Simulating the productivity of a subalpine forest at high elevations under representative concentration pathway scenarios in the Qilian Mountains of northwest China

The current work adopted the Biome-BioGeochemical Cycle model to simulate the net primary productivity (NPP) of a subalpine forest (Picea crassifolia forest) under four representative concentration pathway (RCP) scenarios in the Qilian Mountains of northwest China. This study also investigated the responses of forest’s NPP to different combinations of climatic changes and CO₂ concentration increase. Results showed that (1) under the RCP scenarios, greater increases in temperature, precipitation, and CO₂ concentration caused larger increments in forest NPP; (2) the effect of CO₂ concentration (increased NPP from 19.9% to 21.7%) was more significant than that of climate change (increased NPP from 7.5% to 17.1%); (3) the simultaneous increments in climatic change and atmospheric CO₂ concentration led to a remarkable increase in P. crassifolia forest NPP (ranging from 33.1% to 41.3%), with the combination of the two exerting strong interactive effects on forest NPP; and (4) the response of the forest’s NPP to future global change was more intense at high elevations than at low ones, with the temperature being the main factor controlling forest NPP variation at the high-elevation regions. These valuable predictions can help clarify how subalpine forest ecosystems respond to simultaneous or independent changes in climate and CO₂ concentration.