Controls on soil organic carbon across soil depths in tropical and temperate non-volcanic regions
Soil organic carbon (SOC) is fundamental for climate regulation, soil fertility, biodiversity, and healthy terrestrial ecosystems. Understanding the key controllers and their pathways is required to estimate SOC distribution and predict C sequestration potential. Previous research emphasized the sig...
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Elsevier
2025-06-01
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| Series: | Geoderma |
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| Online Access: | http://www.sciencedirect.com/science/article/pii/S0016706125001739 |
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| author | Han Lyu Kenta Ashida Satomi Urayama Arief Hartono Method Kilasara Antoine David Mvondo Ze Atsushi Nakao Soh Sugihara Randy A. Dahlgren Shinya Funakawa Tetsuhiro Watanabe |
| author_facet | Han Lyu Kenta Ashida Satomi Urayama Arief Hartono Method Kilasara Antoine David Mvondo Ze Atsushi Nakao Soh Sugihara Randy A. Dahlgren Shinya Funakawa Tetsuhiro Watanabe |
| author_sort | Han Lyu |
| collection | DOAJ |
| description | Soil organic carbon (SOC) is fundamental for climate regulation, soil fertility, biodiversity, and healthy terrestrial ecosystems. Understanding the key controllers and their pathways is required to estimate SOC distribution and predict C sequestration potential. Previous research emphasized the significant impact of active Al/Fe (acid-oxalate extractable) on SOC content, especially in volcanic soils, yet gaps persist in understanding the interactions among SOC, active Al/Fe, climate, and non-volcanic parent materials across different soil depths. Herein, we explore these dynamics using random forest regression (RFR) and structural equation modeling (SEM). Our analysis included 17 SOC-related physicochemical soil variables and 4 climatic properties across topsoil and subsoil horizons at 211 sites (2 depths). The study covers 178 tropical and 33 temperate sites from sub-humid to humid non-volcanic regions, predominantly with acidic to neutral soil pH. We found that SOC variance explained by SEMs (54 % for topsoil, 75 % for subsoil) closely matched RFR outcomes (61 % for topsoil, 72 % for subsoil), highlighting the efficacy of our SEMs in identifying key SOC controllers: mean annual temperature (MAT) and excess precipitation (moisture index: precipitation – potential evapotranspiration) for climate, Al2O3 + Fe2O3 (total Al and Fe contents expressed as oxides) for parent material, and active Al/Fe and pH for soil properties. Partial dependence in RFRs and path coefficients in SEM indicated MAT, active Al/Fe, and pH directly contribute to topsoil SOC, whereas active Al/Fe directly controls SOC in subsoil. Furthermore, SEMs indicated bidirectional interaction between SOC and active Al/Fe in topsoil, where active Al/Fe increased SOC and vice versa, while in subsoil, active Al/Fe has substantial unidirectional control over SOC. Importantly, both climate and parent material indirectly affected SOC by regulating active Al/Fe contents, particularly in subsoil. These findings enable predicting SOC distribution and refining SOC dynamics models by focusing on the direct and indirect impacts of active Al/Fe, climate and parent material across different soil depths and climatic zones in non-volcanic regions. |
| format | Article |
| id | doaj-art-7c9038ed2bb04b70a0b9c95c4cd84b63 |
| institution | OA Journals |
| issn | 1872-6259 |
| language | English |
| publishDate | 2025-06-01 |
| publisher | Elsevier |
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| series | Geoderma |
| spelling | doaj-art-7c9038ed2bb04b70a0b9c95c4cd84b632025-08-20T02:26:27ZengElsevierGeoderma1872-62592025-06-0145811733510.1016/j.geoderma.2025.117335Controls on soil organic carbon across soil depths in tropical and temperate non-volcanic regionsHan Lyu0Kenta Ashida1Satomi Urayama2Arief Hartono3Method Kilasara4Antoine David Mvondo Ze5Atsushi Nakao6Soh Sugihara7Randy A. Dahlgren8Shinya Funakawa9Tetsuhiro Watanabe10Institute of Agriculture, Tokyo University of Agriculture and Technology, Fuchu, Tokyo 183-8509, Japan; Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, JapanGraduate School of Agriculture, Kyoto University, Kyoto 606-8502, JapanGraduate School of Agriculture, Kyoto University, Kyoto 606-8502, JapanFaculty of Agriculture, IPB University, Bogor 