scholarly journals Coastal morphology explains global blue carbon distributions

2018 ◽  
Author(s):  
Robert R Twilley ◽  
André S Rovai ◽  
Pablo Riul
Keyword(s):  
Ghg Emissions ◽  
Terrestrial Ecosystem ◽  
Global Scale ◽  
Blue Carbon ◽  
Mangrove Forests ◽  
Coastal Morphology ◽  
C Storage ◽  
C Cycle ◽  
C Stocks

Because mangroves store greater amounts of carbon (C) per area than any other terrestrial ecosystem, conservation of mangrove forests on a global scale represents a potentially meaningful strategy for mitigating atmospheric greenhouse‐gas (GHG) emissions. However, analyses of how coastal ecosystems influence the global C cycle also require the mapping of ecosystem area across the Earth's surface to estimate C storage and flux (movement) in order to compare how different ecosystem types may mitigate GHG enrichment in the atmosphere. In this paper, we propose a new framework based on diverse coastal morphology (that is, different coastal environmental settings resulting from how rivers, tides, waves, and climate have shaped coastal landforms) to explain global variations in mangrove C storage, using soil organic carbon (SOC) as a model to more accurately determine mangrove contributions to global C dynamics. We present, to the best of our knowledge, the first global mangrove area estimate occupying distinct coastal environmental settings, comparing the role of terrigenous and carbonate settings as global “blue carbon” hotspots. C storage in deltaic settings has been overestimated, while SOC stocks in carbonate settings have been underestimated by up to 50%. We encourage the scientific community, which has largely focused on blue carbon estimates, to incorporate coastal environmental settings into their evaluations of C stocks, to obtain more robust estimates of global C stocks.

scholarly journals The role of temperate treed swamps as a carbon sink in southwestern Nova Scotia

2021 ◽  
Vol 51 (1) ◽  
pp. 78-88
Author(s):  
Rachel A. Kendall ◽  
Karen A. Harper ◽  
David Burton ◽  
Kevin Hamdan
Keyword(s):  
Climate Change ◽  
Nova Scotia ◽  
Carbon Sink ◽  
Ghg Emissions ◽  
Forested Wetlands ◽  
C Sequestration ◽  
Soil C ◽  
C Storage ◽  
C Cycle

Forested wetlands may represent important ecosystems for mitigating climate change effects through carbon (C) sequestration because of their slow decomposition and C storage by trees. Despite this potential importance, few studies have acknowledged the role of temperate treed swamps in the C cycle. In southwestern Nova Scotia, Canada, we examined the role of treed swamps in the soil C cycle by determining C inputs through litterfall, assessing decomposition rates and soil C pools, and quantifying C outputs through soil greenhouse gas (GHG) emissions. The treed swamps were found to represent large supplies of C inputs through litterfall to the forest floor. The swamp soils had substantially greater C stores than the swamp–upland edge or upland soils. We found growing season C inputs via litterfall to exceed C outputs via GHG emissions in the swamps by a factor of about 2.5. Our findings indicate that temperate treed swamps can remain a C sink even if soil GHG emissions were to double, supporting conservation efforts to preserve temperate treed swamps as a measure to mitigate climate change.

scholarly journals The role of soil in regulation of climate

2021 ◽  
Vol 376 (1834) ◽  
pp. 20210084 ◽  
Author(s):  
Rattan Lal ◽  
Curtis Monger ◽  
Luke Nave ◽  
Pete Smith
Keyword(s):  
Land Use ◽  
Management Practices ◽  
Ghg Emissions ◽  
Organic C ◽  
Soil C ◽  
C Cycle ◽  
C Stocks ◽  
C Stock ◽  
Land Use And Management

