Remodeling mechanisms of large-scale photovoltaic arrays on the plant-soil-microbe system and multifunctionality in alpine grasslands

The cascading pathways through which large-scale photovoltaic (PV) arrays reshape plant-soil-microbe systems and soil nutrient multifunctionality (SNMF) in alpine grasslands remain largely elusive. Based on a field investigation at a Qinghai-Tibet Plateau PV station, we delineated five microhabitats: unshaded control (CK), front-of-panel eaves (FP), underneath panels (UP), rear-eaves (RP), and inter-panel (IP). Integrating vegetation surveys, amplicon sequencing, and structural equation modeling (SEM), we revealed significant PV-induced habitat differentiation. Water-enriched FP zones promoted vegetation growth (density LRR = 0.63; height LRR = 0.25) and maximized SNMF (0.86). Conversely, persistent shading in UP zones caused severe substrate limitation, drastically reducing aboveground biomass (LRR = −0.60), microbial biomass phosphorus (LRR = −0.38), and SNMF (0.18). Under stringent physical filtering, UP microbial diversity declined (bacterial and fungal Shannon indices fell by 4.7% and 13.6%, respectively), and cross-kingdom co-occurrence networks simplified (average degrees dropped by 56.5% and 73.2%, respectively; robustness decreased by more than 58%). Microbial community composition shifted toward specific taxa frequently associated with resource-limited conditions (e.g., the relative abundance of Arthrobacter increased to 3.9%), alongside an accumulation of putative plant pathogens (16.3%), signaling localized ecological vulnerability. Structural equation modeling suggested a potential pathway where PV microhabitats determined SNMF primarily by reshaping plant phenotypes. Vegetation acted as the central hub (total effect = 0.78), directly driving SNMF (β = 0.63) and regulating bacterial diversity (β = 0.37). Ultimately, shading-induced vegetation decline and substrate limitation drive sub-panel microecological constraints during the peak growing season. Spatially targeted management (e.g., introducing shade-tolerant grasses under panels) is essential to restore plant-mediated positive feedbacks for sustainable solar-pastoral systems.