Effect of nutrient addition and mowing on plant diversity and soil carbon content of meadow steppe in Inner Mongolia.

Meadow steppe, one of China's most critical ecosystems in the Inner Mongolia, plays a vital role in maintaining regional ecological balance and global carbon cycling. However, in recent decades, this ecosystem has been severely degraded due to overgrazing under climate change. Understanding the relationship between plant diversity and soil carbon dynamics is essential for developing effective grassland management strategies, as these factors are highly sensitive to anthropogenic interventions. In this study, we investigated the effects of 7-year nutrient addition and mowing treatments on plant community characteristics and soil carbon content in meadow steppe in the Inner Mongolia. This research revealed that mowing significantly increased plant diversity, but nutrient addition significantly reduced plant diversity. Mowing notably increased the Shannon-Wiener index, Simpson index and species richness, but reduced aboveground net primary productivity (ANPP) and soil organic carbon (SOC) content. Nutrient addition increased ANPP, but failed to offset the SOC loss. Moderate harvesting intensity exerted the strongest influence on the plant diversity-SOC relationship. Critically, higher mowing heights preserved the positive correlation between plant diversity and SOC, suggesting that optimized mowing practices could simultaneously promote SOC accumulation and maintain plant diversity. These results provide a scientific foundation for sustainable management strategies in degraded meadow steppe in the Inner Mongolia.