Optimal growth temperature of Arctic soil bacterial communities increases under experimental warming

Abstract

Future climate warming in the Arctic will likely increase the vulnerability of soil carbon stocks to microbial decomposition. However, it remains uncertain to what extent decomposition rates will change in a warmer Arctic, because extended soil warming could induce temperature adaptation of bacterial communities. Here we show that experimental warming induces shifts in the temperature–growth relationships of bacterial communities, which is driven by community turnover and is common across a diverse set of 8 (sub) Arctic soils. The optimal growth temperature (Topt) of the soil bacterial communities increased 0.27 ± 0.039 (SE) and 0.07 ± 0.028°C per °C of warming over a 0–30°C gradient, depending on the sampling moment. We identify a potential role for substrate depletion and time‐lag effects as drivers of temperature adaption in soil bacterial communities, which possibly explain discrepancies between earlier incubation and field studies. The changes in Topt were accompanied by species‐level shifts in bacterial community composition, which were mostly soil specific. Despite the clear physiological responses to warming, there was no evidence for a common set of temperature‐responsive bacterial amplicon sequence variants. This implies that community composition data without accompanying physiological measurements may have limited utility for the identification of (potential) temperature adaption of soil bacterial communities in the Arctic. Since bacterial communities in Arctic soils are likely to adapt to increasing soil temperature under future climate change, this adaptation to higher temperature should be implemented in soil organic carbon modeling for accurate predictions of the dynamics of Arctic soil carbon stocks.

Maximum summer temperatures predict the temperature adaptation of Arctic soil bacterial communities

“…In the summers of 2018 and 2020, soil samples were collected from 12 soil types at 9 sites ranging from sub-to High Arctic (Figure 1). The 2018 sampling at Toolik Lake Field station, Svalbard, Abisko and Iceland has been previously described in (Rijkers et al, 2022). In brief, soil cores of 10 cm depth were collected from Toolik Field Station, USA (68°38' N, 149°36' W) at the LTER Heath site, LTER Moist Acidic Tussock and LTER Non-Acidic Tussock; on Svalbard, from the Bjorndalen site (78°13'N, 15°19'E), dominated by Carex sp.…”

“…Bacterial soil communities in the Arctic terrestrial region are adapted to perform well at https://doi.org/10.5194/bg-2022-184 low temperatures (Bååth, 2018). However, these bacterial communities are likely to be exposed to increasing soil temperatures in this century (Post et al 2018) and it remains uncertain whether these soil bacterial communities will adapt their response to temperature when exposed to warmed conditions (Rinnan et al, 2011;Weedon et al, 2022;Rousk et al, 2012). Knowledge of the climate conditions under which such an adaption takes place will help in estimations of the potential vulnerability of arctic soil carbon stocks to warmer climate conditions (Bååth, 2018;Bradford et al, 2019;Palacios et al, 2021).…”

“…Despite strong correlations over large spatial scales, an increase in the mean annual soil temperature does not necessarily lead to a shift in temperature-growth relationships of bacterial communities when soils are experimentally warmed in lab incubation and field studies (Pietikäinen et al, 2005;Birgander et al, 2013Birgander et al, , 2018Rinnan et al, 2011;Weedon et al, 2022). Instead, a common observation is a rapid change in the temperature-growth relationships driven by a community turnover when soils are incubated above the optimal growth temperature of the in situ soil bacterial community, (Birgander et al, 2013;Donhauser et al, 2020).…”

“…For example, sub-Arctic bacterial communities exhibit lower cardinal points of their temperature-growth relationships compared to bacterial communities of temperate ecosystems, with a Tmin of -9.6 to -7.0 °C and Topt 25 to 30 °C (Cruz- Rinnan et al, 2011). It is likely that soil warming will shift the temperature-growth relationships of sub-Arctic soil bacterial communities (Weedon et al, 2022;Rijkers et al, 2022). However, the in situ temperature-growth relationships of soil bacterial communities in the mid-to High Arctic are so far unknown and will need to be evaluated to understand the current temperature adaptation of soil bacterial communities and drivers of temperature adaptation under future climate conditions.…”

“…However, soil temperature logger data are particularly scarce in the Arctic region (Lembrechts et al, 2021), leading to a need for potential alternative predictors of soil microbial temperature adaptation. DNA-based bacterial community composition measures have recently been shown to correlate with shifts in the temperature growth relationships of a soil bacterial communities (Donhauser et al, 2020;Rijkers et al, 2022;Weedon et al, 2022). More generally, temperature traits differ between members of bacterial communities from arctic soils (Wang et al, 2021), and specific bacterial OTUs have been associated with warming in forest soils across North America (Oliverio et al, 2017).…”