Element Migration in the Bedrock-Soil-Tea System of Metamorphic Regions and Its Implications for Tea Quality

The migration and enrichment of mineral elements within the bedrock-soil-tea system are critical determinants of tea quality. Understanding how lithological background regu-lates soil nutrient dynamics and tea biochemical traits is essential for optimizing plantation management in metamorphic regions. This study investigated element transfer and enrich-ment patterns in the "rock-soil-tea" system of metamorphic tea plantations in Guizhou Province, China. Field sampling and geochemical analyses were integrated with redundancy analysis (RDA), random forest (RF), and structural equation modeling (SEM) to evaluate their effects on key quality components. Metamorphic slate exhibited higher concentrations of major, lithophile, and chalcophile elements, whereas metasandstone showed relative en-richment of fluid-mobile elements. Weathering induced significant leaching of base cations, particularly K2O and MgO, resulting in their depletion in soil profiles. Tea plants demon-strated selective bioaccumulation, enriching beneficial nutrients such as P and Mn while re-stricting the transfer of toxic metals (As, Pb, Cr, Hg). SEM revealed a strong direct effect of bedrock composition on the soil trace element pool (path coefficient = 0.92, p < 0.001), which subsequently influenced plant uptake (path coefficient = 0.64, p < 0.001). RDA and RF consistently identified soil potassium (K)as the primary factor associated with free ami-no acid and caffeine synthesis. Mass balance calculations further indicated substantial K loss through leaching, suggesting that K supplementation is necessary to enhance tea quality. These findings demonstrate hierarchical controls of lithological inheritance, pedogenic re-distribution, and plant selectivity on tea quality, providing a scientific basis for nutrient management in metamorphic tea-growing regions.