Summary:
Published in Applied Geochemistry 26: 2181-2190
The concentrations and the isotopic compositions of S, N and C were studied in soils and in the dominant plant species of three forested watersheds (Québec, Canada) located along a latitudinal and atmospheric deposition gradient. Large increases in S, N and C isotope ratios (up to 3.9‰, 10‰, 2.6‰, respectively) were observed with increasing soil depth at the three watersheds. These increases were accompanied by a strong decrease in elemental concentrations resulting in a strong negative relationship between these two variables. Both S and N concentrations throughout the soil profile and d34S and d15N in the mineral soil appeared to increase with increasing S and N deposition rates and decreasing latitude. A strong positive linear relationship was found between d34S and d15N (R2 = 0.72) values and between organic S and N concentrations (R2 = 0.96) in soils. The slope of the linear relationship between d34S and d15N (d34S = f(d15N)) indicated that isotopic fractionation was almost 4 times higher for S than for N during transformations that occurred in soil. However, this difference might reflect a higher degree of openness of the S cycle compared to the N cycle rather than an isotope effect per se. Overall, the results suggest that N and S inputs significantly impact the isotope ratios and the concentrations of N and S in the soils, and that S and N were closely associated and subject to similar processes with the same isotopic effects throughout the soil profile. Contrary to most studies, d34S-SO4 in stream water of the most northerly site with the lowest S deposition rate was significantly higher than d34S-SO4 in atmospheric depositions but similar to the d34S of the bulk mineral soil. It suggests that the mineral soil actually contributes a large portion of the stream S-SO4 for this site.
Sector(s):
Forests
Catégorie(s):
Scientific Article
Theme(s):
Ecosystems and Environment, Forest Ecology, Forestry Research, Forests
Departmental author(s):
Author(s):
MARTY, C., Daniel HOULE, C. GAGNON and Louis DUCHESNE
Year of publication:
2011
Format:
Paper
How to get the publication:
Keyword(s):
azote, soufre, carbone, forêt, écologie écosystèmes et environnement, isotope, écosystèmes et environnement, article scientifique de recherche forestière, ecosystems and environment, nitrogen, sulfur, carbon, forest