Composition Characteristics of Dissolved Organic Matter and Its Coupling with Nutrient Stoichiometry in Tea Garden Soils

Nutrient stoichiometry and dissolved organic matter (DOM) govern essential ecosystem processes; however, their coupling in tea garden soils remains obscure, and cultivar-specific effects on this linkage remain virtually unknown. In this study, soil carbon (C), nitrogen (N), and phosphorus (P) contents and their C/N/P stoichiometry were measured in two contrasting tea cultivars, Rougui and Shuixian. DOM composition and sources were resolved using UV–visible spectroscopy, three-dimensional fluorescence spectroscopy, and parallel factor analysis. The tea garden soils exhibited low C/N/P ratios but high nutrient availability. DOM was dominated by fulvic- and tyrosine-like components, indicating low humification and high biodegradability. Soil organic matter and C/N/P stoichiometry jointly controlled the quantity and quality of DOM. In Rougui soils, protein-like DOM accounted for 61.92% ± 7.27% of total fluorescence and was primarily regulated by the N/P ratio. In Shuixian soils, humic-like DOM increased to 53.13% ± 8.58% of total fluorescence and was positively driven by the C/P ratio. These findings demonstrate that tea cultivars modulate the coupling between DOM and C/N/P stoichiometry, providing a basis for cultivar-specific fertilization strategies, efficient regulation of soil nutrient cycling, and sustainable tea garden management.