al. 2004).

Soil Grid

Under Construction

Soil Pits

At selected points on the existing 150-m grid, soil profiles are prepared by digging a pit one meter deep and analyzing the vertical horizon. These are the same grid points where vegetation plots are located. From each horizon, a core is taken to determine bulk density, and samples are taken for nutrient analysis and soil moisture content. At randomly-selected points 10m or more from the soil pit, three satellite samples of the O horizon layer and mineral soil are collected for analysis. Around the center of the soil pit, a 0.1-hectare, circular plot is used to measure large woody debris and live woody vegetation. In 2003, 40 grid points were selected to begin sampling; resulting data will be analyzed to refine the design and more thoroughly sample the soil on KREW. Ultimately, sampling will occur once during the pre-treatment period, and once, immediately following treatment. For a further description of field methods and laboratory analysis, see KREW Study Plan (Hunsaker et al. 2004).