The effects of dynamic root distribution on land-atmosphere carbon and water fluxes in the community earth system model (CESM1.2.0)

Roots are responsible for the uptake of water and nutrients by plants, and they have the plasticity to respond dynamically to different environmental conditions. However, currently, most climate models only prescribe rooting profiles as a function of the vegetation type of the land component, with no consideration of the surroundings. In this study, a dynamic rooting scheme describing root growth as a compromise between water and nitrogen availability in the subsurface was incorporated into the Community Earth System Model 1.2.0 (CESM1.2.0). The dynamic rooting scheme was incorporated to investigate the effects of land-atmosphere carbon and water fluxes, and their subsequent influences on climate. The modeling results of global land-atmosphere coupling simulations from 1982 to 2005 show that the dynamic rooting scheme can improve gross primary production (GPP) and evapotranspiration (ET) in most tropical regions, and in some high-latitude regions with lower mean biases (MBEs) and root mean square errors (RMSEs). Obvious differences in 2-m air temperature were found in low-latitude areas, with decreases of up to 2°C. Under the influence of local land-surface feedback and large-scale moisture advection, total precipitation in the northeastern area of the Amazon and the west coast of Africa increased by 200 mm year, and that of South America, central Africa, and Indonesia increased by 50 to 100 mm year. Overall, the model incorporating the dynamic rooting scheme may reveal cooling and humidifying effects, especially for tropical regions.