Photovoltaic Microhabitats Reorganize Vegetation and Soil Carbon Pools in an Alpine Dryland Grassland

Utility-scale ground-mounted photovoltaic development is expanding across alpine dryland grasslands, creating engineered microhabitats with contrasting shading regimes, surface exposure, and soil hydro-physical conditions. Microhabitat-specific responses of vegetation and soil carbon pools remain poorly quantified in these systems. We assessed carbon-pool responses in the Talatan photovoltaic park on the northeastern Qinghai–Tibet Plateau using 109 plot-level observations across five microhabitats: reference grassland (REF), fixed-panel shaded microhabitat (FS), fixed-panel interspace microhabitat (FI), horizontal single-axis tracking microhabitat (HSA), and tilted single-axis tracking microhabitat (TSA). We estimated aboveground biomass carbon (AGB-C), belowground biomass carbon (BGB-C), 0–30 cm soil organic carbon stock (SOC stock), and total ecosystem carbon storage (TEC). Microhabitat contrasts were evaluated relative to REF, and standardized association models were used to examine relationships between SOC stock, soil moisture, soil fines, and vegetation carbon pools. Carbon responses differed by microhabitat position and carbon-pool compartment. FS showed the clearest vegetation carbon contrast, with AGB-C 29.2% lower than REF and BGB-C 29.8% lower with borderline statistical support. In contrast, FS showed smaller, more uncertain contrasts for SOC stock (−3.2%) and TEC (−6.3%). The SOC stock association model explained 46% of the variance, with positive coefficients for soil moisture (β = 0.496), soil fines (β = 0.256), AGB-C (β = 0.239), and BGB-C (β = 0.171). These findings indicate that photovoltaic carbon assessment in alpine dryland grasslands should distinguish microhabitat position, carbon-pool compartment, and soil hydro-physical background to identify where carbon responses occur and through which carbon pools they are expressed.