Earthworms and soils in the Baltimore Metropolitan Area: Is there an urban-rural gradient?
Katalin Szlavecz, Richard V. Pouyat, Vincent Giorgio and Csaba Csuzdi
We report earthworm abundance and soil data for fieldwork conducted in the Baltimore Metropolitan area during the summer 2001. Fifteen forested sites were selected and classified as urban, suburban, or rural based on geographic and demographic features in the surrounding area. A total of 52 soil samples were collected and analyzed for bulk density, pH, organic matter content, texture, and nutrient content.
For all samples, pH ranged from 3.67 (Mt. Pleasant) to 5.71 (Cylburn Arboretum) with an average of 4.56. Bulk density ranged from 0.69 g/cm3 (Druid Ridge Cemetery) to 1.58 g/cm3 (Cross Keys) with an average of 1.10 g/cm3. Organic matter content ranged from 4.1% (Cross Country Blvd.) to 17.2% (Loch Raven Reservoir) with an average of 8.6%.
Significant differences (p <. 0.05) between urban/rural sites were found for bulk density, soil Ca, Mg, and Na (with urban sites showing higher values than rural for each). Earthworm density and biomass varied between 10 and 71 ind. m-1 and 3.7 and 75.1 g m-1 respectively. Earthworm biomass showed positive correlation with pH, and negative correlation with soil organic matter content and leaf litter depth. Species composition was a better indicator for site conditions, than abundance. Given the variation in parent material and soil type of the Baltimore Metropolitan area, evaluation of site differences should take into account both natural (geology) processes and anthropogenic impact (land use change).
Keywords: earthworms, forest, soil properties, urban-rural gradient

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