Impact of Sundarban mangrove biosphere on the carbon dioxide and methane mixing ratios at the NE Coast of Bay of Bengal, India
TL;DR: In this paper, the authors measured the diurnal and seasonal variations in carbon dioxide and methane fluxes between Sundarban biosphere and atmosphere using micrometeorological method during 1998-2000.
About: This article is published in Atmospheric Environment.The article was published on 2002-02-01. It has received 64 citations till now. The article focuses on the topics: Atmospheric methane & Carbon dioxide.
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TL;DR: In this paper, an attempt has been made through an attempt to estimate the quantitative and temporal variation of 4 CH emission from a subtropical wetland of North India dominated by Scirpus littoralis.
Abstract: Methane emission from wetlands and its upscaling is a frontier area of research in global biogeochemical cycling including global warming. Though process based models are needed to account for variability in various types of wetland ecosystems, due to lack of required field data, it is till in infancy especially in the tropical countries. An attempt has been made through this study to estimate the quantitative and temporal variation of 4 CH emission from a subtropical wetland of North India dominated by Scirpus littoralis. A wide variation in rate of 4 CH emission was observed in an annual cycle with maximum rate reaching up to 129.82± 19.08 mg m -2 h -1 during March to April and negative emission rates were observed in hot and dry summer months between May to July. This finding suggests that tropical wetlands act both as source and sink of 4 CH emission depending upon the specific ecological and environmental conditions. Therefore, extrapolation of single value of rate of emission for the entire year is not correct in estimating total annual 4 CH flux.
10 citations
Cites background from "Impact of Sundarban mangrove biosph..."
...The total biomass ranged between 553.90 g/m2 in May and 2669.89 g/m2 in January....
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TL;DR: In this article, the seasonal cycle of the tropospheric CO2 concentration over India was investigated using the GEOS-Chem atmospheric transport model, Greenhouse gas Observation SATellite (GOSAT) retrievals, and in-situ measurements.
Abstract: In this study, investigation of the seasonal cycle of the tropospheric CO2 concentration over India was carried out using the GEOS-Chem atmospheric transport model, Greenhouse gas Observation SATellite (GOSAT) retrievals, and in-situ measurements. The model simulation is highly coherent with the satellite and in-situ datasets, and it shows a distinct seasonal cycle of the tropospheric CO2 tendency over India with a negative phase (decreasing concentration) during April–August and a positive phase (increasing concentration) during September–March. The model diagnostics were analyzed to estimate budgets of the surface layer CO2, up to 650 hPa pressure level, for the two-phases of the seasonal cycle. A mean tendency, equivalent to −0.70 ppmv month−1, observed during April–August, which results from the loss of CO2 content in the surface layer through horizontal advection (−2.25 ppmv month−1) and vertical diffusion (−0.20 ppmv month−1), that dominates the gain from vertical advection (1.53 ppmv month−1). The negative contribution of horizontal advection in this period comes from the transport of CO2 depleted air-parcels over the oceanic region to India by the southwest monsoon winds and the positive contributions of vertical advection comes from upwelling of CO2 enriched air-parcels. The mean tendency, equivalent to 1.01 ppmv month−1, during September–March results from the gain through vertical advection (0.78 ppmv month−1) and horizontal advection (0.37 ppmv month−1) and a small contribution of vertical diffusion (−0.15 ppmv month−1). In this period, positive contribution of horizontal advection is due to the transport of CO2 enriched air-parcels from the southeast Asian region to India by north-east monsoon winds. At the annual scale, CO2 content of the surface layer over India has a net gain of 0.75 GtC that comes from 14.31 GtC through vertical advection that exceeds the loss due to horizontal advection (−11.10 GtC) and vertical diffusion processes (−2.46 GtC). This net gain is almost 85% higher than the input of 0.4 GtC through surface fluxes, which composed of 0.61 GtC anthropogenic emission and −0.21 GtC net terrestrial ecosystem exchanges. Additional sensitivity experiment was carried out to elucidate the semi-annual features of the seasonal cycle of CO2 for north India, in contrast to the annual characteristics of the seasonal cycle for south India in relation to the GOSAT observation.
