scholarly journals Hysteretic temperature sensitivity of wetland CH<sub>4</sub> fluxes explained by substrate availability and microbial activity

2020 ◽  
Vol 17 (22) ◽  
pp. 5849-5860
Author(s):  
Kuang-Yu Chang ◽  
William J. Riley ◽  
Patrick M. Crill ◽  
Robert F. Grant ◽  
Scott R. Saleska
Keyword(s):  
Temperature Sensitivity ◽  
Seasonal Variability ◽  
Global Climate ◽  
Biogeochemical Model ◽  
Ch4 Emission ◽  
Substrate Availability ◽  
Ch4 Emissions ◽  
Ch4 Production ◽  
Biogeochemical Models ◽  
Abiotic Interactions

Abstract. Methane (CH4) emissions from wetlands are likely increasing and important in global climate change assessments. However, contemporary terrestrial biogeochemical model predictions of CH4 emissions are very uncertain, at least in part due to prescribed temperature sensitivity of CH4 production and emission. While statistically consistent apparent CH4 emission temperature dependencies have been inferred from meta-analyses across microbial to ecosystem scales, year-round ecosystem-scale observations have contradicted that finding. Here, we show that apparent CH4 emission temperature dependencies inferred from year-round chamber measurements exhibit substantial intra-seasonal variability, suggesting that using static temperature relations to predict CH4 emissions is mechanistically flawed. Our model results indicate that such intra-seasonal variability is driven by substrate-mediated microbial and abiotic interactions: seasonal cycles in substrate availability favors CH4 production later in the season, leading to hysteretic temperature sensitivity of CH4 production and emission. Our findings demonstrate the uncertainty of inferring CH4 emission or production rates from temperature alone and highlight the need to represent microbial and abiotic interactions in wetland biogeochemical models.

scholarly journals Hysteretic temperature sensitivity of wetland CH<sub>4</sub> fluxes explained by substrate availability and microbial activity

2020 ◽  
Author(s):  
Kuang-Yu Chang ◽  
William J. Riley ◽  
Patrick M. Crill ◽  
Robert F. Grant ◽  
Scott R. Saleska
Keyword(s):  
Temperature Sensitivity ◽  
Global Climate ◽  
Mechanistic Modeling ◽  
Biogeochemical Model ◽  
Ch4 Emission ◽  
Substrate Availability ◽  
Ch4 Emissions ◽  
Ch4 Production ◽  
Biogeochemical Models ◽  
Abiotic Interactions

Abstract. Methane (CH4) emissions from wetlands are likely increasing and important in global climate change assessments. However, contemporary terrestrial biogeochemical model predictions of CH4 emissions are very uncertain, at least in part due to prescribed temperature sensitivity of CH4 production and emission. While statistically consistent apparent CH4 emission temperature dependencies have been inferred from meta-analyses across microbial to ecosystem scales, year-round ecosystem-scale observations have contradicted that finding. Using flux observations and mechanistic modeling in two heavily studied high-latitude research sites (Stordalen, Sweden, and Utqiaġvik, Alaska, USA), we show here that substrate-mediated hysteretic microbial and abiotic interactions lead to intra-seasonally varying temperature sensitivity of CH4 production and emission. We find that seasonally varying substrate availability drives lower and higher modeled methanogen biomass and activity, and thereby CH4 production, during the earlier and later periods of the thawed season, respectively. Our findings demonstrate the uncertainty of inferring CH4 emission or production from temperature alone, and highlight the need to represent microbial and abiotic interactions in wetland biogeochemical models.

scholarly journals Substantial hysteresis in emergent temperature sensitivity of global wetland CH4 emissions

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Kuang-Yu Chang ◽  
William J. Riley ◽  
Sara H. Knox ◽  
Robert B. Jackson ◽  
Gavin McNicol ◽  
...  
Keyword(s):  
Temperature Sensitivity ◽  
Spatial Scales ◽  
Biogeochemical Model ◽  
Spatial And Temporal Variability ◽  
Biogeochemical Models ◽  
Model Parameterization ◽  
Machine Learning Model ◽  
Meta Analyses ◽  
The Relationship ◽  
Global Carbon

