Divergent recovery trajectories of soil organic and inorganic carbon following artificial grassland restoration in semi-arid mining ecosystems

In arid mining ecosystems, the recovery of soil carbon pools following vegetation restoration is complex, particularly regarding the often-overlooked interplay between soil organic carbon (SOC) and inorganic carbon (SIC). Here, this study investigated a 4-year chronosequence of artificial grasslands sown with legumes to assess the restoration trajectories of SOC and SIC. Integrated Bayesian and correlation analyses were used to disentangle the driving mechanisms. The results showed that SOC and SIC exhibited increasing trends at 0–30 cm soil layer but followed different trajectories. The SOC accumulated gradually with increasing below-ground biomass, which promoted soil organic matter inputs. Conversely, the SIC exhibited a unimodal trend regulated by the soil moisture content and rhizosphere-mediated pH shifts rather than direct plant biomass inputs. These findings indicate that SOC and SIC show close coupling but divergent adjustment pathways during the 4-year restoration period, rather than synchronous and linear increase. This study highlights that assessing soil carbon pool restoration in arid mining ecosystems requires consideration of multiple soil carbon reservoirs, improving the understanding of soil carbon responses to vegetation restoration during early restoration.