Forest fragments in Baltimore make up 34 percent of Baltimore’s tree canopy and provide important ecosystem services such as stormwater runoff reduction, water purification, food and habitat for animals, air temperature reduction, and carbon sequestration. The surrounding urban environment influences these patches many different ways, such as a source of nutrients and invasive species. Over time, these different pressures may affect the general health of the forest. The objective of this study was to characterize the change in forest fragment soils over a period of 17 years along an urban-rural gradient in the Baltimore Metropolitan area. We expected to see soil organic carbon decrease in urban areas due to elevated temperature and earthworm activity. Conversely, we expected to see an increase in pH because of the amount of calcium prevalent in the urban system from cement dust. To investigate these ideas, 15 forested sites were classified as urban, suburban, or rural based on distance from the center of the city. A total of 45 plots in 5 urban, 5 suburban and 5 rural forests were sampled in 2001 and 2018. Soil cores from 0-10 cm depth were taken and measured for soil pH, carbon, nitrogen, nutrients, and metals.
Results/Conclusions
The pH of urban forest soils increased 0.5 units with a corresponding increase in calcium. Other regional retrospective studies show forest soils at 0-10 cm decrease in both pH and Ca over time due to normal pedogenic processes. Generalized linear model results showed that landscape-scale factors such as traffic count, road density, and urban development influenced Ca concentrations. Overall, carbon and nitrogen did not change which may indicate a steady-state forest floor system or a slower rate of change than what is detectable in 17 years. These changes of pH and Ca in urban soil properties over time indicate a different developmental trajectory than native soils. In the near future, we plan to assess potential changes in earthworm community structure and abundance.