Department of Forest and Ecosystem Science - Creswick Seminar Series
Dr Ute Szukics
Department of Bioresources
Austrian Research Centers GmbH, Seibersdorf, Austria
Hot N Wet: Rapid and distinct responses of microbes performing nitrogen cycling in forest soils
U. Szukics12, E. Hackl1, V. Hödl1, G. Abell1, B. Mitter1, A. Sessitsch1, S. Zechmeister-Boltenstern2
1Austrian Research Centers GmbH, Department of Bioresources, Seibersdorf, Austria
2Federal Research and Training Centre for Forests, Natural Hazards and Landscape, Vienna, Austria
Friday 10th October, 9:30pm, Stage 2 Lecture Theatre, Creswick Campus
Environmental concerns about climate change and increasing anthropogenic nitrogen deposition raise questions about resulting feedback effects on microorganisms performing nitrogen cycling in soils. Nitrification and denitrification, the two major biogenic processes contributing to the emission of the greenhouse significant gases nitric oxide (NO) and nitrous oxide (N2O) from soils, show sensitive reactions to modifications in environmental conditions and nitrogen supply.
Ecological responses to nitrate or ammonia amendment and to modifications in soil temperature and moisture were investigated in the pristine Rothwald forest and the managed Schottenwald forest with contrasting soil characteristics. Effects on N turnover rates, N gas emissions, the abundance and community structure of nitrite reducers (nirK) and bacterial and archaeal ammonia oxidizers (amoA), as well as the diversity of these functional groups were investigated.
Results of the study demonstrate a rapid and distinct response of the two forest soils to nitrate and ammonia treatment, which included increased nitrogen oxide emissions and variance in the abundances of ammonia oxidizing archaea (AOA) and ammonia oxidizing bacteria (AOB). Increasing temperature stimulated nitrogen turnover, while soil moisture and nitrogen availability were the major determinants of NO and N2O emission rates. AOA were more abundant than AOB and their ecological response was different. The abundance of AOB increased with soil temperature, whereas the reaction of AOA suggested sensitivity to anaerobic conditions. Nitrite reducers, aside from being more diverse than AOA and AOB, reacted more rapidly to changes made to the soil environment. Changing microbial activities and abundances of nitrifiers and denitrifiers were also reflected in the community structures, which responded within a few weeks to environmental changes.
The study clearly demonstrated that functional groups involved in nitrogen cycling respond differently to short-term changes in the soil environment, affecting the availability of mineral nitrogen forms in forest ecosystems.