Exploring the interplay between roots and soil microbes in high latitude regions under warming

Abstract:Climate change is a major threat to all ecosystems, but its consequences are particularly severe in high latitude regions, where warming intensity is the highest. Because soil microbes have a central role in terrestrial ecosystem functioning, understanding their response to warmer conditions is essential. This thesis aims to explore the response of soil microbial communities to warming, with a particular focus on plant-microbe interactions. We first carried out field experiments in two sites with warming treatments. The first one is a Finnish tundra grassland, where air warming induced by Open-top chambers (ca +1.9), in combination with other environmental changes, has been applied for 10 years. There, warming alone did not affect the general community composition of root-associated fungi, although it clearly affected the relative abundance of mycorrhizal fungi. The other is an Icelandic subarctic grassland, where soils were warmed through geothermal activity for 12 (MTW), and over 55 years (LTW), at an intensity ranging from ca +0.5 to +6C. There, the community composition of both prokaryotes and eukaryotes shifted along the gradient. Besides, in both setups, plant communities have been manipulated by either adding new species (tundra), or excluding plant roots (subArctic grassland). The outputs were similar to untreated conditions in both studies, suggesting a high resistance of soil microbes to plant changes under field conditions. Furthermore, we investigated the effects of warming on soil health and found that, while the microbial diversity remained stable, the microbial connectivity increased along the thermal gradient. The bacterial predicted functional profiles shifted with increasing temperatures, for which genes involved in carbon degradation specifically decreased under LTW. Last, we carried out a greenhouse experiment, where we grew grasses in soils inoculated with soil microbiomes conditioned by different warming intensities and found that plants grown in soils with microbiomes conditioned by LTW displayed lower belowground biomass. We identified some microbial taxa known to associate with plants that suggested that our observations could be due to changed relative abundance of e.g. putative plant pathogens or arbuscular mycorrhiza. Overall, our work shows that soil microbial communities are sensitive to soil warming, but not directly by air temperature. However, we found a modest effect of plant communities on the microbial community assembly, while warming-conditioned microbiomes negatively altered plant performance, reminding the high potential of soil microbes on plants, but also that within plant-microbe interactions, one may mediate the response of the other.

Publication year:2024

Keywords:Biology

Accessibility:Open