AbstractWetland methane (CH4) emissions ($${F}_{{{CH}}_{4}}$$ F C H 4 ) are important in global carbon budgets and climate change assessments. Currently, $${F}_{{{CH}}_{4}}$$ F C H 4 projections rely on prescribed static temperature sensitivity that varies among biogeochemical models. Meta-analyses have proposed a consistent $${F}_{{{CH}}_{4}}$$ F C H 4 temperature dependence across spatial scales for use in models; however, site-level studies demonstrate that $${F}_{{{CH}}_{4}}$$ F C H 4 are often controlled by factors beyond temperature. Here, we evaluate the relationship between $${F}_{{{CH}}_{4}}$$ F C H 4 and temperature using observations from the FLUXNET-CH4 database. Measurements collected across the globe show substantial seasonal hysteresis between $${F}_{{{CH}}_{4}}$$ F C H 4 and temperature, suggesting larger $${F}_{{{CH}}_{4}}$$ F C H 4 sensitivity to temperature later in the frost-free season (about 77% of site-years). Results derived from a machine-learning model and several regression models highlight the importance of representing the large spatial and temporal variability within site-years and ecosystem types. Mechanistic advancements in biogeochemical model parameterization and detailed measurements in factors modulating CH4 production are thus needed to improve global CH4 budget assessments.

Feeding lucerne silage to beef cattle at three allowances and four feeding frequencies affects circadian patterns of methane emissions, but not emissions per unit of intake

2014 ◽  
Vol 54 (9) ◽  
pp. 1350 ◽  
Author(s):  
Arjan Jonker ◽  
German Molano ◽  
Christopher Antwi ◽  
Garry Waghorn
Keyword(s):  
Emission Rate ◽  
Circadian Variation ◽  
Emission Rates ◽  
Ch4 Emission ◽  
Feeding Frequency ◽  
Ch4 Emissions ◽  
Time To Peak ◽  
Ch4 Production ◽  
Ad Libitum ◽  
Circadian Patterns

The objective of this study was to determine the circadian variation in methane (CH4) emissions from cattle fed lucerne silage at different feeding levels and feeding frequencies, to assist with interpretation of short ‘snapshot’ CH4 measurements used for predicting daily emissions. Eight Hereford × Friesian heifers (initially 20 months of age) were used in five consecutive periods (P1–5) of 14 days with CH4 emissions measured using respiration chambers for two consecutive days at the end of each period. Feed was restricted to intakes of ~6, 8, 8, 8 and 11 ± 1.3 (ad libitum) kg lucerne silage dry matter (DM), fed in 2, 2, 3, 4 or ad libitum (refilled twice daily) meals per day in P1–5, respectively. Daily CH4 production (g/day) was lower in P1 than in P2–4 (P < 0.05), which were lower than in P5 (P < 0.05), but CH4 yield (24.3 ± 1.23 g/kg DM) was unaffected by treatment. Among the five periods, CH4 emission rate (g/h) before feeding ranged from 1.8 to 6.5 g/h, time to peak CH4 production after start of feeding ranged from 19 to 40 min and peak CH4 production rate ranged from 11.1 to 17.5 g/h. The range in hourly CH4 emission rates during the day decreased with increasing feed intake level, but was unaffected by feeding frequency. In summary, the circadian pattern of CH4 emissions was affected by feed allowance and feeding frequency, and variation in CH4 emission rate was reduced with increasing intake, without affecting average daily yield (g CH4/kg DM intake).

Development of new drainage factor in ECOSSE model to improve water dynamics and prediction of CO2 fluxes from drained peatlands

2021 ◽  
Author(s):  
Alina Premrov ◽  
David Wilson ◽  
Matthew Saunders ◽  
Jagadeesh Yeluripati ◽  
Florence Renou-Wilson
Keyword(s):  
Water Table ◽  
Empirical Data ◽  
Seasonal Variability ◽  
Model Simulation ◽  
Water Dynamics ◽  
Water Model ◽  
Biogeochemical Model ◽  
Water Table Level ◽  
Biogeochemical Models ◽  
Model Water

