Biochar, as a soil amendment, has been widely confirmed to increase soil carbon sequestration. However, how biochar addition affects soil carbon changes during the vegetation restoration process is still unclear, which constrains our ability to explore biochar’s application in the technology of soil carbon sequestration in forests. We conducted an incubation experiment on biochar and dissolved organic matter (DOM) addition to soil at three stages of revegetation (degraded land (DS), plantation forest (PS), and secondary natural forest (NS) in Changting County in Fujian province, China) to investigate the effects of vegetation restoration, biochar, DOM, and their interaction on soil CO
2 emission and its relative mechanisms. We found that the accumulative release of CO
2-C in the NS and PS soils was 7.6 and 6.8 times higher, respectively, in comparison to that from the DS soil. In the DS, biochar addition significantly increased the accumulative release of CO
2-C, soil pH, NH
4+-N content,
qCO
2, phenol oxidase, and peroxidase activities. Peroxidase activities were positively correlated with the accumulative release of CO
2-C, and oxidase was the most important direct factor influencing the accumulative release of CO
2-C in the DS. However, the accumulative release of CO
2-C, soil NH
4+-N content,
qCO
2, β-glucosidase, and N-acetylglucosaminidase activities was significantly reduced after the application of biochar in the PS and NS. These two hydrolases were positively associated with the accumulative release of CO
2-C, and hydrolase was the most vital direct factor influencing the accumulative release of CO
2-C from the PS and NS soils. The positive effect of DOM addition on CO
2 emission under biochar application declined with a vegetation restoration age increase. Our results indicated that biochar could alter microbial physiological processes, inhibit
qCO
2 and hydrolase activities, and further decrease CO
2 emission in relatively fertile soil from the PS and NS; but in the relatively barren soil from the DS, biochar might promote CO
2 emission by stimulating microorganisms to enhance
qCO
2 and oxidase activities.
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