Effect of water tension on ethylene production and consumption in montane and lowland soils in Austria

The trace gas ethylene affects plant growth and atmospheric chemistry and it interferes with soil restoration. In soil ethylene is simultaneously produced and consumed by different microorganisms. The effects of land use and soil moisture conditions on processes leading to an accumulation of ethylene are still unclear. We measured the rates at which montane and lowland soils from Austria produced and consumed ethylene over a range of water tensions and oxygen supply. Complete anaerobiosis (waterlogging, zero tension) favoured ethylene production, whereas ethylene degradation rates were greatest in soils at 30 kPa water tension. Soils from the lowland region of eastern Austria produced ethylene at rates of up to 12 pmol C₂H₄ g^–1 h^–1 under anaerobic conditions, and they consumed ethylene at rates reaching 231 pmol C₂H₄ g^–1 h^–1, after addition of 20 μl l^–1 ethylene. Deciduous forest soils consumed ethylene fastest. Ethylene formed rapidly and was also consumed rapidly in soils rich in humus and total nitrogen. Soils taken from the mountains both produced and consumed ethylene more rapidly than lowland soils did. Production rates reached 146 pmol C₂H₄ g^–1 h^–1 under anaerobic conditions. Spruce forest soils produced significantly more ethylene than pastures. Ethylene formation was negatively correlated with soil pH. In montane soils ethylene production was related to the availability of simple carbon sources, expressed by the amount of extractable glucose equivalents. Maximum ethylene degradation amounted to 895 pmol g^–1 h^–1. Most of the soils were net sinks for ethylene at a water tension of 30 kPa and drier.