【作者】 封晔；

【导师】 唐明；

【作者基本信息】 西北农林科技大学 ， 森林保护学， 2012， 博士

【摘要】 本研究对黄土高原不同生态区主要树种采用末端片段长度多态性(Terminal restriction fragment length polymorphisms, T-RFLP)分析方法分析了根际细菌与丛枝菌根真菌(Arbuscular mycorrhizal fungi, AMF)群落,揭示了主要树种和根际环境对根际微生物群落结构的影响及根际微生物之间的相互作用。研究了AMF对刺槐根际土壤微生物群落结构、土壤酶活性、土壤养分和土壤水稳性团聚体的影响。同时采用盆栽试验和同位素示踪技术研究了不同施肥水平和不同种类AMF对刺槐生长及养分吸收的影响,初步揭示了AMF在植物吸收传递养分的作用机制。得出以下主要结论：1.对黄土高原神木县六道沟流域、安塞县纸坊沟流域和杨陵区西北农林科技大学苗圃三个不同生态区的植物根际AMF和细菌群落多样性的研究表明：不同植物间根际细菌多样性指数存在较大差异,杨陵区紫穗槐(Amorpha fruticosa)根际细菌的丰富度和Shannon指数最高,分别达到139和4.40；纸坊沟流域紫穗槐和榆树(Ulmus pumila)根际细菌丰富度和Shannon指数最低,与其他植物均呈显著性差异(p<0.05)。植物根际细菌的群落结构与宿主植物没有严格的专一性。不同植物根际AMF多样性指数存在差异,且AMF的多样性指数低于细菌,其中纸坊沟流域垂柳(Salix babylonica)根际AMF的丰富度和Shannon指数最高,分别达到87和3.05,六道沟流域沙棘(Hippophae rhamnoides)根际AMF的丰富度和Shannon指数最低,与其他植物均呈显著性差异(p<0.05)。植物根际AMF群落多样性与宿主植物的专一性较高,但个别植物间根际AMF群落多样性也存在一定相似度。植物根际细菌和AMF多样性指数呈极显著正相关(p<0.01)。在三个区域内,刺槐(Robinia pseudoacacia)根际细菌和AMF的多样性指数显著高于其他植物(p<0.05)。冗余分析(Redundancy Analysis, RDA)表明,根际土壤有机质和pH对细菌群落多样性影响较大,速效磷对AMF群落多样性影响较大。2.不同施肥水平和不同种类AMF对刺槐生长及养分吸收影响的研究表明：不同施肥水平下单接种摩西球囊霉(Glomus mosseae,简称Gm)、缩球囊霉(G. constrictum,简称Gc)和混合接种(Gm+Gc)均能提高刺槐生物量。不同施肥量对接种AMF的刺槐菌根侵染率影响不同,适量施氮可增加菌根侵染率,当施氮量为0.2～0.3g·kg-1时菌根侵染率最高,达74.5%,过量施氮则抑制菌根侵染率；施磷增加了菌根侵染率而施钾对菌根侵染率的影响较小。不同施肥水平下接种AMF均可提高刺槐对氮、磷、钾的吸收,且对磷的作用较大,在施磷量为0.3g·kg-1时,接种AMF使刺槐对磷的吸收量提高了73.0%；不同种类AMF在不同养分条件下作用存在差异。适量施Ca能促进刺槐对氮和磷的吸收,施Ca量为0.1-0.2g.L-1时,AMF和Ca共同作用使刺槐全氮和全磷含量达到峰值,分别为7.85g.kg-1和6.62g.kg-1,但施Ca抑制了刺槐对钾的吸收。结合四室隔网装置和稳定性同位素方法研究发现AMF菌丝之间能形成菌丝桥,两种AMF的菌丝传递率都超过25%,说明养分可通过菌丝桥进行吸收传递且AMF吸收传递的氮素对植株氮营养可产生积极作用。刺槐对硫酸铵-15N的吸收能力要高于尿素-15N,接种Gc后刺槐根、茎、叶中硫酸铵-15N丰度比尿素-15N丰度分别提高了98.36%、111.11%和54.76%。3.对AMF影响刺槐根际土壤微生物群落、土壤酶活性变化及土壤养分的研究表明：单接种GM、Gc和混合接种均显著增加刺槐根际细菌、真菌和放线菌数量(p<0.05)；接种AMF对刺槐根际细菌数量影响较大,单接种Gc比CK提高了360%；其次为放线菌,单接种Gc比CK提高了148%；对真菌数量影响较小。接种AMF均能显著提高刺槐根际土壤碱性磷酸酶、蔗糖酶和过氧化氢酶活性(p<0.05),且单接种作用高于混合接种,其中单接种Gm作用最大,分别比CK提高了291%、204%和51.28%；混合接种显著提高了脲酶活性(p<0.05),比CK提高了15.45%。接种AMF降低了根际土壤pH,其中单接种Gc使根际土壤pH显著低于CK(p<0.05)；接种AMF对土壤养分含量影响较小,与CK相比均差异不显著。植物根际各种因子之间的相关性检验结果表明菌根侵染率与植物干重呈显著正相关(p<0.05),可见接种AMF可显著影响植物生长。4.采用三室隔网装置对AMF影响根际土壤水稳性团聚体的研究表明：接种AMF显著提高了刺槐根际土壤多糖类物质和球囊霉素相关蛋白的含量(p<0.05),且接种Gm作用优于Gc,接种Gm的多糖类物质和球囊霉素相关蛋白的含量比CK分别提高了47.3%和223%。接种AMF提高了>0.25mm粒级的水稳性团聚体含量,对<0.25mm粒级的微团聚体含量影响较小。菌丝室土壤中,接种Gm和Gc的菌丝密度分别达到9.5m.cm3和7.2m.cm3；随着距根系距离增加,>0.5mm粒级的水稳性大团聚体含量逐渐升高,而<0.5mm粒级的微团聚体含量则变化不大。对可能影响土壤水稳性团聚体变化的各因子进行相关性检验,结果表明：AMF对于>0.5mm粒级的土壤团聚体影响显著,团聚体含量与菌丝密度呈显著正相关(p<0.05),与侵染率和球囊霉素呈极显著正相关(p<0.01)。此外,根干重和根含磷量也与>0.5mm粒级的大团聚体显著正相关(p<0.05),表明土壤团聚体的形成和发展与植物根部生长密切相关。粒级在0.25mm-0.5mm之间的团聚体含量与各因子均有一定相关性,但相关性不显著。更多还原

【Abstract】 This study employed Terminal Restriction Fragment Length Polymorphisms (T-RFLP) to analyze community diversity of rhizosphere bacteria and arbuscular mycorrhizal fungi (AMF) of representative plants on Loess Plateau. Results showed impacts of plant species and rhizosphere environment on the microbial community structure, as well as interactions between rhizosphere microorganisms. Experiment was then conducted to study impacts of AMF on soil microbial communities, enzyme activity, nutrient levels and water-stable aggregates in the rhizosphere of Robinia pseudoacacia. In addition, pot experiment and stable isotope technique were used to study impacts of fertilization levels and AMF species on R. pseudoacacia growth and nutrient uptake. These demonstrated the functional mechanism of AMF on plant nutrient