THE GROUND CREW

Right beneath our feet there is a world of living organisms that most people have never seen.   In a typical forest or grassland community the soil surface is covered by one or two inches of humus, a complex mixture of organic matter in various stages of decay.   This layer of humus is teeming with a fascinating variety of living organisms that play important roles in soil fertility and nutrient cycling.   These soil dwellers represent all trophic levels:   herbivores, carnivores, omnivores, and decomposers.   Their foods include roots, seeds, fungi, dead wood, and decaying leaves.   They may be predators, parasites, or saprophytes.   This soil community is a microcosm that illustrates the complex ecological interactions among living organisms.   Its diversity is astonishing -- 15 to 20 major taxonomic groups can usually be collected in a single square-foot sample of humus, with populations of some species exceeding one million individuals per acre.

Activities:

• Build a Berlese Funnel and use it to extract arthropods from a sample of forest soil, compost, or ground cover.

• Use a simple identification key to learn who's who among soil-dwelling arthropods.

• Extrapolate from random samples to calculate population density, create ecological pyramids, and compare various indices of ecological diversity.
  

Animal Diversity in the Soil Community

Aschelminthes -- nematodes, roundworms

Annelida -- earthworms, segmented worms

Arthropods

Chelicerates

Araneae -- spiders

Acarina -- ticks, mites

Pseudoscorpions

Opiliones -- harvestmen, daddylonglegs

Crustacea

Isopoda -- pillbugs, sowbugs, woodlice

Myriapods

Diplopoda -- millipedes, thousand leggers

Chilopoda -- centipedes, hundred leggers

Symphyla

Pauropoda

Insects

Protura

Diplura

Collembola -- springtails

Archeognatha -- bristletails

Thysanura -- silverfish

Orthoptera -- grasshoppers, crickets

Isoptera -- termites

Blattodea -- cockroaches

Dermaptera -- earwigs

Thysanoptera -- thrips

Hemiptera -- true bugs

Homoptera -- leafhoppers, planthoppers, aphids

Psocoptera -- barklice

Neuroptera -- lacewings, antlions, aphislions

Hymenoptera -- ants, wasps

Coleoptera -- beetles, weevils

Lepidoptera -- moths

Diptera -- flies

Siphonaptera -- fleas