Cryptogamic stem covers may contribute to nitrous oxide consumption by mature beech trees. Issue 1 (December 2017) - Machacova, Katerina
Abstract Naturally produced by microbial processes in soil, nitrous oxide (N2 O) is an important greenhouse gas contributing to climate change. Accordingly, there is a need to accurately quantify the capability of forest ecosystems to exchange N2 O with the atmosphere. While N2 O emissions from soils have been well studied, trees have so far been overlooked in N2 O inventories. Here, we show that stems of mature beech trees (Fagus sylvatica ) may act as a substantial sink of N2 O from the atmosphere under conditions of soils consuming N2 O. Consistent consumption of N2 O by all stems investigated (ranging between −2.4 and −3.8 µg m−2 h−1 ) is a novel finding in contrast to current studies presenting trees as N2 O emitters. To understand these fluxes, N2 O exchange of photoautotrophic organisms associated with beech bark (lichens, mosses and algae) was quantified under laboratory conditions. All these organisms were net N2 O sinks at full rehydration and temperature of 25 °C. The consumption rates were comparable to stem consumption rates measured under field conditions. Cryptogamic stem covers could be a relevant sink of N2 O in European beech forests.