Relationships among atmospheric deposition, throughfall, and soil properties in oak forest ecosystems

Relationships among pollutant (H+, SO42−, NO3−) deposition, throughfall ionic fluxes, and soil properties were examined at six oak forest sites in the southern Great Lakes region. At each site, precipitation, throughfall, and soil samples were collected and chemically analyzed. Sulfate and NO3− deposition increased from southern Michigan to northern Ohio in both precipitation and throughfall. Throughfall H+ fluxes also increased between these two areas. Throughfall fluxes of H+, SO42−, NO3−, and Ca2+ were significantly related to wet pollutant deposition. Throughfall Ca2+ and Mg2+ fluxes also tended to reflect soil cation abundance, but H+ consumption in the canopy was a major contributor to cation fluxes at certain sites. After accounting for differences in inherent soil properties, additional variation in both surface and subsurface soil properties was statistically related to atmospheric deposition. While topographic position and impeded drainage also may be implicated, elevated extractable SO42−, decreased potential to adsorb SO42−, and lower nutrient cation saturation in the solum of the most polluted site were consistent with pollutant deposition impacts. Results suggest that certain oak ecosystems in the southern Great Lakes region have experienced alteration in throughfall chemistry and soil properties as a result of elevated pollutant deposition.