Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 2.332
Filtrar
1.
Huan Jing Ke Xue ; 41(8): 3804-3810, 2020 Aug 08.
Artigo em Chinês | MEDLINE | ID: mdl-33124357

RESUMO

The impact of exogenous carbon input changes on forest soil respiration provides the basis for an intensive analysis of the forest carbon cycle. Based on a plant residue addition and removal control experiment, this study investigated the short-term soil respiration response to carbon input changes of Picea schrenkiana on the Tianshan Mountains during their growing season with five different carbon input treatments:control, double litter, no root, no litter, and no input. The results revealed that, during the entire observation period, the cumulative soil respiration rates were 3.38, 3.94, 2.65, 2.87, and 2.01 µmol·(m2·s)-1 in the double litter, control, no litter, no root, and no input treatments, respectively. Compared with the control treatment, the cumulative soil CO2 efflux increased by 402.65 g·m-2 in the double litter treatment, whereas it decreased by 515.00, 354.73, and 967.15 g·m-2 in the no litter, no root, and no input treatments, respectively. The mineral soil respiration, litterfall respiration, and root respiration contributed 59.46%, 21.49%, and 14.79%, respectively, to the total soil respiration rate. PCA analysis revealed that the soil respiration rate was positively correlated with the soil temperature, soil moisture, soil total phosphorus content, pH, and soil organic carbon content, and negatively correlated with the soil bulk density, while the soil total nitrogen content, carbon nitrogen ratio, and soil electrical conductivity had no effect on the soil respiration rate.


Assuntos
Picea , Solo , Carbono/análise , Ciclo do Carbono , China , Florestas
2.
Nat Commun ; 11(1): 5184, 2020 10 14.
Artigo em Inglês | MEDLINE | ID: mdl-33056977

RESUMO

The global monsoon is characterised by transitions between pronounced dry and wet seasons, affecting food security for two-thirds of the world's population. Rising atmospheric CO2 influences the terrestrial hydrological cycle through climate-radiative and vegetation-physiological forcings. How these two forcings affect the seasonal intensity and characteristics of monsoonal precipitation and runoff is poorly understood. Here we use four Earth System Models to show that in a CO2-enriched climate, radiative forcing changes drive annual precipitation increases for most monsoon regions. Further, vegetation feedbacks substantially affect annual precipitation in North and South America and Australia monsoon regions. In the dry season, runoff increases over most monsoon regions, due to stomatal closure-driven evapotranspiration reductions and associated atmospheric circulation change. Our results imply that flood risks may amplify in the wet season. However, the lengthening of the monsoon rainfall season and reduced evapotranspiration will shorten the water resources scarcity period for most monsoon regions.


Assuntos
Dióxido de Carbono/metabolismo , Modelos Teóricos , Chuva , Recursos Hídricos , Vento , Atmosfera/química , Austrália , Ciclo do Carbono , Dióxido de Carbono/análise , Mudança Climática , Planeta Terra , Inundações , América do Norte , Estações do Ano , América do Sul , Temperatura , Ciclo Hidrológico
3.
Nat Commun ; 11(1): 5154, 2020 10 14.
Artigo em Inglês | MEDLINE | ID: mdl-33056993

RESUMO

Blue carbon (C) ecosystems are among the most effective C sinks of the biosphere, but methane (CH4) emissions can offset their climate cooling effect. Drivers of CH4 emissions from blue C ecosystems and effects of global change are poorly understood. Here we test for the effects of sea level rise (SLR) and its interactions with elevated atmospheric CO2, eutrophication, and plant community composition on CH4 emissions from an estuarine tidal wetland. Changes in CH4 emissions with SLR are primarily mediated by shifts in plant community composition and associated plant traits that determine both the direction and magnitude of SLR effects on CH4 emissions. We furthermore show strong stimulation of CH4 emissions by elevated atmospheric CO2, whereas effects of eutrophication are not significant. Overall, our findings demonstrate a high sensitivity of CH4 emissions to global change with important implications for modeling greenhouse-gas dynamics of blue C ecosystems.


