LAUSR

Abstract Afforestation of arable land has been proposed as one of the most effective strategies for climate change mitigation. However, the effects of afforestation on soil CO2 emissions have not been well investigated due to a lack of information on the capacity of carbon pools to sequester CO2 over the long term. In this study, we conducted a 414-day incubation experiment to monitor changes in CO2 emission, soil extracellular enzymes, and microbial biomass at soils collected from a site afforested with R. pseudoacacia L and an adjacent cropland system under 15 °C and 25 °C constant temperatures. The study was to reveal how soil organic carbon decomposed under different temperatures during incubation along an afforestation gradient. Our results showed that: 1) after warming, active pool respiration increased from 0.64% to 12.57%, passive pool respiration increased from 20.62% to 46.77%, and slow pool respiration decreased from 21.27% to 59.35% for cropland to afforested land; 2) active and slow carbon pool increased in young and middle-aged afforested lands while the passive carbon pool increased in the late stage; and 3) microbial biomass and enzyme activities affected the respiration rate and the fraction of respiration during warming, especially enzyme affected active and slow pools. Our findings indicate that the temperature sensitivity of soil organic carbon decomposition changed mainly due to shifts of soil extracellular enzymes after afforestation, and provides insight into how SOC decomposition in afforested ecosystems may respond to future changes in climate.