&lt;p&gt;ABSTRACT&lt;/p&gt;&lt;p&gt;Drained peatlands often act as carbon source and their drainage characteristics can be challenging to accommodate in biogeochemical models. This study uses the ECOSSE process-based&amp;#160; biogeochemical model [to simulate water-table level and CO&lt;sub&gt;2&lt;/sub&gt; fluxes (heterotrophic respiration) &lt;sub&gt;[1]&lt;/sub&gt;], and empirical data from two Irish drained peatlands: Blackwater and Moyarwood, which were partly rewetted (both sites are extensively described in earlier studies &lt;sub&gt;[2]&lt;/sub&gt;). Here we explain details on the development of a new drainage factor with seasonal variability Dfa(i) for drained peatlands, based on our recently published work &lt;sub&gt;[3] &lt;/sub&gt;&amp;#160;that we hope can contribute towards the potential future development of IPCC Tier 3 emissions reporting. The Dfa(i) was developed using empirical data from Blackwater drained bare-peat site (BWdr) and its application was further tested at the Moyarwood site under drained (MOdr) and rewetted conditions (MOrw) &lt;sub&gt;[3]&lt;/sub&gt;. The development of the Dfa(i) was carried out in three main steps &lt;sub&gt;[3]&lt;/sub&gt;: 1 - identification of the &amp;#8216;wt-discrepancy event&amp;#8217;; 2 - development of Dfa without seasonal variability, and 3 - accounting for seasonal variability and development of Dfa(i). Dfa(i) was then applied to the rainfall inputs for the periods of active drainage in conjunction with the measured water-table inputs &lt;sub&gt;[3]&lt;/sub&gt;. As explained in our published work &lt;sub&gt;[3]&lt;/sub&gt;, the results indicate that the application of Dfa(i) could improve the model performance to predict water-table level (BWdr: r&lt;sup&gt;2 &lt;/sup&gt;= 0.89 MOdr: r&lt;sup&gt;2 &lt;/sup&gt;= &amp;#160;0.94); and CO&lt;sub&gt;2&lt;/sub&gt; fluxes [BWdr: r&lt;sup&gt;2&lt;/sup&gt; = 0.66 and MOdr: r&lt;sup&gt;2 &lt;/sup&gt;= 0.78) under drained conditions, along with ability of the model to capture seasonal trends &lt;sub&gt;[2]&lt;/sub&gt;. The model simulation of CO&lt;sub&gt;2&lt;/sub&gt; fluxes at MOrw site was also satisfactory (r&lt;sup&gt;2&lt;/sup&gt;=0.75); however, the MOrw water-table simulation results suggest that additional work on the water model component under rewetted conditions is still needed &lt;sub&gt;[3]&lt;/sub&gt;. We further discuss our insights into potential opportunities for future additional improvements and upgrading of the ECOSSE model water module.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;&amp;#160;&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Acknowledgements&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;The authors are grateful to the Irish Environmental Protection Agency (EPA) for funding the AUGER: Project (2015-CCRP-MS.30) under EPA Research Programme 2014&amp;#8211;2020. Full acknowledgements are provided in Premrov et. al (2020) &lt;sub&gt;[3]&lt;/sub&gt;.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Literature&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;[1] Smith, J., et al. 2010. ECOSSE. User Manual.&lt;/p&gt;&lt;p&gt;[2] Renou-Wilson, F., et. al. 2019. Rewetting degraded peatlands for climate and biodiversity benefits: Results from two raised bogs. Ecol. Eng. 127:547-560.&lt;/p&gt;&lt;p&gt;[3] Premrov, A., D. Wilson, M. Saunders, J. Yeluripati and F. Renou-Wilson (2020). CO&lt;sub&gt;2 &lt;/sub&gt;fluxes from drained and rewetted peatlands using a new ECOSSE model water table simulation approach. Sci. Total Environ. (https://doi.org/10.1016/j.scitotenv.2020.142433; on-line 2020; in print Vol. 754, 2021; under CC BY 4.0).&lt;/p&gt;

scholarly journals Evaluating alternative ebullition models for predicting peatland methane emission and its pathways via data-model fusion

2021 ◽  
Author(s):  
Shuang Ma ◽  
Lifen Jiang ◽  
Rachel M. Wilson ◽  
Jeff P. Chanton ◽  
Scott Bridgham ◽  
...  
Keyword(s):  
Model Parameters ◽  
Ch4 Emission ◽  
Deep Soil ◽  
Concentration Data ◽  
Ch4 Flux ◽  
Ch4 Emissions ◽  
Ch4 Production ◽  
Underlying Mechanisms ◽  
Improved Model ◽  
Threshold Approach

