Canopy interaction with precipitation and sulphur deposition in two boreal forests of Quebec, Canada

Marty, C.; Houle, D.; Duchesne, L.; Gagnon, C.

Canopy interaction with precipitation and sulphur deposition in two boreal forests of Quebec, Canada

2012

Marty, C. | Houle, D. | Duchesne, L. | Gagnon, C.

The interaction of atmospheric sulphur (S) was investigated within the canopies of two boreal forests in Québec, Canada. The net canopy exchange approach, i.e. the difference between S–SO₄ in throughfall and precipitation, suggests high proportion of dry deposition in winter (up to 53%) as compared to summer (1–9%). However, a 3.5‰ decrease in δ¹⁸O–SO₄ throughfall in summer compared to incident precipitation points towards a much larger proportion of dry deposition during the warm season. We suggest that a significant fraction of dry deposition (about 1.2 kg ha⁻¹ yr⁻¹, representing 30–40% of annual wet S deposition) which contributed to the decreased δ¹⁸O–SO₄ in throughfall was taken up by the canopy. Overall, these results showed that, contrary to what is commonly considered, S interchanges in the canopy could be important in boreal forests with low absolute atmospheric S depositions.

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