Xi Dan, Jin Shaofei, Wu Jianping
Lushan Botanical Garden, Chinese Academy of Sciences, Jiujiang, China.
College of Forestry, Fujian Agriculture and Forestry University, Fuzhou, China.
Front Microbiol. 2022 Oct 12;13:1015936. doi: 10.3389/fmicb.2022.1015936. eCollection 2022.
Soil microorganisms are key regulators for plant growth and ecosystem health of forest ecosystem. Although previous research has demonstrated that soil microorganisms are greatly affected by understory nitrogen (N) addition, little is known about the effects of canopy N addition (CNA) and understory management on soil microorganisms in forests. In this study, we conducted a full designed field experiment with four treatments: CNA (25 kg N ha year), understory removal (UR), canopy N addition, and understory removal (CNAUR) (25 kg N ha year), and control in a Chinese fir plantation. High-throughput sequencing and qPCR techniques were used to determine the abundance, diversity, and composition of bacterial and fungal communities in three soil layers. Our results showed that CNA increased bacterial diversity in the 10-20 cm soil layer but decreased bacterial abundance in the 20-40 cm soil layer and fungal diversity in the 0-10 cm soil layer. UR increased bacterial abundance only in the 20-40 cm soil layer. CNA, not UR significantly altered the compositions of soil bacterial and fungal community compositions, especially in the 0-20 cm soil layer. CNA sharply reduced the relative abundance of copiotrophic taxa (i.e., taxa in the bacterial phylum Proteobacteria and the orders Eurotiales and Helotiales in the fungal phylum Ascomycota) but increased the relative abundance of oligotrophic taxa (i.e., in the bacterial phylum Verrucomicrobia). RDA analysis revealed that soil pH, DON, and DOC were the main factors associated with the variation in bacterial and fungal communities. Our findings suggest that short-term CNA changes both soil bacterial and fungal communities, with stronger responses in the surface and middle soil than in the deep soil layer, and that UR may enhance this effect on the soil bacterial abundance. This study improves our understanding of soil microorganisms in plantations managed with understory removal and that experience increases in N deposition.
土壤微生物是森林生态系统中植物生长和生态系统健康的关键调节者。尽管先前的研究表明林下施氮会对土壤微生物产生重大影响，但关于林冠层施氮（CNA）和林下管理对森林土壤微生物的影响却知之甚少。在本研究中，我们在中国杉木人工林中进行了一项完全设计的田间试验，设置了四种处理：林冠层施氮（25千克氮/公顷·年）、林下清除（UR）、林冠层施氮与林下清除（CNAUR）（25千克氮/公顷·年）以及对照。采用高通量测序和qPCR技术测定了三个土壤层中细菌和真菌群落的丰度、多样性和组成。我们的结果表明，林冠层施氮增加了10 - 20厘米土层的细菌多样性，但降低了20 - 40厘米土层的细菌丰度以及0 - 10厘米土层的真菌多样性。林下清除仅增加了20 - 40厘米土层的细菌丰度。林冠层施氮而非林下清除显著改变了土壤细菌和真菌群落的组成，尤其是在0 - 20厘米土层。林冠层施氮大幅降低了富营养类群的相对丰度（即细菌门变形菌纲以及真菌门子囊菌纲中的散囊菌目和锤舌菌目的类群），但增加了贫营养类群的相对丰度（即疣微菌门细菌）。冗余分析表明，土壤pH值、溶解性有机氮和溶解性有机碳是与细菌和真菌群落变化相关的主要因素。我们的研究结果表明，短期林冠层施氮会改变土壤细菌和真菌群落，表层和中层土壤的响应比深层土壤更强，并且林下清除可能会增强对土壤细菌丰度的这种影响。本研究增进了我们对林下清除管理且氮沉降增加的人工林中土壤微生物的理解。
