High temperatures enhance the microbial genetic potential to recycle C and N from necromass in high‐mountain soils

Abstract

Climate change is strongly affecting high‐mountain soils and warming in particular is associated with pronounced changes in microbe‐mediated C and N cycling, affecting plant‐soil interactions and greenhouse gas balances and therefore feedbacks to global warming. We used shotgun metagenomics to assess changes in microbial community structures, as well as changes in microbial C‐ and N‐cycling potential and stress response genes and we linked these data with changes in soil C and N pools and temperature‐dependent measurements of bacterial growth rates. We did so by incubating high‐elevation soil from the Swiss Alps at 4°C, 15°C, 25°C, or 35°C for 1 month. We found no shift with increasing temperature in the C‐substrate‐degrader community towards taxa more capable of degrading recalcitrant organic matter. Conversely, at 35°C, we found an increase in genes associated with the degradation and modification of microbial cell walls, together with high bacterial growth rates. Together, these findings suggest that the rapidly growing high‐temperature community is fueled by necromass from heat‐sensitive taxa. This interpretation was further supported by a shift in the microbial N‐cycling potential towards N mineralization and assimilation under higher temperatures, along with reduced potential for conversions among inorganic N forms. Microbial stress‐response genes reacted inconsistently to increasing temperature, suggesting that the high‐temperature community was not severely stressed by these conditions. Rather, soil microbes were able to acclimate by changing the thermal properties of membranes and cell walls as indicated by an increase in genes involved in membrane and cell wall modifications as well as a shift in the optimum temperature for bacterial growth towards the treatment temperature. Overall, our results suggest that high temperatures, as they may occur with heat waves under global warming, promote a highly active microbial community capable of rapid mineralization of microbial necromass, which may transiently amplify warming effects.

Root exudates increase soil respiration and alter microbial community structure in alpine permafrost and active layer soils

“…We thus suggest that PF soils contained a highly metabolic versatile microbial community which is becoming active at elevated temperature which is in line with previous findings of permafrost soils (Ernakovich and Wallenstein, 2015;Lulakova et al, 2019). These taxonomic changes could be coupled to the increase in microbial C decomposition, as suggested in genomic surveys of Arctic and alpine soils undergoing warming (Coolen and Orsi, 2015;Feng et al, 2020;Donhauser et al, 2021).…”

“…The phylum Mortierellomycota declined in SE and particularly strong in NW soils. Members within this phylum are commonly found in alpine and Arctic habitats and contain psychrophilic or psychrotolerant species (Frisvad, 2008;Brunner et al, 2011;Dresch et al, 2019). The genus Mortierella also responded negatively to AREs in NW soils.…”

Interference of Climate Change on Plant-Microbe Interaction: Present and Future Prospects

“…Studies conducted reveals that elevated temperature has considerable effects on cyanobacterial growth and development (Deng et al, 2021). Increased temperature coupled with heat waves as consequences of global warming enhances the activity of microbial community able to mineralize microbial necromass, recycling C and N and thus, amplify warming effects in mountainous soil (Donhauser et al, 2020). Similarly, Wang et al (2020) also reported the increased microbial necromass nitrogen and microbial turnover in the soil with temperature.…”

Playing with FiRE: A genome resolved view of the soil microbiome responses to high severity forest wildfire

“…The heating of organic soil horizons during wildfire lyses heat-sensitive microorganisms, resulting in an influx of labile organic C and N associated with necromass 76 . This likely opens up niche space to fireresistant heterotrophic taxa and stimulates growth rates of these taxa 77 . Each of the abundant featured Actinobacteria MAGs expressed peptidase genes (88 total genes) in High O samples, of which approximately twenty were differentially expressed (p<0.05) between High O and Low O conditions.…”