历史因素对土壤微生物群落与外来细菌入侵间关系的影响

群落的组成和结构如何影响其可入侵性一直是入侵生态学的研究热点。然而关于群落可入侵性和群落特征间关系的认知却很不统一。采用交叉互换的试验方法,首先将野外采集的两种长期不同施肥土壤(有机肥和化肥)进行灭菌并回接已方和对方的土壤悬液,研究土壤环境(历史非生物因素)和土壤微生物群落(历史生物因素)对重建土壤微生物群落特征的相对贡献。随后将用红色荧光蛋白标记的青枯菌作为外来种接入重建的土壤中,探究不同土壤微生物群落特征对外来细菌存活数量(前期入侵潜力)和存活时间(后期入侵潜力)的影响。结果表明,历史生物因素对重建土壤的原生动物数量、革兰氏阴性与阳性细菌比等群落特征和外来细菌的存活数量有影响;历史非生物因素对土壤微生物活性、细菌物种多样性和功能多样性等群落特征以及外来细菌入侵土壤后总的存活时间有影响;外来细菌入侵前期状况仅与原生动物数量、革兰氏阴性与阳性细菌比相关,而入侵后期的状况则仅与微生物活性、细菌物种多样性和功能多样性相关。总之,外来细菌在土壤中各时期的入侵潜力和土著微生物群落特征的相关性主要取决于二者是否由同种历史影响因素控制。本研究对于阐明生物群落结构与群落可入侵性之间关系,及指导土壤外来病原菌的防控均具有重要意义。

Legacy impacts on the relationships between soil microbial community and the invasion potential of non-indigenous bacteria

Human activities, such as transportation, agriculture, and aquaculture, have significantly introduced alien species to their non-native habitats, leading to widespread ecological, economic, and social consequences. So far, numerous studies for a better understanding of the invasibility of resident communities in relation to its community characteristics, however, has yielded few generalizations. Therefore, it is timely to disentangle the factors that mediate the relationship between community characteristics and their invasibility. In this study, two paddy soils of plowing layers receiving long-term chemical or organic fertilizers were collected to be used in the reciprocal transplant experiment. Soils were sterilized with gamma ray (50 kGy) irradiation and swap inoculated. Microbial inoculum from organic amended soils was introduced into sterilized soils with either chemical (self-inoculation control, CsCm) or organic (CsOm) groups. Correspondingly, the microbial inoculum from chemically fertilized soils was introduced into sterilized soils with either chemical (OsCm) or organic (self-inoculation control, OsOm) groups. We assessed the relative contribution of sterilized soil (i.e. representing legacy of historical abiotic factor) and microbial inoculum (i.e. representing legacy of historical biotic factor) to the reconstructed microbial community, and explored the factors influencing the abundance (i.e. representing invasion potential of early stage) and time needed to reach detection limit (ttd, i.e. representing the invasion potential of late stage) of non-indigenous bacteria (RFP-tagged Ralstonia solanacearum). Our results showed that historical biotic factors (microbial inoculum) significanty affected (P<0.05) on protozoa abundance and the ratio of gram-positive bacteria to gram-negative bacteria (G^-/G⁺) of the reconstructed microbial community, as well as the abundance of R. solanacearum in soil after fifty-five days inoculation. In contrast, historical abiotic factors (sterilized soil) had a significant effect on microbial respiration, bacterial species and functional diversity in the reconstructed microbial community, and the ttd of R. solanacearum in soil. The abundance of soil R. solanacearum was significantly correlated with protozoa abundance and G^-/G⁺ ratio, while the ttd was significantly correlated with microbial respiration and bacterial species and functional diversity. In conclusion, the relationship between community characteristics and invasibility is regulated simultaneously by the invasion stage and historical factors. More importantly, the current findings not only elucidated the relationship between community composition and non-indigenous species invasion potential but also promoted the resolution of the biodiversity paradox, as well as guide the bio-control of non-indigenous pathogens in the soil ecosystem.