Biology
Biodiversity of Soil Invertebrates
Name:
Date:
Points:
Introduction
Soil invertebrates are a diverse group of organisms that spend all or part of their life cycle in the
soil and that are dependent on soil organic matter to live and reproduce. Some feed directly on
organic matter and the bacteria and fungi that are actively forming the organic matter. Others
prey on theses species. The number of soil invertebrates is truly staggering – in a square meter
of soil, there can easily be millions of nematodes and hundreds of thousands of mites. The
number of invertebrates in soil is closely linked to the amount of organic matter in the soil.
Desert and alpine soils have few soil invertebrates, although the small number of organisms can
have very significant effects on those environments. Desert soils often support abundant ant
populations. Tropical and temperate grasslands and forests generally contain the most abundant
populations of soil invertebrates. Cropland that is tilled every year can be depleted of soil
organisms, but the adoption of no-till methods can greatly enhance the biodiversity of soils. In
this lesson, you will explore the world of soil invertebrates, compare the diversity of soil
invertebrates in different soils, classify the invertebrates into morpho-species, and calculate the
abundance and diversity of invertebrates in the soil.
Procedures
1. Read the Biodiversity Fact Sheet; alternately, use the following websites to obtain
background information:
 Ecological and Ecosystem Diversity, National Biological Information Infrastructure
 Biodiversity Fact Sheet, Ecological Society of America
2. Read the Soil Invertebrates Fact Sheet.
3. Read the Soil Organic Matter Fact Sheet.
4. Based on the information you have just read, develop a hypothesis and state it on the data
sheet.
5. Follow the directions for constructing and using the Berlese funnels and Baermann funnels.
6. Follow the instructions in Choosing a Sample Site and Preparing Soil Samples for collecting
litter and soil samples.
7. Place a litter/soil sample in the Berlese funnels and allow 1 week for the invertebrates to
move into the collection vessel.
8. Place a soil sample in the Baermann funnel and allow 2 days to extract out nematodes.
9. Sort samples into groups (see Soil Organism Picture Guide), count the individuals, and
record the data on the data sheet.
10. Calculate abundance and diversity indices for each habitat; record the data in the table.
 See: Diversity Data Analysis
11. Construct a graph showing the effect of habitat on diversity.
 See: Constructing Bar and Line Graphs
12. Prepare a formal Lab Report
 See: Scientific Experiments and Publication Formats for Lab Reports
Hypothesis:
Response or Dependent Variable:
Independent Variable:
Sample size:
Table. Number of individuals extracted from soil samples
Habitat – Soil Type
Morpho-species
Crop field
Forest
Springtails 1
Springtails 2
Mites 1
Mites 2
Centipedes
Spiders
Ants 1
Beetle larvae
Total number
Number of species
H’
eH’
Questions
Which soil type had the most individuals? Why?
What is a morpho-species and why is it used instead of real species?
List 3 hypotheses to explain why abundance and diversity differ between soil types.
Is the data representative of the total diversity of the habitats? Why or why not?
What is the advantage and disadvantage of using species richness as an estimate of diversity?
What would happen if the diversity of invertebrates in the soil was suddenly reduced by 50%?
95%?
Does this type of experiment have a control?
What is the relationship between organic matter and the abundance and diversity of soil
invertebrates?
Draw a food web with the organisms you extracted from the soil.