Soil water content as a critical factor for stable bacterial community structure and degradative activity in maritime An
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Soil water content as a critical factor for stable bacterial community structure and degradative activity in maritime Antarctic soil Dockyu Kim1†*, Namyi Chae2†, Mincheol Kim1, Sungjin Nam1, Eungbin Kim3, and Hyoungseok Lee1 1
Division of Life Sciences, Korea Polar Research Institute, Incheon 21990, Republic of Korea 2 Institutes of Life Sciences and Natural Resources, Korea University, Seoul 02841, Republic of Korea 3 Department of Systems Biology, Yonsei University, Seoul 03722, Republic of Korea (Received Sep 21, 2020 / Revised Oct 26, 2020 / Accepted Oct 29, 2020)
Recent increases in air temperature across the Antarctic Peninsula may prolong the thawing period and directly affect the soil temperature (Ts) and volumetric soil water content (SWC) in maritime tundra. Under an 8°C soil warming scenario, two customized microcosm systems with maritime Antarctic soils were incubated to investigate the differential influence of SWC on the bacterial community and degradation activity of humic substances (HS), the largest constituent of soil organic carbon and a key component of the terrestrial ecosystem. When the microcosm soil (KS1-4Feb) was incubated for 90 days (T = 90) at a constant SWC of ~32%, the initial HS content (167.0 mg/g of dried soil) decreased to 156.0 mg (approximately 6.6% loss, p < 0.05). However, when another microcosm soil (KS1-4Apr) was incubated with SWCs that gradually decreased from 37% to 9% for T = 90, HS degradation was undetected. The low HS degradative activity persisted, even after the SWC was restored to 30% with water supply for an additional T = 30. Overall bacterial community structure remained relatively stable at a constant SWC setting (KS1-4Feb). In contrast, we saw marked shifts in the bacterial community structure with the changing SWC regimen (KS1-4Apr), suggesting that the soil bacterial communities are vulnerable to drying and re-wetting conditions. These microcosm experiments provide new information regarding the effects of constant SWC and higher Ts on bacterial communities for HS degradation in maritime Antarctic tundra soil. Keywords: Antarctic tundra soil, bacterial composition, degradative activity, humic substances, microcosm
† These authors contributed equally to this work. *For correspondence. E-mail: [email protected]; Tel.: +82-32-760-5525; Fax: +82-32-760-5509 Copyright G2020, The Microbiological Society of Korea
Introduction Recent global warming is likely to lead to increased precipitation across maritime Antarctica (Horrocks et al., 2020). Soil water content (SWC) is influenced, not only by precipitation, but also by the local microclimate, topography, and hydrologic reservoirs such as snow patches. Soil temperature (Ts) varies according to air temperature, incoming solar radiation, cloud, and snow cover (Mauro, 2004; Kowalewski et al., 2006). The Ts and SWC are two critical environmental factors that individually or interactively influence microbial community structure and function (Lupatini et al., 2019). SWC may determine m
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