Assuntos
Ciclo do Carbono , Dióxido de Carbono/metabolismo , Metano/metabolismo , Plantas/metabolismo , Elevação do Nível do Mar , Atmosfera/química , Eutrofização , Efeito Estufa , Áreas Alagadas
4.
Environ Monit Assess ; 192(11): 674, 2020 Oct 03.
Artigo em Inglês | MEDLINE | ID: mdl-33011837

RESUMO

Prediction of dissolved organic carbon (DOC) based on catchment characteristics is a useful tool for efficient and effective water management, but in the case of arid and semi-arid regions, such predictive capacity is scarce. Accordingly, the main objective of this study was to evaluate the significance of principal components for predicting DOC concentrations and fluxes in nine headwater catchments of the Hiv catchment located in the Southern Alborz Mountains in the west of Tehran, Iran. To achieve this aim, data were assembled on 24 headwater catchment characteristics comprising soil properties, physiography, seasonal rainfall, and flow attributes, as well as estimates of DOC concentrations and fluxes across four seasons. The results revealed a major positive correlation between DOC and soil organic matter parameters related to soil biological processes. Using general linear modelling, an organic matter component related to soil biology, a seasonal component related to the dummy effect of sampling seasons, and a soil physical component related to soil texture were found to be the best predictors for DOC responses in the study area.


Assuntos
Ciclo do Carbono , Monitoramento Ambiental , Carbono/análise , Irã (Geográfico) , Solo
5.
Mar Environ Res ; 162: 105179, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-33065520

RESUMO

Nutrient enrichment can alter negatively benthic communities and reduce their ecological services. This study explores in two contrasting seasons (winter and summer), the effects of in situ nutrient enrichment at the community level on carbon metabolism and dissolved organic carbon (DOC) fluxes in two benthic communities dominated by the seagrass Cymodocea nodosa and by the macroalga Caulerpa prolifera. Under nutrient enrichment, C. nodosa increased total community biomass and diversity in summer, while net community production shifted from net autotrophic to net heterotrophic in winter. In contrast, C. prolifera became heterotrophic in summer, while no significant effects were found in winter. Regarding DOC fluxes, nutrient enrichment shifted C. nodosa from net DOC consumer in winter to a strong net DOC producer in summer, while C. prolifera seemed unaffected. Therefore, nutrient enrichment can promote conditional effects (positive, negative or neutral) in coastal areas depending both on macrophyte assemblages and season.


Assuntos
Carbono , Ecossistema , Ciclo do Carbono , Nutrientes , Estações do Ano
6.
PLoS One ; 15(9): e0238997, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32970703

RESUMO

Net primary production (NPP) can regulate global climate change and carbon balance. Although scholars have qualitatively studied the influencing factors of NPP, few have quantified the contribution of different degrees of drought aggravation or mitigation and major land-use changes to NPP changes. Based on the temporal and spatial characteristics of NPP for 2000-2015 in the Chinese Loess Plateau, we quantified the contribution of drought, land use and land cover change (LUCC), and hydrothermal conditions to changes in NPP. Particularly, we analyzed the contribution of major land-use change and different drought levels to NPP. Our results showed that the 15-years average NPP was approximately 227 gC/m2 and decreased from southeast to northwest. Overall, NPP showed a linear increasing trend over the 15-years period. The results suggested that changes in hydrothermal conditions had the strongest impact on NPP (~61%), followed by drought (~33%), and land use and land cover change had the weakest impact (~1.4%). In particular, ~13% of the NPP decreases was affected by light drought aggravation, ~10% of the NPP decreases was affected by moderate drought aggravation, and ~0.3% was affected by the conversion of cropland to grassland or non-NPP main production land. Moreover, ~12.7% of the NPP increase was affected by light drought alleviation, ~9.4% was affected by moderate drought alleviation, and ~1.1% was affected by the conversion of grassland to cropland or forestland. The mechanisms underlying the effect of drought and land-use change on NPP were clarified and provide an important reference value for future research on the carbon cycle and regional ecological environmental restoration.


Assuntos
Mudança Climática/economia , Secas/economia , Recuperação e Remediação Ambiental/economia , Carbono/análise , Ciclo do Carbono , China , Ecossistema , Recuperação e Remediação Ambiental/métodos , Florestas , Pradaria , Humanos , Modelos Teóricos
7.
J Vis Exp ; (162)2020 08 14.
Artigo em Inglês | MEDLINE | ID: mdl-32865530

