Changes in soil organic carbon and microbial carbon storage projected during the 21st century using TRIPLEX-MICROBE

Abstract Microbial physiology is very important in the biogeochemical cycles of the Earth system. Considerable uncertainty exists in the responses of global soil organic and microbial carbon to future climate change. In this study, future changes in the global soil organic carbon (SOC) and microbial carbon (MBC) pools are simulated using TRIPLEX-MICROBE, which considers and predicts microbial activity, under three future representative concentration pathways (RCPs) in the 21st century. Between 2013 and 2100, TRIPLEX-MICROBE simulates decreases in SOC from 1099 Pg (petagrams, 10 12 kg) to 1032 Pg, 996 Pg and 924 Pg under RCP scenarios RCP2.6, RCP4.5 and RCP8.5, respectively, representing reductions of approximately 6.1%, 9.4% and 15.9%, respectively. The MBC reaches a stable state after 2030 under RCP2.6, and it increases from 20.89 Pg to 23.78 Pg between 2013 and 2100. Under RCP4.5 and RCP8.5, MBC increases by 20.3% and 39.6%, respectively, between 2013 and 2100. The SOC stored in the Arctic declines under the priming effect; however, as the climate gradually warms from the equator to the mid-latitudes, the Northern Hemisphere becomes a larger carbon sink, which could offset the carbon losses from high-latitude and high-altitude regions. The latitude where the MBC reaches its maximum during the coldest season of a year in the Northern Hemisphere moves northward approximately 10 degrees under the three RCPs from the latitude in the historical period. Tropical and temperate vegetation expand northward gradually with warming, and vegetation fixes more carbon as it migrates northward to offset the increase in atmospheric CO 2 .