ORIGINAL RESEARCH article
Front. Environ. Sci.
Sec. Soil Processes
Evaluation of Forest Conversion Effects on Soil Erosion and Soil Organic Carbon Using 137Cs and 210Pbex Tracers in the Low Mountain–Hill Region of Southwest China
Provisionally accepted
JunZhi Chu1
Yang Cao2YuYi Shen3QiuMei Teng4JianLin Liao4YingJie Sun4DeNan Zhang4YueMing Liang4KeChao Huang4Hao Shi4Guangping Xu4*- 1Karst Dynamics Laboratory, MLR and GZAR, GvLin, China
- 2Xinye First High School, Nanyang, China
- 3Guangxi Key Laboratory of Functional Phytochemicals and Sustainable Utilization, Guangxi Institute of Botany, GvLin, China
- 4Guangxi Key Laboratory of Plant Conservation and Restoration Ecology in Karst Terrain, Guangxi Institute of Botany, GvLin, China
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Estimating both soil erosion and sedimentation in southern China's hilly regions is essential for planning soil-conservation measures. However, the patterns of soil erosion and their influence on soil organic carbon (SOC) in different forest types remain insufficiently understood. Using a dual-tracer approach with 137Cs and 210Pbex, this study assessed soil erosion dynamics across three forest types—mixed broadleaf forest (MBF), Masson pine plantation (MPP), and Eucalyptus plantation (EUP)—in the low mountainous hills of northern Guangxi, southwest China. Both radionuclides showed exponential declines in activity concentrations with depth, with pronounced surface enrichment (peak values in the 0–5 cm layer) in all forest types. EUP exhibited significantly lower clay content and higher sand proportions compared with MPP and MBF. SOC content was consistently lowest in EUP across all slope gradients. Mean 137Cs and 210Pbex inventories followed the order MBF (1491.84, 15,183.42 Bq·m–2) > MPP (1443.35, 14,822.64 Bq·m–2) > EUP (1134.95, 10,117.21 Bq·m– 2), while slope position followed lower-slope > mid-slope > upper-slope. Soil erosion rate ranged from –466.90 to 2159.78 t·km–2·a–1 for 137Cs and –398.83 to 3023.27 t·km–2·a–1 for 210Pbex. Erosion intensity increased from lower to upper slopes and was highest in Eucalyptus plantation, followed by Masson pine and mixed broadleaf forest. Significant positive correlations (p < 0.01) were observed between both radionuclides and SOC and clay content, whereas negative correlations occurred with sand content in vertical profiles. Overall, the conversion of mixed forests to economic plantations intensified soil erosion, particularly in EUP. Targeted management practices in EUP are essential for improving soil conservation and promoting sustainable forest management. The close agreement between 137Cs-and 210Pbex-derived erosion estimates highlights the potential of 210Pbex as an alternative or complementary tracer to 137Cs for monitoring soil erosion in this region.
Keywords: Forest conversion, Plantation, slope position, Soil erosion, Soil Organic Carbon, Soil texture
Received: 11 Sep 2025; Accepted: 17 Dec 2025.
Copyright: © 2025 Chu, Cao, Shen, Teng, Liao, Sun, Zhang, Liang, Huang, Shi and Xu. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Guangping Xu
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