Actinomycetes are less well known but play an important role in the decomposition of soil organic matter. They are particularly abundant in low pH, droughty soils, similar to many of our highly productive horticultural soils. Algae help to decompose organic matter. Most commonly seen in poorly drained soils, often they become visible around wet areas but there are also algae throughout the soil. Macroscopic soil animals include arthropods, earthworms and rodents.
Arthropods represent a wide variety of soil dwelling insects, spiders and mites.
Microarthropods are extremely numerous in undisturbed soils or soils with perennial crops with populations over 1 million per square metre. These microarthropods are involved in the decomposition of plant residues, but they also stimulate fungal growth and microbial activity. A few of these creatures are pests but some also provide some biocontrol of nematodes. The earthworms in Ontario are immigrants like most of us. The glaciers that receded over 10,000 years ago, scoured and deposited the parent materials for our soils, leaving little or no life behind.