A global dataset on paired leaf Na and root Na contents

Aim: Plants allocate sodium (Na) to leaves and roots as an adaptation to salinity and drought, potentially modulating herbivory and ecosystem carbon cycling. However, large-scale spatial pattern and environmental drivers of plant Na allocation remain unclear.
Location: China and the world.
Time period: Field data were collected between 2013 and 2019. Literature data were collected between 1970 and 2024.
Major taxa studied: Vascular plants.
Methods: We compiled a global database of paired leaf Na (NaLeaf) and root Na (NaRoot) content, combining field observations from 2183 species across 72 Chinese ecosystems with global synthesized literature records.
Results: The spatial pattern of plant Na allocation between leaves and roots is primarily regulated by aridity. Generally, plants allocate more Na to roots in humid zone but more to leaves in arid zone. Furthermore, aridification leads to abrupt and nonlinear increases in the NaLeaf to NaRoot ratio (NaLeaf: Root) when aridity exceeds critical threshold (0.814 for the Chinese plant species and 0.774 for the Chinese plant community). Importantly, the threshold response is consistently observed from species to community levels and from China to global biomes.
Main conclusions: Our findings demonstrate the flexible allocation of plant Na in response to salinity and drought on a large scale. Projected aridification could amplify leaf Na allocation in threshold-exceeding regions, possibly enhancing activity of herbivores and decomposers and triggering cascading impacts on plant community structure and carbon cycling rate.

Methods
Based on a field investigation following the consistent method, we compiled a regional dataset of the Na content in paired leaves (NaLeaf) and roots (NaRoot), which included 2183 species from 72 natural ecosystems in China. We also synthesized literature data on paired NaLeaf and NaRoot contents across global terrestrial ecosystems at the species level. First, we used ISI Web of Science (https://webofscience.clarivate.cn/wos) and Google Scholar (http://scholar.google.com) for a 1970–2024 literature search with the following keywords: “sodium” OR “Na” OR “mineral element” OR “beneficial element” AND “leaf and root” OR “plant organ” AND “forest” OR “grassland” OR “desert.” Second, we screened all literature and extracted leaf and root Na contents based on the following criteria: (i) reported paired observations of NaLeaf and NaRoot from mature individuals; (ii) plants were collected from terrestrial ecosystems, specifically forests, grasslands, and deserts; and (iii) plants were sampled in the field rather than through greenhouse experiments. Third, ancillary information, including the species name, life form (tree, shrub, and herb), vegetation type (forest, grassland, and desert), and geographical location (latitude and longitude), was collected. Data from multiple years at the same sampling site were averaged to ensure independence of observations. When data were only available as figures, the GetData Graph Digitizer (http://www.getdata-graph-digitizer.com) was used. Overall, 70 independent publications were included. The final global dataset contained 175 paired measurements of NaLeaf and NaRoot from 169 species (56 families) spanning 70 sites worldwide.