Effect of microbe-mediated allelochemicals derived from soil of a plant species on two co-occurring native plant species

Many studies on allelopathic plants have focused on the negative effects of allelochemicals on the growth of other plants; however, few studies have considered the interactions between soil microbes and soil properties. This study used a controlled field pot experiment in which pots were filled with soil from natural grasslands either lacking Ligularia virgaurea or containing L. virgaurea. Using activated carbon and live/sterilized soil microbial inocula, we tested the effects of allelochemicals, soil microbes, and soil origin on seed germination, plant survival, and biomass accumulation of a native grass (Elymus nutans) and forb (Halenia elliptica) in alpine meadows. The allelochemicals significantly reduced the germination of H. elliptica seeds. Soil microbes from non-L. virgaurea enhanced the negative effects of allelochemicals on E. nutans survival and biomass accumulation of H. elliptica in these soils, but soil microbes from L. virgaurea soil reduced the negative effects of allelochemicals on E. nutans survival in L. virgaurea soil. Furthermore, the positive effects of L. virgaurea soil on the seed germination, survival and biomass of E. nutans were increased by the addition of soil microbes. Our study reveals multiple mechanisms by which allelopathic plants can affect plant populations and dynamics, and provides new insights into native plant responses to the expansion of allelopathic weeds in relation to grassland management.