Effects of Elevated Atmospheric CO_2 Concentrations on Soil Microorganisms

Chris Freeman,김선영,Seung-Hoon Lee,강호정 한국미생물학회 2004 The journal of microbiology Vol.42 No.4

Effects of elevated CO2 on soil microorganisms are known to be mediated by various interactions with plants, for which such effects are relatively poorly documented. In this review, we summarize and synthesize results from studies assessing impacts of elevated CO2 on soil ecosystems, focusing primarily on plants and a variety the of microbial processes. The processes considered include changes in microbial biomass of C and N, microbial number, respiration rates, organic matter decomposition, soil enzyme activities, microbial community composition, and functional groups of bacteria mediating trace gas emission such as methane and nitrous oxide. Elevated CO2 in atmosphere may enhance certain microbial processes such as CH4 emission from wetlands due to enhanced carbon supply from plants. However, responses of extracellular enzyme activities and microbial community structure are still controversy, because interferences with other factors such as the types of plants, nutrient availabilitial in soil, soil types, analysis methods, and types of CO2 fumigation systems are not fully understood. Effects of elevated CO2 on soil microorganisms are known to be mediated by various interactions with plants, for which such effects are relatively poorly documented. In this review, we summarize and synthesize results from studies assessing impacts of elevated CO2 on soil ecosystems, focusing primarily on plants and a variety the of microbial processes. The processes considered include changes in microbial biomass of C and N, microbial number, respiration rates, organic matter decomposition, soil enzyme activities, microbial community composition, and functional groups of bacteria mediating trace gas emission such as methane and nitrous oxide. Elevated CO2 in atmosphere may enhance certain microbial processes such as CH4 emission from wetlands due to enhanced carbon supply from plants. However, responses of extracellular enzyme activities and microbial community structure are still controversy, because interferences with other factors such as the types of plants, nutrient availabilitial in soil, soil types, analysis methods, and types of CO2 fumigation systems are not fully understood.

Effects of Elevated Atmospheric $CO_2$ Concentrations on Soil Microorganisms

Freeman Chris,Kim Seon-Young,Lee Seung-Hoon,Kang Hojeong The Microbiological Society of Korea 2004 The journal of microbiology Vol.42 No.4

Effects of elevated $CO_2$ on soil microorganisms are known to be mediated by various interactions with plants, for which such effects are relatively poorly documented. In this review, we summarize and syn­thesize results from studies assessing impacts of elevated $CO_2$ on soil ecosystems, focusing primarily on plants and a variety the of microbial processes. The processes considered include changes in microbial biomass of C and N, microbial number, respiration rates, organic matter decomposition, soil enzyme activities, microbial community composition, and functional groups of bacteria mediating trace gas emission such as methane and nitrous oxide. Elevated $CO_2$ in atmosphere may enhance certain micro­bial processes such as $CH_4$ emission from wetlands due to enhanced carbon supply from plants. How­ever, responses of extracellular enzyme activities and microbial community structure are still controversy, because interferences with other factors such as the types of plants, nutrient availabilitial in soil, soil types, analysis methods, and types of $CO_2$ fumigation systems are not fully understood.

Impacts of Elevated CO^2 on Algal Growth, CH^4 Oxidation and N^2O Production in Northern Peatland

