Abstract: Abstract Aims This research investigates the variations in ecological stoichiometric characteristics of carbon (C), nitrogen (N), and phosphorus (P) between plant roots and soil at different latitudes, and explores the homeostasis of plant roots stoichiometry and analyzes its coupling relationship with climatic and environmental factors. The results contribute to elucidating the nutrient dynamics and adaptation strategies of the plant-soil system along a latitudinal gradient, thereby providing a theoretical basis for the vegetation restoration of coastal wetland ecosystems. Methods In this study, 102 plant and 102 soil samples are collected from seven coastal wetlands at different latitudes (19.87°- 41.03°N): Dongzhai Harbor, Zhangjiang Estuary, Minjiang Estuary, Hangzhou Bay, Yancheng Estuary, the Hanghe Estuary, and Liaohe Estuary, and their carbon (C), nitrogen (N), and phosphorus (P) contents are measured. The contents of carbon (C), nitrogen (N), and phosphorus (P) in the aboveground parts of plants, underground roots, and soil are measured. In addition, environmental indicators such as climatic element, soil water content, soil pondus hydrogenii, and soil electrical conductivity are also obtained. Important findings The results demonstrat the following: (1) In comparison to the aboveground parts, the content of carbon (C), nitrogen (N), and phosphorus (P) in roots, as well as their stoichiometric ratios, exhibit variation with latitude and are more responsive to environmental changes. (2) Significant interspecific differences are observed in the response of plant root stoichiometric characteristics to latitudinal changes. Specifically, with increasing latitude, the N content in mangrove roots decrease significantly, while the changes in C content, P content, and the stoichiometric ratios of C:N:P show opposing trends between the two mangrove species. Among salt marsh plants, the C content in the roots of S. alterniflora. significantly decrease, whereas the C content in the roots of ×B. mariqueter. increase. (3) As latitude increase, soil C and N contents, as well as the C:P and N:P ratios, are significantly lower than the national average in high-latitude regions. The plant root N:P ratio is generally less than 14, indicating that root growth is nitrogen-limited. (4) Based on homeostasis index analysis, the order of stoichiometric internal stability among the six plant roots is as follows: A. marina. > P. australis. > S. alterniflora. > ×B. mariqueter. > A. corniculatum. > S. salsa. Among them, the root stoichiometric homeostasis of S. salsa. is the weakest., the random forest model reveals that climatic element and soil water content significantly influence the homeostasis characteristics of root P content, C:P ratio, and N:P ratio, while the homeostasis characteristics of the root N:P ratio is primarily regulated by soil salinity.

Key words: latitude gradient, plant roots, ecological stoichiometry, homeostasis, coastal wetland