Discussion
Our study addressed a key knowledge gap, namely, how past environmental conditions and plant communities influence soil microbial diversity which subsequently creates PSFs that can fundamentally alter plant diversity-productivity relationships. We found that 1) plant diversity and drought resulted in different soil microbial communities, leading to soil legacies that had subsequent effects of plant-soil feedbacks; 2) and that these soil legacies of drought and plant diversity influenced the strength of subsequent plant diversity-productivity relationships; 3) plant communities in soil that experienced past drought conditions usually had more positive complementarity effects and more negative selection effects.