Warming Promotes Deterministic Assembly of Bacterial and Fungal Communities in Drylands.

Warming is altering the functioning of desert ecosystems in global drylands. Microbial communities are crucial for maintaining these ecosystems, yet how their co-occurrence networks and assembly mechanisms respond to warming remains unclear. Using 16 S and ITS rRNA amplicon sequencing, we examined bacterial and fungal community composition and structure. Further, we investigated cross-trophic bacterial-fungal interactions via inter-domain ecological network analysis. Warming significantly altered the diversity, composition, and structure of both bacterial and fungal communities. It increased bacterial network complexity but simplified the fungal network. Notably, warming enhanced cross-trophic interactions between bacteria and fungi, facilitating the maintenance of microbial hierarchical interactions, particularly bacterial network complexity. However, microbial keystone taxa declined dramatically under warming, 41.18% of these belonged to Ascomycota. Neutral community models and normalized stochastic ratio-based analyses revealed that deterministic processes dominated community assembly, with warming increasing their relative importance by 8-46%. This suggests a potential deterministic environmental filtering induced by warming. Collectively, these findings advance our understanding of the ecological mechanisms and microbial interactions underpinning rhizospheric communities in drylands under future climate change.