Response of buried mineral soil bags to experimental acidification of forest ecosystem

M. J. Mitchell, M. B. David, I. J. Fernandez, R. D. Fuller, K. Nadelhoffer, L. E. Rustad, A. C. Stam

Research output: Contribution to journalArticlepeer-review


At Bear Brook Watershed in Maine, H2SO4 and/or HNO3 was added to 15 by 15 m plots (three replicates per treatment) from 1988 through 1990. Total loading above ambient treatments for the 3 yr was 0 (control), 5100 (low S, low N), 10 200 (high S and N + S), and 11 950 (high N) mol ha-1 yr-1. Changes in soil chemistry were evaluated using tension lysimeters and buried mineral soil bags placed below the forest floor before treatments were initiated. Total soil S was highest in the high S treatment (355 mg S kg-1 soil), intermediate in the low S and N + S treatments (314 and 310 mg S kg-1 soil, respectively), and lowest in the low N, high N, and control treatments (278, 275, and 270 mg S kg-1 soil, respectively). Differences in total S were mostly attributed to phosphate-extractable SO4, although smaller changes in ester sulfate and C-bonded S were also detected. Low pH and elevated SO4 in solution resulted in increased SO4 adsorption. There were no differences caused by treatments in N or C constituents in the soil bags, although N was strongly linked with C (r = 0.86). Nitric and sulfuric acid additions lowered soil pH (H2O) from 4.83 in the control to 4.67 and 4.70, respectively. Sulfuric acid treatments increased exchangeable Ca to 0.32 cmolc kg-1 compared with 0.24 cmolc kg-1 in the control, whereas HNO3 treatments decreased Ca to 0.18 cmolc kg-1. A strong correlation (r = 0.94) between exchangeable Ca and base saturation reflected the quantitative dominance of exchangeable Ca among base cations. Similarities in effects of the N + S and the low S treatments were due to identical additions of SO4 and the absence of a marked effect of NO3 additions on the mineral soil. Changes in the chemistry of the buried mineral soil bags can be explained by both the effects of H2SO4 and HNO3 additions as well as pedogenic processes.

Original languageEnglish (US)
Pages (from-to)556-563
Number of pages8
JournalSoil Science Society of America Journal
Issue number2
StatePublished - 1994
Externally publishedYes

ASJC Scopus subject areas

  • Soil Science


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