Pedosphere 36(3): 683--692, 2026
ISSN 1002-0160/CN 32-1315/P
©2026 Soil Science Society of China
Published by Elsevier B.V. and Science Press
| Assessing humus to predict soil organic carbon in Northwest China: A case study of Ningxia |
Xinnian GUO2, Zhuonan HOU3, Xia WU2, Huaiyu LONG4, Zehua XU2, Baiyun LI2, Shaoshan AN3 |
1State Key Laboratory of Soil and Water Conservation and Desertification Control, College of Natural Resource and Environment, Northwest A&F University, Yangling 712100 (China);
2 Institute of Agricultural Resources and Environment, Ningxia Academy of Agriculture and Forestry Science, Yinchuan 750000 (China);
3 The Research Center of Soil and Water Conservation and Ecological Environment, Chinese Academy of Sciences and Ministry of Education, Yangling 712100 (China);
4 State Key Laboratory of Efficient Utilization of Arid and Semi-arid Arable Land in Northern China, Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081 (China) |
| ABSTRACT |
| The spatial distribution and influencing factors of soil organic carbon (SOC), closely related to climate change and global carbon (C) cycling, have received widespread attention. As an important component of the SOC pool, humus is vital to soil C turnover and levels. However, humus parameters are rarely used to predict SOC in terrestrial ecosystems, presumably due to the evolving understanding of SOC sources and fractions. Here, we measured the levels of SOC, fulvic acid C (FAC), and humic acid C (HAC) in the topsoil (0-20 cm) and subsoil (20-40 cm) of cropland, desert, forest, and grassland in Ningxia, Northwest China, and integrated humus and environmental factors to predict the SOC prediction models. The SOC, HAC, and FAC generally decreased with soil depth and showed a trend of forest > cropland > grassland > desert. The contribution of humus C (i.e., HAC + FAC) to SOC was higher in forest (47.6%) than in cropland (40.6%), desert (38.4%), and grassland (37.2%). In the 0-40 cm soil of all four ecosystems, the average content of FAC (1.61 g kg-1) was higher than that of HAC (0.88 g kg-1), and FAC (26.6%) contributed more to SOC compared to HAC (14.5%). The geoclimatic and soil physicochemical factors used to predict the SOC content were grouped into six categories: humus, nutrient, soil texture, geoclimate, mineral, and soil chemical property. Humus and nutrient had significant (P < 0.05) and direct positive effects on SOC. Although the levels and predictors of SOC differed among ecosystems, FAC was a significant and common driver. Additionally, mineral and soil chemical property explained a large proportion of SOC variation, related to the chemical characteristics of humus. These findings indicated that SOC was highly humus-dependent and context-dependent, and integrating humus parameters had important implications for the prediction of SOC in terrestrial ecosystems. |
| Key Words: distribution pattern|fulvic acid carbon|humic acid carbon|minerals|soil nutrients|soil chemical properties|terrestrial ecosystems |
| Citation: Guo X N, Hou Z N, Wu X, Long H Y, Xu Z H, Li B Y, An S S. 2026. Assessing humus to predict soil organic carbon in Northwest China: A case study of Ningxia. Pedosphere. 36(3): 683-692. |
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