Sulphur addition has negative impacts on individual species abundance in natural plant species communities

Industrial and agricultural activities as well as the combustion of fossil fuels lead to increased levels of sulphur (S) deposition in terrestrial and aquatic ecosystems, affecting soil acidity and plant communities. Local empirical studies have provided insights into potential effects of high S deposition on plant biodiversity but are restricted by their focus on specific plant species and locations. An estimate of the impact of S deposition on natural plant communities across environmental contexts is lacking. We aimed to quantify the effects of S addition on the abundance of natural plant species, while considering potential interactions between the effects of S addition and nitrogen (N) addition as well as with environmental conditions (e.g., temperature and soil cation exchange capacity). For this, we compiled experimental data from literature on the effects of S addition on natural plant species abundance and ran mixed-effects regression models to estimate the effects across species and regions. We found that S addition has a negative effect on plant individual species abundance, even though the negative effects of N addition on individual plant species abundance are generally stronger. Based on the negative relationship, we estimated that S addition has reduced individual plant species abundance in natural communities up to 8% in the United States and 10% in Europe between 2000 and 2022. Our models can be used to estimate global effects of S addition on plant biodiversity.