Increasing Soil Organic Carbon but Decoupling of Ecological Attributes After Loss of Dominant Functional Groups in...

Due to the sensitivity of alpine meadow ecosystems in the Qinghai-Tibet Plateau to climate change and human activities, dominant plants are gradually being replaced, potentially triggering ecosystem shifts and affecting soil organic carbon (SOC) sequestration. We conducted a three-year dominant plant removal experiment to assess impacts on SOC and related ecological attributes. The results showed a significant increase in SOC across all removal treatments, with the greatest increase following the loss of the dominant species. This increase was enhanced by changes in soil moisture and nitrogen, and was also partly attributed to the presence of remaining plant species. On the contrary, SOC accumulation was less responsive to soil moisture and nutrients under the dominant functional group or total removal, indicating that more severe disturbances reduce the supporting factors of SOC. Metal ions also positively influenced SOC following the loss of the dominant plant group. In particular, this study focused on shallow soil layers (0-10 cm), where SOC gains raise concerns about long-term stability. Correlation analyses and structural equation model revealed that, after the removal of the dominant species, the remaining species maintained the coupling between ecological attributes, preserving ecosystem functioning. However, the removal of dominant functional groups completely disrupted the connections between ecological attributes, reducing the complexity of SOC regulation and key mediating effects. Therefore, prioritizing the restoration of dominant species groups and functional groups is essential for maintaining ecosystem interactions and promoting effective recovery in meadow restoration.