High-resolution community-level sodium variation on the Tibetan Plateau: Content, density, and storage

Sodium (Na), a beneficial mineral element, stimulates plant growth through osmotic adjustment. Previous studies focused on Na content at the individual or species level, however, it is hard to link to ecosystem functions without exploring the characteristics (content, density, and storage) of Na at the community level. We conducted grid-plot sampling of different plant organs in 2040 natural plant communities on the Tibetan Plateau (TP) to comprehensively characterize community-level Na on a regional scale. The Na content was 0.57, 0.09, 0.07, and 0.71 mg g^-1 in leaves, branches, trunks, and roots, respectively. Across biomes Na content was higher in deserts under drought stress. Oxygen partial pressure, radiation, precipitation, soil Na supply, and temperature significantly affected the spatial variation in Na content. Furthermore, we accurately simulated the spatial variation in Na density and produced a highly precise 1 km × 1 km spatial map of plant Na density on the TP using random forest algorithm, which demonstrated higher Na density in the southeast of TP. The total plant Na storage on the TP was estimated as 111.80 × 10⁴ t. These findings provide great insights and references for understanding the plant community-level adaptation strategies and evaluating the mineral element status on a large scale, and provide valuable data for ecological model optimization in the future.