Land-use change affects stoichiometric patterns of soil organic carbon, nitrogen, and phosphorus in the red soil of Southeast China

Soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) play a vital in plant growth, and their stoichiometric ratios (RCN, RCP, RNP, and RCNP) are important indicators of the elemental balance in the soil ecosystem. However, the effects of land-use change (from natural forest to high-intensity orchards) on dynamics of SOC, TN, TP, and their stoichiometric ratios along the deep soil profile remain poorly understood, especially in the red soil of Southeast China. Therefore, in the present study, we selected the high-intensity managed pomelo orchard systems (7-year-old and 20-year-old) of Pinghe County developed from the natural forest and investigated their soil nutrients distribution and stoichiometric ratios at a depth of 0–200 cm. We found that conversion of natural forest into highly managed pomelo orchard systems effectively increased the SOC (5.01 to 9.05%), TN (98.80 to 126.79%), and TP (507.50 to 1914.65%) contents in the depth of 0–20 cm. On the contrary, in this same depth, RCP and RNP consistently decreased with increasing planting years, while no significant differences were found in RCN between 7-year-old and 20-year-old pomelo orchards. Nonetheless, planting year affected the SOC, TN, RCN, and RCP in the deep soil at 0–200 cm, while TP and RNP at 0–80-cm soil depth. These findings strengthen our understanding of soil nutrients and stoichiometry changes as a result of land-use change and could also provide a vital resource for the evaluation of different land uses.