Soil microbial sensitivity to temperature remains unchanged despite community compositional shifts along geothermal gradients

Abstract

Climate warming may be exacerbated if rising temperatures stimulate losses of soil carbon to the atmosphere. The direction and magnitude of this carbon-climate feedback are uncertain, largely due to lack of knowledge of the thermal adaptation of the physiology and composition of soil microbial communities. Here, we applied the macromolecular rate theory (MMRT) to describe the temperature response of the microbial decomposition of soil organic matter (SOM) in a natural long-term warming

Substrate availability and not thermal-acclimation controls microbial temperature sensitivity response to long term warming

“…However, the connection between the temperature sensitivity of respiration and extracellular enzyme activity is not equally linked to all SOM pools equally; soils with a bigger pool of cellulolytic enzymes are more capable of responding to increasing temperatures and consequently respired more in response to changing temperatures, but the same was not true for soils with high NAG activity. Therefore, our results implicate the interaction between the quantity and quality of SOM in driving microbial community activity (Kirschbaum, 2004;Moinet et al, 2021) and functioning (Domeignoz-Horta et al, 2021).…”

“…This seasonal dependence of warming effects on SOM chemistry was further associated with temporally-inconsistent effects of warming on microbial physiology. Limited substrate availability has been cited as necessary condition for microbial community physiological acclimation under warming (Bradford, 2013; Kirschbaum, 2004; Alster et al, 2022; Luo, Wan, Hui, & Wallace, 2001; Fierer, Colman, Schimel, & Jackson, 2006; Moinet et al, 2021). We only observed apparent thermal acclimation of C cycling processes when the input of fresh plant material was limited (i.e.…”

“…Direct responses include changes in protein or membrane stability at the cellular level (Hall, Singer, Kainz, & Lennon, 2010; Bradford, 2013) or a shift in the extracellular enzyme pool towards isoenzymes characterized by distinct activation energies and temperature optima (Davidson & Janssens, 2006; Robinson et al, 2017). Indirect drivers of community thermal acclimation can also include changes in resource composition and supply (Kirschbaum, 2004; Moinet et al, 2021; Pold et al, 2016), whose effects on microbial physiology can act through changes in soil microbial community structure (Rocca et al, 2019) and/or reduction of bacterial cellular ribosome content (Söllinger et al, 2022). By shaping the degree to which microbial processes responsible for soil C cycling vary with temperature, thermal acclimation can determine whether soils serve as a source or sink for carbon (Allison, Wallenstein, & Bradford, 2010).…”

“…Since microbial community members differ in their ability to consume various components of DOM (Zhalnina et al, 2018), substrate-dependent responses of microbial physiology to temporary increases in temperature can emerge (S. D. Frey, Lee, Melillo, & Six, 2013). While numerous studies have linked substrate depletion to changes in the apparent temperature sensitivity of microbial respiration (Alster et al, 2022; Bradford et al, 2008; Hartley, Heinemeyer, & Ineson, 2007; Moinet et al, 2021), there is an acute need to understand how potential changes in substrate chemistry under climate warming can affect soil microbial activity. The recent extension of technologies such as Rock-Eval ® thermal pyrolysis and LC-MS-based metabolomics to soil microbial ecology create opportunities to study how chemistry of soil organic matter and of dissolved organic matter correlate with microbial short-term thermal response, and allow us to begin to disentangle the SOM quality component of apparent thermal acclimation of microbial communities.…”

Cyanobacterial‐ and moss‐forming biocrusts consistently decrease the temperature sensitivity of microbial respiration along a continental precipitation gradient

“…Soil microbial biomass carbon (MBC) and nitrogen (MBN) were estimated using the chloroform fumigation extraction method (Brookes et al, 1985). Microbial community composition was evaluated using the phospholipid fatty acid (PLFA) analysis (Bossio & Scow, 1998), and the ratio of fungal to bacterial PLFAs (F:B) was used to indicate microbial community composition (Moinet et al, 2021; Strickland & Rousk, 2010). The soil used for the determination of microbial properties was sub‐samples from pre‐incubation.…”