transmission. The major conclusions are as following:1. The community diversity analysis of rhizosphere bacteria and AMF in Liudaogou watershed in Shenmu County, Zhifanggou watershed in Ansai County and nursery in Yangling indicated that there was a great difference between rhizosphere bacteria according to plants species. The abundance and Shannon diversity index of bacteria were highest in the rhizosphere of Amorpha fruticosa in Yangling nursery (139and4.40, respectively), and lowest in the rhizosphere of A. fruticosa and Ulmus pumila in Zhifanggou watershed, significantly different from other plants (p<0.05). Rhizosphere bacterial community diversity and host plant species were not strictly specificity. The AMF community diversity varied in three regions and occurred at lower levels than bacteria. The abundance and Shannon diversity index of AMF were highest in the rhizosphere of Salix babylonica in Zhifanggou watershed (87and3.05, respectively), and lowest in the rhizosphere of Hippophae rhamnoides in Liudaogou watershed, significantly different from other plants (p<0.05). Despite high specificity of AMF community diversity of the same type of plants, there was high similarity amongst individual plants. Rhizosphere bacteria and AMF community diversity index were positively correlated (p<0.05). Bacterial and AMF community diversity in the rhizosphere of R. pseudoacacia was significantly higher than other plants in three regions (p<0.01). Redundancy analysis showed that rhizosphere soil organic matter and pH had great impact on bacterial community diversity and that available phosphorus had great impact on AMF community diversity.2. The study of impacts of fertilization levels and AMF species on the biomass and nutrition uptake of R. pseudoacacia indicated that single inoculation of Glomus mosseae (Gm) and G. constrictum (Gc) and mixed inoculation of (Gm+Gc) increased biomass of R. pseudoacacia. Different fertilization levels for R. pseudoacacia affected the mycorrhiza infection rate, and defined amount of nitrogen (N) fertilizer could increase mycorrhiza infection rate. The mycorrhiza infection rate was highest (74.5%)0.2～0.3g·kg-1N fertilizer was applied. Excessive N fertilizer appeared to decrease the mycorrhiza rate. By comparison, phosphorus (P) and potassium (K) had less affect on the mycorrhiza infection rate. AMF inoculation under different nutrient levels promoted the uptake of N, P and K by R. pseudoacacia. Among these, the uptake of P was most seriously affected. Inoculation of R. pseudoacacia increased the amount of absorbed P by73.0%when0.3g·kg-1P fertilizer was applied. There were differences between different type of AMF. Defined amount of calcium (Ca) fertilizer promoted the uptake of N and P by R. pseudoacacia. When0.1～0.2g·L-1Ca fertilizer was applied, AMF elevated total N and total P adsorbed by R. pseudoacacia to the peak,(7.85g·kg-1and6.62g·kg-1, respectively). However, applicatoin of Ca fertilizer restrained the uptake of K. Combined four compartment box and stable isotope technique, hyphal links were discovered between AMF. The hypha transfer rate of two kinds of AMF was exceeded25%. This indicated that nutrition could be absorbed and transmitted to the host plant by AMF hyphal links, which exerted positive effects on plant N nutrition. The uptake rate