【作者】 张涛；

【导师】 宋冰；

【作者基本信息】 鲁东大学 ， 地理学， 2023， 硕士

【摘要】 外来植物入侵是全球生态环境安全和经济发展面临的重要威胁因素之一。近几年,入侵植物互花米草在我国北方滨海湿地的分布面积呈指数性爆发增长。互花米草对土壤有效氮素的竞争优势可能是其迅速扩张的原因之一,然而以往研究较少考虑其氮素利用策略与根际氮循环功能微生物之间的互作关系。本研究以黄河三角洲湿地为研究区域,采用¹⁵N稳定性同位素示踪技术研究了互花米草（Spartina alterniflora）与本土竞争植物盐地碱蓬（Suaeda salsa）对不同形态氮素的吸收利用特征,采用高通量测序及q PCR基因芯片技术探究了互花米草与盐地碱蓬群落中土壤微生物（细菌、真菌）及氮循环相关功能微生物群落结构的差异,旨在为黄河三角洲地区互花米草的防治与生态环境修复提供科学依据。得到主要结论如下:（1）¹⁵N同位素示踪结果显示,互花米草与盐地碱蓬对两种形态氮素(¹⁵NO₃^-、¹⁵NH₄⁺)的吸收没有显著的偏好性,对不同形态氮素的吸收速率也没有显著差异。但是,在取样时间内,盐地碱蓬对¹⁵NO₃^-(0.056±0.009μg N g^-1d.w.root h^-1)、¹⁵NH₄⁺(0.024±0.008μg N g^-1d.w.root h^-1)的吸收速率均显著高于互花米草(0.011±0.001μg N g^-1d.w.root h^-1、0.013±0.002μg N g^-1d.w.root h^-1)。互花米草将吸收的氮素更多地分配于叶和根中,茎中的氮分配量较低;而盐地碱蓬对¹⁵N的分配量主要集中在叶和茎中。（2）互花米草入侵改变了土壤细菌和真菌的群落结构与多样性。互花米草的入侵提高了土壤细菌群落的微生物alpha多样性,其中Shannon、Ace和Chao等多样性指数分别比盐地碱蓬样地高出6%、20.77%、21.62%;而对土壤真菌群落的alpha多样性没有显著影响。互花米草入侵后,土壤细菌群落中拟杆菌门（Bacteroidota）（11.57～15.59%）、脱硫杆状菌门（Desulfobacterota）（8.13～13.62%）、弯曲杆菌门（Campilobacterota）（0.22～4.46%）的相对丰度显著增加,芽单胞菌门（Gemmatimonadota）的相对丰度从8.82%急剧减少到2.32%;土壤真菌群落中壶菌门（Chytridiomycota）（2.95～8.47%）的相对丰度显著提高,而被孢霉门（Mortierellomycota）（0.35～0.06%）和油壶菌门（Olpidiomycota）（0.07～0.001%）的相对丰度显著降低。土壤中盐分、电导率及氮素含量是驱动黄河三角洲湿地互花米草与盐地碱蓬土壤细菌和真菌群落结构和多样性变化的最重要因素。（3）互花米草入侵简化了土壤微生物群落之间的共生网络关系。土壤微生物共生网络分析结果显示,互花米草样地的土壤细菌和真菌群落的连接数、平均度和平均路径长度等网络参数明显低于盐地碱蓬样地,这说明互花米草入侵简化了土壤微生物的共生网络,减弱了微生物之间的互作关系。（4）互花米草入侵影响了土壤细菌和真菌群落的功能。通过功能预测,在细菌群落中与土壤氮循环相关的好氧化能异养（Aerobic chemoheterotrophy）（20.67～26.86%）、硝酸盐还原型（Nitrate reduction）（1.21～3.58%）及尿解型（Ureolysis）（0.03～0.12%）等相关的细菌功能团的相对丰度显著上升,与好氧氨氧化型（Aerobic ammonia oxidation）（0.20～0.01%）相关的细菌功能团的相对丰度显著下降;在真菌群落中,腐生菌（Saprotroph）的相对丰度从12.3%显著增加到17.53%,而病原菌（Pathotroph）和共生营养菌（Symbiotroph）的相对丰度却显著降低。然而,基因芯片测定结果显示,互花米草入侵没有显著改变与土壤氮循环相关的功能基因的多样性及绝对丰度。以上结果表明,互花米草与盐地碱蓬的氮素利用特征略有差异。互花米草的入侵能显著影响土壤微生物群落结构,并简化土壤微生物共生网络。未来研究需进一步探讨互花米草入侵下土壤微生物对其氮素利用特征的调控。更多还原