RESUMO

In the United States, 35% of the total carbon dioxide (CO2) emissions come from the electrical power industry, of which 30% represent natural gas electricity generation. Microalgae can biofix CO2 10 to 15 times faster than plants and convert algal biomass to products of interest, such as biofuels. Thus, this study presents a protocol that demonstrates the potential synergies of microalgae cultivation with a natural gas power plant situated in the southwestern United States in a hot semi-arid climate. State-of-the-art technologies are used to enhance carbon capture and utilization via the green algal species Chlorella sorokiniana, which can be further processed into biofuel. We describe a protocol involving a semi-automated open raceway pond and discuss the results of its performance when it was tested at the Tucson Electric Power plant, in Tucson, Arizona. Flue gas was used as the main carbon source to control pH, and Chlorella sorokiniana was cultivated. An optimized medium was used to grow the algae. The amount of CO2 added to the system as a function of time was closely monitored. Additionally, other physicochemical factors affecting algal growth rate, biomass productivity, and carbon fixation were monitored, including optical density, dissolved oxygen (DO), electroconductivity (EC), and air and pond temperatures. The results indicate that a microalgae yield of up to 0.385 g/L ash-free dry weight is attainable, with a lipid content of 24%. Leveraging synergistic opportunities between CO2 emitters and algal farmers can provide the resources required to increase carbon capture while supporting the sustainable production of algal biofuels and bioproducts.


Assuntos
Ciclo do Carbono , Dióxido de Carbono/metabolismo , Microalgas/crescimento & desenvolvimento , Microalgas/metabolismo , Tanques , Centrais Elétricas , Biocombustíveis , Biomassa , Chlorella/química , Chlorella/crescimento & desenvolvimento , Chlorella/metabolismo , Lipídeos/análise , Microalgas/química , Oxigênio/metabolismo
8.
PLoS One ; 15(9): e0238689, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32903284

RESUMO

MOTIVATION: Determining intracellular metabolic flux through isotope labeling techniques such as 13C metabolic flux analysis (13C-MFA) incurs significant cost and effort. Previous studies have shown transcriptomic data coupled with constraint-based metabolic modeling can determine intracellular fluxes that correlate highly with 13C-MFA measured fluxes and can achieve higher accuracy than constraint-based metabolic modeling alone. These studies, however, used validation data limited to E. coli and S. cerevisiae grown on glucose, with significantly similar flux distribution for central metabolism. It is unclear whether those results apply to more diverse metabolisms, and therefore further, extensive validation is needed. RESULTS: In this paper, we formed a dataset of transcriptomic data coupled with corresponding 13C-MFA flux data for 21 experimental conditions in different unicellular organisms grown on varying carbon substrates and conditions. Three computational flux-balance analysis (FBA) methods were comparatively assessed. The results show when uptake rates of carbon sources and key metabolites are known, transcriptomic data provides no significant advantage over constraint-based metabolic modeling (average correlation coefficients, transcriptomic E-Flux2 0.725 and SPOT 0.650 vs non-transcriptomic pFBA 0.768). When uptake rates are unknown, however, predictions obtained utilizing transcriptomic data are generally good and significantly better than those obtained using constraint-based metabolic modeling alone (E-Flux2 0.385 and SPOT 0.583 vs pFBA 0.237). Thus, transcriptomic data coupled with constraint-based metabolic modeling is a promising method to obtain intracellular flux estimates in microorganisms, particularly in cases where uptake rates of key metabolites cannot be easily determined, such as for growth in complex media or in vivo conditions.


Assuntos
Bactérias/genética , Ciclo do Carbono/genética , Transcriptoma/genética , Bacillus subtilis/efeitos dos fármacos , Bacillus subtilis/genética , Bacillus subtilis/crescimento & desenvolvimento , Bactérias/efeitos dos fármacos , Bactérias/crescimento & desenvolvimento , Carbono/farmacologia , Ciclo do Carbono/efeitos dos fármacos , Árvores de Decisões , Escherichia coli/efeitos dos fármacos , Escherichia coli/genética , Escherichia coli/crescimento & desenvolvimento , Regulação Bacteriana da Expressão Gênica/efeitos dos fármacos , Synechococcus/efeitos dos fármacos , Synechococcus/genética , Synechococcus/crescimento & desenvolvimento , Synechocystis/efeitos dos fármacos , Synechocystis/genética , Synechocystis/crescimento & desenvolvimento
9.
Proc Natl Acad Sci U S A ; 117(37): 22873-22879, 2020 09 15.
Artigo em Inglês | MEDLINE | ID: mdl-32900930