of ammonium sulphate-15N by R. pseudoacacia was higher than that of urea-15N. Compared to urea-15N, the ammonium sulphate-15N abundance in root, stem and leaves of R. pseudoacacia in single inoculation of Gc treatment was improved by98.36%,111.11%and54.76%, respectively.3. The study of AMF impact on soil microbial communities, enzyme activity and soil nutrients in R. pseudoacacia indicated that single inoculation of Gc and Gm, as well as mixed inoculation Gc and Gm all increased the abundance of bacteria, fungi and actinomycetes in the rhizosphere of R. pseudoacacia(p<0.05). Inoculation of AMF had greatest influence on the abundance of bacteria, and single inoculation of Gc lead to a3.6times increase in bacterial abundance compare to CK. In addition, single inoculation of Gc lead to a1.5times increase in the abundance of actinomycetes, whereas the influence of AMF inoculation on the abundance of fungi was minimum. Inoculation of AMF significantly improved the activity of soil alkaline phosphatase, sucrase and catalase(p<0.05), with impacts of single AMF inoculation was greater than mixed inoculation, Compare to CK, single inoculation of Gm increased enzyme activity by2.9,2.0and0.5times, respectively. In addition, mixed inoculation of Gc and Gm significantly improved urease activity (p<0.05), which increased by15.45%compare to CK. Inoculation of AMF decreased rhizosphere soil pH, and the effect of single inoculation of Gc was statistically significant (p<0.05). Inoculation of AMF had little influence on soil nutrient. Correlation coefficient test of various factors in the rhizosphere of plant showed mycorrhizal colonization rate and plant dry weight were positively related(p<0.05), indicating inoculation of AMF strongly influenced plant growth.4. The study of AMF impact on rhizospheric soil water-stable aggregate using three compartment box indicated that inoculation of AMF significantly increased rhizosphere soil polysaccharides and glomalin-related protein content(p<0.05), and the effect of single inoculation of Gm which increased by0.5and2.2times compare to CK, was superior to single inoculation of Gc. Inoculation of AMF substantially increased water-stable macro-aggregate content of particle size>0.25mm but had little influence on that of particle size<0.25mm. In soil of hypha room, hyphal density of single inoculation of Gm and Gc were9.5and7.2m·cm-3, respectively. Water-stable macro-aggregate content of particle size>0.5mm increased with the distance from plant roots, but micro-aggregate content of particle size<0.5mm did not change significantly. Results of correlation test showed that AMF had significant effects on water-stable macro-aggregate content of particle size>0.5mm, and aggregate content and hypha density were significantly correlated (p<0.05), with infection rates and glomalin content were significant positively correlated (p<0.01). In addition, water-stable macro-aggregate content of particle size>0.5mm and root dry weight and root phosphorus were significantly correlated (p<0.05). This showed the formation and development of soil aggregates were bound up with plant root growth. Water-stable aggregate content of particle size in0.25-0.5mm were to some extent correlated with various environmental factors, but the correlation was not significant.更多还原