Soil is a complex portion of the forest ecosystem. Trees depend on soil for water, nutrients, and stability. Since the 1950's, Pack Forest has been a study site for forest nutrition research. The late Professor Emeritus Stanley P. Gessel pioneered efforts in applying urea to Douglas-fir. His installations are still being monitored today.

Beginning in the early 1970's, the College of Forest Resources began conducting "biosolids" research. Biosolids are treated solids screened from the wastewater treatment process. They are used at Pack Forest as fertilizer. Tree growth, soil productivity, and potential water table pollution are monitored. Biosolids are added to the soil because they contain high quantities of nitrogen, a necessary element for tree growth, which is often deficient in Pack Forest's glacial outwash soils. They also increase soil moisture retention, decrease soil erosion, and enhance soil structure. For a close view of what's new in biosolids, head to the Biosolids Recycling Demonstration Area, northeast of the gatehouse.

Microbial (microscopic animal) populations in the soil regulate the decomposition of forest floor litter (needles, branches, and other tree debris) and make this litter suitable for microfloral (microscopic plant) decomposition. This decomposition process adds nutrients to the soil that can be utilized by trees. In 1992, a study at Pack Forest looked at how the number of live trees on a site affects soil microbial activity. Variations in harvest retention (the number of trees left on a site after harvest) cause variations in soil temperature, moisture, and organic matter. These variations affect microbial populations and activity that are necessary in the nutrient cycling process.

Click on the map for a description of our forest's soils.

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