Metagenomic Insights into How Understory Vegetation Enhances Soil Nitrogen Availability via Microbial Nitrogen Transformation in Poplar Plantations
Long-term monoculture of poplar plantations for industrial material production has been widely reported to cause severe soil degradation, while the presence of understory vegetation might enhance soil nitrogen (N) transformation and supply. This study employed a field experiment using a randomized b...
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MDPI AG
2025-06-01
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| author | Wenyu Jia Tong Li Peilei Ye Yuxin Chen Ruoning Zhu Ruixin Yan Haoran Yue Ye Tian |
| author_facet | Wenyu Jia Tong Li Peilei Ye Yuxin Chen Ruoning Zhu Ruixin Yan Haoran Yue Ye Tian |
| author_sort | Wenyu Jia |
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| description | Long-term monoculture of poplar plantations for industrial material production has been widely reported to cause severe soil degradation, while the presence of understory vegetation might enhance soil nitrogen (N) transformation and supply. This study employed a field experiment using a randomized block design with three blocks and four understory treatments, including understory removal, N-fixing species planting, single-species retention, and diverse vegetation retention, in poplar plantations on a mid-latitude alluvial plain in China over 6 years to assess the effects of different species and richness of understory on soil N transformation and related microbial traits via <sup>15</sup>N assays and shotgun metagenomics. The results showed that understory removal significantly reduced soil N transformation rates, bacterial abundance, and gene abundance associated with N transformation. Compared to a single-species understory, retaining a diverse understory with high species richness significantly increased soil gross N transformation rate of mineralization by 149%, nitrification by 221%, and immobilization by 85%; comprehensively enriched dominant bacterial phyla; and elevated gene abundances of <i>gdh_</i>K15371, <i>ure</i>B, <i>hao</i>, and <i>amo</i>A_B associated with N transformation. No significant difference in N transformation rates existed between N-fixing species planting treatment and single-species retention treatment, while N-fixing species planting treatment specifically promoted the soil bacterial phyla Nitrospirae and Chloroflexi, and increased the gene abundances of <i>gdh</i>_K15371 and <i>hao</i>. These findings demonstrate that both introducing N-fixing species and an increase in species richness of the understory effectively promoted soil N transformation but that different underlying mechanisms existed. Planting N-fixing species selectively increased the soil bacterial phyla of Nitrospirae and Chloroflexi, whereas the increase in species richness broadly enriched soil bacterial diversity, thereby inducing the enrichment of the functional genes and enhancing soil N transformation. In conclusion, both planting N-fixing species and retaining diverse understory vegetation were effective strategies for maintaining sustainable management of poplar plantations by increasing soil N availability. |
| format | Article |
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| institution | DOAJ |
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| language | English |
| publishDate | 2025-06-01 |
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| spelling | doaj-art-a88dbeebac194dcb83bec4b76425c09a2025-08-20T03:13:42ZengMDPI AGAgronomy2073-43952025-06-01157153710.3390/agronomy15071537Metagenomic Insights into How Understory Vegetation Enhances Soil Nitrogen Availability via Microbial Nitrogen Transformation in Poplar PlantationsWenyu Jia0Tong Li1Peilei Ye2Yuxin Chen3Ruoning Zhu4Ruixin Yan5Haoran Yue6Ye Tian7College of Forestry and Grassland, Nanjing Forestry University, Nanjing 210037, ChinaCollege of Forestry and Grassland, Nanjing Forestry University, Nanjing 210037, ChinaCollege of Forestry and Grassland, Nanjing Forestry University, Nanjing 210037, ChinaCollege of Forestry and Grassland, Nanjing Forestry University, Nanjing 210037, ChinaThird Construction Co., Ltd. of China Construction First Bureau Group, Beijing 100161, ChinaCollege of Forestry and Grassland, Nanjing Forestry University, Nanjing 210037, ChinaCollege of Forestry and Grassland, Nanjing Forestry University, Nanjing 210037, ChinaCollege of Forestry and Grassland, Nanjing Forestry University, Nanjing 210037, ChinaLong-term monoculture of poplar plantations for industrial material production has been widely reported to cause severe soil degradation, while the presence of understory vegetation might enhance soil nitrogen (N) transformation and supply. This study employed a field experiment using a randomized block design with three blocks and four understory treatments, including understory removal, N-fixing species planting, single-species retention, and diverse vegetation retention, in poplar plantations on a mid-latitude alluvial plain in China over 6 years to assess the effects of different species and richness of understory on soil N transformation and related microbial traits via <sup>15</sup>N assays and shotgun metagenomics. The results showed that understory removal significantly reduced soil N transformation rates, bacterial abundance, and gene abundance associated with N transformation. Compared to a single-species understory, retaining a diverse understory with high species richness significantly increased soil gross N transformation rate of mineralization by 149%, nitrification by 221%, and immobilization by 85%; comprehensively enriched dominant bacterial phyla; and elevated gene abundances of <i>gdh_</i>K15371, <i>ure</i>B, <i>hao</i>, and <i>amo</i>A_B associated with N transformation. No significant difference in N transformation rates existed between N-fixing species planting treatment and single-species retention treatment, while N-fixing species planting treatment specifically promoted the soil bacterial phyla Nitrospirae and Chloroflexi, and increased the gene abundances of <i>gdh</i>_K15371 and <i>hao</i>. These findings demonstrate that both introducing N-fixing species and an increase in species richness of the understory effectively promoted soil N transformation but that different underlying mechanisms existed. Planting N-fixing species selectively increased the soil bacterial phyla of Nitrospirae and Chloroflexi, whereas the increase in species richness broadly enriched soil bacterial diversity, thereby inducing the enrichment of the functional genes and enhancing soil N transformation. In conclusion, both planting N-fixing species and retaining diverse understory vegetation were effective strategies for maintaining sustainable management of poplar plantations by increasing soil N availability.https://www.mdpi.com/2073-4395/15/7/1537species richnessN-fixing speciesnitrogen mineralizationnitrificationfunctional gene |
| spellingShingle | Wenyu Jia Tong Li Peilei Ye Yuxin Chen Ruoning Zhu Ruixin Yan Haoran Yue Ye Tian Metagenomic Insights into How Understory Vegetation Enhances Soil Nitrogen Availability via Microbial Nitrogen Transformation in Poplar Plantations Agronomy species richness N-fixing species nitrogen mineralization nitrification functional gene |
| title | Metagenomic Insights into How Understory Vegetation Enhances Soil Nitrogen Availability via Microbial Nitrogen Transformation in Poplar Plantations |
| title_full | Metagenomic Insights into How Understory Vegetation Enhances Soil Nitrogen Availability via Microbial Nitrogen Transformation in Poplar Plantations |
| title_fullStr | Metagenomic Insights into How Understory Vegetation Enhances Soil Nitrogen Availability via Microbial Nitrogen Transformation in Poplar Plantations |
| title_full_unstemmed | Metagenomic Insights into How Understory Vegetation Enhances Soil Nitrogen Availability via Microbial Nitrogen Transformation in Poplar Plantations |
| title_short | Metagenomic Insights into How Understory Vegetation Enhances Soil Nitrogen Availability via Microbial Nitrogen Transformation in Poplar Plantations |
| title_sort | metagenomic insights into how understory vegetation enhances soil nitrogen availability via microbial nitrogen transformation in poplar plantations |
| topic | species richness N-fixing species nitrogen mineralization nitrification functional gene |
| url | https://www.mdpi.com/2073-4395/15/7/1537 |
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