【Abstract】 Invasive alien plant species pose a significant threat to global ecological security and economic development.In recent years,the invasive plant species Spartina alterniflora has experienced an exponential increase in distribution area in the northern coastal wetlands of China.Its competitive advantage for soil available nitrogen may be one of the reasons for its rapid expansion.However,previous studies have paid little attention to the interactive relationship between its nitrogen utilization strategy and rhizosphere microorganisms involved in nitrogen cycling.This study aimed to investigate the characteristics of nitrogen uptake and utilization by S.alterniflora and its native competitor Suaeda salsa for different forms of nitrogen using stable isotope tracing technology in the wetlands of the Yellow River Delta.The study also explored the differences in microbial community structure of soil bacteria,fungi,and nitrogen cycling-related functional microorganisms between the S.alterniflora and S.salsa communities using high-throughput sequencing and q PCR gene chip technology.The results will provide scientific evidence for the control of S.alterniflora and ecological restoration in the Yellow River Delta region.The main results are as follows:（1）The results of ¹⁵N stable isotope tracing showed that there was no significant preference for the absorption of two forms of nitrogen(¹⁵NO₃^-and ¹⁵NH₄⁺)between S.alterniflora and S.salsa,and there was no significant difference in the absorption rate of different forms of nitrogen.However,during the sampling period,the absorption rate of¹⁵NO₃^-(0.056±0.009μg N g^-1d.w.root h^-1)、¹⁵NH₄⁺(0.024±0.008μg N g^-1d.w.root h^-1)by S.salsa was significantly higher than that of S.alterniflora(0.011±0.001μg N g^-1d.w.root h^-1,0.013±0.002μg N g^-1d.w.root h^-1).S.alterniflora allocated more absorbed nitrogen to leaves and roots,with a lower allocation to stems;while the allocation of ¹⁵N in S.salsa was mainly concentrated in leaves and stems.（2）The invasion of S.alterniflora has changed the community structure and diversity of soil bacteria and fungi.The invasion of S.alterniflora has increased the microbial alpha diversity of soil bacterial communities,with Shannon,Ace,and Chao diversity indices being 6%,20.77%,and 21.62%higher than those of S.salsa,respectively.However,there was no significant effect on the alpha-diversity of soil fungal communities.After the invasion of S.alterniflora,the relative abundances of Bacteroidota（11.57～15.59%）,Desulfobacterota（8.13～13.62%）,and Campilobacterota（0.22～4.46%）in soil bacterial communities significantly increased,while the relative abundance of Gemmatimonadota decreased sharply from 8.82%to 2.32%.In soil fungal communities,the relative abundance of Chytridiomycota（2.95～8.47%）significantly increased,while the relative abundances of Mortierellomycota（0.35～0.06%）and Olpidiomycota（0.07～0.001%）significantly decreased.Soil salinity,conductivity and nitrogen content were the most important factors driving changes in the structure and diversity of soil bacterial and fungal communities of intercalary S.alterniflora and S.salsa ponies in the Yellow River Delta wetlands.（3）The invasion of S.alterniflora has simplified the symbiotic network relationships between soil microbial communities.The analysis of the soil microbial symbiotic network shows that the connection number,average degree,and average path length of the bacterial and fungal communities in the soil of S.alterniflora are significantly lower than those of S.salsa.This suggests that the invasion of S.alterniflora has simplified the symbiotic networks of soil microbes and weakened the interactions among them.（4）The invasion of S.alterniflora affects the functioning of soil bacterial and fungal communities.Through functional predictions,the relative abundance of bacterial functional groups related to soil nitrogen cycling,such as Aerobic chemoheterotrophy（20.67～26.86%）,Nitrate reduction（1.21～3.58%）,and Ureolysis（0.03～0.12%）,significantly increased,while the relative abundance of bacterial functional groups related to aerobic ammonia oxidation（0.20～0.01%）significantly decreased in the bacterial community.In the fungal community,the relative abundance of Saprotroph increased significantly from 12.3%to 17.53%,while the relative abundance of Pathotroph and Symbiotroph decreased significantly.However,gene chip testing results show that the invasion of S.alterniflora did not significantly alter the diversity and absolute abundance of functional genes associated with soil nitrogen cycling.The above results indicate that there are slight differences in nitrogen utilization characteristics between S.alterniflora and S.salsa.The invasion of S.alterniflora can significantly affect the structure of soil microbial communities and simplify the soil microbial symbiotic network.Future studies need to further explore the regulation of soil microbes on its nitrogen utilization characteristics under the invasion of S.alterniflora.更多还原