RESUMO

All life on Earth is built of organic molecules, so the primordial sources of reduced carbon remain a major open question in studies of the origin of life. A variant of the alkaline-hydrothermal-vent theory for life's emergence suggests that organics could have been produced by the reduction of CO2 via H2 oxidation, facilitated by geologically sustained pH gradients. The process would be an abiotic analog-and proposed evolutionary predecessor-of the Wood-Ljungdahl acetyl-CoA pathway of modern archaea and bacteria. The first energetic bottleneck of the pathway involves the endergonic reduction of CO2 with H2 to formate (HCOO-), which has proven elusive in mild abiotic settings. Here we show the reduction of CO2 with H2 at room temperature under moderate pressures (1.5 bar), driven by microfluidic pH gradients across inorganic Fe(Ni)S precipitates. Isotopic labeling with 13C confirmed formate production. Separately, deuterium (2H) labeling indicated that electron transfer to CO2 does not occur via direct hydrogenation with H2 but instead, freshly deposited Fe(Ni)S precipitates appear to facilitate electron transfer in an electrochemical-cell mechanism with two distinct half-reactions. Decreasing the pH gradient significantly, removing H2, or eliminating the precipitate yielded no detectable product. Our work demonstrates the feasibility of spatially separated yet electrically coupled geochemical reactions as drivers of otherwise endergonic processes. Beyond corroborating the ability of early-Earth alkaline hydrothermal systems to couple carbon reduction to hydrogen oxidation through biologically relevant mechanisms, these results may also be of significance for industrial and environmental applications, where other redox reactions could be facilitated using similarly mild approaches.


Assuntos
Dióxido de Carbono/química , Ciclo do Carbono , Transporte de Elétrons , Hidrogênio/química , Concentração de Íons de Hidrogênio , Fontes Hidrotermais/química , Oxirredução , Força Próton-Motriz
10.
PLoS One ; 15(9): e0216019, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32946438

RESUMO

Similar to many large river valleys globally, the Sacramento River Valley has been extensively drained and leveed, hydrologically divorcing river channels from most floodplains. Today, the former floodplain is extensively managed for agriculture. Lack of access to inundated floodplains is recognized as a significant contributing factor in the decline of native Chinook Salmon (Oncorhynchus tshawytscha). We observed differences in salmon growth rate, invertebrate density, and carbon source in food webs from three aquatic habitat types-leveed river channels, perennial drainage canals in the floodplain, and agricultural floodplain wetlands. Over 23 days (17 February to 11 March, 2016) food web structure and juvenile Chinook Salmon growth rates were studied within the three aquatic habitat types. Zooplankton densities on the floodplain wetland were 53x more abundant, on average, than in the river. Juvenile Chinook Salmon raised on the floodplain wetland grew at 0.92 mm/day, 5x faster than fish raised in the adjacent river habitat (0.18 mm/day). Two aquatic-ecosystem modeling methods were used to partition the sources of carbon (detrital or photosynthetic) within the different habitats. Both modeling approaches found that carbon in the floodplain wetland food web was sourced primarily from detrital sources through heterotrophic pathways, while carbon in the river was primarily photosynthetic and sourced from in situ autotrophic production. Hydrologic conditions typifying the ephemerally inundated floodplain-shallower depths, warmer water, longer water residence times and predominantly detrital carbon sources compared to deeper, colder, swifter water and a predominantly algal-based carbon source in the adjacent river channel-appear to facilitate the dramatically higher rates of food web production observed in the floodplain. These results suggest that hydrologic patterns associated with seasonal flooding facilitate river food webs to access floodplain carbon sources that contribute to highly productive heterotrophic energy pathways important to the production of fisheries resources.


Assuntos
Pesqueiros/estatística & dados numéricos , Inundações , Cadeia Alimentar , Oncorhynchus/fisiologia , Zooplâncton/fisiologia , Animais , California , Ciclo do Carbono , Hidrologia , Modelos Biológicos , Dinâmica Populacional/estatística & dados numéricos , Rios , Estações do Ano , Áreas Alagadas
11.
Nat Commun ; 11(1): 4897, 2020 09 29.
Artigo em Inglês | MEDLINE | ID: mdl-32994415

