New England WSC seminar series Lawrence 20170509

Science Center Objects

A consistent decreasing trend in acidic deposition levels over the past several decades has led to partial chemical recovery of surface waters. However, depletion of soil Ca from acidic deposition has slowed surface water recovery and led to the impairment of both aquatic and terrestrial ecosystems.

Tuesday, May 9, 2017, 12:00 pm

Title: Declining acidic deposition begins reversal of forest-soil acidification in the Northeastern U.S. and Eastern Canada

Presented by: Gregory Lawrence, Research Physical Scientist, USGS New York WSC

Location: USGS, New Hampshire Office, Pembroke, NH

Abstract: 

Declining acidic deposition begins reversal of forest-soil acidification in the Northeastern U.S. and Eastern Canada

Gregory Lawrence, USGS, New York Water Science Center, Troy, NY

Authors:

G. Lawrence, U.S. Geological Survey P. Hazlett, Natural Resources Canada–Canadian Forest Service;

I. Fernandez, University of Maine;

R. Ouimet, Direction de la recherche forestiere, ministere des Foret, de la Faune et des Parcs du Que ́bec;

S. Bailey, USDA Forest Service;

W. Shortle, USDA Forest Service;

K. Smith, USDA Forest Service;

M. Antidormi, U.S. Geological Survey

A consistent decreasing trend in acidic deposition levels over the past several decades has led to partial chemical recovery of surface waters. However, depletion of soil Ca from acidic deposition has slowed surface water recovery and led to the impairment of both aquatic and terrestrial ecosystems. Nevertheless, documentation of acidic deposition effects on soils has been limited, and little is known regarding the response of soils to ongoing declines in acidic deposition. To address this problem, resampling of soils in eastern Canada and the northeastern U.S. was done at 27 sites exposed to reductions in wet sulfate deposition of 5.7% to 76%, over intervals of 8 to 24 years. Decreases of exchangeable Al in the O horizon, and increases in pH in the O and B horizons were seen at a majority of sites. Among all sites, reductions in sulfate deposition were positively correlated with base saturation (P < 0.01), and negatively correlated with exchangeable Al (P < 0.05) in the O horizon. However, base saturation in the B horizon decreased at one-third of the sites, with no increases. It’s not clear whether this change is part of the recovery response, but it’s not consistent with the conceptual model of recovery that assumes replenishment of bases from weathering as cation leaching fluxes are reduced by decreases in deposition. Nevertheless, this study is the first to link declines in acidic deposition to soil changes that represent a reversal of acidic deposition effects on soils.