Threshold effects and driving mechanisms of desert photovoltaic power stations on soil carbon pools

Photovoltaic power stations (PVPS) are crucial for achieving carbon balance goals. The coupling of large-scale photovoltaic arrays with native ecosystems has formed photovoltaic ecosystems with unique energy and material exchanges, impacting key ecological processes like carbon cycling. Deserts as a critical carbon pool with high ecological sensitivity, their stability is vital for the global carbon balance. However, disturbances from PVPS may alter soil structure, resulting in the destabilization of carbon pools and changes in nutrient availability. Therefore, elucidating the impact mechanisms of PVPS on carbon pools and their threshold effects is crucial for achieving synergy between photovoltaic development and ecological conservation. This study investigates the carbon sequestration effects of the Talatan desert PVPS located in the northeastern Qinghai-Tibet Plateau. Results show that PVPS significantly enhances the carbon sink potential of desert soils. The carbon enrichment effect is most pronounced under tracking brackets, followed by semi-tracking and fixed brackets. Total carbon content decreases with soil depth. PVPS influences organic and inorganic carbon dynamics by altering the spatiotemporal distribution of soil physicochemical factors. Available nitrogen, moisture, and clay content are primary controlling factors, indirectly governing total carbon distribution. Notably, the response of total carbon to its primary control factor exhibits a threshold; beyond this point, their relationship shifts from negative to positive feedback. Compared to natural deserts, the positive effects of this artificial-natural composite ecosystem on total carbon vary seasonally. Freezing and freeze-thaw periods primarily promote inorganic carbon accumulation, while the contribution of organic carbon is significantly enhanced during the non-freezing period.