5 Conclusions
This study shows that the drought adaptation and response mechanisms ofS. krylovii are related to their seed source of regions, with significant different mechanisms for individuals from the western region and those from the other two regions. In addition, there is relatively higher drought adaptability and tolerance for individuals from western region. In the area of grassland vegetation in the Inner Mongolia Steppe, increasing aridity would cause a significant reduction of grassland regions, but the distribution area of S. krylovii increased. The present findings could provide some explanations for the distribution areas increase and eastern shifts of S. krylovii , and could help us understand and predict the evolution potential of this important species.