Soil nutrient contents and stoichiometry within aggregate size classes varied with tea plantation age and soil depth in southern Guangxi in China

Abstract

Abstract. Soil ecological stoichiometry offers a tool to explore the distribution, cycling, limitation, and balance of chemical elements in tea plantation ecosystems. This study aimed to explore how soil organic C (OC) and nutrient contents (total N (TN), total P (TP), Ca2+, Mg2+, Fe2+, and Mn2+) as well as their stoichiometric ratios (C/N, C/P, N/P, Ca/Mg, and Fe/Mn) varied with tea plantation age (8, 17, 25, and 43 years) and soil depth (0–10, 10–20, 20–40, and 40–60 cm) within aggregates in southern Guangxi in China. Our results showed that tea plantation age and soil depth significantly affected soil nutrient stoichiometry in different sizes of aggregates. Among different ages of tea plantations, soil OC, TN, and TP contents as well as C/N, C/P, and N/P ratios significantly decreased as the soil depth increased. In addition, soil Ca2+ and Mg2+ contents were significantly lower in the surface soil layer than the deeper soil layer, whereas soil Fe2+ and Mn2+ contents showed opposite trends, and no significant differences were detected in Ca/Mg and Fe/Mn ratios among different soil depths. At the 0–40 cm soil depth, continuous planting of tea corresponded to increases in soil OC, TN, Fe2+, and Mn2+ contents, whereas soil Ca2+ and Mg2+ contents significantly decreased over time. During the process of tea growth, the losses of soil Ca2+ and Mg2+, especially Ca2+ (as indicated by the decrease in the soil Ca/Mg ratio), led to soil acidification, which reduced Fe2+ absorption and enhanced Mn2+ uptake by tea plants (as indicated by the increase in the soil Fe/Mn ratio). In general, tea plantation age affected the variations of soil nutrient contents and stoichiometry, and such effects were more obvious at the 0–40 cm soil depth, in contrast to the 40–60 cm soil depth.