Decade-long active restoration induced positive priming effects on soil organic carbon in desertified grassland: The amplifying effect of biochar

• Negative impact of grassland restoration and biochar on carbon sequestration. • Biochar addition leads to positive priming effect under active restoration. • Priming effects after passive and active restoration are affected by PLFA and pH. Grassland restoration can be achieved through active or passive methods. Biochar enhances soil structure and nutrient availability and, therefore, can play a crucial role in restoring degraded grassland. However, the long-term effects of biochar addition on both active and passive restoration of desertified grasslands remain unclear. This aim of this study was to fill this gap by determining how biochar influences organic carbon mineralization and priming effects in grasslands undergoing more than a decade of active or passive restoration. The results demonstrated that, compared to degraded grassland, biochar application under active restoration increased soil CO 2 emissions significantly. Positive priming effects were observed in both the topsoil (120.5–297.0 %) and subsoil (157.2–287.3 %). Conversely, under passive restoration, priming effects were positive in the topsoil (34.7–80.9 %) but negative in the subsoil (−67.1% to −47.7 %). In passive restoration, phospholipid fatty acids (PLFA) were the primary drivers of priming effects, while in active restoration, soil pH was the primary driver. This study bridges the fields of restoration and soil ecology by evaluating the effects of biochar on organic carbon mineralization and priming effects in degraded grasslands. The findings highlight the importance of understanding how different restoration approaches interact with biochar addition to influence soil mineralization processes. This research provides valuable insights for grassland managers and policymakers in developing effective restoration strategies, particularly in the context of climate change.