RESUMO

Soil microbial respiration is an important source of uncertainty in projecting future climate and carbon (C) cycle feedbacks. However, its feedbacks to climate warming and underlying microbial mechanisms are still poorly understood. Here we show that the temperature sensitivity of soil microbial respiration (Q10) in a temperate grassland ecosystem persistently decreases by 12.0 ± 3.7% across 7 years of warming. Also, the shifts of microbial communities play critical roles in regulating thermal adaptation of soil respiration. Incorporating microbial functional gene abundance data into a microbially-enabled ecosystem model significantly improves the modeling performance of soil microbial respiration by 5-19%, and reduces model parametric uncertainty by 55-71%. In addition, modeling analyses show that the microbial thermal adaptation can lead to considerably less heterotrophic respiration (11.6 ± 7.5%), and hence less soil C loss. If such microbially mediated dampening effects occur generally across different spatial and temporal scales, the potential positive feedback of soil microbial respiration in response to climate warming may be less than previously predicted.


Assuntos
Carbono/análise , Metagenoma/genética , Microbiota/fisiologia , Microbiologia do Solo , Solo/química , Aclimatação/genética , Archaea/genética , Archaea/isolamento & purificação , Archaea/metabolismo , Bactérias/genética , Bactérias/isolamento & purificação , Bactérias/metabolismo , Carbono/metabolismo , Ciclo do Carbono , Celulose/metabolismo , DNA Ambiental/genética , DNA Ambiental/isolamento & purificação , Fungos/genética , Fungos/isolamento & purificação , Fungos/metabolismo , Aquecimento Global , Pradaria , Temperatura Alta/efeitos adversos , Metagenômica , Modelos Genéticos , Raízes de Plantas/química , Poaceae/química
12.
Proc Natl Acad Sci U S A ; 117(36): 22452-22461, 2020 09 08.
Artigo em Inglês | MEDLINE | ID: mdl-32820073

RESUMO

Carbon fixation via the Calvin cycle is constrained by the side activity of Rubisco with dioxygen, generating 2-phosphoglycolate. The metabolic recycling of phosphoglycolate was extensively studied in photoautotrophic organisms, including plants, algae, and cyanobacteria, where it is referred to as photorespiration. While receiving little attention so far, aerobic chemolithoautotrophic bacteria that operate the Calvin cycle independent of light must also recycle phosphoglycolate. As the term photorespiration is inappropriate for describing phosphoglycolate recycling in these nonphotosynthetic autotrophs, we suggest the more general term "phosphoglycolate salvage." Here, we study phosphoglycolate salvage in the model chemolithoautotroph Cupriavidus necator H16 (Ralstonia eutropha H16) by characterizing the proxy process of glycolate metabolism, performing comparative transcriptomics of autotrophic growth under low and high CO2 concentrations, and testing autotrophic growth phenotypes of gene deletion strains at ambient CO2 We find that the canonical plant-like C2 cycle does not operate in this bacterium, and instead, the bacterial-like glycerate pathway is the main route for phosphoglycolate salvage. Upon disruption of the glycerate pathway, we find that an oxidative pathway, which we term the malate cycle, supports phosphoglycolate salvage. In this cycle, glyoxylate is condensed with acetyl coenzyme A (acetyl-CoA) to give malate, which undergoes two oxidative decarboxylation steps to regenerate acetyl-CoA. When both pathways are disrupted, autotrophic growth is abolished at ambient CO2 We present bioinformatic data suggesting that the malate cycle may support phosphoglycolate salvage in diverse chemolithoautotrophic bacteria. This study thus demonstrates a so far unknown phosphoglycolate salvage pathway, highlighting important diversity in microbial carbon fixation metabolism.


Assuntos
Crescimento Quimioautotrófico/fisiologia , Glicolatos/metabolismo , Fotossíntese/fisiologia , Acetilcoenzima A/metabolismo , Proteínas de Bactérias/metabolismo , Ciclo do Carbono/fisiologia , Cupriavidus necator/genética , Cupriavidus necator/metabolismo , Malato Sintase/metabolismo , Malatos/metabolismo , Oxirredução
13.
Proc Natl Acad Sci U S A ; 117(35): 21079-21087, 2020 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-32817563

