Comment on soil-2021-147

Abstract

Soil ecological stoichiometry offers a sort of effective way to explore the distribution, cycling, limitation, and balance of chemical elements in tea plantation ecosystems. This study was aim 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) vary with tea-planting age (8, 17, 25, and 43 years) and soil depth (0–10, 10–20, 20–40, and 40–60 cm) at the aggregate scales in the southern Guangxi of China. Our results showed that tea-planting age and soil depth significantly influenced soil stoichiometric characteristics in various sized aggregates. In different aged 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 totally opposite trends, and no significant differences were detected among different soil depths in Ca / Mg and Fe / Mn ratios. Tea-planting age could influence the variations in soil stoichiometric characteristics, but such effects were more obvious at the 0–40 cm soil depth in contrast to the 40–60 cm soil depth. At the 0–40 cm soil depth, continuous planting of tea was beneficial for the cumulation of soil OC, total N (TN), Fe2+, and Mn2+, whereas soil Ca2+ and Mg2+ were susceptible to leaching losses over time. Compared with other tea-planting regions in China, soil C / N ratio was higher in this tea-planting region, whereas soil C / P and N / P ratios were much lower, indicating the lower contents of soil OC and TN, especially the TN. Therefore, an appropriate increase in the amount of N fertilizer should be applied in this tea-planting region. During the process of tea planting, the losses of soil Ca2+ and Mg2+, especially the Ca2+ (as indicated by the decrease in soil Ca / Mg ratio), could lead to the soil acidification. Soil acidification could reduce Fe2+ absorption and enhance Mn2+ uptake by tea plant (as indicated by the increase in soil Fe / Mn ratio), thereby causing the aggravation of Fe2+ insufficiency and the emergence of Mn2+ toxicity to tea plant. Overall, this study improved the understanding of soil OC and nutrient dynamics in tea plantation ecosystems, and also provided supplementary information for soil ecological stoichiometry in global terrestrial ecosystems.