Gaseous nitrogen and carbon fluxes in riparian alder stands

• Published in: Boreal environment research 2008-06, Vol.13 (3), p.231-241
• Main Authors: MANDER, Ulo, LOHMUS, Krista, TEITER, Sille, URI, Veiko, AUGUSTIN, Jürgen
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Earth sciences; Earth, ocean, space; Exact sciences and technology; Freshwater; Fundamental and applied biological sciences. Psychology; General aspects; Marine and continental quaternary; Surficial geology; Synecology
• ISSN: 1239-6095; 1797-2469

Riparian buffer zones are considered to be important elements of agricultural watersheds, in that they control nutrient and carbon fluxes. Although the water purification effect of riparian ecosystems has been well studied, there is little knowledge of their internal cycling, especially in the area of gaseous emissions. We measured fluxes of nitrous oxide (N2O), dinitrogen (N2), methane (CH4), and carbon dioxide (CO2) in riparian grey alder stands in southern Estonia and black alder stands in Brandenburg, Germany. Dinitrogen emission was the most important component in N retention in the studied riparian grey alder forests. In 2001–2003, the median values of N2 emission in the grey alder sites significantly exceeded the N2 emission rates in the black alder sites, varying from 700 to 1200 and from 360 to 400 kg N2-N ha–1 year–1, respectively. In contrast, the median values of N2O flux were higher in the black alder sites than in the grey alder sites, i.e., 0.9–2.6 and 0.2–0.7 kg N2O-N ha–1 year–1, respectively. The black alder sites acted as a sink for CH4, whereas the grey alder sites emitted a small amount of CH4. The CO2-C flux was higher in the black alder stands. The estimated N2-N emission in the grey alder stands for 1994–1995 was 51.2, whereas N2O-N emission was 0.5 kg N ha–1 year–1. The significant increase in N2 emission from 1994–1995 to 2001–2003 can be related to changes in microbial activity during the succession of the pioneer grey alder stand into a more stable mixed forest community. Due to CO2 fluxes and N2O fluxes from sites with altered water regime, the estimated GWP of the studied riparian alder stands was relatively high. Further investigations should concentrate on the factors that regulate rates of N2O and N2 emission from riparian buffer zones.