Increasing acidity of rain in subtropical tea plantation alters aluminum and nutrient distributions at the root-soil interface and in plant tissues

Background and aims: Acid rain alters aluminum (Al) and nutrient cycling in tea (Camellia sinensis) plantations. However, the underlying mechanisms of the interaction among Al, nitrogen (N) and phosphorus (P) dynamics in response to increasing acidity of rain remain unclear. Methods: A typical tea plantation was selected for an experimental treatment by pH 4.5, 3.5, and 2.5 acid rains and control in southern China. After 3 years, rhizosphere and bulk soils were collected to analyze extractable Al fractions and available nutrients. Roots, stems, young and old twigs, tea and mature leaves were sampled to measure total Al, total N and P concentrations. Results: Extractable Al fractions in rhizosphere soils generally increased with increasing rain acidity until pH 3.5 and dropped treated by pH 2.5 acid rain. In contrast, NO₃ ⁻-N, mineral N and available P in rhizosphere soils monotonically decreased with increasing acidity. Average total Al and total P in plant tissues, respectively increased and decreased with increasing acidity. Soluble sugar in tea leaves was directly and inversely related to Al/N and N/P, respectively. Free amino acids were inversely related to Al/P. Conclusion: Prolonged elevation of rain acidity altered Al and nutrient stoichiometry in rhizosphere soils and plant tissues, and severe acid rain decreased tea quality.