The soil carbon (C) stock, comprising soil organic C (SOC) and soil inorganic C (SIC) and being the largest reservoir of the terrestrial biosphere, is a critical part of the global C cycle. Soil has been a source of greenhouse gases (GHGs) since the dawn of settled agriculture about 10 millenia ago. Soils of agricultural ecosystems are depleted of their SOC stocks and the magnitude of depletion is greater in those prone to accelerated erosion by water and wind and other degradation processes. Adoption of judicious land use and science-based management practices can lead to re-carbonization of depleted soils and make them a sink for atmospheric C. Soils in humid climates have potential to increase storage of SOC and those in arid and semiarid climates have potential to store both SOC and SIC. Payments to land managers for sequestration of C in soil, based on credible measurement of changes in soil C stocks at farm or landscape levels, are also important for promoting adoption of recommended land use and management practices. In conjunction with a rapid and aggressive reduction in GHG emissions across all sectors of the economy, sequestration of C in soil (and vegetation) can be an important negative emissions method for limiting global warming to 1.5 or 2°C This article is part of the theme issue ‘The role of soils in delivering Nature's Contributions to People’.

scholarly journals Carbon dioxide and methane fluxes at the air–sea interface of Red Sea mangroves

2018 ◽  
Vol 15 (17) ◽  
pp. 5365-5375 ◽  
Author(s):  
Mallory A. Sea ◽  
Neus Garcias-Bonet ◽  
Vincent Saderne ◽  
Carlos M. Duarte
Keyword(s):  
Carbon Dioxide ◽  
Organic Matter ◽  
Red Sea ◽  
Ghg Emissions ◽  
Eastern Coast ◽  
Relative Role ◽  
Emission Rates ◽  
Mangrove Forests ◽  
Ch4 Production

Abstract. Mangrove forests are highly productive tropical and subtropical coastal systems that provide a variety of ecosystem services, including the sequestration of carbon. While mangroves are reported to be the most intense carbon sinks among all forests, they can also support large emissions of greenhouse gases (GHGs), such as carbon dioxide (CO2) and methane (CH4), to the atmosphere. However, data derived from arid mangrove systems like the Red Sea are lacking. Here, we report net emission rates of CO2 and CH4 from mangroves along the eastern coast of the Red Sea and assess the relative role of these two gases in supporting total GHG emissions to the atmosphere. Diel CO2 and CH4 emission rates ranged from −3452 to 7500 µmol CO2 m−2 d−1 and from 0.9 to 13.3 µmol CH4 m−2 d−1 respectively. The rates reported here fall within previously reported ranges for both CO2 and CH4, but maximum CO2 and CH4 flux rates in the Red Sea are 10- to 100-fold below those previously reported for mangroves elsewhere. Based on the isotopic composition of the CO2 and CH4 produced, we identified potential origins of the organic matter that support GHG emissions. In all but one mangrove stand, GHG emissions appear to be supported by organic matter from mixed sources, potentially reducing CO2 fluxes and instead enhancing CH4 production, a finding that highlights the importance of determining the origin of organic matter in GHG emissions. Methane was the main source of CO2 equivalents despite the comparatively low emission rates in most of the sampled mangroves and therefore deserves careful monitoring in this region. By further resolving GHG fluxes in arid mangroves, we will better ascertain the role of these forests in global carbon budgets.

scholarly journals Optimal soil carbon sampling designs to achieve cost-effectiveness: a case study in blue carbon ecosystems

2018 ◽  
Vol 14 (9) ◽  
pp. 20180416 ◽  
Author(s):  
Mary A. Young ◽  
Peter I. Macreadie ◽  
Clare Duncan ◽  
Paul E. Carnell ◽  
Emily Nicholson ◽  
...  
Keyword(s):  
Soil Depth ◽  
Linear Equations ◽  
Cost Effective ◽  
Blue Carbon ◽  
Climate Mitigation ◽  
Sampling Effort ◽  
Natural Ecosystems ◽  
Soil C ◽  
C Storage ◽  
C Stocks

Researchers are increasingly studying carbon (C) storage by natural ecosystems for climate mitigation, including coastal ‘blue carbon’ ecosystems. Unfortunately, little guidance on how to achieve robust, cost-effective estimates of blue C stocks to inform inventories exists. We use existing data (492 cores) to develop recommendations on the sampling effort required to achieve robust estimates of blue C. Using a broad-scale, spatially explicit dataset from Victoria, Australia, we applied multiple spatial methods to provide guidelines for reducing variability in estimates of soil C stocks over large areas. With a separate dataset collected across Australia, we evaluated how many samples are needed to capture variability within soil cores and the best methods for extrapolating C to 1 m soil depth. We found that 40 core samples are optimal for capturing C variance across 1000's of kilometres but higher density sampling is required across finer scales (100–200 km). Accounting for environmental variation can further decrease required sampling. The within core analyses showed that nine samples within a core capture the majority of the variability and log-linear equations can accurately extrapolate C. These recommendations can help develop standardized methods for sampling programmes to quantify soil C stocks at national scales.

