Soil microbiomes conditioned by long-term warming affect plant belowground performance

Area of Science:

• Ecology
• Plant Science
• Microbiology

Background:

• Global change, including warming, affects plant performance directly and indirectly through environmental modifications.
• Soil microbes play a crucial role in plant health but are sensitive to warming, complicating the assessment of warming's direct vs. indirect effects on plants.
• Distinguishing between direct warming effects on plants and indirect effects mediated by soil microbial community shifts is challenging in field studies.

Purpose of the Study:

• To investigate how soil microbiomes conditioned by different durations of geothermal warming influence the performance of two grass species (Agrostis capillaris and Anthoxanthum odoratum).
• To differentiate the direct effects of warming on plants from indirect effects mediated by soil microbial communities.
• To assess the impact of warming-conditioned soil microbiomes on plant stress resistance under drought conditions and analyze associated root-associated fungal communities.

Main Methods:

• Controlled glasshouse experiments using soils conditioned by ambient, medium-term (14 years), and long-term (>55 years) geothermal warming.
• Monitoring plant performance (aboveground and belowground biomass) of Agrostis capillaris and Anthoxanthum odoratum under normal watering and drought stress.
• Metabarcoding analysis of soil inocula to identify and quantify root-associated fungi and their relative abundance under different warming regimes.

Main Results:

• Plants grown in soils conditioned by long-term warming (LTW) exhibited decreased belowground biomass for both species.
• The negative effect on belowground biomass was exacerbated under drought conditions for Agrostis capillaris.
• An increased aboveground to belowground biomass ratio was observed, coinciding with a higher relative abundance of putative plant pathogens and arbuscular mycorrhizal fungi.

Conclusions:

• Soil microbes significantly mediate the effects of global warming on plant performance, primarily through the reduction of belowground biomass.
• Long-term warming exposure alters soil microbiomes in ways that can negatively impact plant growth, particularly under stressful conditions like drought.
• Changes in soil microbial communities, including shifts in pathogen and arbuscular mycorrhizal fungi abundance, are key mechanisms through which warming influences plant belowground development.