Record ID No. |
639 |
Author(s) |
Ste-Marie, C., Houle, D* , 2006 |
Affiliation |
*Environment Canada, St. Laurent Centre, 105,Rue McGill 7ieme Etage, Montreal, PQ H2Y 2E7, Canada |
Title |
Forest floor gross and net nitrogen mineralization in three forest types in Quebec, Canada |
Source. Vol.(no):Page |
Soil biology & biochemistry. 38(8):2135-2143p. |
Categories |
Mycorrhiza General |
Subjects |
General |
Host |
n.a. |
Organism |
n.a. |
Country |
Canada, N. America |
Abstracts |
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 (1317) and a black spruce (BS) forest was characterized using a short term 15 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+ and NO3- in the FH material of the three sites were low (< 1d). 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 Quebec, the sugar maple forest is more likely to be affected by N saturation than coniferous forests. |