Can sustained climate warming intensify the carbon source potential of saline lakes on the Qingzang Plateau?

Under global climate change intensification, the debate over whether high-altitude saline lakes act as carbon (C) emission sinks or sources remains unresolved. Moreover, there is currently a lack of systematic metabolic and mechanistic C assessments for saline lake ecosystems on the Qingzang Plateau (QZP), especially regarding their associative changes under climate change. Here, we used ^18/16O technology and regression models to assess saline lake C metabolism on the QZP between 2000 and 2020. Additionally, we predicted the C metabolism of these lakes between 2030 and 2050 under three future scenario models: SSP126, SSP245, and SSP585. Results showed that saline lakes on the QZP have long acted as C sources. The average annual GPP of these lakes is 12.26 ± 0.23 g O₂ m^-2 d^-1, the average annual ER is 23.96 ± 0.46 g O₂ m^-2 d^-1, and the average annual NEP is -11.70 ± 0.22 g O₂ m^-2 d^-1. Higher temperatures, wind speeds, and total nitrogen (TN) concentrations in low-altitude saline lakes collectively promote GPP and ER. Between 2000 and 2020, under increases in temperature, surface pressure, wind speed, and TN, both GPP and ER significantly increased while NEP significantly decreased. Between 2030 and 2050, GPP and ER will gradually increase under the three future scenario models while NEP will decrease. However, under the SSP126 scenario, saline lakes on the QZP will emit the least amount of atmospheric carbon dioxide (CO₂). These findings not only enhance our understanding of aquatic plateau C cycling processes but also provide a theoretical basis for the future C management of saline lakes on the QZP.