Abstract: Alpine cushion plants are recognized as keystone species essential for sustaining plant communities and biodiversity. However, their contributions to the structures of plant–plant co-occurrence networks remain poorly understood. This study constructed plant–plant co-occurrence networks within cushion microhabitats at both regional and local scales in the Himalaya–Hengduan Mountains, focusing on the influences of multiple cushion plants in shaping plant–plant network structures. Results reveal that cushion plants significantly influence the network structures. Compared to random expectations, these networks display lower linkage density, weighted connectance and weighted nestedness (wNODF), but higher modularity, implying distinct organizational principles driven by cushion plant facilitation. Non-cushion plants show stronger associations with cushion microhabitats than with open ground microhabitats. Additionally, the spatial influence of cushion plants extends beyond their immediate canopies, highlighting their role in structuring surrounding plant assemblages. Moreover, the facilitation strength of cushion plants positively correlates with network metrics, indicating that network complexity increases with increasing facilitation by cushion plants. Simulations suggest that the loss of cushion plants would likely trigger cascading extinctions of associated non-cushion plants, particularly when high-degree centrality cushion species—those with the greatest network connectivity—are removed. These results highlight the keystone roles of cushion plants’ facilitation in supporting biodiversity via enhancing network complexity and robustness. Given the vulnerability of alpine ecosystem to environmental disturbances, our study emphasizes the urgent need to prioritize the conservation of cushion plant diversity. Future conservation strategies should adopt an integrated approach that protects not only individual cushion species but also the micro-communities they support.

Key words: alpine ecosystem, climate change, cushion plant, plant co–occurrence network, plant diversity, species extinction