Soil AMF community structure and assembly mechanism of medical sativa field in Loess Plateau
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摘要: 为揭示多年种植苜蓿对土壤丛枝菌根真菌(AMF)群落结构和多样性的影响, 本研究通过布设在黄土高原半干旱区的田间试验, 基于2019、2012和2003年建植的紫花苜蓿(Medicago sativa), 以农田玉米(Zea mays)为对照, 采用高通量测序和PCR技术, 结合分子生态网络研究不同种植年限紫花苜蓿地土壤AMF群落组成和丰度, 并基于零模型揭示了土壤AMF群落的组装过程。结果表明: 黄绵土区AMF属于球囊菌门的1纲4目7科7属, 球囊霉属、类球囊霉属和多孢囊霉属为紫花苜蓿地和农田土壤共有类群, 且均以球囊霉属(65.15%~99.12%)为优势属, 其主要贡献了不同处理分组中土壤AMF群落结构的改变。长期种植紫花苜蓿使得和平囊霉属和无梗囊霉属消亡, 但促生了双型囊霉属和盾巨孢囊霉属, 其中双型囊霉属相对丰度表现为L2019处理显著高于其他处理(P<0.05)。网络关联分析发现, 高丰度的球囊霉属和类球囊霉属之间呈现负相关, 而低丰度的和平囊霉属和无梗囊霉之间呈现正相关。基于零模型的群落组装结果表明, 农田与L2019处理由确定性过程主导(66.67%), L2012和L2003处理由随机性过程主导(100%), 这表明长期种植紫花苜蓿形成稳定的土壤环境使其随机性过程增加, 利于维持人工草地生态系统功能的可持续性和稳定性。Abstract: Arbuscular mycorrhizal fungi (AMF) mediate interactions between plants and soils, which play crucial role in terrestrial symbiosis and one of the important components in soil microbial community. However, little is known about how soil AMF community varies in relation to soil properties loessial soil. Therefore, the present study investigated soil AMF diversity community structure and soil physicochemical properties in Medicago sativa field and Farmland in the semi-arid area of the Loess Plateau. Soil samples (0-20 cm) were taken from four treatments in June 2021:1) farmland (Zea mays) and Medicago sativa established in 2019(L2019), 2012(L2012), 2003(L2003). The Illumina MiSeq high-throughput sequencing and real-time fluorescent quantitative PCR technology were used to explore the structure and diversity of AMF communities under four treatments (Farmland, L2003, L2012 and L2019). The statistical methods (such as redundancy analysis and molecular ecological network analysis) were used to explore the relationship between soil physicochemical properties and AMF community. Zero model analysis were used to reveal the assembly process of soil AMF community. The results showed that long-term planting of alfalfa decreased soil total phosphorus and available phosphorus. The AMF gene abundance ranged from 1.02×104~copies∙g−1 to 1.50×104copies·g-1 in dry soil, being significantly higher in Medicago sativa established in 2003(L2003) than other treatment (P<0.05). The correlation analysis between the abundance of AMF gene and physicochemical factors showed that soil AMF gene abundance was positively correlated with Total nitrogen, and negatively correlated with total phosphorus content, and available phosphorus. A total of 1 class, 4 orders, 7 families, and 7 genera of AMF were identified. Glomus, Diversispora and Paraglomus were the common genera of Medicago sativa field and Farmland, the dominant genera of Medicago sativa field and Farmland were Glomus (65.15%−99.12%), It mainly contributed to the changes of soil AMF community structure in different treatment groups. Long-term cultivation of Medicago sativa propagated the rare microbial taxa, including Ambispora and Scutellospora, whereas Pacispora and Acaulospora were sterilized. Ambispora Were significantly higher in Medicago sativa established in 2019(L2019) than other treatment (P<0.05), The analysis of molecular ecological network showed that there were high-abundance genera (Glomus and Paraglomus) had a cooperative relationship in the ecological network, while the low-abundance genera (Pacispora and Acaulospora )had a competitive relationship in the ecological network. RDA analysis showed that there was no main environmental factor affecting the community structure of AMF. Null model was used to infer AMF community assembly processes. Farmland and Medicago sativa established in 2019 (L2019) communities mechanism were dominantly assembled with the deterministic process (66.67%), the heterogeneous selection contributed the most. Medicago sativa established in 2012 (L2012) and 2003 (L2003) communities mechanism were dominantly assembled with random process (100%), the undominated processes contributed the most in Medicago sativa established in 2012 (L2012) and the dispersal limitation contributed the most in Medicago sativa established in 2003 (L2003). Mantel test showed that there was no main driving environmental factor for AMF community assembly. Long-term Medicago sativa cultivation increased the random processes. It is beneficial to maintain the sustainability and stability of artificial grassland ecosystem function. In summary, long-term planting of Medicago sativa significantly affected the composition of AMF community in soil. This study provides basic data and theoretical basis for further study on the microbial mechanism of AMF in the Loess Plateau after years of Medicago sativa planting.
