Methane flux in montane and subalpine soils of the Central and Northern Alps

Abstract

Aerobic soils are generally known as potent sinks for the atmospheric greenhouse gas methane (CH4). However, uptake rates vary greatly depending on the soil site, and hence estimation of the global soil sink is difficult. Here, we measured the in situ CH4 flux of 15 forests and 14 grasslands on siliceous or calcareous parent materials in summer 2013. To cover the topography of North Tyrol (Austria), sampling sites were distributed over four typical altitudes (500, 1000, 1500, and 2000m above sea level). Twenty-three of the soils were net sinks for CH4, whereas net CH4 emission occurred at four grassland sites and two sites neither showed net removal nor emission. Flux rates ranged between −3.2 and 2218.2μgCH4-Cm−2h−1 for grasslands, and between −3.2 and −45.0μgCH4-Cm−2h−1 for forests, thus showing that forest soils are significantly more efficient sinks than grassland soils. Soils derived from siliceous parent material were significantly more effective sinks than those derived from calcareous parent material, when only negative flux rates were considered. Multiple regressions indicated that soil dry mass and NH4+-N shaped CH4 flux of grasslands, whereas CH4 flux of forest soils was regulated by soil pH and NO3−-N. Our results provide insights into the CH4 turnover of the so far scarcely studied Central European alpine regions and thus add to the knowledge on this relevant topic.