9 citations
6 citations
01 Jan 2013
TL;DR: In this article, the spatial variability of atmosphere-biosphere CO2 exchange was evaluated in Jharkhali, Bonnie Camp and Henry Island, respectively, in the inner, middle and outer estuarine part of Indian Sundarban mangrove ecosystem, between 15th April and 15th May, 2011.
Abstract: Spatial variability of atmosphere-biosphere CO2 exchange was evaluated in Jharkhali, Bonnie Camp and Henry Island - situated, respectively, in the inner, middle and outer estuarine part of Indian Sundarban mangrove ecosystem - using micrometeorological methods, between 15th April and 15th May, 2011. Henry Island and Jharkhali acted as a sink for CO2 with a rate of 18.94 g m -2 d -1 and 51.06 g m -2 d -1 , respectively, whereas the sink strength of Bonnie camp was 1.51 g m -2 d -1 . A positive correlation was obtained between solar radiation and 'atmosphere to biosphere' CO2 flux. Varying magnitudes in leaf chlorophyll may be another decisive factor controlling CO2 exchange. Greater chlorophyll content of the dominant species of a site leads to higher photosynthetic rate and hence increases the magnitude of 'atmosphere to biosphere' CO2 influx. A mean daytime water vapor flux of 7.83 ± 4.95 m mol m -2 s -1 and a nighttime of 3.38 ± 3.32 m mol m -2 s -1 was observed at the three sites. The observed Bowen ratio values reflected a dominance of latent heat flux, compared to that of sensible heat flux in this ecosystem. The ecosystem on the whole acted as a sink for CO2 (23.83 g m -2 d -1 ) but the magnitude of CO2 influx was found to vary spatially. Resumen: La variabilidad espacial del intercambio atmosfera-biosfera de CO2 fue evaluada en Jharkhali, Bonnie Camp y Henry Island - ubicados, respectivamente, en la parte interna, intermedia y externa de la porcion estuarina del ecosistema de manglar de los Sundarbans - usando metodos micrometeorologicos, entre el 15 de abril y el 15 de mayo de 2011. Henry Island y Jharkhali funcionaron como un resumidero de CO2, con tasas de 18.94 g m -2 d -1 y 51.06 g m -2 d -1 , respectivamente, mientras que la fuerza como resumidero de Bonnie Camp fue de 1.51 g m -2 d -1 . Se obtuvo una correlacion positiva entre la radiacion solar y el flujo de CO2 'atmosfera a biosfera'. La variacion en la cantidad de clorofila foliar puede constituir otro factor decisivo en el control del intercambio de CO2. Un mayor contenido de clorofila de las especies dominantes de un sitio resulta en una mayor tasa fotosintetica y por lo tanto incrementa la magnitud del flujo de CO2 'atmosfera a biosfera'. En los tres sitios se observo un flujo promedio diurno de vapor de agua de 7.83 ± 4.95 m mol m -2 s -1 y uno nocturno de 3.38 ± 3.32 m mol m -2 s -1 . Los valores observados del cociente de Bowen reflejaron una dominancia del flujo de calor latente en comparacion con el flujo de calor sensible en este sistema. El ecosistema como un todo funciono como un resumidero de CO2 (23.83 g m -2 d -1 ), pero la magnitud del flujo de entrada de CO2 vario espacialmente. Resumo: A variabilidade espacial da troca de CO2 na atmosfera-biosfera foi avaliada entre 15 de abril e 15 de Maio de 2011 em Jharkhali, Camp Bonnie e Ilha Henry - situados, respectivamente, na parte interior, central e externa do estuario do ecossistema de mangal do
5 citations
Dissertation•
10 May 2013
TL;DR: In this paper, the effects of tree removal on the fluxes of greenhouse gases, surface elevation and other ecosystem functions of mangrove forests and root production were investigated. And the root in-growth technique was used to estimate root productivity.
