College of Grassland Science and Technology, China Agricultural University, 2 Yuan Ming Yuan West Road, Haidian District, Beijing 100193, China.
College of Grassland Science and Technology, China Agricultural University, 2 Yuan Ming Yuan West Road, Haidian District, Beijing 100193, China; Key Laboratory of Grassland Management and Rational Utilization, Ministry of Agriculture, Beijing 100193, China.
Sci Total Environ. 2023 Nov 15;899:165556. doi: 10.1016/j.scitotenv.2023.165556. Epub 2023 Jul 15.
Soil organic carbon (SOC) sequestration is a key grassland ecosystem function, and the magnitude of SOC reservoirs depends on microbial involvement, especially that of fungi. Mycelia developed by macrofungi potentially influence carbon (C) fixation and decomposition; however, the mechanisms underlying their effects on SOC storage in grassland ecosystems remain poorly understood. The fairy rings formed by macrofungi in grasslands are natural platform for exploring macrofungal effects on SOC. In this study, we collected topsoil (0-10 cm) from four different fairy ring zones in a temperate steppe to reveal the macrofungal effects on SOC fractions, including particulate organic carbon (POC) and mineral-associated organic carbon (MAOC), and the SOC storage microbial mechanism using metagenomic sequencing technology. Both POC and MAOC decreased after macrofungal passage, resulting in a 7.37 % reduction in SOC. Macrofungal presence reduced microbial biomass carbon (MBC), but significantly enhanced the β-1,4-glucosidase (BG) activity, which increased dissolved organic carbon (DOC). In addition, the abundance of copiotrophs (Proteobacteria and Bacteroidetes) with lower C metabolic rates increased, and that of oligotrophs (Actinobacteria, Acidobacteria, Chloroflexi, and Verrucomicrobia) with higher substrate utilization efficiency decreased in the presence of macrofungi. This may further promote SOC decomposition. Correspondingly, there was a lower abundance of C-fixation genes but more C-degradation genes (especially hemicellulosic degradation genes) during macrofungal passage. Our results indicate that the presence of macrofungi can modulate the soil microbial community and functional genes to reduce SOC storage by inhibiting microbial C sequestration while promoting C decomposition in grassland ecosystems. These findings refine our mechanistic understanding of SOC persistence through the interactions between macrofungi and other microbes.
土壤有机碳（SOC）固存是草原生态系统的一个关键功能，SOC 储量的大小取决于微生物的参与，尤其是真菌。大型真菌的菌丝体可能会影响碳（C）的固定和分解；然而，其对草原生态系统中 SOC 储存的影响机制仍知之甚少。草原上由大型真菌形成的仙女环是探索大型真菌对 SOC 影响的天然平台。在这项研究中，我们从温带草原的四个不同的仙女环区域采集了表层土壤（0-10cm），以揭示大型真菌对包括颗粒有机碳（POC）和矿物结合有机碳（MAOC）在内的 SOC 各组分的影响，以及利用宏基因组测序技术揭示 SOC 储存的微生物机制。大型真菌通过后，POC 和 MAOC 均减少，导致 SOC 减少了 7.37%。大型真菌的存在降低了微生物生物量碳（MBC），但显著增强了β-1,4-葡萄糖苷酶（BG）活性，从而增加了溶解有机碳（DOC）。此外，具有较低 C 代谢率的富养生物（变形菌门和拟杆菌门）的丰度增加，而具有较高基质利用效率的贫养生物（放线菌门、酸杆菌门、绿弯菌门和疣微菌门）的丰度减少。这可能进一步促进 SOC 分解。相应地，在大型真菌存在的情况下，SOC 固存基因的丰度降低，但 SOC 降解基因（特别是半纤维素降解基因）的丰度增加。我们的研究结果表明，大型真菌的存在可以通过抑制微生物 C 固存，同时促进草原生态系统中 C 的分解，来调节土壤微生物群落和功能基因，从而减少 SOC 储存。这些发现通过大型真菌与其他微生物的相互作用，细化了我们对 SOC 持久性的机制理解。
