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Laboratory examination of greenhouse gaseous and microbial dynamics during thawing of frozen soil core collected from a black spruce forest in Interior Alaska

内陸アラスカのクロトウヒ林で採取した凍結土壌コアを融解させながら培養した時の温室効果ガス動態および微生物群集構造の変化

永野 博彦   ; Kim, Y.*; Lee, B.-Y.*; 重田 遥*; 犬伏 和之*

Nagano, Hirohiko; Kim, Y.*; Lee, B.-Y.*; Shigeta, Haruka*; Inubushi, Kazuyuki*

北半球の高緯度生態系における年間温室効果ガス(GHG)収支を決定する重要なプロセスである凍結土壌の融解中に起きる炭素動態の変化を調べるために、本研究では、内陸アラスカのクロトウヒ林から採取した凍結土壌コアの培養実験を行った。地表面から永久凍土がある深さ90cmまでのコアを、3層(表層,中間層,下層)に分けた。次いで、各層から分取した12土壌(1層につき4土壌)を3週間培養し、二酸化炭素(CO$$_{2}$$)およびメタン(CH$$_{4}$$)フラックスを測定した。培養中、温度を0から10$$^{circ}$$Cまで1週間ずつ変化させた。表層および中間層の8土壌のうち6土壌では、CO$$_{2}$$放出量が0$$^{circ}$$Cよりも5$$^{circ}$$Cで1.5-19.2倍大きかったが、これら6土壌のうち3土壌のCO$$_{2}$$放出は、10$$^{circ}$$Cでの培養で減少した。CH$$_{4}$$放出は、0$$^{circ}$$Cで培養した下層土壌で最大であった。0$$^{circ}$$Cで培養した表層および中間層の土壌でも、CH$$_{4}$$放出が観察された。5および10$$^{circ}$$Cでは、下層土壌のCH$$_{4}$$放出が減少し、表層および中間層の土壌はCH$$_{4}$$吸収を示した。嫌気的CH$$_{4}$$酸化および生成の阻害物質(2-bromoethane sulfonate)を添加すると、CH$$_{4}$$吸収と放出の両方が減少した。細菌および古細菌群集のゲノム情報は土壌の深さとともに変化したが、融解に対しては安定であった。以上より、北方のクロトウヒ林における土壌のGHGフラックスは土壌融解に敏感かつ多様に反応する一方、細菌および古細菌の全体的な群集構造は融解に対して安定的であることが判明した。

In this study, we conducted an incubation experiment on a frozen soil core collected from a black spruce forest in Interior Alaska, in order to investigate potential changes in greenhouse gaseous (GHG) and microbial dynamics during thawing of frozen soil. The soil thawing is an important environmental process determining the annual GHG balance in the northern high-latitude ecosystem. A core spanning the ground surface to upper permafrost with a depth of 90 cm was vertically grouped into three layers (top, middle, and bottom layers). Then, 12 soil samples from 3 layers (i.e., 4 soil samples per layer) were incubated for 3 weeks, and net carbon dioxide (Co$$_{2}$$) and methane (CH$$_{4}$$) release/uptake rates were estimated. During the incubation, temperature was changed weekly from 0 to 5, then 10$$^{circ}$$C. The net amounts of CO$$_{2}$$ released by six of the eight soil samples from the top and middle layers were 1.5 to 19.2-fold greater at 5$$^{circ}$$C than at 0$$^{circ}$$C, while the release at 10$$^{circ}$$C was reduced in the cases of three of these six soil samples. Net CH$$_{4}$$ release was the greatest in bottom-layer soil samples incubated at 0$$^{circ}$$C. Then, low but apparent CH$$_{4}$$ release was observed in top and middle-layer soil samples incubated at 0$$^{circ}$$C. At 5 and 10$$^{circ}$$C, net CH$$_{4}$$ release from bottom-layer soil samples was decreased. Then, net CH$$_{4}$$ uptake was observed in the top and the middle-layer soil samples. Both net uptake and release of CH$$_{4}$$ were reduced upon the addition of a chemical inhibitor (i.e., 2-bromoethane sulfonate) of anaerobic methanotrophic and methanogenic activity. The bacterial and archaeal community structures based on 16S rRNA amplicon analysis were changed along the depth, while they were less changed during thawing. Thus, it was found that soil GHG dynamics responded sensitively and variously to thawing, while there was less change in 16S rRNA-based microbial community structures during the thawing prog

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パーセンタイル:27.33

分野:Plant Sciences

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