Amount of carbon stored as soil organic carbon (SOC) globally

Range almost 3,000 (>50% of which in subsoil, deeper than 20cm) Pg C
Organism Biosphere
Reference Hicks Pries CE, Castanha C, Porras RC, Torn MS. The whole-soil carbon flux in response to warming. Science. 2017 Mar 31355(6332):1420-1423. doi: 10.1126/science.aal1319. P.1420 left column top paragraphPubMed ID28280251
Primary Source [1] M. Köchy, R. Hiederer, A. Freibauer, Global distribution of soil organic carbon—Part 1: Masses and frequency distributions of SOC stocks for the tropics, permafrost regions, wetlands, and the world. Soil 1, 351–365 (2015). doi:10.5194/soil-1-351-2015 link [3] E. G. Jobbágy, R. B. Jackson, The vertical distribution of soil organic carbon and its relation to climate and vegetation. Ecol. Appl. 10, 423–436 (2000). doi: 10.1890/1051-0761(2000)010[0423:TVDOSO]2.0.CO2 link
Comments P.1420 left column top paragraph: "Globally, almost 3000 Pg C is stored as soil organic carbon (SOC) (primary source 1). Warming is expected to increase microbial decomposition of SOC, thereby releasing more CO2 into the atmosphere. However, the amount and rate of this response are highly uncertain because the mechanisms controlling the microbial accessibility of SOC are not fully understood (ref 2). Empirical determination of the temperature response from whole-soil profiles (0 to >100 cm) has been difficult. The majority of in situ warming experiments focus on warming the top 5 to 20 cm of surface soil (table S1), thus, they may miss the response of subsoils (below 20 cm), which contain >50% of global SOC stocks (primary source 3). Alternatives to field manipulations are not ideal, incubations have large experimental artifacts, whereas seasonal temperature gradients confound warming with factors such as phenology and soil moisture (ref 4). As a result, [investigators] currently lack data on the whole-soil response to warming (ref 5)." Pg=Peta gram=10^15 grams
Entered by Uri M
ID 113322