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.
Bibliographical noteFunding Information:
This work was supported by a grant (PE20170) funded by the Korea Polar Research Institute and a National Research Foundation of Korea grant funded by the Korean government (MSIP) (NRF-2018R1D1A1B07047778 and NRF-2016-M1A5A1901790). We thank Mr. Minsuk Park, Dr. Young Jun Yoon, and Ms. Sujeong Jeong for designing the microcosm system, for collecting the soil samples at the King Sejong Station in 2016, and for characterizing the physical and chemical properties of the soil samples, respectively.
© 2020, The Microbiological Society of Korea.
All Science Journal Classification (ASJC) codes
- Applied Microbiology and Biotechnology