Abstract: Mangrove forests are considered one of the most efficient natural carbon sinks and their preservation is thus important in climate change mitigation. However, they are declining at higher rates than terrestrial forests, due to human activities; with Kenyan mangroves being no of exception. One of the main drivers of mangrove decline in Kenya is over-exploitation for wood products. The present study aimed to assess (a) the effects of tree removal on the fluxes of greenhouse gases, surface elevation and other ecosystem functions of mangrove forests and (b) mangrove root production. To explore these objectives two experiments were established in the mangrove forests at Gazi bay, Kenya: (i) tree harvest and (ii) mangrove productivity studies. For the tree harvest experiment, ten 12 m x 12 m plots were established in March 2009 in a Rhizophora mucronata (Lam.) forest. Five plots were randomly selected and all trees within them were girdled in November 2009 and then cut in May 2010. Gas fluxes of CO2 and CH4 were sampled using the chamber technique at monthly intervals from June 2009 to April 2011. Surface elevation dynamics were observed using surface elevation stations (SES). Other variables measured included, macrofaunal abundance and diversity and natural regeneration patterns. For the root productivity experiment, twenty eight 10 m x 10 m plots were established in four mangrove forest types; with each type comprising of Avicennia marina (Forsk) Vierh., Ceriops tagal (Perr) C. B. Robinson, R. mucronata and Sonneratia alba (Sm) forests. Ten of the plots were established in A. marina and R. mucronata forests in Makongeni; while 18 plots comprising all the four species were established at Gazi; six plots each for A. marina and R. mucronata and three plots each for C. tagal and S. alba forests. Root production was estimated using the root in-growth technique (two in-growth trenches per plot), while the aboveground productivity was estimated from measurements of girth increment. Girth increment was measured using dendrometers installed on selected trees, one per plot, in combination with periodic girth measurements of 10 trees per plot. Environmental variables such as height above datum, salinity, grain size and redox potential were measured at the beginning of each experiment and during treatment periods for the tree harvest experiment. Treatment significantly elevated carbon emissions from the mangrove sediments by 14.2 ± 10.3 tCO2 ha-1 (rate of 9.8 ± 7.1 tCO2 ha-1 yr-1) within two years. Similarly, treatment significantly induced subsidence of -51.3 ± 24.3 mm (at a rate of -32.1 ± 8.4 mm yr-1) compared to 11.1±10.1 mm (at a rate of 4.2 ± 1.4 mm yr-1) in control plots in over 2 years after treatment. Decomposition of labile roots in the treated plots was most likely the driver of high emissions of carbon in the treated plots. Soil compaction due to collapse of aeranchyma tissue in roots might have been responsible for subsidence in cut plots. Natural regeneration was drastically affected by cutting, with treated plots having sparse seedlings 450 days after treatment. Gap-preferring ocypodid crabs colonized and became more abundant than sesarmids (usually found in closed canopy forest) in treated plots.
There was significant variation in mangrove forest productivity between Makongeni and Gazi sites, with the mangroves in the former having higher production than those of the latter. Rhizophora mucronata forest at Makongeni had a higher aboveground biomass (AGB) than all other forest types. On the other hand A. marina forest at Makongeni had the highest belowground biomass (BGB) production. Differences in microtopographical settings and soil factors might have influence the variation in forest productivity between the two sites and between the forest types.
These results underscore the importance of putting in place management options that ensure maintenance of continuous canopy cover and fast regeneration in mangrove forests under wood extraction. In addition, mangrove areas at the seafront should be protected. These results also support other work showing that mangrove forests often allocate a higher proportion of carbon to belowground roots than other forests. A high investment in belowground carbon helps facilitate surface elevation and peat formation, which not only forms important carbon sinks but may also enable mangroves to keep pace with projected sea level rise. Therefore, mangrove management in Kenya and the Western Indian Ocean region should explore options that consider trade-offs between mangrove utilization and minimizing loss of ecosystem functioning such as coastal stabilization and protection. In addition initiatives such as the payment for ecosystem services (PES) schemes e.g. reducing emissions from deforestation and degradation (REDD+) and should be explored as some of the strategies to reverse the declining trend in mangrove forest cover.
