Soils —Field Characterization, Collection, and Laboratory Analysis
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Field characterization of soil profiles in coniferous and deciduous settings; sample collection of soils from different horizons; laboratory analysis of soil moisture, soil organic carbon (by loss on ignition), and grain size distribution (by sieving)
Equivalent of 100 or 200 level geology class with soils, weathering, or Earth surface processes focus
Skills and concepts that students must have mastered
Students would benefit from prior reading on soil horizons and soil formations (because students sometimes have a hard time identifying distinctions between soil horizons without a sense of "what to look for"). I used the Chapter 3 of the Chapin textbook, Principles of Terrestrial Ecosystem Ecology.
How the activity is situated in the course
Sequence of field and lab sessions to allow for soil characterization and collection (in the field) and analysis (in the lab, including overnight step for loss on ignition)
Content/concepts goals for this activity
soil formation and development, investigating role of geology in influencing soil development, influence of different types of vegetation on organic matter input and storage in underlying soils
Higher order thinking skills goals for this activity
Formulation of hypotheses (soil development in coniferous vs. deciduous forests), Analysis of data (comparing coniferous vs. deciduous forests, and surface vs. deeper soil horizons)
Other skills goals for this activity
-introduction to fieldwork, sample collection, and maintaining a field notebook
-developing familiarity with lab setting (balances, oven)
-working in groups
Description and Teaching Materials
This sequence of field and laboratory "lab sessions" work well with groups of 3-4. Students' work and learning are reported in their field/lab notebooks, their calculations, and the depth of interpretations.
Student handout for "Soils —Field Characterization, Collection, and Laboratory Analysis" (Microsoft Word 2007 (.docx) 173kB Jun10 13)
Day 1- students dig soil pits (or work in pre-dug soil pits), characterize soils in the field, and collect samples from O and B or C horizons to bring back to lab. Students pre-weigh samples and place samples in ~60-70 deg C oven to dry (and later quantify soil moisture)
Day 2- students post-weigh soils to quantify soil moisture content and take subsamples for analysis of soil organic carbon by loss on ignition. Bake samples ~6 hours to overnight in ~550 deg C oven. Use remainder of dried soil with series of seives to quantify grain size distribution (basically for pebble vs. sand vs. silt/clay).
Day 3- students post-weigh baked soils to quantify soil organic matter content and complete sieving to quantify grain size distribution. Students report their data on board and discuss reasons for differences among groups (to address human error), sites (to address different settings), depths (to address soil formation processes), etc. and complete summarizing their methods, results, and interpretations/conclusions.
Teaching Notes and Tips
I assessed their lab and field notebook for details, calculations, depth of interpretations/conclusions. I later asked about soil profiles and a soil development scenarios in long/answer or essay questions on subsequent exams.
References and Resources
Chapin textbook, Principles of Terrestrial Ecosystem Ecology, Ch.3