Summary:
Published in Soil Biology and Biochemistry 38: 2135-2143.
The effect of high nitrogen (N) depositions on forest ecosystems is an important concern in North America and may lead to N saturation of forest ecosystems and contribute to soils and surface water acidification. In this study, nitrogen dynamics in the FH layers of a sugar maple (SM), a balsam fir (BF) and a black spruce (BS) forest was characterized using a short term 15N isotopic pool dilutions approach and mid-term FH material incubation both in situ and in the laboratory. The short term dilutions approach indicated that the mean residence times of NH4+ and NO3- in the FH material of the three sites were low (< 1 d). The amount of inorganic nitrogen (NH4+ + NO3- ) recycled annually within the exchangeable forest floor reservoir was between one and two orders of magnitude larger than the annual atmospheric N deposition found at each of the sites. The BS site was clearly distinct than the two other forest types in that net N mineralization was negligible, even in absence of root uptake, suggesting that soil microorganisms were severely N limited. While net nitrification was not observed within the FH material of the BF site, NO3- did accumulate in the FH of the SM despite a low pH of 3.72 presumably because of heterotrophic nitrification or as a result of acid-tolerant autotrophic nitrification. The difference in N dynamics between the sites were most probably caused by dominant tree species. Transformation rates of inorganic N were higher in SM, followed by BF and BS stands. Given that the potential to mineralize inorganic N matches with a superimposed N atmospheric deposition gradient in Québec, the sugar maple forest is more likely to be affected by N saturation than coniferous forests.
Sector(s):
Forests
Catégorie(s):
Scientific Article
Theme(s):
Ecosystems and Environment, Forest Ecology, Forestry Research, Forests
Author(s):
STE-MARIE, Catherine and Daniel HOULE
Year of publication:
2006
How to get the publication:
Keyword(s):
dilution isotopique 15N, minéralisation en N, nitrification, immobilisation de N, saturation en N, écologie écosystèmes et environnement, écosystèmes et environnement, ecosystems and environment, 15N isotopic dilution, N mineralization, nitrification, N immobilisaton, N saturation