Grades 9–12 · Soil & schoolyard
Belowground Biodiversity: what's really living in our soil?
Turn the schoolyard soil beneath students' feet into a genetic biodiversity survey.
Students compare soil health across two schoolyard plots (e.g., garden bed vs. compacted lawn) by targeting soil organisms with a single composite soil sample, then argue from eDNA evidence about which management practices support belowground life.
Grade band
Grades 9–12
Time required
4 class periods
Class size
20–35 students, one kit
Sample type
Soil, one vial
Standards and outcomes
- HS-LS2-6 & HS-LS2-7 — Evaluate evidence for factors affecting biodiversity and ecosystem services in soil systems
- HS-LS2-1 — Use mathematical representations to support explanations of factors affecting carrying capacity of soil ecosystems
- HS-ESS2-5 — Evaluate evidence about processes that shape the properties of Earth's soil systems
- Science & Engineering Practices — planning investigations, analyzing data, constructing explanations (CER), engaging in argument from evidence
How one kit serves a whole class
The Starter Kit holds one soil collection vial, targets up to five species or species categories, and returns results in 7–10 days for $200. The class runs a composite batching protocol: crews pull soil cores from several points within one plot and combine them into one representative composite sample, repeating the process across a term to compare plots or seasons using separate kits.
Choose one
Research tracks
Track A — Decomposer Detectives
Nutrient cycling and soil health
Driving question. Which decomposer organisms are actively breaking down organic matter in our healthiest soil plot?
Species to pick. Up to five decomposer or soil-invertebrate categories common across regions: an earthworm species, a soil-dwelling beetle, a fungal decomposer group, a soil nematode category, and a mycorrhizal fungus category.
What students take away. Students connect detected decomposer diversity to measured soil organic matter and infer nutrient cycling health.
Track B — Compaction & Disturbance
Land management impact on soil life
Driving question. Does foot traffic or mowing frequency change which organisms are detectable in the soil?
Species to pick. Five species or categories that are sensitive vs. tolerant to compaction (e.g., a burrowing invertebrate sensitive to compaction, paired with a hardy microbial or invertebrate group known to persist in compacted soils).
What students take away. Students use presence/absence across two plots as evidence for how human activity reshapes soil communities.
Track C — Root Zone Partners
Plant-soil interactions
Driving question. What belowground organisms are associated with our healthiest garden or native plants?
Species to pick. Species tied to plant root health: a mycorrhizal fungus category, a nitrogen-fixing bacterium category, a root-feeding pest species, and a beneficial soil predator (e.g., predatory nematode or ground beetle).
What students take away. Students evaluate whether current planting or composting practices support a beneficial root-zone community.
The lesson sequence
Step by step, with teacher notes
- 01
Plot selection and pre-lab hypothesis building
50 minutesStudents walk the schoolyard, select two contrasting plots (e.g., garden bed vs. compacted lawn, or mulched vs. bare), and research which soil organisms they would expect to find in each, based on organic matter, moisture, and traffic level.
Teacher notes
- Say: "We only get one vial per plot — choose sites that are genuinely different, not two spots that happen to look the same."
- Bring a simple soil probe or trowel on the walkthrough so students can feel differences in compaction and moisture before choosing plots.
- Require each team to justify their five species picks with a one-sentence habitat rationale tied to organic matter or disturbance level.
- Remind students this round only samples one plot with the kit; the second plot is compared using data, prior classes' results, or a follow-up kit if budget allows — clarify this up front so expectations are correct.
Materials
- Soil probe or trowel
- Site map of schoolyard
- Regional soil-organism reference sheet
- Hypothesis log sheet
Student prompts
- What signs of soil health (color, smell, moisture, plant cover) do you see at each plot?
- Which of our five target species would you expect in high-organic-matter soil, and why?
- What would it mean if a species we expect to find is absent from the sample?
- 02
Composite soil sampling protocol
50–60 minutesCrews take soil cores from multiple points within the chosen plot at a consistent depth, then combine them into one composite sample. Gloves stay on throughout; tools are cleaned between plots to avoid cross-contamination.
Teacher notes
- Demonstrate the coring depth (typically the top several centimeters, per kit instructions) before crews begin, so every core is consistent.
- Say: "Clean the trowel between every core. Soil from one point contaminating another point defeats the purpose of a composite sample."
- Assign a fixed sampling grid (e.g., five points in a W-pattern across the plot) so the composite genuinely represents the whole plot rather than one corner.
- Have the chain-of-custody crew double-check the label (plot name, date, depth) before sealing — soil samples from two plots can look identical once bagged.
Materials
- 1 classroom eDNA soil collection vial and prepaid mailer
- Nitrile gloves
- Trowels or soil corer
- Sampling grid map
- Field data sheet
Student prompts
- Coring crew — collects soil cores from five points across the plot in a consistent W-pattern.
- Field scribe — records depth, moisture, texture, temperature, and visible organic matter at each core point.
- Composite crew — combines and gently mixes cores into the single kit vial.
- Chain-of-custody crew — labels, seals, and prepares the sample for mailing.
- 03
Understanding soil eDNA and the lab process
50 minutes, during the 7–10 day turnaroundStudents learn how soil differs from water as a sample matrix — DNA can persist longer in soil, bound to particles, but extraction is more complex. They explore how labs process soil samples and what 'relative signal' means for organisms that live in soil year-round versus those that pass through.
Teacher notes
- Contrast water and soil eDNA directly: soil DNA can bind to clay/organic particles and persist longer, but this also means older DNA may be detected alongside recent DNA.
