Published in Soil Biology and Biochemistry 38: 2135-2143.<\/b><\/p>
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 15<\/sup>N 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<\/sub>+<\/sup> and NO3<\/sub>–<\/sup> in the FH material of the three sites were low (< 1 d). The amount of inorganic nitrogen (NH4<\/sub>+<\/sup> + NO3<\/sub>–<\/sup> ) 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<\/sub>–<\/sup> 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 Qu\u00e9bec, the sugar maple forest is more likely to be affected by N saturation than coniferous forests.<\/p>\n","protected":false},"excerpt":{"rendered":" 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 […]<\/p>\n","protected":false},"template":"","format":"standard","cptt_secteur":[1179],"cptt_theme":[1183,1185,1180,1181],"cptt_categ_publi":[1149],"cptt_auteurs_ministeriels":[],"class_list":["post-82286","cpt_publication","type-cpt_publication","status-publish","format-standard","hentry","cptt_secteur-forests","cptt_theme-ecosystems-and-environment","cptt_theme-forest-ecology","cptt_theme-forestry-research","cptt_theme-forests","cptt_categ_publi-scientific-article"],"acf":[],"yoast_head":"\n