Abstract. Understanding the dynamics of peatland methane (CH4) emissions and quantifying sources of uncertainty in estimating peatland CH4 emissions are critical for mitigating climate change. The relative contributions of CH4 emission pathways through ebullition, plant-mediated transport, and diffusion together with their different transport rates and vulnerability to oxidation determine the quantity of CH4 to be oxidized before leaving the soil. Notwithstanding their importance, the relative contributions of the emission pathways have not been well characterized by experiments or modeling approaches. In particular, the ebullition process is more uncertain and can lead to large uncertainties in modeled CH4 emissions. To improve model simulations of CH4 emission and its pathways, we evaluated two model structures: 1) the Ebullition Bubble Growth volume threshold approach (EBG) and 2) the modified Ebullition Concentration Threshold approach (ECT) using CH4 flux and concentration data collected in a peatland in northern Minnesota, USA. When model parameters were constrained using observed CH4 fluxes, the CH4 emissions simulated by the EBG approach (RMSE = 0.53) had a better agreement with observations than the ECT approach (RMSE = 0.61). Further, the EBG approach simulated a smaller contribution from ebullition but more frequent ebullition events than the ECT approach. The EBG approach yielded greatly improved simulations of pore water CH4 concentrations, especially in the deep soil layers, compared to the ECT approach. When constraining the EBG model with both CH4 flux and concentration data in model-data fusion, uncertainty of the modeled CH4 concentration profiles was reduced by 78 to 86 % in comparison to constraints based on CH4 flux data alone. The improved model capability was attributed to the well-constrained parameters regulating the CH4 production and emission pathways. Our results suggest that the EBG modeling approach better characterizes CH4 emission and underlying mechanisms. Moreover, to achieve the best model results both CH4 flux and concentration data are required to constrain model parameterization.

scholarly journals Methane production and nitrogen balance of dairy heifers grazing palisade grass cv. Marandu alone or with forage peanut

2019 ◽  
Vol 97 (11) ◽  
pp. 4625-4634 ◽  
Author(s):  
Andressa S Berça ◽  
Abmael Da S Cardoso ◽  
Vanessa Z Longhini ◽  
Luís O Tedeschi ◽  
Robert Michael Boddey ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Management Strategies ◽  
N Fertilization ◽  
Neutral Detergent Fiber ◽  
N Balance ◽  
Ch4 Emission ◽  
Purine Derivatives ◽  
Ch4 Emissions ◽  
Dairy Heifers ◽  
Ch4 Production

Abstract Livestock production systems are an essential agribusiness activity in Brazil, but a critical challenge of Brazilian farmers is to maintain the equilibrium of the ecosystem, using herbage resources efficiently with a minimum impact on the environment. Nitrogen (N) fertilization and the inclusion of forage legumes into tropical grass pastures are management strategies which increase the productivity and nutritive value of pastures and may also affect methane (CH4) production by ruminants. The objective of this study was to examine the effects of either fertilizing palisade grass pastures with N or including the forage peanut (Arachis pintoi) into grass pastures on enteric CH4 emission, microbial protein production in the rumen via purine derivatives in the urine, and N balance. Twenty-one nonlactating crossbred dairy heifers were used in a completely randomized design with 3 treatments. The treatments consisted of pastures of palisade grass without N fertilization (control), fertilized with urea (fertilized), and palisade grass mixed with forage peanut (mixed). Seven animals (replications) were used to evaluate dry matter intake, digestibility, CH4 emission, urea, purine derivatives, and volume of urine, and N ingestion and excretion. Four paddocks (replications) were used to measure herbage mass; morphological, botanical, and chemical composition of herbage; and herbage allowance. The CH4 emissions were determined using the sulfur hexafluoride (SF6) tracer gas technique. The efficiency of N utilization (ENU) was calculated using the N balance data. Crude protein (CP) concentration of herbage increased with fertilization or legumes inclusion (P < 0.0001) while neutral detergent fiber (NDF) concentration decreased (P = 0.0355). The leaf allowance was higher in the fertilized treatment (P = 0.0294). Only uric acid excretion increased with N fertilization (P = 0.0204). The ENU was not affected by fertilized or mixed compared to control and averaged 55% (P = 0.8945). The enteric CH4 production was similar between treatments and averaged 129 g/d (P = 0.3989). We concluded that the changes in chemical composition of herbage provided by N fertilization or the inclusion of the legume showed no reduction in enteric CH4 emissions, but the ENU was more significant than previous studies with palisade grass, suggesting that different management strategies might alter the ENU under grazing conditions.

