Changes in soil microbial communities due to biological invasions can reduce allelopathic effects

Abstract

Summary Soil microbes are important in mediating allelopathic interactions between invasive and native plants in the field. However, it was not known how these interactions vary in the process of biological invasions and the effects of soil microbes; this knowledge may facilitate understanding the dynamics and mechanisms of biological invasions and managing invaded ecosystems. We conducted competition and seed germination experiments to determine the allelopathic effects of Ageratina adenophora in soils from 42 sites with varying abundances of the invasive plant. Then we isolated the microbes that could degrade the allelochemicals of the invasive plant and tested their functions. In both experiments, the allelopathic effects of the invasive plant were much stronger in soils from non‐invaded sites than in soils from invaded sites. Activities of the allelochemical‐degrading microbes were higher and degradation of the allelochemicals of the invasive plant was faster in soils from invaded sites than in soils from non‐invaded sites. In living soils from 30 sites with increasing abundance of A. adenophora, the allelopathic effects of the invasive plant decreased and degradation of the allelochemicals and activity of the allelochemical‐degrading microbes gradually increased. Two bacterial strains were isolated from the soils. Inoculation of Arthrobacter sp. ZS, which was isolated from soil invaded by A. adenophora, greatly increased the degradation of the allelochemicals, thereby decreasing its allelopathic effects. Synthesis and applications. Our results indicate that soils may accumulate microbes that can degrade allelochemicals in the process of biological invasions, gradually reducing the allelopathic effects of invasive species. The effects of soil microbes should be considered when studying dynamics and mechanisms of biological invasions. Application of allelochemical‐degrading microbes may facilitate ecological restoration of invaded or newly disturbed ecosystems by alleviating allelopathic inhibition of invasive plants on native plants.

Tissue-Specific and Geographical Variation in Endophytic Fungi of Ageratina adenophora and Fungal Associations With the Environment

“…Multiple studies have shown significant impacts of invasive plant populations on soil microbial communities (Xu et al, 2012;Li et al, 2017;Malinich et al, 2017); however, such an effect on airborne microbes has received no attention. In fact, plants contribute microbes to the air around them (Lymperopoulou et al, 2016).…”

“…There is evidence that strong allelopathy (Inderjit et al, 2011) and high resource capture and use efficiency (Wang et al, 2013) promote its competitive advantages over native species. Recent studies have shown that A. adenophora frequently changes soil microbial communities to contribute to its invasion (Xu et al, 2012;Li et al, 2017;Zhu et al, 2017). In addition, Mei et al (2014) indicated that the diversity and isolation frequency of foliar fungal endophytes have increased with time since the introduction of A. adenophora.…”

The Effects of Soils from Different Forest Types on the Growth of the Invasive Plant Phytolacca americana

“…Prior studies have observed that soil microbes play an important role in determining allelopathic activity [28,74]. In the present study, the effects of allelopathy and soil microbes, the latter being explored by comparison of plant growth between sterilized and non-sterilized soil, showed opposing effects for P. americana growth (Figure 2).…”

“…We calculated the response index (RI) [28,58] to evaluate the allelopathic effects of forest litter on P. americana seed germination and seedling growth, as follows: (Variable leachate − Variable water )/Variable water , where Variable leachate was the individual value of replicates with leachate application and Variable water the average value of replicates with water addition. RI > 0 indicates a positive effect, RI < 0 indicates an inhibitory effect, and RI = 0 indicates no effect.…”

Evidence for chemical interference effect of an allelopathic plant on neighboring plant species: A field study

“…herba-alba between previous laboratory studies and our field experiment might be because of differences in the experimental conditions, including the soil microbial community, level of exposure to allelopathic compounds, the specific mixture or the relative concentrations of compounds acting jointly under natural conditions. For instance, it is known that in the field, associated soil microorganisms can metabolize chemical compounds and diminish their allelopathic effects [ 55 , 56 ]. This emphasizes that laboratory studies might overestimate the significance of allelopathy in nature, as discussed in previous studies [ 57 – 60 ].…”