Inclination controls CO2 and N2O fluxes, but not CH4 uptake, from a temperate upland forest soil

Abstract Inclination and spatial variability in soil and litter properties influence soil greenhouse gas (GHG) fluxes, and thus on-going climate change, but their relationship in forest ecosystems is poorly understood. To elucidate this, we explored the effect of inclination, distance to a stream, soil moisture, soil temperature, and other soil and litter properties on soil-atmosphere fluxes of carbon dioxide (CO 2 ), methane (CH 4 ), and nitrous oxide (N 2 O) with automated static chambers in a temperate upland forest in Eastern Austria. We hypothesised that soil CO 2 emissions and CH 4 uptake are higher in sloped locations with lower soil moisture content, whereas soil N 2 O emissions are higher in flat, wetter locations. During the measurement period, soil CO 2 emissions were significantly higher on flat locations ( p < 0.05), and increased with increasing soil temperature ( p < 0.001) and decreasing soil moisture ( p < 0.001). The soil acted as a CH 4 sink, and CH 4 uptake was not significantly related to inclination. However, CH 4 uptake was significantly higher at locations furthest away from the stream compared to at the stream ( p < 0.001), and positively related to litter weight and soil C content ( p < 0.01). N 2 O fluxes were significantly higher on flat locations and further away from the stream ( p < 0.05), and increased with increasing soil moisture ( p < 0.001), soil temperature ( p < 0.001) and litter depth ( p < 0.05). Overall, this study underlines the importance of inclination and the resulting soil and litter properties in predicting GHG fluxes from forest soils and therefore their potential source-sink balance.