SOIL, 1, 351–365, 2015 www.soil-journal.net/1/351/2015/ doi:10.5194/soil-1-351-2015 SOIL © Author(s) 2015. CC Attribution 3.0 License. Global distribution of soil organic carbon – Part 1: Masses and frequency distributions of SOC stocks for the tropics, permafrost regions, wetlands, and the world M. Köchy1,*, R. Hiederer2, and A. Freibauer1 1Thünen Institute of Climate-Smart Agriculture, Bundesallee 50, 38116 Braunschweig, Germany 2Joint Research Centre, Institute for Environment and Sustainability, Via E. Fermi 2749, 21027 Ispra (VA), Italy *now at: Thünen Institute of Market Analysis, Bundesallee 50, 38116 Braunschweig, Germany Correspondence to: M. Köchy (offi
[email protected]) Received: 24 July 2014 – Published in SOIL Discuss.: 3 September 2014 Revised: 27 February 2015 – Accepted: 16 March 2015 – Published: 16 April 2015 Abstract. The global soil organic carbon (SOC) mass is relevant for the carbon cycle budget and thus atmo- spheric carbon concentrations. We review current estimates of SOC stocks and mass (stock × area) in wetlands, permafrost and tropical regions and the world in the upper 1 m of soil. The Harmonized World Soil Database (HWSD) v.1.2 provides one of the most recent and coherent global data sets of SOC, giving a total mass of 2476 Pg when using the original values for bulk density. Adjusting the HWSD’s bulk density (BD) of soil high in organic carbon results in a mass of 1230 Pg, and additionally setting the BD of Histosols to 0.1 g cm−3 (typ- ical of peat soils), results in a mass of 1062 Pg. The uncertainty in BD of Histosols alone introduces a range of −56 to C180 Pg C into the estimate of global SOC mass in the top 1 m, larger than estimates of global soil respiration.