Salinity Induces Allometric Accumulation of Sulfur in Plants and Decouples Plant Nitrogen-Sulfur Correlation in Alpine and Arid Wetlands

Salinization alters the elemental balance of wetlands and induces variations in plant survival strategies. Sulfur (S) plays vital roles in serving regulatory and catalytic functions in stress resistance of plants. Yet, how plant S and its relationships with nitrogen (N) vary across natural environmental gradients are not well documented. We collected 1,366 plant samples and 230 water and sediment samples from 230 wetlands in Tibetan Plateau and adjacent arid regions of western China, to analyze the effects of environmental variables on plant S accumulation and N-S correlations. We found that plant S correlated with N in unimodal patterns. Salinity, rather than temperature or nutrient supply, promoted disproportionate accumulation of S but limited N uptake, inducing decoupling of N-S correlation in plants. Toward high salinity, the faster increasing rates of total S than that of glutathione, the most abundant organic-S compound in plant resistance, provided potential evidences explaining the decoupled plant N-S correlation. A salinity of 3.9 was calculated to be a threshold at which substantial changes in plant N-S correlation occurred. We designed a conceptual model to illustrate the mechanisms driving variations of N-S correlation in plants and environments along salinity gradient. Furthermore, high salinity filtered out the salt-sensitive species and reassembled the communities. In conclusion, increased salinity affected wetland plants by inducing S accumulation in plants and selecting salt-tolerant species with high S concentrations at community level, providing evidences for plant adaptive mechanisms to salinity in arid regions.

Automated summary

Salinization affects the elemental balance of wetlands and alters the relationships between sulfur and nitrogen in plants. This study found that plant sulfur and nitrogen showed non-linear correlations, with salinity being a major factor influencing this relationship. High salinity promoted sulfur accumulation but limited nitrogen uptake, leading to the decoupling of sulfur-nitrogen correlation in plants. Additionally, high salinity also affected the composition of wetland plant communities.