红毛草入侵程度对根际土壤微生物的影响

Effect of invasive degree of Rhynchelytrum repens on microorganisms in rhizosphere soil

【目的】研究外来种入侵对地下土壤微生物的影响,从植物与地下微生物互作的角度探索外来种的入侵机制。【方法】通过磷脂脂肪酸(PLFA)分析法和比色法,研究红毛草(Rhynchelytrum repens)不同入侵程度(未入侵、轻度入侵和中度入侵)对根际土壤理化性质、微生物群落结构、特殊功能微生物及其多样性水平的影响。【结果】供试土样中共检测到33种PLFA生物标记,其中细菌24种、放线菌4种、真菌4种、原生动物1种。随红毛草入侵程度增加,土壤碱解氮、全氮含量显著增加,含水量显著减少,速效磷、速效钾含量和pH无显著变化;根际土壤中细菌、真菌、原生动物以及PLFA标记物总含量均呈现逐渐增加的趋势;革兰氏阳性菌与革兰氏阴性菌含量比值逐渐减小;功能微生物含量逐渐增加,与未入侵地相比,红毛草重度入侵地根际土壤中的丛枝菌根真菌含量增加了42.46%,伯克霍尔德菌含量增加了22.32%,嗜热解氢杆菌增加了13.08%。红毛草入侵对根际土壤中微生物多样性水平有一定影响,Shannon-Wiener多样性和丰富度指数随入侵程度增加呈现升高的趋势,Pielou均匀度指数降低,Simpson优势度指数无显著变化。土壤中细菌含量与土壤全氮、碱解氮含量之间呈显著正相关;真菌含量与土壤碱解氮含量呈显著正相关。【结论】红毛草的入侵改变了根际土壤微生物的群落结构和土壤理化性质。随入侵的加剧,土壤全氮和碱解氮含量增加,细菌、真菌和原生动物含量以及一些特殊功能性微生物含量增多,土壤微生物群落多样性指数和丰富度指数增大。

[Objective] The study investigated the effect of invasive plant on microorganisms in underground soil to understand the mechanism of exotic species invasion from the respect of interactions between plants and underground microbes. [Method] The effects of different Rhynchelytrum repens invasion intensities （non-invasion, mild-invasion, and strong invasion） on physical and chemical properties, microbial community structure, and functional microorganisms and variety in rhizospheric soil were investigated using phospholipids fatty acid （PLFA） and colorimetric methods. [Result] There were 33 PLFA hiomarkers in studied soil plots, including 24 bacteria species, 4 actinobacterias,4 fungus, and 1 protozoa. With the increase of R. repens invasion, total nitrogen and alkali-hydrolysable nitrogen in soil significantly increased,water content reduced,while available phosphorus and potassium and pH value had no significant change. The contents of bacteria, fungi,protozoa, and total PLFAs showed a trend of increasing. Compared with the non-invasive soil, the contents of Abuscular mycorrhizal fungi, Burkholderia, and Hydrogenobacter were increased by 42. 46%, 22. 32% and 13. 08%, respectively, indicating that these functional microorganisms may play an important role in R. repens invasion. Shannon-Wiener index and Margalef index displayed an increasing trend with the increase of invasion,Pielou index decreased slightly, while Simpson index had no significant change. There were significantly positive correlations between contents of bacteria and total nitrogen and alkali-hydrolyzable nitrogen,as well as between contents of fungi and alkali-hydrolyzable nitrogen. [Conclusion] The invasion of R. repens changed the microbial community structure as well as physical and chemical properties of soil. With the increase of invasion, the contents of total nitrogen, alkali-hydrolyzable nitrogen content, bacteria, fungi, protozoa, total PLFAs, and some special functional microbes in- creased. The diversity of microbial community in soil was also increased.