Wu Di, Yin Changwei, Fan Yuxin, Chi Haiyu, Liu Zhili, Jin Guangze
Center for Ecological Research, Northeast Forestry University, Harbin, China.
Key Laboratory of Sustainable Forest Ecosystem Management, Ministry of Education, Northeast Forestry University, Harbin, China.
Front Microbiol. 2023 Dec 22;14:1327481. doi: 10.3389/fmicb.2023.1327481. eCollection 2023.
Litter decomposition is an important source of soil organic carbon, and it plays a key role in maintaining the stability of forest ecosystems. The microbial mechanism of soil organic carbon (SOC) formation in different urban forest planting patterns during litter lignocellulose degradation is still unclear. The key genes, microbes, and metabolites in the process of lignocellulose degradation and SOC formation were determined by metagenomics and metabolomics in different litter decomposition layers and soil layers in different urban forest planting patterns, including three types of broadleaf forests (BP forests), three types of coniferous forests (CP forests), and two types of mixed coniferous and broadleaf forests (MCBP forests). The results indicated that the cellulose, hemicellulose, and lignin concentrations from the undecomposed layer to the totally decomposed layer decreased by 70.07, 86.83, and 73.04% for CP litter; 74.30, 93.80, and 77.55% for BP litter; and 62.51, 48.58, and 90.61% for MCBP litter, respectively. The soil organic carbon of the BP forests and MCBP forests was higher than that of the CP forests by 38.06 and 94.43% for the 0-10 cm soil layer and by 38.55 and 20.87% for the 10-20 cm soil layer, respectively. Additionally, the gene abundances of glycoside hydrolases (GHs) and polysaccharide lyases (PLs) in the BP forests were higher than those in the MCBP forests and CP forests. Amino acid metabolism, sugar metabolism, TCA metabolism, and cAMP signaling metabolism were mainly between the CP forests and BP forests, while the TCA cycle, pyruvate metabolism, phenylalanine metabolism, and tyrosine metabolism were mainly between the BP forests and MCBP forests during litter decomposition. Additionally, ammonia nitrogen and hemicellulose were key factors driving SOC formation in the CP forests, while ammonia nitrogen, hemicellulose, and lignocellulose-degrading genes were key factors driving SOC formation in the BP forests. For the MCBP forests, cellulose, pH, ammonia nitrogen, and lignin were key factors driving SOC formation. Our findings revealed that the BP forests and MCBP forests had stronger lignocellulose degradation performance in the formation of SOC. This study provided a theoretical basis for the flow and transformation of nutrients in different urban forest management patterns.
凋落物分解是土壤有机碳的重要来源，在维持森林生态系统稳定性方面发挥着关键作用。不同城市森林种植模式下，凋落物木质纤维素降解过程中土壤有机碳（SOC）形成的微生物机制尚不清楚。通过宏基因组学和代谢组学，对不同城市森林种植模式（包括三种阔叶林（BP林）、三种针叶林（CP林）和两种针阔混交林（MCBP林））的不同凋落物分解层和土壤层中木质纤维素降解及SOC形成过程中的关键基因、微生物和代谢产物进行了测定。结果表明，CP凋落物从未分解层到完全分解层，纤维素、半纤维素和木质素浓度分别下降了70.07%、86.83%和73.04%；BP凋落物分别下降了74.30%、93.80%和77.55%；MCBP凋落物分别下降了62.51%、48.58%和90.61%。BP林和MCBP林的土壤有机碳在0 - 10 cm土层分别比CP林高38.06%和94.43%，在10 - 20 cm土层分别比CP林高38.55%和20.87%。此外，BP林中糖苷水解酶（GHs）和多糖裂解酶（PLs）的基因丰度高于MCBP林和CP林。在凋落物分解过程中，氨基酸代谢、糖代谢、三羧酸（TCA）代谢和环磷酸腺苷（cAMP）信号代谢主要存在于CP林和BP林之间，而TCA循环、丙酮酸代谢、苯丙氨酸代谢和酪氨酸代谢主要存在于BP林和MCBP林之间。此外，氨氮和半纤维素是CP林中驱动SOC形成的关键因素，而氨氮、半纤维素和木质纤维素降解基因是BP林中驱动SOC形成的关键因素。对于MCBP林，纤维素、pH值、氨氮和木质素是驱动SOC形成的关键因素。我们的研究结果表明，BP林和MCBP林在SOC形成过程中具有更强的木质纤维素降解性能。本研究为不同城市森林管理模式下养分的流动和转化提供了理论依据。