Kang, Ho Jeong,Chris Freeman 한국육수학회 2001 생태와 환경 Vol.34 No.4

이산화탄소 농도가 증가할 때에 북구 이탄 습지에서 나타나는 생지화학적 변화과정을 살펴보았다. 표면 식생을 포함한 온전한 코어를 북웨일스의 이탄습지로부터 채취하여, 높은 이산화탄소농도(700ppm)와 자연상태(350ppm) 환경에서 4개월간 배양하였다. 배양 후, 화학적인 저해제를 이용하여 습지 토양에서 미량기체의 생성과 소비를 측정하였다. 메탄의 경우, 불화메탄(CH_3F)를 이용하여 메탄 산화율을 결정하였고, 질산화와 탈질작용을 측정하기위해 아세틸렌(C_2H_2) 저해 방법을 적용하였다. 이를 위해, 먼저 각 측정 방법을 습지 시료에 적합하도록 최적화 시켰고, 둘째로 두 수준의 이상화탄소에서 배양한 시료에 이 방법들을 적용하였다. 높은 이산화탄소 농도는 메탄의 생성량을 증가 시켰으나(210 대 100 ng CH_4 g^-1 hr^-1), 메탄 산화의 양도 증가시켜서(128 대 15 ng CH_4 g^-1 hr^-1) 결국에는 순메탄 방출량에는 변화가 없었다. 아산화질소의 경우에는 증가된 발생량이 탈질 보다는 질산화 과정에서 생성된 것으로 사료된다. 이러한 변화들은 높은 이산화탄소 하에서 조류의 성장이 증가되어 야기된 것으로 추측된다. Effects of elevated carbon dioxide (CO_2) on soil microbial processes were studied in a northern peatland. Intact peat cores with surface vegetation were collected from a northern Welsh fen, and incubated either under elevated carbon dioxide(700 ppm) or ambient carbon dioxide (350 ppm) conditions for 4 months. Higher algal biomass was found under the elevated CO_2 condition, suggesting CO_2 fertilization effect on primary production. At the end of the incubation, trace gas production and consumption were analyzed using chemical inhibitors. For methane (CH_4), methyl fluoride (CH_3F) was applied to determine methane oxidation rates, while acetylene(C_2H_2) blocking method were applied to determine nitrification and denitrification rates. First, we have adopted those methods to optimize the reaction conditions for the wetland samples. Secondly, the methods were applied to the samples incubated under two levels of CO_2. The results exhibited that elevated carbon dioxide increased both methane production(210 vs. 100 ng CH_4 g^-1 hr^-1) and oxidation(128 vs. 15 ng CH_4 g^-1 hr^-1), resulting in no net increase in methane flux. For nitrous oxide(N_2O), elevated carbon dioxide enhanced nitrous oxide emission probably from activation of nitrification process rather than denitrification rates. All of these changes seemed to be substantially influenced by higher oxygen diffusion from enhanced algal productivity under elevated CO-2.

Importance of Extracellular Enzyme Activities inNorthern Peatland Biogeochemistry-Possible Couplingwith Trace Gas Emission and DOC Dynamics

Kang, Hojeong,Chris Freeman,Seok-Soon Park 한국하천호수학회 2006 생태와 환경 Vol.39 No.4

A suite of extracellular enzyme activities involved in organic carbon decomposition were determined in three northern peatlands (a bog, a fen, and a swamp) over a 12 month period along with trace gas (CO2 and N2O) flux and DOC dynamics in the wetlands. The activities varied 0.008-0.066 μmole g-1 min-1, 0.003-0.021 μmole g-1 min-1, 0.003-0.016 μmole g-1 min-1, 0.004-0.047 μmole g-1 min-1, for β-glucosidase, cellobiohydrolase, β-xylosidase, and N-acetylglucosaminidase, respectively. In general, the activities were highest in the forested swamp followed by the fen and the bog. When the data from three wetlands are combined, the enzyme activities exhibited significant positive correlations with trace gas emission and available carbon.Further, the average activity of 4 enzymes explained about 20-40% of the variations of trace gas emssion and available carbon. The results indicate that enzymes related to the mineralization of organic carbon may play an important role in trace gas flux and DOC dynamics in northern peatlands. A suite of extracellular enzyme activities involved in organic carbon decomposition were determined in three northern peatlands (a bog, a fen, and a swamp) over a 12 month period along with trace gas (CO2 and N2O) flux and DOC dynamics in the wetlands. The activities varied 0.008-0.066 μmole g-1 min-1, 0.003-0.021 μmole g-1 min-1, 0.003-0.016 μmole g-1 min-1, 0.004-0.047 μmole g-1 min-1, for β-glucosidase, cellobiohydrolase, β-xylosidase, and N-acetylglucosaminidase, respectively. In general, the activities were highest in the forested swamp followed by the fen and the bog. When the data from three wetlands are combined, the enzyme activities exhibited significant positive correlations with trace gas emission and available carbon. Further, the average activity of 4 enzymes explained about 20-40% of the variations of trace gas emssion and available carbon. The results indicate that enzymes related to the mineralization of organic carbon may play an important role in trace gas flux and DOC dynamics in northern peatlands.

