Soil Calcium Status and the Response of Stream Chemistry to Changing Acidic Deposition Rates

Abstract

Despite a decreasing trend in acidic deposition rates over the past two to three decades, acidified surface waters in the northeastern United States have shown minimal changes. Depletion of soil Ca pools has been suggested as a cause, although changes in soil Ca pools have not been directly related to long‐term records of stream chemistry. To investigate this problem, a comprehensive watershed study was conducted in the Neversink River Basin, in the Catskill Mountains of New York, during 1991–1996. Spatial variations of atmospheric deposition, soil chemistry, and stream chemistry were evaluated over an elevation range of 817–1234 m to determine whether these factors exhibited elevational patterns. An increase in atmospheric deposition of SO4 with increasing elevation corresponded with upslope decreases of exchangeable soil base concentrations and acid‐neutralizing capacity of stream water. Exchangeable base concentrations in homogeneous soil incubated within the soil profile for one year also decreased with increasing elevation. An elevational gradient in precipitation was not observed, and effects of a temperature gradient on soil properties were not detected. Laboratory leaching experiments with soils from this watershed showed that (1) concentrations of Ca in leachate increased as the concentrations of acid anions in added solution increased, and (2) the slope of this relationship was positively correlated with base saturation. Field and laboratory soil analyses are consistent with the interpretation that decreasing trends in acid‐neutralizing capacity in stream water in the Neversink Basin, dating back to 1984, are the result of decreases in soil base saturation caused by acidic deposition.

Acid soil indicators in forest soils of the Cherry River Watershed, West Virginia

“…In 2002, West areas streams had higher pH and alkalinity than East area streams. Lawrence et al (1999) found alkalinity of streams in the Ratios were calculated based on Ca and Al values, and risk categories were assigned based on Table 1. Horizon values are averages of n = 36 in the East area and n = 31 in the West area a See horizon designations in Table 4 b Risk categories are shown in Table 1 c Analyte values within a horizon are significantly different between areas at α = 0.05 Catskill Mountains of New York correlated well with acid soil conditions and acid deposition trends.…”

Chronic and episodic acidification of streams along the Appalachian Trail corridor, eastern United States

“…Responses to decreasing acid deposition may result in changes in the natural and anthropogenic drivers of episodic acidification, but not necessarily to changes in the magnitude of ANC depressions that occur during events (Kline et al, ), though decreases in episodic acidification have also been reported (Riscassi et al, ). Moreover, base cation dilution and increases in organic acidity are also influenced indirectly by atmospheric deposition as reflected by soil base cation depletion resulting from enhanced acid leaching and by increases in dissolved organic carbon (DOC) concentrations resulting from declines in the acidity of atmospheric deposition (Gavin et al, ; Lawrence et al, ).…”

Effects of experimental manipulation of light and nutrients on establishment of seedlings of native and invasive woody species in Long Island, NY forests

“…Studies have demonstrated that increases in N deposition cause soil Ca to move into solution and leach from the terrestrial ecosystem into stream water (Vitousek et al 1997;Likens 1998;Lawrence et al 1999); as these ecosystems become enriched in N from anthropogenic deposition, they can become depleted in Ca (Aber et al 1998). The potential role of resource availability in facilitating invasion (e.g., Levine and D'Antonio 1999;Stohlgren et al 1999) may be particularly important in the eastern USA because of the large influences that human activities have had on the availabilities of both N and Ca over the last 50 years (Aber et al 1998;Likens 1998;Lawrence et al 1999). These changes in resource availability could profoundly alter the susceptibility of these ecosystems to invasions (e.g., Dukes and Mooney 1999).…”