- Say: "In soil, a detection might reflect an organism from this season, or DNA that's persisted from months ago — that changes how confidently we can claim 'currently present.'"
- Diagram the soil DNA extraction challenge (needing to separate DNA from organic material and inhibitors) as a contrast to the water workflow.
- Ask students to predict, before the reveal, which of their five targets is most likely to show a false negative due to patchy distribution in soil.
Materials
- Diagram comparing water vs. soil eDNA persistence
- Vocabulary handout (soil matrix, DNA binding, inhibitors, relative signal)
- Sample redacted Field Journal report
Student prompts
- Why might DNA persist longer in soil than in water, and how does that affect interpretation?
- What extra challenges does soil add to the lab extraction process compared to water?
- Which of our target species do you predict is hardest to detect reliably, and why?
- 04
Field Journal reveal and soil health argument
50 minutesStudents review the Field Journal detections for their plot, compare them to what soil health indicators (organic matter, compaction, moisture) predicted, and build a CER argument about the health of the belowground community.
Teacher notes
- Reveal results plot-by-plot and let students connect the pattern of detections to their physical soil observations from Phase 1.
- Ask: "If we had sampled the other plot too, what result would have supported or challenged today's claim?" — this keeps the comparison logic alive even with a single kit.
- Push students past 'we found X' to 'X's presence tells us Y about nutrient cycling or disturbance in this soil.'
- Close with a management recommendation: what would the class suggest the school do differently based on this data (less mowing, more mulch, compost addition)?
Materials
- Class Field Journal report (projected)
- CER writing frame
- Soil health indicator reference sheet
Student prompts
- Claim — does this plot's soil currently support a healthy decomposer/root-zone community?
- Evidence — cite specific detections, relative signal, and the physical soil conditions recorded.
- Reasoning — connect each detected (or missing) organism's known role to what that means for soil function.
Student handout
For every student
Thinking prompts
- Describe the two plots you considered and explain why you chose the one you sampled.
- List your five target species/categories and your hypothesis for each.
- Record your composite sampling grid and depth in detail.
- Explain how soil DNA persistence differs from water DNA persistence.
- Predict which species is least likely to be detected reliably and explain why.
- After the reveal, write one soil-management recommendation based on your data.
Data sheet
- Date and time of collection:
- Plot name / description and general land use:
- Soil moisture, texture, and temperature at each core point:
- Visible organic matter, roots, and disturbance signs:
- Number and location of core points sampled (grid map):
- Target species list with pre-reveal hypotheses:
- Weather and recent precipitation before sampling:
Discussion questions
- Why does a composite sample matter even more in soil, where organisms can be very patchily distributed?
- What's the risk of interpreting a soil eDNA detection as 'the organism is here right now'?
- How might mowing, foot traffic, or composting change belowground biodiversity over a school year?
- If you had a second kit, would you sample the same plot again or a different one — and why?
Field checklist
- Nitrile gloves on before touching any sampling equipment.
- Trowel or corer cleaned between every core point.
- Five core points sampled in a consistent grid pattern.
- Depth, moisture, texture, and organic matter recorded at each point.
- Composite sample mixed gently, preserved and sealed without touching the vial interior.
- Plot label double-checked before sealing to avoid mix-ups.
Analysis
CER: Is this plot's soil biologically healthy?
- 1.Claim — write one sentence stating whether the plot supports a healthy belowground community.
- 2.Evidence — list the specific detections, relative signal values, and physical soil conditions recorded.
- 3.Reasoning — connect each species' known ecological role (decomposer, root partner, pest, predator) to what its presence or absence implies.
- 4.Counter-evidence — identify one result that complicates the claim (e.g., a detected pest species) and address it.
- 5.Revise — propose one soil management change and predict how it would shift the results if resampled.
Assessment
20-point rubric
Pre-lab research and plot rationale
5 ptsA clear biological rationale is given for the plot chosen and each of the five target species/categories.
Field discipline and sampling consistency
5 ptsConsistent core depth, clean tool technique, and accurate condition logging are followed across all sample points.
Data interpretation
5 ptsField Journal results are read correctly, including the distinction between detection and abundance in a soil matrix.
CER conclusion
5 ptsA well-defended explanation links detected organisms to soil function and proposes a sound management recommendation.
Go further
Extensions
- Order a second kit next season to sample the same plot and compare belowground community change over time.
- Partner with the school's garden or grounds crew to test whether a management change (e.g., adding compost) shifts the detected community.
- Compare soil kit results with a simple physical soil health test (infiltration rate, organic matter estimate) done by the class.
- Have students design a public one-page report for the school on what's living beneath the schoolyard.
For the teacher
Answer key and misconceptions
- Expected: plots with more organic matter and less compaction typically show higher decomposer diversity; a bare, heavily trafficked plot may show few or no detections — this is meaningful data, not a failed test.
- Common misconception: 'no detection means no life in the soil.' Correct framing: soil supports enormous microbial life the kit isn't targeting; the kit only reports on the five chosen species/categories.
- Common misconception: a detection means the organism is currently active there. Correct framing: soil DNA can persist longer than water DNA, so a detection reflects presence within a broader recent window, not necessarily 'right now.'
- Expected: students should be able to explain that composite sampling across a grid reduces the risk that one lucky or unlucky core point skews the whole plot's result.
- Common misconception: comparing two plots requires sampling them on the same day with the same kit. Correct framing: valid comparisons can be built across a term or year using separate kits, as long as conditions (season, weather) are documented and considered.