Collaborative Innovation Center for Modern Crop Production co-sponsored by Province and Ministry, College of Agriculture, Nanjing Agricultural University, Nanjing, China.
Geo-Biosphere Interactions, Department of Geosciences, Faculty of Sciences, University of Tuebingen, Tuebingen, Germany.
Sci Total Environ. 2024 Dec 10;955:176732. doi: 10.1016/j.scitotenv.2024.176732. Epub 2024 Oct 10.
Arbuscular mycorrhizal fungi (AMF) form symbioses with most terrestrial plants and critically modulate soil organic carbon (C) dynamics. Whether AMF promote soil C storage and stability is, however, largely unknown. Since microbial necromass C (MNC) and glomalin-related soil protein (GRSP) are stable microbial-derived C in soils, we therefore evaluated how AMF symbiosis alters both soil C pools and their contributions to soil organic C (SOC) under nitrogen fertilization, based on a 16-weeks mesocosm experiment using a mutant tomato with highly reduced AMF symbiosis. Results showed that SOC content is 4.5 % higher following AMF symbiosis. Additionally, the content of MNC and total GRSP were 47.5 % and 22.3 % higher under AMF symbiosis than at AMF absence, respectively. The accumulations of GRSP and microbial necromass in soil were closely associated with mineral-associated organic C and the abundance of AMF. The increased soil living microbial biomass under AMF symbiosis was mainly derived from AMF biomass, and fungal necromass C significantly contributed to SOC accumulation, as evidenced by the higher fungal:bacterial necromass C ratio under AMF symbiosis. On the contrary, bacterial necromass was degraded to compensate for the increased microbial nutrient demand because of the aggravated nutrient limitation under AMF symbiosis, leading to a decrease in bacterial necromass. Redundancy analysis showing that bacterial necromass was negatively correlated with soil C:N ratio supported this argument. Moreover, the relative change rate of total GRSP was consistently greater in nitrogen-limited soil than that of microbial necromass. Our findings suggested GRSP accumulates faster and contributes more to SOC pools under AMF symbiosis than microbial necromass. The positive correlation between the contributions of GRSP and MNC to SOC further provided valuable information in terms of enhancing our understanding of mechanisms underlying the maintenance of SOC stocks through microbial-derived C.
丛枝菌根真菌 (AMF) 与大多数陆生植物形成共生关系，并对土壤有机碳 (C) 动态具有重要的调节作用。然而，AMF 是否促进土壤 C 储存和稳定性在很大程度上还不清楚。由于微生物残体 C（MNC）和球囊霉素相关土壤蛋白（GRSP）是土壤中稳定的微生物衍生 C，因此我们评估了在氮施肥下，AMF 共生如何改变土壤 C 库及其对土壤有机 C（SOC）的贡献，这是基于使用高度减少 AMF 共生的突变番茄进行的 16 周中观实验。结果表明，SOC 含量在 AMF 共生后增加了 4.5%。此外，在 AMF 共生下，MNC 和总 GRSP 的含量分别比 AMF 缺失时高 47.5%和 22.3%。GRSP 和微生物残体在土壤中的积累与矿物结合有机碳和 AMF 的丰度密切相关。在 AMF 共生下，土壤中生活微生物生物量的增加主要来自 AMF 生物量，真菌残体 C 对 SOC 积累有显著贡献，这可以从 AMF 共生下真菌：细菌残体 C 比值较高得到证明。相反，由于 AMF 共生下加剧的养分限制，细菌残体被降解以补偿增加的微生物养分需求，导致细菌残体减少。冗余分析表明，细菌残体与土壤 C:N 比呈负相关，支持了这一观点。此外，在氮限制土壤中，总 GRSP 的相对变化率始终大于微生物残体。我们的研究结果表明，在 AMF 共生下，GRSP 比微生物残体更快地积累，并对 SOC 库的贡献更大。GRSP 和 MNC 对 SOC 的贡献之间的正相关关系进一步提供了有价值的信息，有助于我们理解通过微生物衍生 C 维持 SOC 储量的机制。