RESUMO

The amplitude of the atmospheric CO2 seasonal cycle has increased by 30 to 50% in the Northern Hemisphere (NH) since the 1960s, suggesting widespread ecological changes in the northern extratropics. However, substantial uncertainty remains in the continental and regional drivers of this prominent amplitude increase. Here we present a quantitative regional attribution of CO2 seasonal amplification over the past 4 decades, using a tagged atmospheric transport model prescribed with observationally constrained fluxes. We find that seasonal flux changes in Siberian and temperate ecosystems together shape the observed amplitude increases in the NH. At the surface of northern high latitudes, enhanced seasonal carbon exchange in Siberia is the dominant contributor (followed by temperate ecosystems). Arctic-boreal North America shows much smaller changes in flux seasonality and has only localized impacts. These continental contrasts, based on an atmospheric approach, corroborate heterogeneous vegetation greening and browning trends from field and remote-sensing observations, providing independent evidence for regionally divergent ecological responses and carbon dynamics to global change drivers. Over surface midlatitudes and throughout the midtroposphere, increased seasonal carbon exchange in temperate ecosystems is the dominant contributor to CO2 amplification, albeit with considerable contributions from Siberia. Representing the mechanisms that control the high-latitude asymmetry in flux amplification found in this study should be an important goal for mechanistic land surface models moving forward.


Assuntos
Atmosfera/química , Dióxido de Carbono/química , Carbono/química , Regiões Árticas , Ciclo do Carbono/fisiologia , Dióxido de Carbono/análise , Clima , Mudança Climática , Ecossistema , América do Norte , Fotossíntese , Estações do Ano , Sibéria
14.
Nat Commun ; 11(1): 4024, 2020 08 12.
Artigo em Inglês | MEDLINE | ID: mdl-32788652

RESUMO

Soil microbial communities remain active during much of the Arctic winter, despite deeply frozen soils. Overwinter microbial activity affects the global carbon (C) budget, nutrient cycling, and vegetation composition. Microbial respiration is highly temperature sensitive in frozen soils, as liquid water and solute availability decrease rapidly with declining temperature. Climate warming and changes in snowpack are leading to warmer Arctic winter soils. Warmer winter soils are thought to yield greater microbial respiration of available C, greater overwinter CO2 efflux and greater nutrient availability to plants at thaw. Using field and laboratory observations and experiments, we demonstrate that persistently warm winter soils can lead to labile C starvation and reduced microbial respiration, despite the high C content of most Arctic soils. If winter soils continue to warm, microbial C limitation will reduce expected CO2 emissions and alter soil nutrient cycling, if not countered by greater labile C inputs.


Assuntos
Carbono , Microbiota/fisiologia , Estações do Ano , Microbiologia do Solo , Solo/química , Árvores/microbiologia , Alaska , Regiões Árticas , Atmosfera , Ciclo do Carbono , Dióxido de Carbono , Mudança Climática , Ecossistema , Glucose/metabolismo , Modelos Teóricos , Plantas , Temperatura
15.
Nature ; 584(7820): 234-237, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32788738

RESUMO

Tropical soils contain one-third of the carbon stored in soils globally1, so destabilization of soil organic matter caused by the warming predicted for tropical regions this century2 could accelerate climate change by releasing additional carbon dioxide (CO2) to the atmosphere3-6. Theory predicts that warming should cause only modest carbon loss from tropical soils relative to those at higher latitudes5,7, but there have been no warming experiments in tropical forests to test this8. Here we show that in situ experimental warming of a lowland tropical forest soil on Barro Colorado Island, Panama, caused an unexpectedly large increase in soil CO2 emissions. Two years of warming of the whole soil profile by four degrees Celsius increased CO2 emissions by 55 per cent compared to soils at ambient temperature. The additional CO2 originated from heterotrophic rather than autotrophic sources, and equated to a loss of 8.2 ± 4.2 (one standard error) tonnes of carbon per hectare per year from the breakdown of soil organic matter. During this time, we detected no acclimation of respiration rates, no thermal compensation or change in the temperature sensitivity of enzyme activities, and no change in microbial carbon-use efficiency. These results demonstrate that soil carbon in tropical forests is highly sensitive to warming, creating a potentially substantial positive feedback to climate change.