The Regulation by Phenolic Compounds of Soil Organic Matter Dynamics under a Changing Environment

Min, Kyungjin,Freeman, Chris,Kang, Hojeong,Choi, Sung-Uk Hindawi Publishing Corporation 2015 BioMed research international Vol.2015 No.-

<P>Phenolics are the most abundant plant metabolites and are believed to decompose slowly in soils compared to other soil organic matter (SOM). Thus, they have often been considered as a slow carbon (C) pool in soil dynamics models. Here, however, we review changes in our concept about the turnover rate of phenolics and quantification of different types of phenolics in soils. Also, we synthesize current research on the degradation of phenolics and their regulatory effects on decomposition. Environmental changes, such as elevated CO<SUB>2</SUB>, warming, nitrogen (N) deposition, and drought, could influence the production and form of phenolics, leading to a change in SOM dynamics, and thus we also review the fate of phenolics under environmental disturbances. Finally, we propose the use of phenolics as a tool to control rates of SOM decomposition to stabilize organic carbon in ecosystems. Further studies to clarify the role of phenolics in SOM dynamics should include improving quantification methods, elucidating the relationship between phenolics and soil microorganisms, and determining the interactive effects of combinations of environmental changes on the phenolics production and degradation and subsequent impact on SOM processing.</P>

Variations of DOC and Phenolics in Pore-water of Peatlands

( Ho Jeong Kang ),( Chris Freeman ),( Seon Young Kim ) 한국하천호수학회 2002 생태와 환경 Vol.35 No.4

습지내의 용존유기탄소의 함량과 구성은 이차생산, 다양한 생지화학적 반응, 그리고 수생태계의 기능에 중요한 영향을 미친다. 본 연구에서는 북구이탄습지(bog, fen, swamp)의 공극수내의 용존유기탄소와 페놀계열 물질의 농도를 1997년도에 1년에 걸쳐 조사하였다. 일반적인 미생물의 활성(토양 호흡도)와 페놀산화효소의 활성도 측정하여, 용존유기탄소와 페놀계열 물질의 변화에 대한 기작을 밝히고자 했다. 용존유기탄소 농도는 25.5-45.4(bog), 29.2-71.4(fen), and 13.5-87.6(swamp) ㎎/ℓ를 보였고, 페놀계열 물질의 경우에는 13.3-48.1(bog), 7.6-29.5(fen), and 4.9-30.8(swamp) ㎎/ℓ의 변화정도를 보였다. Swamp에서의 계절적인 변화양상을 살펴보면, 낙엽생산이 용존유기탄소의 변화에 많은 영향을 미침을 알 수 있었다. Bog에서의 미생물활성도와 페놀산화효소의 활성이 가장 낮게 나타났는데 이것이 bog 내의 높은 페놀계열물질의 농도를 야기시킨 것으로 사료된다. 본 연구의 결과는 습지내 용존유기탄소의 양 뿐만 아니라 그 화학적인 구성이 습지 생지화학에서 중요함을 보여주었다. The amount and composition of dissolved organic carbon in wetlands are of great importance for their influence in secondary productivity, various biogeochemical processes, and aquatic ecosystem functions. In the present study, we measured variations of DOC and phenolics concentrations in pore-water of three northern peatlands(bog, fen, and swamp) over a 1-year period. General microbial activity(soil respirometry) and phenol oxidase enzyme activity were determined in the same peatlands to elucidate mechanisms underlying the differences in DOC and phenolics contents. The concentrations of DOC varied 25.5-45.4(bog), 29.2-71.4(fen), and 13.5-87.6(swamp) ㎎/ℓ, while phenolic concentrations ranged 13.3-48.1(bog), 7.6-29.5(fen), and 4.9-30.8(swamp) ㎎/ℓ. The seasonal variations of DOC and phenolics in the swamp suggest that litterfall may be one of the most important actors for the DOC dynamics in such systems. The lowest microbial activity and phenol oxidase activity were found in the bog, which appears to induce high percentage of phonolic contents in pore-water from bogs. It is also suggested that not only the DOC concentrations but also composition of DOC is of great importance in wetland biogeochemistry.

