Invasive alien plant species can threaten native diversity, disrupt ecosystem functions and services, and cause large economic damage. Consequently, understanding the factors that contribute towards invasion success is crucial.

Previous studies on plant invasions have focused mainly on competitions between one alien and one native species. Very few experiments have examined how a third plant affects competitive outcomes between the alien and native plants.

A third plant can affect alien-native competitions through shared resource such as nutrients and sunlight, which is the most intuitive way. It can also occur through other trophic levels, for instance soil microbes. However, exactly how a third plant modify soil microbes as they grow, and then affect competitions between alien and native plants which later grow on this soil (“soil-legacy effect”) had remained unclear.

To address this issue, Prof. Dr. Yanjie Liu from the Northeast Institute of Geography and Agroecology (IGA) of the Chinese Academy of Sciences, in collaboration with his colleagues Dr. Zhijie Zhang and Prof. Dr. Mark van Kleunen from University of Konstanz (Germany), and Dr. Caroline Brunel from the French National Research Institute for Sustainable Development and the Joint Research Unit for Plant-Microorganism-Environment Interactions (France) conducted a large multi-species experiment consisting of two stages.

They first conditioned soil with one of ten species (six natives and four aliens) or without plants. And then, they grew on these 11 soils five aliens and five natives without competition, or with intra- or interspecific competition, mimicking different competition scenarios in the nature. To assess the role of microbes, they further analysed how soil-conditioning species affected the soil microbial communities, and how soil microbial communities affected later plants, taking aboveground biomass production as an indication of competitive ability.

They found that aliens were not more competitive than natives when grown on soil conditioned by other natives or on non-conditioned soil. However, aliens were more competitive than natives on soil conditioned by other aliens (that is, invasional meltdown). They also pinpoint the underlying mechanism to the soil microbiome: the legacy effect of soil-conditioning species on later species became less negative as their microbial communities became less similar, and aliens were observed to share fewer fungal endophytes with other aliens than with native species, which comes with a lower chance of fungal endophytes spilling over.

“Our study shows for the first time that soil microbiomes drive invasional meltdown in plants. This is a timely and novel study to understand the role of soil microorganisms during plant invasion. There is no doubt that more research will come out in future.” said Prof. Dr. Yanjie Liu.

The study entitled "Soil-microorganism-mediated invasional meltdown in plants" was published in appear in the latest issue of Nature Ecology & Evolution.

Contact:

LIU Yanjie

Northeast Institute of Geography and Agroecology

E-mail: liuyanjie@iga.ac.cn