Purpose

Soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) play a vital in plant growth, and their stoichiometric ratios (R_CN, R_CP, R_NP, and R_CNP) 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.

Materials and methods

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.

Results and discussion

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, R_CP and R_NP consistently decreased with increasing planting years, while no significant differences were found in R_CN between 7-year-old and 20-year-old pomelo orchards. Nonetheless, planting year affected the SOC, TN, R_CN, and R_CP in the deep soil at 0–200 cm, while TP and R_NP at 0–80-cm soil depth.

Conclusions

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.