Grant Award Year:
2013 - 2014
We propose a retrospective study of the effects of acid rain on Northeast US forests using a new biogeochemical tracer. We will measure Ca stable isotope ratios on streamwater samples collected and archived at Hubbard Brook Experimental Forest during, and subsequent to the peak of historical acid deposition in New England. Recent studies have demonstrated that Ca stable isotope ratios are fractionated during plant uptake of Ca, resulting in forest Ca pools with distinct Ca isotope ratios. We suggest that changes in Ca loss mechanisms due to acidification, deforestation, etc., should result in systematic shifts in the isotope ratios of Ca exported by streamwater, which should provide insight in the mechanisms and sources of Ca loss from forests. Analytical work will be carried out in the BU TIMS Facility by BU graduate student Ken Takagi as a component of his dissertation research. The federal funding that we request will support one month of Takagi's summer 2013 salary plus analytical costs for approximately 25 samples. Our preliminary work at Hubbard Brook demonstrates a resolvable shift in streamwater Ca isotopes in response to a clearcutting experiment conducted at Hubbard Brook in the 1980's. The work we propose here will be the first application of Ca stable isotopes to the problem of acid deposition. We intend to use data collected in this study to motivate a larger-scale proposal to be submitted to NSF.