Assuntos
Ciclo do Carbono , Dióxido de Carbono/análise , Florestas , Aquecimento Global , Solo/química , Clima Tropical , Retroalimentação , Ilhas , Panamá , Fatores de Tempo , Água/análise
16.
J Environ Manage ; 274: 111144, 2020 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-32798851

RESUMO

Drought is one of the most prominent natural threats to grassland productivity, although the magnitude of this threat is uncertain due to the different drought-levels. However, drought-productivity dynamics has not yet received much attention. It is necessary to establish the method to evaluate quantitatively the effect of different drought-levels on grassland productivity. To better understand the impact of different drought-levels on productivity dynamics, an assessment method to assess the quantitative effects of different drought-levels on grassland productivity was proposed based-on long-term observation data, standardized precipitation index (SPI) and Biome-BGC process model. Based-on assessment indicator of net primary productivity (NPP), NPP loss caused by moderate, severe and extreme drought was dramatically different in grasslands with a significant exponential change with gradient of different drought-levels. Furthermore, NPP loss variation in different grassland types under the same drought level was significantly different. Besides, the effect of drought on NPP gradually decreased by an exponential relationship in desert, typical and meadow steppe. However, the percentage of NPP loss in desert, typical and meadow steppe reduced by 20.5%, 13.1% and 17.5% with U-shaped, respectively. Meanwhile, our results can offer scientific basis to improve assessment impact of extreme climate events used by ecosystem model and data, and cope with carbon cycling management and climate change.


Assuntos
Secas , Ecossistema , Ciclo do Carbono , Mudança Climática , Pradaria
17.
Nat Commun ; 11(1): 3941, 2020 08 07.
Artigo em Inglês | MEDLINE | ID: mdl-32770005

RESUMO

Anaerobic oxidation of methane (AOM) mediated by anaerobic methanotrophic archaea (ANME) is the primary process that provides energy to cold seep ecosystems by converting methane into inorganic carbon. Notably, cold seep ecosystems are dominated by highly divergent heterotrophic microorganisms. The role of the AOM process in supporting heterotrophic population remains unknown. We investigate the acetogenic capacity of ANME-2a in a simulated cold seep ecosystem using high-pressure biotechnology, where both AOM activity and acetate production are detected. The production of acetate from methane is confirmed by isotope-labeling experiments. A complete archaeal acetogenesis pathway is identified in the ANME-2a genome, and apparent acetogenic activity of the key enzymes ADP-forming acetate-CoA ligase and acetyl-CoA synthetase is demonstrated. Here, we propose a modified model of carbon cycling in cold seeps: during AOM process, methane can be converted into organic carbon, such as acetate, which further fuels the heterotrophic community in the ecosystem.


Assuntos
Acetatos/metabolismo , Archaea/enzimologia , Proteínas de Bactérias/metabolismo , Coenzima A Ligases/metabolismo , Metano/metabolismo , Anaerobiose , Archaea/genética , Proteínas de Bactérias/genética , Ciclo do Carbono/fisiologia , Coenzima A Ligases/genética , Genoma Arqueal , Sedimentos Geológicos/microbiologia , Redes e Vias Metabólicas/genética , Oxirredução , Água do Mar/microbiologia
18.
Sci Total Environ ; 746: 141184, 2020 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-32768783

RESUMO

This study presents a first estimate of the country-specific enteric methane (CH4) emission factors (EFs) and the net CH4 fluxes for the local and improved cattle breeds (LCB and ICB) in Nepal using the IPCC Tier 2 methodology. The country-specific herd structure, morphological and feed characteristics data of cattle were collected from the field survey. In LCB, adult males had the highest mean live body weights (BWs) ranging from 222 ± 42 kg in the Hill to 237 ± 36 kg in the Plain region, while for improved cattle, adult females had the highest BW of 334 ± 45 kg in the Hill to 308 ± 38 kg in the Plain regions. Weight gains of ICB were higher than the LCB. Local calves gained BWs of 97 ± 20 g day-1, while improved calves gained a weight of 202 ± 41 g day-1. The CH4 EFs ranged from 13 ± 3 to 46 ± 9 kg CH4 head-1 yr-1 for different age-groups of the LCB, while for the ICB, the EFs ranged from 14 ± 3 to 75 ± 15 kg CH4 head-1 yr-1. Overall, the EFs were 33 ± 7 and 46 ± 9 kg CH4 head-1 yr-1 for LCB and ICB, respectively. The estimated enteric EFs of cattle in the Hill and Plain regions were not statistically different (p > 0.05), but a significant difference existed between the breeds (LCB and ICB; p < 0.05). The net CH4 flux was 254 ± 51 Gg yr-1 from enteric fermentation in cattle of Nepal using the country-specific EFs, about 15% higher than using the default EFs (221 ± 66 Gg yr-1). We underline that the emission estimation, deploying the country-specific EFs, will be more accurate, contributing to reduce the uncertainties in the national GHG inventories and supporting the mitigation actions.