5 citations
Cites background from "Impact of Sundarban mangrove biosph..."
...Dozens of studies have been published on the emission of GHGs from mangrove ecosystems (e.g. Mukhopadhyay et al., 2002; Lovelock, 2008; Poungparn et al., 2009), however only a few have attempted to study the effects of anthropogenic impacts on the emissions of these gases (e.g. Purvaja and Ramesh,…...
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References
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Book•
01 Jun 1996
TL;DR: The most comprehensive and up-to-date assessment available for scientific understanding of human influences on the past present and future climate is "Climate Change 1995: The Science of Climate Change" as mentioned in this paper.
Abstract: This extensive report entitled “Climate Change 1995: The Science of Climate Change” is the most comprehensive and up-to-date assessment available for scientific understanding of human influences on the past present and future climate. Its aim is to provide objective information on which to base global climate change that will ultimately meet the aim of the UN Framework Convention on Climate Change. The report includes an overview of the factors governing climate and climate change and quantification of the sources of globally important greenhouse gases and other pollutants arising from human activities. A review of the chemical and biological processes governing their removal from the atmosphere is presented. Also included is an assessment of recent trends in climate during the industrial era which has witnessed the ever-growing impact of human activities on the global environment. The strengths and weaknesses of various climate mathematical models used by researchers for understanding the past and present climate and for calculating possible future climates are assessed. Furthermore the report discusses research aimed at the detection of human influence on the climate of the last century and presents future change projections in global climate and sea level based on a range of scenarios of future emissions of pollutants due to human activity. Finally a list of research and observational priorities needed to improve scientific understanding in key areas is presented.
4,397 citations
TL;DR: In this paper, the influence of variability in wind speed on the calculated gas transfer velocities and the possibility of chemical enhancement of CO2 exchange at low wind speeds over the ocean is illustrated using a quadratic dependence of gas exchange on wind speed.
Abstract: Relationships between wind speed and gas transfer, combined with knowledge of the partial pressure difference of CO2 across the air-sea interface are frequently used to determine the CO2 flux between the ocean and the atmosphere. Little attention has been paid to the influence of variability in wind speed on the calculated gas transfer velocities and the possibility of chemical enhancement of CO2 exchange at low wind speeds over the ocean. The effect of these parameters is illustrated using a quadratic dependence of gas exchange on wind speed which is fit through gas transfer velocities over the ocean determined by the natural-14C disequilibrium and the bomb-14C inventory methods. Some of the variability between different data sets can be accounted for by the suggested mechanisms, but much of the variation appears due to other causes. Possible causes for the large difference between two frequently used relationships between gas transfer and wind speed are discussed. To determine fluxes of gases other than CO2 across the air-water interface, the relevant expressions for gas transfer, and the temperature and salinity dependence of the Schmidt number and solubility of several gases of environmental interest are included in an appendix.
4,187 citations
TL;DR: In this paper, the authors identify and evaluate several constraints on the budget of atmospheric methane, its sources, sinks and residence time, and construct a list of sources and sinks, identities, and sizes.
Abstract: Methane is the most abundant organic chemical in Earth's atmosphere, and its concentration is increasing with time, as a variety of independent measurements have shown. Photochemical reactions oxidize methane in the atmosphere; through these reactions, methane exerts strong influence over the chemistry of the troposphere and the stratosphere and many species including ozone, hydroxyl radicals, and carbon monoxide. Also, through its infrared absorption spectrum, methane is an important greenhouse gas in the climate system. We describe and enumerate key roles and reactions. Then we focus on two kinds of methane production: microbial and thermogenic. Microbial methanogenesis is described, and key organisms and substrates are identified along with their properties and habitats. Microbial methane oxidation limits the release of methane from certain methanogenic areas. Both aerobic and anaerobic oxidation are described here along with methods to measure rates of methane production and oxidation experimentally. Indicators of the origin of methane, including C and H isotopes, are reviewed. We identify and evaluate several constraints on the budget of atmospheric methane, its sources, sinks and residence time. From these constraints and other data on sources and sinks we construct a list of sources and sinks, identities, and sizes. The quasi-steady state (defined in the text) annual source (or sink) totals about 310(±60) × 1012 mol (500(±95) × 1012 g), but there are many remaining uncertainties in source and sink sizes and several types of data that could lead to stronger constraints and revised estimates in the future. It is particularly difficult to identify enough sources of radiocarbon-free methane.
