Summer 2002, Soil Organisms

Urban areas provide habitats for a variety of species. Some of these species are pests while others play important roles in the ecosystems, being natural predators of these pests, or facilitating decomposition and soil development. The objective of the study is to see how management practices affect biodiversity in the soil. The study focuses on two groups of invertebrates: arthropods (insects, centipedes, spiders, pill bugs) and earthworms.

Sampling in forest and residential lawns for arthropods and earthworms began in the summer of 2002 in a 150 meter radius around the Cub Hill tower, and will continue until the end of the summer of 2003. In the summer of 2002 worm sampling was conducted. The results from this sampling were not very successful, due to the extreme drought; only five species of worms were found. Most worms were of an exotic species, however a very rare native species, Diplocardia texensis, was found in the forest. Seasons affect the number and type of earthworms and arthropods found, so more sampling is scheduled for 2003. By sampling at different times of the year a better picture about the distribution and density of the different earthworm species will be available.

The spring 2003 sampling has already been completed and the summer 2003 sampling is approaching fast. The samplings that have been conducted consist of arthropod and earthworm sampling. Small arthropod samples were taken using a soil corer, 2 inch by 2 inch, which removed the soil from the ground. In the laboratory the soil samples were extracted from the corer in order to look for any arthropods in the soil core. In place of the soil cores a small solo cup was placed which was filled halfway with water. This cup, called a bug-cup, caught insects that crawled on the surface of the lawn. A small cover was placed on the cup about an inch above its rim, to prevent rain and leaves from falling into the cup. The bug-traps were checked and emptied daily, and water was replaced. After five days the cups were picked up, and the hole was filled with soil and the surface replaced with sod. There were three cores and three pitfall traps per lawn.

Earthworm sampling was also conducted and it seems to have been very successful. Earthworm sampling is conducted on lawns and in flower beds. To sample for earthworms a mixture of mustard seed powder and water is poured in a1 foot by 1 foot grid, which causes the earthworms to come to the surface. The worms are then picked up so they can be weighed and identified.

In the study it is expected that different species of arthropods will become dominant in different seasons, which is why sampling was done in the summer of 2002, spring of 2003, and is scheduled for the summer of 2003. This research provides an opportunity for student involvement. Currently two biology majors from Taws University, Janelle Harris and Jennifer Stiltz, are involved with this project. During spring and summer they will devote most of their time to sampling, species identification, and data analysis. In the fall of 2003 the students will present their results at the 6th Annual Meeting of the Baltimore Ecosystem Study.