Atmospheric Deposition and the Ecosystem Impacts Along an Agricultural-to-Urban Gradient in Ohio, U.S.

Ansley Grider, Kenyon College

Abstract

Due to the potential negative ecosystem impacts from increased atmospheric nitrogen (N) and dust deposition, there has been a vast amount of research on the topic. However, many questions remain about the spatial variation in N and dust deposition, as well as ecosystem impacts, across land-use gradients, especially agricultural-to-urban gradients. To address this knowledge gap, we measured bulk atmospheric N deposition, dust deposition, and ecosystem impacts along an agricultural-to-urban transect at four sites in Ohio, U.S., during the summer of 2021 (for nine weeks). We found no significant differences in N deposition from agricultural to urban sites during the summer period of this study, but average weekly total inorganic N loads varied from 0.167 kg ha-1 at the agricultural/suburban site to 0.199 kg ha-1 at the urban site. Dust flux was significantly elevated at the urban site (20.48 +/- 9.52 mg m-2 day-1) compared to two of the other sites (11.11 +/- 6.11 to 11.19 +/- 5.20 mg m-2 day-1), and we found evidence for the ‘urban scrubber effect’ causing elevated bulk deposition pH at the urban site. N concentrations in two plants (Solidago canadensis and Andropogon gerardii) and in the soil were all highest at the most urban site, and C:N ratios were lowest at the most urban site for both plants and soil. Our results indicate that agricultural and urban areas in Ohio possibly have similar N deposition loads; however, future work should explore this hypothesis further. Ecosystem impacts varied from agricultural to urban sites even though no significant differences in N deposition were observed, indicating that even small changes in N deposition can have significant impacts and these impacts can differ among species. Our results suggest S. canadensis may have a competitive advantage in environments with excess N, which implies that elevated N deposition could decrease species biodiversity in Ohio, especially in urban areas.