scholarly journals Barriers to predicting changes in global terrestrial methane fluxes: analyses using CLM4Me, a methane biogeochemistry model integrated in CESM

2011 ◽  
Vol 8 (1) ◽  
pp. 1733-1807 ◽  
Author(s):  
W. J. Riley ◽  
Z. M. Subin ◽  
D. M. Lawrence ◽  
S. C. Swenson ◽  
M. S. Torn ◽  
...  
Keyword(s):  
High Latitude ◽  
Model Development ◽  
Global Scale ◽  
Surface Fluxes ◽  
Component Community ◽  
Ch4 Emissions ◽  
Community Land Model ◽  
Ch4 Production ◽  
Biogeochemical Models ◽  
High Level

Abstract. Terrestrial net CH4 surface fluxes often represent the difference between much larger gross production and consumption fluxes and depend on multiple physical, biological, and chemical mechanisms that are poorly understood and represented in regional- and global-scale biogeochemical models. To characterize uncertainties, study feedbacks between CH4 fluxes and climate, and to guide future model development and experimentation, we developed and tested a new CH4 biogeochemistry model (CLM4Me) integrated in the land component (Community Land Model; CLM4) of the Community Earth System Model (CESM1). CLM4Me includes representations of CH4 production, oxidation, aerenchymous transport, ebullition, aqueous and gaseous diffusion, and fractional inundation. As with most global models, CLM4Me lacks important features for predicting current and future CH4 fluxes, including: vertical representation of soil organic matter, accurate subgrid scale hydrology, realistic representation of inundated system vegetation, anaerobic decomposition, thermokarst dynamics, and aqueous chemistry. We compared the seasonality and magnitude of predicted CH4 emissions to observations from 18 sites and three global atmospheric inversions. Simulated net CH4 emissions using our baseline parameter set were 270, 160, 50, and 70 Tg CH4 m−2 yr−1 globally, in the tropics, temperate zone, and north of 45° N, respectively; these values are within the range of previous estimates. We then used the model to characterize the sensitivity of regional and global CH4 emission estimates to uncertainties in model parameterizations. Of the parameters we tested, the temperature sensitivity of CH4 production, oxidation parameters, and aerenchyma properties had the largest impacts on net CH4 emissions, up to a factor of 4 and 10 at the regional and gridcell scales, respectively. In spite of these uncertainties, we were able to demonstrate that emissions from dissolved CH4 in the transpiration stream are small (<1 Tg CH4 yr−1) and that uncertainty in CH4 emissions from anoxic microsite production is significant. In a 21st century scenario, we found that predicted declines in high-latitude inundation may limit increases in high-latitude CH4 emissions. Due to the high level of remaining uncertainty, we outline observations and experiments that would facilitate improvement of regional and global CH4 biogeochemical models.

scholarly journals Strategies for Reducing Methane Emissions from Ruminants (Estratégias para a Redução da Emissão de Metano por Ruminantes)

2012 ◽  
Vol 4 (6) ◽  
pp. 1315
Author(s):  
Carlos E. Lascano ◽  
Juan E. Carulla ◽  
Juan De Jesus Vargas
Keyword(s):  
Production Systems ◽  
Global Climate ◽  
Small Ruminants ◽  
Live Weight ◽  
Feed Conversion ◽  
Enteric Fermentation ◽  
Ch4 Emissions ◽  
Animal Product ◽  
Ch4 Production ◽  
Grazing System

