Potential methane production rates and its carbon isotopic composition from ornithogenic tundra soils in coastal Antarctic

• Main Authors: Tao, Bao, Renbin, Zhu, Bo, Bai, Hua, Xu
• Format: Article in Journal/Newspaper
• Language: English
• Published: Polar Research Institute of China - PRIC 2016
• Subjects: Cryosphere; Fauna; Terrestrial; Advances in Polar Science; Antarc*; Antarctic; Antarctica; Polar Science; Tundra
• Online Access: http://library.arcticportal.org/2591/; http://library.arcticportal.org/2591/1/A020160104.pdf

Methane (CH4) is one of important greenhouse gases with chemical activity. The determination of isotopic compositions for CH4 emitted from the soils helps us to understand its production mechanisms. CH4 isotope measurements have been conducted for different types of global terrestrial ecosystems. However, no isotopic data of CH4 have been reported from Antarctic tundra soils. In this paper, ornithogenic soil profiles were collected from four penguin colonies, and potential CH4 production rates and its 13C ratio (δ13C) were investigated based upon laboratory incubation experiments. The mean CH4 production rates are highly variable in these soil profiles, ranging from 0.7 to 20.3 μg CH4−C kg−1∙h−1. These ornithogenic soils had high potential production rates of CH4 under ambient air incubation or under N2 incubation, indicating the importance of potential CH4 emissions from penguin colonies. Most of the soil samples had higher δ13C-CH4 under N2 incubation (−39.28%~−43.53%) than under the ambient air incubation (−42.81%~−57.19%). Highly anaerobic conditions were conducive to the production of CH4 enriched in 13C, and acetic acid reduction under N2 incubation might be a predominant source for soil CH4 production. Overall the δ13C-CH4 showed a significant negative correlation with CH4 production rates in ornithogenic tundra soils under N2 incubation (R2=0.41, p<0.01) or under the ambient air incubation (R2=0.50, p<0.01). Potential CH4 production from ornithogenic soils showed a significant positive correlation with total phosphorus (TP) and NH4+−N contents, pH and soil moisture (Mc), but the δ13C-CH4 showed a significant negative correlation with TP and NH4+−N contents, pH and Mc, indicating that the deposition amount of penguin guano increased potential CH4 production rates from tundra soils, but decreased the δ13C-CH4. The CH4 emissions from the ornithogenic soils affect carbon isotopic compositions of atmospheric CH4 in coastal Antarctica.