Permafrost thaw with warming reduces microbial metabolic capacities in subsurface soils

Abstract

Microorganisms are major constituents of the total biomass in permafrost regions, whose underlain soils are frozen for at least two consecutive years. To understand potential microbial responses to climate change, here we examined microbial community compositions and functional capacities across four soil depths in an Alaska tundra site. We showed that a 5-year warming treatment increased soil thaw depth by 25.7% (p = .011) within the deep organic layer (15-25 cm). Concurrently, warming reduced 37% of bacterial abundance and 64% of fungal abundances in the deep organic layer, while it did not affect microbial abundance in other soil layers (i.e., 0-5, 5-15, and 45-55 cm). Warming treatment altered fungal community composition and microbial functional structure (p < .050), but not bacterial community composition. Using a functional gene array, we found that the relative abundances of a variety of carbon (C)-decomposing, iron-reducing, and sulphate-reducing genes in the deep organic layer were decreased, which was not observed by the shotgun sequencing-based metagenomics analysis of those samples. To explain the reduced metabolic capacities, we found that warming treatment elicited higher deterministic environmental filtering, which could be linked to water-saturated time, soil moisture, and soil thaw duration. In contrast, plant factors showed little influence on microbial communities in subsurface soils below 15 cm, despite a 25.2% higher (p < .05) aboveground plant biomass by warming treatment. Collectively, we demonstrate that microbial metabolic capacities in subsurface soils are reduced, probably arising from enhanced thaw by warming.

Distinct patterns of soil bacterial and fungal community assemblages in subtropical forest ecosystems under warming

“…Our NCM and NST analyses indicated that passive dispersal and ecological drift may contribute more to community assembly of bacteria than fungi, possibly due to their contrasting body sizes (Luan et al, 2020). The trend for bacterial community assembly under warming was progressively dominated by deterministic factors in the dry season, similar to previous studies in high‐latitude tundra and grassland (Feng et al, 2020; Guo et al, 2018; Wu et al, 2022), suggests that temperature may be a major driver in ecosystem (Zhou et al, 2016).…”

Tundra Soil Viruses Mediate Responses of Microbial Communities to Climate Warming

“…2B ), filling major knowledge gaps in the understanding of the linkage between viruses and edaphic conditions ( 44 ). Markedly, soil depth, rather than warming treatment, was a strong factor in determining viral community and functional gene structures, which was consistent with previous study of bacterial communities in this region ( 23 ). The beta diversity, the abundance patterns of vOTUs, and the similarity clustering network based on viral shared protein clusters revealed that viral community composition was highly endemic by soil depth.…”

“…Interestingly, warming significantly decreased (Student t test, P < 0.05) the stochastic ratio of viral communities at 45 to 55 cm ( Fig. 2C ), suggesting that warming could impose deterministic effects on viruses ( 23 ). For viral function, stochastic ratios were consistently <50%, indicating that viral functional traits were highly deterministic ( Fig.…”

“…Linear mixed-effects models were analyzed using the lme4 package in R v4.0.2 ( 97 ). In linear mixed-effects models, warming and soil depths were used as fixed effects, and the block was used as random intercept effect ( 23 ). ANOVA was used to calculated the P values, and the partR2 package was used to obtain the marginal R 2 (the variance of each fixed effect) from the linear mixed-effects models ( 98 ).…”

Soil CO2 and N2O emissions and microbial abundances altered by temperature rise and nitrogen addition in active-layer soils of permafrost peatland

“…This result indicated that bacteria in permafrost peatlands were adapted to a low temperature and N-limited environment. In line with our results, warming reduced 37% of bacterial abundance and microbial metabolic capacity in the deep organic layer of an Alaska tundra ( Wu et al, 2022 ). Our results showed that the combined effects of temperature rising and N addition significantly increased fungal abundances and there were significantly positively correlations between fungal abundances and the emissions of CO 2 and N 2 O, suggesting that there were differences in sensitivity of different microbial communities to environmental changes and fungi communities played a vital part in the variations of CO 2 and N 2 O emissions at higher temperature and under the addition of N. Consistent with the outcomes of the current study, Xu et al (2017) determined that fungal tolerance to high temperatures played a significant part in N 2 O emissions.…”