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Key words:
- Medicago sativa /
- Arbuscular mycorrhizal fungi /
- Community structure /
- Community assembly /
- Loessal soil
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图 2 不同处理土壤AMF群落主坐标分析
Farmland、L2019、L2012、L2003分别表示农田、2019年建植苜蓿、2012 年建植苜蓿和2003年建植苜蓿。Farmland, L2019, L2012, and L2003 denote farmland and Medicago sativa planting years of 2019, 2012, and 2003, respectively.
Figure 2. Principal co-ordinates analysis (PcoA) of soil AMF communities under different treatments
图 3 不同处理土壤AMF属水平群落结构(A)和双型囊霉属相对丰度(B)
Farmland、L2019、L2012、L2003分别表示农田、2019年建植苜蓿、2012 年建植苜蓿和2003年建植苜蓿。Farmland, L2019, L2012, and L2003 denote farmland and Medicago sativa planting years of 2019, 2012, and 2003, respectively.
Figure 3. Soil AMF community at the genus levels (A) and relative abundance of Ambispora (B) under different treatments
图 5 土壤AMF群落与土壤理化因子冗余分析
Farmland、L2019、L2012、L2003分别表示农田、2019年建植苜蓿、2012 年建植苜蓿和2003年建植苜蓿。Glomus, Paraglomus, Diversispora, Scutellospora, Ambispora, Acaulospora and pacispora分别表示球囊霉属、类球囊霉属、多孢囊霉属、盾巨孢囊属、双型囊霉属、无梗囊霉属和平囊霉属。Farmland, L2019, L2012, and L2003 denote farmland and Medicago sativa planting years of 2019, 2012, and 2003, respectively.
Figure 5. Redundancy analysis (RDA) of soil AMF communities and soil physicochemical properties
图 6 不同处理土壤AMF群落组装生态过程
Farmland、L2019、L2012、L2003分别表示农田、2019年建植苜蓿、2012 年建植苜蓿和2003年建植苜蓿。Stochasticity: 随机性过程; Dil: 扩散限制; Hod: 同质性扩散; Und: 非主导过程; Determinism: 确定性过程; Hes: 异质性选择; Hos: 同质性选择。Farmland, L2019, L2012, and L2003 denote farmland and Medicago sativa planting years of 2019, 2012, and 2003, respectively. Dil: dispersal limitation; Hod: homogenizing dispersal; Und: undominated processes; Hes: heterogeneous selection; Hos: homogeneous selection.