Sources and Variations of Extracellular Enzymes in a Wetland Soil

( Ho Jeong Kang ),( Chris Freeman ) 한국하천호수학회 2002 생태와 환경 Vol.35 No.4

A wetland soil was sterilised by two methods and changes in microbial enzyme activities were assessed. The short-term effects were determined by toluene addition, while the longer-term effects of elimination was monitored by γ-radiation. The changes in β-glucosidase, β-xylosidase, cellobiohydrolase, phosphatase, arylsulphatase, and N-acetylglucosaminidase activities were determined by using methylumbelliferyl model substrates and comparing with the activities of control samples. Toluene addition induced different responses of enzymes. For example, phosphatase activity increased by the treatment while β-glucosidase and arylsulphatase activities decreased. In contrast, γ-radiation decreased all enzyme activities compared to control by 40-80%. The overall results of the toluene and γ-radiation experiments indicate that the large amounts of enzymes are stabilised outside of living cells, at least in the short term, but that the persistence of enzymes is maintained by de-nove synthesis of microbes.

Effects of Water Table Fluctuation on Carbon Dynamics in Northern Peatland

Jinhyun Kim(김진현),Line Rochefort,Chris Freeman,Hojeong Kang 한국토양비료학회 2021 한국토양비료학회 학술발표회 초록집 Vol.2021 No.11

Northern peatlands are substantial carbon sinks because organic matter in peat is highly stable due to the low rate of decomposition. Waterlogged anaerobic conditions induce accumulation of Sphagnum-derived phenolic compounds that inhibit peat organic matter decomposition, a mechanism referred to as the “enzymic latch”. Recent studies have predicted that the water table in northern peatlands may become unstable. We observed that such unstable water table levels can impede the development of Sphagnum mosses. In this study, we determined the effects of low and high frequency water table fluctuation regimes on Sphagnum growth and peat organic matter decomposition, by conducting a year-long mesocosm experiment. In addition, we conducted a molecular analysis to examine changes in abundance of fungal community which may play a key role in the decomposition of organic matter in peatlands. We found that rapid water table fluctuation inhibited the growth of Sphagnum due to fungal infection but stimulated decomposition of organic matter that may dramatically destabilize peatland carbon storage. Increased pH, induced by the fluctuation, may contribute to the enhanced activity of hydrolases in peat. We demonstrated that the water table fluctuation in peatlands impeded Sphagnum growth and accelerates decomposition due to fungal proliferation. Thus, we suggested that understanding the microbial community in the northern peatlands is essential for elucidating the possible changes in carbon cycle of peatland under the changing world

이탄습지 수위 변동에 따른 균류 증식으로 인한 물이끼 성장 저해와 유기물 분해 가속

김진현(Line Rochefort),Line Rochefort,Chris Freeman,강호정(Hojeong Kang) 대한환경공학회 2020 대한환경공학회 학술발표논문집 Vol.2020 No.11

Global Increases in Dissolved Organic Carbon in Rivers and Their Implications

Kang, Ho-Jeong,Jang, In-Young,Freeman, Chris The Korean Society of Limnology 2010 생태와 환경 Vol.36 No.4

DOC (Dissolved Organic Carbon) is an operational terminology for organic carbon molecules dissolved in natural waters. DOC has been studied by ecologists extensively, because it plays a key role in various ecological functions such as substrates for secondary production and the carbon cycle. DOC also represents a substrate for microbial growth within potable water distribution systems, and can react with disinfectants (e.g., chloride) to form harmful disinfection by-products. In addition, residual DOC may carry with it organically bound toxic heavy metals. DOC in aquatic ecosystems may ultimately be transported to the oceans, or released back to the atmosphere by heterotrophic respiration, which can accelerate global climate change. There is evidence that DOC concentrations in aquatic ecosystems are increasing in many regions of the world including Europe, North America, and even in Korea. Land use changes, elevated temperature, elevated $CO_2$, recovery from acidification, and nitrogen deposition have been proposed as mechanisms for the trend. However, the key driving mechanism is yet to be conclusively determined. We propose that more extensive and longer-term observations, research of chemical properties of DOC, impacts of elevated DOC on environmental issues and interdisciplinary approaches are warranted as future studies to fill the gaps in our knowledge about DOC dynamics.