Black alder (Alnus glutinosa (L.) Gaertn.) trees mediate methane and nitrous oxide emission from the soil to the atmosphere

• Published in: Plant and soil 1998-04, Vol.201 (1), p.1-7
• Main Authors: Rusch, H. (Fraunhofer-Institute for Atmospheric Environmental Research, Garmisch-Partenkirchen (Germany).), Rennenberg, H
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; ALNUS GLUTINOSA; Atmosphere; Bark; Biological and medical sciences; Chemical, physicochemical, biochemical and biological properties; ECHANGE GAZEUX; Emission measurements; Fundamental and applied biological sciences. Psychology; GAS EXCHANGE; Gases; Greenhouse gases; Indigenous species; INTERCAMBIO DE GASES; METANO; METHANE; Mixing ratios; NITROUS OXIDE; Organic matter; OXIDO NITROSO; OXYDE NITREUX; Physics, chemistry, biochemistry and biology of agricultural and forest soils; Plant roots; Plant species; Plants; PLANTULAS; PLANTULE; Rhizosphere; Root zone; SEEDLINGS; Soil air; Soil science; Soils; Wetland soils; Wetlands; Woody plants
• ISSN: 0032-079X; 1573-5036
• DOI: 10.1023/A:1004331521059

Three-year-old seedlings of black alder (Alnus glutinosa (L.) Gaertn.), a common European wetland tree species, were grown in native soil taken from an alder swamp. Fluxes of methane (CH₄) and nitrous oxide (N₂O) between the tree stem and the atmosphere were determined under controlled conditions. Both CH₄ and N₂O were emitted through the bark of the stem into the atmosphere when the root zone exhibited 'higher-than-ambient' CH₄ and N₂O gas mixing ratios. Flooding of the soil caused a decreased N₂O emission but an increased CH₄ efflux from the stem. Immediately after flooding of the soil, N₂O was emitted from the seedlings' bark at a rate of 350 μmol N₂O m⁻² h⁻¹ whereas CH₄ flux could not be detected. After more than 40 days of flooding CH₄ fluxes up to 3750 μmol CH₄ m⁻² h⁻¹ from the stem were measured, while N₂O emission had decreased below the limit of detection. Gas efflux decreased with increasing stem height and correlated with gas mixing ratios in the soil, indicating diffusion through the aerenchyma as the major path of gas transport. From these results it is assumed that woody species with aerenchyma can serve as conduits for soil-derived trace gases into the atmosphere, to date only shown for herbaceous plants. This, yet unidentified, 'woody plant pathway' contributes to the total greenhouse gas source strength of wetlands.