Earthworm activities alter soil structure, microbial activity, and nutrient availability in ecosystems colonized by earthworms compared to those lacking earthworms. Where earthworm populations are abundant, their activities increase surface leaf litter decomposition, and mixing of surface litter into the soil by earthworms and likely provides organic matter that enhances soil microbial activity. However, seasonal and inter-annual timing of earthworm activities are sensitive to weather conditions (Eggleton et al. 2009; Stoscheck et al. 2012), and little is known about effects of that variation on major soil processes. Therefore, understanding ecosystem responses to weather variations requires that we more specifically examine consequences of variation in earthworm activities. This research focused on the effect of earthworm activity on soil microbial activity in the hardwood forest of Miami University’s Natural Areas. We simulated decreased earthworm activity by excluding earthworms from the leaf litter using fine mesh screens and tested effects on microbial activity by quantifying respiration from soil cores and earthworm middens, the digested material that earthworms deposit on the soil surface around their burrows. Results suggest that higher earthworm activity, by mixing surface litter into soil, promotes soil microbial activity. Excluding earthworm activities from litter also substantially reduced the frequency of middens. Because these middens are highly enriched in organic material from consumed leaf litter, the reduction in their frequency causes less heterogeneity in microbial activity across the soil surface. This study suggests that earthworm activities directly promote soil microbial activity and soil CO2 emissions from middens and soils. This research experience has benefitted me as a student by allowing me to apply concepts I have studied in a practical way. I was able to practice different lab procedures to collect, analyse, and interpret data, as well as contribute to the understanding of variable earthworm effects on the ecosystems of earthworm-colonized areas.
Author: Ami Schulte
Faculty Advisor: Melany Fisk, Department of Biology
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