Microbial response to warming and cellulose addition in a maritime Antarctic soil

• Published in: Permafrost and Periglacial Processes
• Main Authors: Pradel, Paulina, Bravo, León A., Merino, Carolina, Trefault, Nicole, Rodríguez, Rodrigo, Knicker, Heike, Jara, Claudia, Larama, G., Matus, Francisco
• Other Authors: Comisión Nacional de Investigación Científica y Tecnológica (Chile)
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2023
• Subjects: 13C-NMR; Carbon mineralization; Carbon sequestration; Global warming; King George Island; Microbial respiration; Open top chamber; Q10; Soil organic matter; Take urgent action to combat climate change and its impacts; Antarctic; South Shetland Islands; Antarc*; Antarctica; Permafrost and Periglacial Processes
• Online Access: http://hdl.handle.net/10261/306357; https://doi.org/10.1002/ppp.2182

14 páginas.- 7 figuras.- 2 tablas.-71 referencias.- Additional supporting information can be found online in the Supporting Information section at the end of this article. Maritime Antarctic King George Island (South Shetland Islands) has experienced rapid warming in recent decades, but the impacts on soil organic matter (SOM) decomposition remain ambiguous. Most vegetation cover is dominated by bryophytes (mosses), whereas a few vascular plants, such as Deschampsia antarctica and Colobanthus quitensis grow interspersed. Therefore, SOM is mainly enriched with carbohydrates and C-alkyl, provided by mosses, which lack lignin as a precursor for aromatic compounds and humus formation. However, there is no clear answer to how substrate and temperature increase changes in Antarctic microbial respiration. We determined in what way SOM mineralization changes with temperature and substrate addition by characterizing the temperature sensitivity (Q10) of soil respiration in an open-top chamber warming experiment. We hypothesized that: (a) cold-tolerant microorganisms are well adapted to growing in maritime Antarctic soils (~ 0°C), so would not respond to low and moderate temperature increases because they undergo various metabolic mechanism adjustments until they experience increasing temperatures toward optimum growth (e.g., by enzyme production); and (b) cellulose, as a complex carbonaceous substrate of vegetated areas in Maritime Antarctic soils, activates microorganisms, increasing the Q10 of soil organic carbon (SOC) mineralization. Soils (5–10 cm) were sampled after four consecutive years of experimental warming for SOC composition, microbial community structure, and C mineralization at 4, 12, and 20°C with and without cellulose addition. Functional group chemoheterotrophs, represented mainly by Proteobacteria, decomposed more refractory SOC (aromatic compounds), as indicated by nuclear magnetic resonance (NMR) spectroscopy, in ambient plots than in warming plots where plants were growing. The C-CO2 efflux from the ...