Signal of carbon exchange in Qilian mountain based on eddy covariance and remote sensing data

Climate change threatens carbon sequestration on the Qinghai-Tibet plateau, particularly in the Qilian mountains on its northeastern edge. We combined eddy covariance measurements from five sites at altitudes of 3,000-4,200 m spanning 2011 to 2022 with remote sensing data to evaluate carbon sink dynamics. Mean net ecosystem productivity (NEP) from eddy data were 311.2 g C m^-2 year^-1, compared with 185.3 g C m^-2 year^-1 from remote sensing. NEP trends varied with altitude. Above roughly 3,700 m NEP may increase, whereas lower elevations show mixed signals. Overall, gross primary productivity increased faster than ecosystem respiration, producing a net NEP rise of 8.6 ± 4.3 g C m^-2 year^-2. Upscaled tower estimates indicate a regional carbon uptake of 6.25 × 10¹⁰ kg C year^-1, while remote sensing estimates give 3.72 × 10¹⁰ kg C year^-1. This substantial carbon sink could significantly lower the cost of achieving carbon neutrality.