1,513 citations
TL;DR: The terrestrial biosphere plays an important role in the global carbon cycle as mentioned in this paper, which is the fluxes of carbon among four main reservoirs: fossil carbon, the atmosphere, the oceans, and the terrestrial Biosphere.
Abstract: The terrestrial biosphere plays an important role in the global carbon cycle. In the 1994 Intergovernmental Panel Assessment on Climate Change (IPCC), an effort was made to improve the quantification of terrestrial exchanges and potential feedbacks from climate, changing CO2, and other factors; this paper presents the key results from that assessment, together with expanded discussion. The carbon cycle is the fluxes of carbon among four main reservoirs: fossil carbon, the atmosphere, the oceans, and the terrestrial biosphere. Emissions of fossil carbon during the 1980s averaged 5.5 Gt y−1. During the same period, the atmosphere gained 3.2 Gt C y−1 and the oceans are believed to have absorbed 2.0 Gt C y−1. The regrowing forests of the Northern Hemisphere may have absorbed 0.5 Gt C y−1 during this period. Meanwhile, tropical deforestation is thought to have released an average 1.6 Gt C y−1 over the 1980s. While the fluxes among the four pools should balance, the average 198Ds values lead to a ‘missing sink’ of 1.4 Gt C y−1 Several processes, including forest regrowth, CO2 fertilization of plant growth (c. 1.0 Gt C y−1), N deposition (c. 0.6 Gt C y−1), and their interactions, may account for the budget imbalance. However, it remains difficult to quantify the influences of these separate but interactive processes. Uncertainties in the individual numbers are large, and are themselves poorly quantified. This paper presents detail beyond the IPCC assessment on procedures used to approximate the flux uncertainties.
Lack of knowledge about positive and negative feedbacks from the biosphere is a major limiting factor to credible simulations of future atmospheric CO2 concentrations. Analyses of the atmospheric gradients of CO2 and 13 CO2 concentrations provide increasingly strong evidence for terrestrial sinks, potentially distributed between Northern Hemisphere and tropical regions, but conclusive detection in direct biomass and soil measurements remains elusive.
Current regional-to-global terrestrial ecosystem models with coupled carbon and nitrogen cycles represent the effects of CO2 fertilization differently, but all suggest longterm responses to CO2 that are substantially smaller than potential leaf- or laboratory whole plant-level responses. Analyses of emissions and biogeochemical fluxes consistent with eventual stabilization of atmospheric CO2 concentrations are sensitive to the way in which biospheric feedbacks are modeled by c. 15%. Decisions about land use can have effects of 100s of Gt C over the next few centuries, with similarly significant effects on the atmosphere.
Critical areas for future research are continued measurements and analyses of atmospheric data (CO2 and 13CO2) to serve as large-scale constraints, process studies of the scaling from the photosynthetic response to CO2 to whole-ecosystem carbon storage, and rigorous quantification of the effects of changing land use on carbon storage.
1,510 citations
TL;DR: An overview of micrometeorological theory and the different micromETeorological techniques available to make flux measurements is provided.
Abstract: Ecologists are expected to play an important role in future studies of the biosphere/atmosphere exchange of materials associated with the major biogeochemical cycles and climate. Most studies of material exchange reported in the ecological literature have relied on chamber techniques. Micrometeorological techniques provide an alternative means of measuring these exchange rates and are expected to be used more often in future ecological studies, since they have many advantages over the chamber techniques. In this article we will provide an overview of micrometeorological theory and the different micrometeorological techniques available to make flux measurements.
1,258 citations