Purpose To explore the effects of conversion of tropical rainforests to rubber and rubber-Amomum villosum plantations on the soil environments of the 0-90 cm soil layers, and to evaluate the feasibility of large-scale promotion of rubber-A. villosum plantations.
Methods Field sampling combined with laboratory analysis was employed to quantitatively assess soil moisture content, pH, total carbon, total nitrogen, total phosphorus, ammonium nitrogen, nitrate nitrogen, available phosphorus, exchangeable aluminum, available copper, and available manganese in the 0-90 cm soil layers of tropical rainforests, rubber plantations, and rubber-A. villosum plantations.
Results Conversion of tropical rainforests to rubber plantations reduced soil moisture content in the 0-90 cm soil layers, and the establishment of rubber-A. villosum plantations further exacerbated soil moisture depletion. Both conversion types led to decreased soil total carbon and total nitrogen in the 0-30 cm soil layers, as well as reductions in total phosphorus, nitrate nitrogen, available copper, and available manganese in the 0-90 cm soil layers. Exchangeable aluminum content in the 30-90 cm soil layer of rubber plantations was significantly higher than that found in tropical rainforests and rubber-A. villosum plantations. The establishment of rubber-A. villosum plantations decreased soil exchangeable aluminum in the surface soils and increased available phosphorus.
Conclusion The conversion of tropical rainforests to rubber plantations not only adversely affects the moisture and nutrient levels of the surface soils but also exacerbates the depletion of moisture and nutrients in deeper soil layers. The rubber-A. villosum plantations have some ameliorative effects on the soil environment; however, they continue to intensify the consumption of soil moisture. Therefore, the large-scale promotion of rubber-A. villosum plantations must take into account their impact on regional water balance.
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