Assuntos
Ciclo do Carbono , Metano/análise , Animais , Carbono , Bovinos , Dieta , Feminino , Fermentação , Masculino , Nepal
19.
PLoS One ; 15(8): e0237351, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32764813

RESUMO

Karst systems represent an important carbon sink worldwide. However, several phenomena such as the CO2 degassing and the exchange of cave air return a considerable amount of CO2 to the atmosphere. It is therefore of paramount importance to understand the contribution of the ecosystem to the carbon budget of karst areas. In this study conducted in a mid-succession ecosystem developed on abandoned karst grassland, two types of model were assessed, estimating the gross primary production (GPP) or the net ecosystem exchange (NEE) based on seven years of eddy covariance data (2013-2019): (1) a quadratic vegetation index-based empirical model with five alternative vegetation indices as proxies of GPP and NEE, and (2) the vegetation photosynthesis model (VPM) which is a light use efficiency model to estimate only GPP. The Enhanced Vegetation Index (EVI) was the best proxy for NEE whereas SAVI performed very similarly to EVI in the case of GPP in the empirical model setting. The empirical model performed better than the VPM model which tended to underestimate GPP. Therefore, for this ecosystem, we suggest the use of the empirical model provided that the quadratic relationship observed persists. However, the VPM model would be a good alternative under a changing climate, as it is rooted in the understanding of the photosynthesis process, if the scalars it involves could be improved to better estimate GPP.


Assuntos
Ciclo do Carbono , Sequestro de Carbono , Pradaria , Clima , Ecossistema , Modelos Biológicos , Fotossíntese
20.
PLoS One ; 15(8): e0237730, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32857799

RESUMO

Freshwater ecosystems play a key role in shaping the global carbon cycle and maintaining the ecological balance that sustains biodiversity worldwide. Surficial water bodies are often interconnected with groundwater, forming a physical continuum, and their interaction has been reported as a crucial driver for organic matter (OM) inputs in groundwater systems. However, despite the growing concerns related to increasing anthropogenic pressure and effects of global change to groundwater environments, our understanding of the dynamics regulating subterranean carbon flows is still sparse. We traced carbon composition and transformations in an arid zone calcrete aquifer using a novel multidisciplinary approach that combined isotopic analyses of dissolved organic carbon (DOC) and inorganic carbon (DIC) (δ13CDOC, δ13CDIC, 14CDOC and 14CDIC) with fluorescence spectroscopy (Chromophoric Dissolved OM (CDOM) characterisation) and metabarcoding analyses (taxonomic and functional genomics on bacterial 16S rRNA). To compare dynamics linked to potential aquifer recharge processes, water samples were collected from two boreholes under contrasting rainfall: low rainfall ((LR), dry season) and high rainfall ((HR), wet season). Our isotopic results indicate limited changes and dominance of modern terrestrial carbon in the upper part (northeast) of the bore field, but correlation between HR and increased old and 13C-enriched DOC in the lower area (southwest). CDOM results show a shift from terrestrially to microbially derived compounds after rainfall in the same lower field bore, which was also sampled for microbial genetics. Functional genomic results showed increased genes coding for degradative pathways-dominated by those related to aromatic compound metabolisms-during HR. Our results indicate that rainfall leads to different responses in different parts of the bore field, with an increase in old carbon sources and microbial processing in the lower part of the field. We hypothesise that this may be due to increasing salinity, either due to mobilisation of Cl- from the soil, or infiltration from the downstream salt lake during HR. This study is the first to use a multi-technique assessment using stable and radioactive isotopes together with functional genomics to probe the principal organic biogeochemical pathways regulating an arid zone calcrete system. Further investigations involving extensive sampling from diverse groundwater ecosystems will allow better understanding of the microbiological pathways sustaining the ecological functioning of subterranean biota.


Assuntos
Ciclo do Carbono , Isótopos de Carbono/análise , Monitoramento Ambiental/métodos , Água Subterrânea/química , Microbiota/fisiologia , Solo/química , Austrália , Isótopos de Carbono/metabolismo , Código de Barras de DNA Taxonômico , DNA Bacteriano/genética , DNA Bacteriano/isolamento & purificação , Água Subterrânea/microbiologia , RNA Ribossômico 16S/genética , Chuva , Salinidade , Microbiologia do Solo , Espectrometria de Fluorescência
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA