Earthworm Distribution and Soil Microbiology

Chris Pickering

Anne Bruner

Ecology, Fall 1998

PURPOSE:

The purpose of our experiment was to determine the relationship between soil microbiology (the absence or presence of microbes as food sources) and the absence or presence of earthworms. Another goal was to determine the most suitable habitat for earthworm populations, i.e. compost piles, grassy areas, or forest floors.

METHODS:

There were two main components of our project: the collection of earthworms from various sites, and the analysis of microbes found at each site.

Methods of Earthworm Collection:

Volumes of soil 10 cm X 10cm from specific areas were examined for the presence of earthworms. The collection of specimens occurred on 9 October 1998 from 2-4 PM. The day was partly cloudy and approximately 68^o F. Fourteen sites were examined, soil samples were taken, and the number of specimens per site was recorded.

The central area in question was a compost pile of yard debris that was in constant use throughout the summer and fall seasons. The debris included leaves, mulch, top soil, and vegetation scraps. This compost pile was bordered by a small hardwood forest to the northeast and south and by open, manicured grass to the west.

Compost pile sites:

Site A) middle of the compost pile, next to site B

Site B) middle of the compost pile, next to site A

Site C) 10 cm underneath site B

Site D) far north edge of compost pile

Site E) far south edge of compost pile

Site F) dirt pile, northern border of compost pile

Grassy area sites:

Site G) under a large hardwood tree in the middle of the grassy area

Site H) open, well-manicured grass

Site I) under a vine of ivy in a grassy, open space

Site J) 10 cm underneath site I

Forest floor sites:

Site K) under a log on the periphery of the forest area, next to site L

Site L) under a long on the periphery of the forest area, next to site K

Site M) periphery of forest floor

Site N) forest floor

Methods of Microbe Analysis:

One gram of each soil sample was added to 20 mL of deionized water in a 50 mL beaker, and mixed for one minute with a glass stirring rod. An SAB (fungal and bacterial medium) and an EMB (bacterial medium) plate were each streaked using a pre0measured 0.001 mL inoculating loop.

The plates were placed in an incubator at 26^o C for 45 hours. The plates were then examined for growth, and each distinguishable species was described.

RESULTS:

According to the above numerical data, a greater number of specimens can be found in areas with a larger food supply.