Slow response of soil organic matter to the reduction in atmospheric nitrogen deposition in a Norway spruce forest

authored by: Nicole Dörr, Klaus Kaiser, Robert Mikutta, Georg Guggenberger
Abstract: Global nitrogen (N) deposition rates in terrestrial environments have quadrupled since preindustrial times, causing structural and functional changes of ecosystems. Different emission reduction policies were therefore devised. The aim of our study was to investigate if, and over what timescale, processes of soil organic matter (OM) transformation respond to a decline in atmospheric N deposition. A N-saturated spruce forest (current N deposition: 34 kg ha^-1 yr^-1; critical N load: 14 kg ha^-1 yr^-1), where N deposition has been reduced to 11.5 kg ha^-1 yr^-1 since 1991, was studied. Besides organic C and organic and inorganic N, noncellulosic carbohydrates, amino sugars and amino acids were determined. A decline in organic N in litter indicated initial effects at plant level. However, there were no changes in biomarkers upon the reduction in N deposition. In addition, inorganic N was not affected by reduced N deposition. The results showed that OM cycling and transformation processes have not responded so far. It was concluded that no direct N deposition effects have occurred due to the large amount of stored organic N, which seems to compensate for the reduction in deposited N. Obviously, the time span of atmospheric N reduction (about 14.5 years) is too short compared with the mean turnover time of litter to cause indirect effects on the composition of organic C and N compounds. It is assumed that ecological processes, such as microbial decomposition or recycling of organic N and C, react slowly, but may start within the next decade with the incorporation of the new litter.
Organisation(s): Institute of Soil Science
External Organisation(s): Martin Luther University Halle-Wittenberg
Type: Article
Journal: Global change biology
Volume: 16
Pages: 2990-3003
No. of pages: 14
ISSN: 1354-1013
Publication date: 16.12.2009
Publication status: Published
Peer reviewed: Yes
ASJC Scopus subject areas: Global and Planetary Change, Environmental Chemistry, Ecology, General Environmental Science
Sustainable Development Goals: SDG 15 - Life on Land
Electronic version(s): https://doi.org/10.1111/j.1365-2486.2009.02148.x (Access: Closed)