Há fortes evidências que as atividades humanas estão afetando o clima global por meio da produção de Gases de Efeito Estufa (GEE), dos quais o metano (CH4) tem elevado potencial de aquecimento. A fermentação entérica e o esterco dos ruminantes representam cerca de 30 a 40% do total das emissões antropogênicas de CH4. Este artigo traz um resumo de tecnologias existentes para reduzir as emissões de CH4 entéricas dos ruminantes, com ênfase à manipulação dietética e ruminal, à seleção/reprodução animal e à melhoria dos sistemas de produção. As diferenças na produção de CH4 entérica entre as espécies animais com base na anatomia do trato gastrointestinal, fisiologia digestiva, fermentação ruminal e nos hábitos de pastejo também são discutidas. A inibição da emissão de CH4 entérica é possível por meio do uso de ionóforos, ácidos orgânicos e óleos. Plantas alimentares contendo metabólitos secundários (taninos e saponinas i.e.) também podem reduzir a produção de CH4. O uso de animais reprodutores para melhorar a eficiência de conversão alimentar (menor consumo residual) pode contribuir com a redução da emissão total de CH4, além de reduzir a emissão por unidade de produto. Resultados utilizando o modelo IPCC nível II prevê que caprinos e vacas de elevada produção leiteira podem apresentar menor emissão de CH4 por unidade de produto em comparação com animais zebuínos e ovinos, enquanto os pequenos ruminantes (caprinos e ovinos) produzem menos CH4 por unidade de ganho de peso corporal (carne), em relação aos bovinos. A melhoria da qualidade das forragens e a implementação de práticas eficientes de uso das pastagens (sistema de pastejo e taxas de lotação) podem na maioria dos casos promover maior produção animal e incrementar a emissão absoluta de CH4, mas também reduzir a emissão de CH4 por unidade de produto animal. Palavras - chave: mudanças climáticas, gases do efeito estufa, bovinos, ovinos, caprinos, manipulação da dieta, manipulação ruminal, criação de animais, intensificação, modelagem.  Estratégias para a Redução da Emissão de Metano por Ruminantes  A B S T R A C T There is irrefutable evidence that human activities are affecting the global climate through the production of Green House Gases (GHG) of which methane (CH4) has a high warming potential. Enteric fermentation and manure from ruminants represent about 30 to 40% of the total anthropogenic CH4 emissions. This paper summarizes existing technologies to reduce enteric CH4 emissions in ruminants given emphasis to dietary and rumen manipulation, animal selection/ breeding and improvement of production systems. Differences in enteric CH4 production among animal species based on anatomy of the GI tract, digestive physiology, rumen fermentation and grazing habits are also discussed. Inhibition of enteric CH4 emission is possible through the use of ionophores, organic acids and oils. Feeding plants containing secondary metabolites (i.e. tannins and saponins) can reduce CH4 production. Breeding for improved feed conversion efficiency (lower residual feed intake) is likely to reduce total and per unit product CH4 emissions. Results using the IPCC Tier II model predict that goats and high producing dairy cattle can potentially produce less CH4 emissions per unit of milk than Cebu cattle or sheep, while small ruminants (goats and sheep) produce less CH4 per unit of live weight gain (meat) than cattle. The introduction of improved high quality forages and the implementation of efficient pasture utilization practices (grazing system and stocking rate) can result in most cases in improved animal production and in increased absolute CH4 emissions, but in reduced CH4 per unit of animal product. Keywords: climate change, greenhouse gases, cattle, sheep, goats, dietary manipulation, rumen manipulation, animal breeding, intensification, modelling

scholarly journals Pendugaan Emisi Metana pada Sistem Pengelolaan Tanaman Padi di Kabupaten Minahasa (The Estimation of Methane Emission in The Rice Management System in Minahasa Rregency)

2012 ◽  
Vol 2 (1) ◽  
Author(s):  
Susan Marlein Mambu
Keyword(s):  
Methane Emission ◽  
Rice Fields ◽  
Soil Types ◽  
Wetland Rice ◽  
Calculation Formula ◽  
Ch4 Emission ◽  
Irrigated Rice ◽  
Ch4 Emissions ◽  
Ch4 Production ◽  
Over Time

