Interactions of atmospheric deposition with a mixed hardwood and a coniferous forest canopy at the Lake Clair Watershed (Duchesnay, Québec)

Published in Canadian Journal of Forest Research 29: 1944-1957

From 1989 to 1996, ion deposition in precipitation, throughfall, and stemflow were measured under a deciduous and a coniferous stand, located in the Lake Clair Watershed, during the growing and the dormant seasons. During the growing season, throughfall deposition under both stands was significantly depleted in H⁺ and NH₄⁺ compared with wet deposition, and a significant uptake of NO₃^- was observed under the coniferous canopy. Deposition of Ca²⁺, Mg²⁺, K⁺, Na⁺, Cl^-, and S0₄^2- was significantly higher in the throughfall than in the wet precipitation. During the growing season, the coniferous stand was more efficient in retaining nitrogen (NH₄⁺ and N0₃^-), while H⁺ was more intensively retained in the deciduous stand. Significant interactions between precipitation and forest canopies were also observed during the dormant season: throughfall depositions of Ca²⁺, Mg²⁺, K⁺, Na⁺, and Cl^- were significantly higher than wet precipitation under both canopies, while throughfall S0₄^2- was significantly enriched only under the coniferous stand. Using a Na⁺ ratio method, foliar leaching was found mostly responsible for the throughfall enrichment on a full-year basis in both stands, with values averaging 61, 73, and 96% of the total throughfall fluxes for Ca²⁺, Mg²⁺, and K⁺, respectively. Under both stands, net canopy exchange (NCE) of base cations, expressed on a monthly basis, were correlated to water volume and to H⁺ and S0₄^2- deposition. Multiple regression models including wet S0₄^2- deposition and an estimate of dry S deposition, explained up to 88% (Ca²⁺ in the coniferous stand) of the variance in base cation NCE under both stands.

Forests

Scientific Article

Ecosystems and Environment, Forest Ecology, Forestry Research, Forests

Ouimet, Rock

HOULE, Daniel, Rock OUIMET, Raynald PAQUIN and Jean-Guy LAFLAMME

1999

Available at the Direction de la recherche forestière

ion deposition, atmospheric deposition, canopy, coniferous forest, mixed hardwood forest, chemical analysis, hydrologic flux, cations, nitrogen, sulfur, chloride, lixiviation, Lake Clair Watershed, Duchesnay, écologie écosystèmes et environnement, écosystèmes et environnement, ecosystems and environment, analyse chimique, soufre, dépôt atmosphérique, cation, nitrogène, feuillu, chlorure