The effect of seasonal drying on sulphate dynamics in streams across southeastern Canada and the northeastern USA

Published in Biogeochemistry 111: 393-409 https://doi.org/10.1007/s10533-011-9664-1

Within the southeast Canada and northeast USA region, a peak in sulphate (SO₄^2-) concentration has been reported for some streams following periods of substantial catchment drying during the summer months (ON, Canada; VT, NH and NY, USA). However, it is currently unclear if a SO₄^2- response to seasonal drying is widespread across the broader region, or to what extent the level of response varies among catchments. In our study, SO₄^2- response to seasonal drying was compared in 20 catchments from 11 locations across southeastern Canada (ON, QC and NS) and northeastern USA (NH, NY, VT, WV and ME). Using long-term monitoring data of stream discharge and chemistry, the number of days for each month of the dry season (# d) when discharge (Q) was below a threshold level (25th percentile; Q₂₅) was calculated for each catchment to give a measure of ‘seasonal dryness’ (# d Q < Q₂₅). A SO₄^2- response score (rs) was then calculated for each catchment based on linear regression analysis of # d Q < Q₂₅ versus either the annual SO₄^2- concentration, or the residual of annual SO₄^2- concentration as a function of time (year). The final rs values for each catchment provided an estimate of the proportion of variation in annual SO₄^2- concentration which could be explained by seasonal drying (possible rs range = 0–1). Of the 20 catchments, 13 exhibited some level of a SO₄^2- response to seasonal drying (rs = 0.04–0.72) with an additional two catchments exhibiting a SO₄^2- response for one or more seasons. SO₄^2- response scores were positively related to percent wetland area(w) (rs = 1.000 - 0.978e^-0.054*w, r² = 0.44) and percent saturated area (sat) (rs = 0.481 - 0.488e^-0.101*sat, r² = 0.54) indicating that wetlands/saturated areas were an important driver of regional variation in the SO₄^2- response to seasonal drying. Our results suggest that any shift towards drier summers as a result of climate change could impact SO₄^2- dynamics in a large number of catchments throughout the region.

Forests

Scientific Article

Ecosystems and Environment, Forest Ecology, Forestry Research, Forests

KERR, J.G., M.C. EIMERS, I.F. CREED, M.B. ADAMS, F. BEALL, D.BURNS, J.L. CAMPBELL, S.F. CHRISTOPHER, T.A. CLAIR, F. COURCHESNE, L. DUCHESNE, I. FERNANDEZ, D. HOULE, D.S. JEFFRIES, G.E. LIKENS, M.J. MITCHELL, J. SHANLEY and H. YAO

2012

Paper

Available at the Direction de la recherche forestière

sécheresse, nutrition, sulphate, bassin versant, biogéochimie, écologie forestière, écosystèmes et environnement, article scientifique de recherche forestière, ecosystems and environment, forest ecology, drought, nutrition, sulphate, watershed, biogeochemistry