AbstrakPemanasan bumi secara global karena emisi gas rumah kaca ke atmosfir yang disebabkan oleh kegiatan manusia, cenderung mengalami peningkatan dari waktu ke waktu. Pertanian padi sawah, khususnya sawah teririgasi juga merupakan penyumbang terbesar gas metana ke atmosfer. Oleh karena itu, perlu adanya upaya pengurangan emisi CH4 dari kegiatan budidaya tanaman padi sawah. Penelitian dilakukan untuk mengetahui emisi CH4 dari budidaya padi sawah di kabupaten Minahasa, dengan melakukan estimasi emisi CH4 menggunakan model perhitungan formula untuk estimasi emisi CH4 pada padi sawah. Hasil penelitian ini memberikan informasi keberadaan CH4 dan jumlah produksi emisi CH4 dari lahan padi sawah di Kabupaten Minahasa, yang cenderung mengalami peningkatan dari tahun ke tahun (data tahun 2002 – 2010). Peningkatan emisi CH4 dari lahan padi sawah di Kabupaten Minahasa disebabkan oleh beberapa faktor yaitu luas panen, jenis tanah, jenis varietas, jenis pengairan dan kegiatan budidaya lainnya seperti pemupukan dan pemberian bahan organik (jerami).Kata kunci: emisi metana, padi sawahAbstractGlobal warming from greenhouse gas emissions to the atmosphere that is caused by human activities tends to be increased over time. Fields of wetland rice, particularly irrigated rice, are also the largest contributor to methane gas to the atmosphere. Therefore, CH4 emissions should be reduced from paddy rice cultivation. This research aimed to measure the production of CH4 emission in the wetland rice fields of Minahasa, using a model calculation formula to estimate CH4 emissions in the rice fields. The results informed the existence and the amount of CH4 production resulted from wetland rice fields in Minahasa, which tended to be increased from year to year (data of year 2002 to 2010). The increment of CH4 emission from wetland rice fields in Minahasa was caused by several factors, i.e. the harvested area, soil types, types of variety, types of irrigation and other cultivation activities such as fertilization and providing organic material (straw).Keywords: methane emission, wetland rice

scholarly journals Barriers to predicting changes in global terrestrial methane fluxes: analyses using CLM4Me, a methane biogeochemistry model integrated in CESM

2011 ◽  
Vol 8 (7) ◽  
pp. 1925-1953 ◽  
Author(s):  
W. J. Riley ◽  
Z. M. Subin ◽  
D. M. Lawrence ◽  
S. C. Swenson ◽  
M. S. Torn ◽  
...  
Keyword(s):  
High Latitude ◽  
Model Development ◽  
Global Scale ◽  
Surface Fluxes ◽  
Component Community ◽  
Ch4 Emissions ◽  
Community Land Model ◽  
Ch4 Production ◽  
Biogeochemical Models ◽  
High Level

Abstract. Terrestrial net CH4 surface fluxes often represent the difference between much larger gross production and consumption fluxes and depend on multiple physical, biological, and chemical mechanisms that are poorly understood and represented in regional- and global-scale biogeochemical models. To characterize uncertainties, study feedbacks between CH4 fluxes and climate, and to guide future model development and experimentation, we developed and tested a new CH4 biogeochemistry model (CLM4Me) integrated in the land component (Community Land Model; CLM4) of the Community Earth System Model (CESM1). CLM4Me includes representations of CH4 production, oxidation, aerenchyma transport, ebullition, aqueous and gaseous diffusion, and fractional inundation. As with most global models, CLM4 lacks important features for predicting current and future CH4 fluxes, including: vertical representation of soil organic matter, accurate subgrid scale hydrology, realistic representation of inundated system vegetation, anaerobic decomposition, thermokarst dynamics, and aqueous chemistry. We compared the seasonality and magnitude of predicted CH4 emissions to observations from 18 sites and three global atmospheric inversions. Simulated net CH4 emissions using our baseline parameter set were 270, 160, 50, and 70 Tg CH4 yr−1 globally, in the tropics, in the temperate zone, and north of 45° N, respectively; these values are within the range of previous estimates. We then used the model to characterize the sensitivity of regional and global CH4 emission estimates to uncertainties in model parameterizations. Of the parameters we tested, the temperature sensitivity of CH4 production, oxidation parameters, and aerenchyma properties had the largest impacts on net CH4 emissions, up to a factor of 4 and 10 at the regional and gridcell scales, respectively. In spite of these uncertainties, we were able to demonstrate that emissions from dissolved CH4 in the transpiration stream are small (<1 Tg CH4 yr−1) and that uncertainty in CH4 emissions from anoxic microsite production is significant. In a 21st century scenario, we found that predicted declines in high-latitude inundation may limit increases in high-latitude CH4 emissions. Due to the high level of remaining uncertainty, we outline observations and experiments that would facilitate improvement of regional and global CH4 biogeochemical models.

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