Figure 6. Ecological processes governing soil AMF community assembly under different treatment
表 1 不同处理土壤基本理化性状及AMF基因丰度
Table 1. Soil physicochemical properties and Abundance of AMF gene under different treatments
指标 Index Farmland L2019 L2012 L2003 土壤水分 Soil water (%) 15.65±0.76a 8.76±0.46b 8.72±0.34b 9.62±0.13b 容重 Bulk Density (g∙cm−3) 1.18±0.01a 1.21±0.01a 1.23±0.02a 1.24±0.03a 有机碳 Organic carbon (g∙kg−1) 10.50±0.20b 9.83±0.21b 9.89±0.05b 11.49±0.32a 全氮 Total nitrogen (g∙kg−1) 0.92±0.03b 0.77±0.02c 0.85±0.05bc 1.11±0.05a 硝态氮 Nitrate nitrogen (mg∙kg−1) 23.14±0.33a 13.93±0.07c 12.35±0.07d 14.85±0.08b 全磷 Total phosphorus (g∙kg−1) 0.99±0.01a 0.93±0.01b 0.86±0.03c 0.82±0.01c 速效磷 Available phosphorus (mg∙kg−1) 6.21±0.05a 5.02±0.15b 3.92±0.13c 3.54±0.09d 速效钾 Available potassium (mg∙kg−1) 223.00±11.14a 222.00±2.89a 228.67±7.06a 229.33±0.88a pH 8.38±0.03a 8.49±0.01a 8.47±0.04a 8.45±0.03a AMF基因丰度
Abundance of AMF gene [×104 copy∙g−1(dry soil)]1.15±0.01bc 1.02±0.00c 1.26±0.04b 1.50±0.08a 数据为平均值±标准误(n=3), 同行不同小写字母表示不同处理间差异显著(P<0.05), Farmland、L2019、L2012、L2003分别表示农田、2019年建植苜蓿、2012年建植苜蓿和2003年建植苜蓿。Data in table are mean ± standard error (n=3). Different lowercase letters in the same line indicate significant difference between different treatments (P<0.05). Farmland, L2019, L2012, and L2003 denote farmland and Medicago sativa planting years of 2019, 2012, and 2003, respectively. 表 2 AMF基因丰度与土壤理化因子相关分析
Table 2. Correlation analysis of AMF gene abundance and environmental factors
指标 Index Abundance of AMF gene SW BD OC TN NO3−-N TP AP AK pH Abundance of AMF gene 1 SW 0.105 1 BD 0.298 −0.495 1 OC 0.522 0.522 0.165 1 TN 0.789** 0.474 0.023 0.786** 1 NO3--N 0.007 0.888** −0.488 0.648* 0.523 1 TP −0.711** 0.438 −0.627* −0.202 −0.304 0.529 1 AP −0.774** 0.326 −0.560 −0.263 −0.397 0.396 0.961** 1 AK 0.462 −0.042 0.229 0.109 0.305 −0.112 −0.385 −0.392 1 pH −0.102 −0.615* 0.456 −0.252 −0.515 −0.566 −0.327 −0.322 0.162 1 **: P<0.01; *: P<0.05. 表中Abundance of AMF gene、SW、BD、OC、TN、NO3−-N、TP、AP、AK、pH 分别表示AMF基因丰度、土壤水分、容重、有机碳、全氮、硝态氮、全磷、速效磷、速效钾、pH。In the table, Abundance of AMF gene, SW, BD, SOC, TN, NO3−-N, TP, AP, AK, pH were soil water, bulk Density, organic carbon, total nitrogen, nitrate nitrogen, total phosphorus, available phosphorus, available potassium, pH. 表 3 不同处理方式间AMF群落组成差异的优势属贡献率
Table 3. Contributions of dominant species to AMF community compositions under different treatment
% 分组
Groups球囊霉属
Glomus类球囊霉属
Paraglomus多孢囊霉属
Diversispora盾巨孢囊属
Scutellospora双型囊霉属
Ambispora无梗囊霉属
Acaulospora和平囊霉属
pacisporaFarmland vs L2019 48.08 5.27 1.23 0.00 0.93 0.18 0.18 Farmland vs L2012 49.00 1.91 0.56 1.39 0.35 0.27 0.27 Farmland vs L2003 49.18 2.64 0.64 1.14 0.06 0.27 0.26 L2019 vs L2012 49.16 6.06 1.53 0.99 0.74 0.00 0.00 L2019 vs L2003 49.26 5.64 1.32 0.84 0.96 0.00 0.00 L2012 vs L2003 40.57 27.44 5.50 21.19 4.45 0.00 0.00 Farmland、L2019、L2012、L2003分别表示农田、2019年建植苜蓿、2012 年建植苜蓿和2003年建植苜蓿。Farmland, L2019, L2012, and L2003 denote farmland and Medicago sativa planting years of 2019, 2012, and 2003, respectively. 表 4 土壤理化因子与βNTI的Mantel分析
Table 4. Mantel tests of soil physicochemical properties and βNTI
因子 Factor βNTI r P SW −0.126 0.818 BD −0.131 0.846 OC 0.109 0.198 TN −0.102 0.754 NO3−-N −0.071 0.651 TP −0.056 0.627 AP −0.124 0.843 AK −0.032 0.518 pH 0.099 0.242 -
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