Mei Tangyingze, Zeng Quanchao, Chen Ruifeng, Tan Wenfeng
College of Resources and Environment, Huazhong Agricultural University, Wuhan, China.
Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing, China.
Front Microbiol. 2025 May 14;16:1589966. doi: 10.3389/fmicb.2025.1589966. eCollection 2025.
Citrus is one of the most economically significant fruits globally, and soil organic carbon (SOC) plays a central role in maintaining soil health and fertility. Consequently, enhancing SOC content directly influences both the yield and quality of citrus crops. However, the sources of SOC in citrus orchards and their mechanisms of contribution remains poorly understood.
This study investigated citrus soils from orchards of varying planting ages by collecting 0-20 cm soil samples. We analyzed amino sugars, glomalin, particulate organic carbon (POC), and mineral-bound organic carbon (MAOC) to examine the source of microbial residue carbon and its contribution to SOC.
The results revealed a significant decrease in microbial residue carbon (MNC), fungal residue carbon (FNC), and bacterial residue carbon (BNC) with increasing orchard age ( < 0.05). Specifically, the MNC in 30-year-old citrus soils was reduced by 46.27% compared to 10-year-old soils, FNC decreased by 45.61%, and BNC by 48.91%. The proportion of microbial residue carbon within SOC significantly decreased as planting years increased ( < 0.05), from 76.82 ± 2.84% in 10-year-old citrus soils to 20.54 ± 4.70% in 30-year-old soils. Furthermore, soil pH, NO₃-N and MAOC were the main factors controlling MNC. MNC showed a significant negative correlation with SOC, indicating a weakened microbial carbon pump function in citrus soils and an increased reliance on other carbon sources, such as plant-derived carbon. Although citrus cultivation had led to a decline in microbial residue carbon over time, it remained a primary source of organic carbon, with its contribution depending on the age of the orchard.
These findings offered novel insights into the mechanisms through which intensive citrus cultivation influences microbial necromass contributions to SOC. This study also highlighted the negative impacts of long-term citrus cultivation on soil microbial necromass and offered recommendations for the rehabilitation of aging orchards.
柑橘是全球经济意义最为重大的水果之一，土壤有机碳（SOC）在维持土壤健康和肥力方面发挥着核心作用。因此，提高SOC含量直接影响柑橘作物的产量和品质。然而，柑橘果园SOC的来源及其贡献机制仍知之甚少。
本研究通过采集0 - 20厘米的土壤样本，对不同种植年限果园的柑橘土壤进行了调查。我们分析了氨基糖、球囊霉素、颗粒有机碳（POC）和矿物结合有机碳（MAOC），以研究微生物残体碳的来源及其对SOC的贡献。
结果显示，随着果园年限的增加，微生物残体碳（MNC）、真菌残体碳（FNC）和细菌残体碳（BNC）显著减少（P < 0.05）。具体而言，与10年树龄土壤相比，30年树龄柑橘土壤中的MNC减少了46.27%，FNC减少了45.61%，BNC减少了48.91%。随着种植年限的增加，SOC中微生物残体碳的比例显著下降（P < 0.05），从10年树龄柑橘土壤中的76.82 ± 2.84%降至30年树龄土壤中的20.54 ± 4.70%。此外，土壤pH、NO₃ - N和MAOC是控制MNC的主要因素。MNC与SOC呈显著负相关，表明柑橘土壤中微生物碳泵功能减弱，对其他碳源（如植物源碳）的依赖增加。尽管随着时间的推移，柑橘种植导致微生物残体碳下降，但它仍然是有机碳的主要来源，其贡献取决于果园的树龄。
这些发现为集约化柑橘种植影响微生物坏死物质对SOC贡献的机制提供了新的见解。本研究还强调了长期柑橘种植对土壤微生物坏死物质的负面影响，并为老化果园的修复提供了建议。