16680, IndonesiaCollege of Agriculture, Sokoine University of Agriculture, Morogoro, TanzaniaFaculté d’Agronomie et des Sciences Agricoles, Université de Dschang, Dschang, CameroonGraduate School of Life and Environmental Sciences, Kyoto Prefectural University, Kyoto 606-8522, JapanInstitute of Agriculture, Tokyo University of Agriculture and Technology, Fuchu, Tokyo 183-8509, JapanDepartment of Land, Air and Water Resources, University of California, Davis, CA 95616, USAGraduate School of Agriculture, Kyoto University, Kyoto 606-8502, JapanGraduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan; Corresponding author.Soil organic carbon (SOC) is fundamental for climate regulation, soil fertility, biodiversity, and healthy terrestrial ecosystems. Understanding the key controllers and their pathways is required to estimate SOC distribution and predict C sequestration potential. Previous research emphasized the significant impact of active Al/Fe (acid-oxalate extractable) on SOC content, especially in volcanic soils, yet gaps persist in understanding the interactions among SOC, active Al/Fe, climate, and non-volcanic parent materials across different soil depths. Herein, we explore these dynamics using random forest regression (RFR) and structural equation modeling (SEM). Our analysis included 17 SOC-related physicochemical soil variables and 4 climatic properties across topsoil and subsoil horizons at 211 sites (2 depths). The study covers 178 tropical and 33 temperate sites from sub-humid to humid non-volcanic regions, predominantly with acidic to neutral soil pH. We found that SOC variance explained by SEMs (54 % for topsoil, 75 % for subsoil) closely matched RFR outcomes (61 % for topsoil, 72 % for subsoil), highlighting the efficacy of our SEMs in identifying key SOC controllers: mean annual temperature (MAT) and excess precipitation (moisture index: precipitation – potential evapotranspiration) for climate, Al2O3 + Fe2O3 (total Al and Fe contents expressed as oxides) for parent material, and active Al/Fe and pH for soil properties. Partial dependence in RFRs and path coefficients in SEM indicated MAT, active Al/Fe, and pH directly contribute to topsoil SOC, whereas active Al/Fe directly controls SOC in subsoil. Furthermore, SEMs indicated bidirectional interaction between SOC and active Al/Fe in topsoil, where active Al/Fe increased SOC and vice versa, while in subsoil, active Al/Fe has substantial unidirectional control over SOC. Importantly, both climate and parent material indirectly affected SOC by regulating active Al/Fe contents, particularly in subsoil. These findings enable predicting SOC distribution and refining SOC dynamics models by focusing on the direct and indirect impacts of active Al/Fe, climate and parent material across different soil depths and climatic zones in non-volcanic regions.http://www.sciencedirect.com/science/article/pii/S0016706125001739Sub-humid to humid regionsTopsoil and subsoilOxalate extractable active Al and FeClimateParent materialStructural equation modeling |
| spellingShingle | Han Lyu Kenta Ashida Satomi Urayama Arief Hartono Method Kilasara Antoine David Mvondo Ze Atsushi Nakao Soh Sugihara Randy A. Dahlgren Shinya Funakawa Tetsuhiro Watanabe Controls on soil organic carbon across soil depths in tropical and temperate non-volcanic regions Geoderma Sub-humid to humid regions Topsoil and subsoil Oxalate extractable active Al and Fe Climate Parent material Structural equation modeling |
| title | Controls on soil organic carbon across soil depths in tropical and temperate non-volcanic regions |
| title_full | Controls on soil organic carbon across soil depths in tropical and temperate non-volcanic regions |
| title_fullStr | Controls on soil organic carbon across soil depths in tropical and temperate non-volcanic regions |
| title_full_unstemmed | Controls on soil organic carbon across soil depths in tropical and temperate non-volcanic regions |
| title_short | Controls on soil organic carbon across soil depths in tropical and temperate non-volcanic regions |
| title_sort | controls on soil organic carbon across soil depths in tropical and temperate non volcanic regions |
| topic | Sub-humid to humid regions Topsoil and subsoil Oxalate extractable active Al and Fe Climate Parent material Structural equation modeling |
| url | http://www.sciencedirect.com/science/article/pii/S0016706125001739 |
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