Institute of Tibet Plateau Ecology & Key Laboratory of Forest Ecology in Tibet Plateau (Tibet Agriculture and Animal Husbandry University), Ministry of Education & Key Laboratory of Alpine Vegetation Ecological Security in Tibet, Tibet Agriculture and Animal Husbandry University, Nyingchi, Tibet 860000, China; CAS Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization and Ecological Restoration and Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041, China.
CAS Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization and Ecological Restoration and Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041, China.
Sci Total Environ. 2023 Jun 1;875:162701. doi: 10.1016/j.scitotenv.2023.162701. Epub 2023 Mar 9.
Root activity regulates rhizosphere soil carbon (C) dynamics, thereby profoundly affecting soil C sequestration and associated climate feedback. However, whether and how rhizosphere soil organic C (SOC) sequestration responds to atmospheric N deposition remains unclear. We distinguished and quantified the direction and magnitude of soil C sequestration between the rhizosphere and bulk soil of a spruce (Picea asperata Mast.) plantation after 4-year field N additions. Moreover, the contribution of microbial necromass C to SOC accumulation under N addition was further compared between the two soil compartments, considering the crucial role of microbial necromass in soil C formation and stabilization. The results showed that although both the rhizosphere and bulk soil facilitated SOC accumulation in response to N addition, the rhizosphere exerted a greater C sequestration than that of bulk soil. Specifically, compared to the control, SOC content increased 15.03 mg/g and 4.22 mg/g in the rhizosphere and bulk soil under N addition, respectively. Further numerical model analysis showed that SOC pool in the rhizosphere increased by 33.39 % induced by N addition, which was nearly four times of that in the bulk soil (7.41 %). The contribution of increased microbial necromass C to SOC accumulation induced by N addition was significantly higher in the rhizosphere (38.76 %) than that in the bulk soil (31.31 %), which was directly related to the greater accumulation of fungal necromass C in the rhizosphere. Our findings highlighted the vital role of the rhizosphere processes in regulating soil C dynamics under elevating N deposition, and also provided a clear evidence for importance of the microbial-derived C in the SOC sequestration from the rhizosphere perspective.
根系活动调节根际土壤碳（C）动态，从而深刻影响土壤 C 固存和相关气候反馈。然而，根际土壤有机碳（SOC）固存是否以及如何响应大气氮（N）沉降仍不清楚。我们在云杉（Picea asperata Mast.）人工林进行了 4 年的田间 N 添加后，区分并量化了根际和非根际土壤中土壤 C 固存的方向和幅度。此外，考虑到微生物残体 C 在土壤 C 形成和稳定中的关键作用，我们进一步比较了两个土壤区室中 N 添加对 SOC 积累的微生物残体 C 的贡献。结果表明，尽管根际和非根际都有利于 SOC 积累对 N 添加的响应，但根际的 C 固存作用大于非根际。具体而言，与对照相比，N 添加下根际和非根际的 SOC 含量分别增加了 15.03mg/g 和 4.22mg/g。进一步的数值模型分析表明，N 添加引起的根际 SOC 库增加了 33.39%，几乎是非根际的四倍（7.41%）。N 添加引起的 SOC 积累中增加的微生物残体 C 的贡献在根际（38.76%）明显高于非根际（31.31%），这与根际真菌残体 C 的更大积累直接相关。我们的研究结果强调了根际过程在调节高氮沉降下土壤 C 动态中的重要作用，并从根际角度为 SOC 固存中微生物衍生 C 的重要性提供了明确的证据。