scholarly journals Carbon Dioxide and Methane Emissions from Red Sea Mangrove Sediments

2018 ◽  
Author(s):  
Mallory A. Sea ◽  
Neus Garcias-Bonet ◽  
Vincent Saderne ◽  
Carlos M. Duarte
Keyword(s):  
Carbon Dioxide ◽  
Organic Matter ◽  
Red Sea ◽  
Ghg Emissions ◽  
Relative Role ◽  
Emission Rates ◽  
Mangrove Forests ◽  
Carbon Sinks ◽  
Mangrove Sediments

Abstract. Mangrove forests are highly productive tropical and subtropical coastal systems that provide a variety of ecosystem services, including the sequestration of carbon. While mangroves are reported to be the most intense carbon sinks among all forests, their sediments can also support large emissions of greenhouse gases (GHG), such as carbon dioxide (CO2) and methane (CH4), to the atmosphere. However, data derived from arid mangrove systems like the Red Sea are lacking. Here, we report emission rates of CO2 and CH4 from mangrove sediments along the Saudi Arabian coast of the Red Sea, and assess the relative role of these two gases in supporting total GHG emissions. Diel CO2 and CH4 emission rates in Red Sea mangrove sediments ranged from −3452 to 7500 µmol CO2 m−2 d−1 and from 0.9 to 13.3 µmol CH4 m−2 d−1, respectively. The rates reported here fall within previously reported ranges for both CO2 and CH4, but maximum CO2 and CH4 flux rates in the Red Sea are 10 to 100-fold below those previously reported for mangroves elsewhere. Based on the isotopic composition of the CO2 and CH4 produced by mangrove sediments, we identified the origin of the organic matter that supports GHG emissions. In most of the mangrove stands, GHG emissions were supported by organic matter from mixed sources while only in one mangrove stand the GHG emissions were supported by organic matter derived from mangrove tissues. Moreover, the organic matter derived from mangrove tissues reduced CO2 fluxes and enhanced CH4 production, pointing out the importance of the origin of the organic matter in GHG emissions. Methane was the main source of CO2-equivalents, despite the comparatively low emission rates, in most of the sampled mangroves, and therefore deserves careful monitoring in this region. Despite the mean net emission of CO2 and CH4 by Red Sea mangroves reported here, these forests become net organic carbon sinks when taking into account the existing carbon burial rates for the Red Sea mangroves. By further resolving GHG fluxes in arid mangroves, we will better ascertain the role of these forests in global carbon budgets.

scholarly journals Changes in productivity and carbon storage of grasslands in China under future global warming scenarios of 1.5°C and 2°C

2019 ◽  
Vol 12 (5) ◽  
pp. 804-814 ◽  
Author(s):  
Zhaoqi Wang ◽  
Jinfeng Chang ◽  
Shushi Peng ◽  
Shilong Piao ◽  
Philippe Ciais ◽  
...  
Keyword(s):  
Global Warming ◽  
Coupled Model ◽  
Terrestrial Ecosystem ◽  
Earth System ◽  
Sea Ice Concentration ◽  
Terrestrial Ecosystem Model ◽  
C Storage ◽  
C Cycle ◽  
Future Global Warming ◽  
The Mean

Abstract Aims The impacts of future global warming of 1.5°C and 2°C on the productivity and carbon (C) storage of grasslands in China are not clear yet, although grasslands in China support ~45 million agricultural populations and more than 238 million livestock populations, and are sensitive to global warming. Methods This study used a process-based terrestrial ecosystem model named ORCHIDEE to simulate C cycle of alpine meadows and temperate grasslands in China. This model was driven by high-resolution (0.5° × 0.5°) climate of global specific warming levels (SWL) of 1.5°C and 2°C (warmer than pre-industrial level), which is downscaled by EC-EARTH3-HR v3.1 with sea surface temperature and sea-ice concentration as boundary conditions from IPSL-CM5-LR (low spatial resolution, 2.5° × 1.5°) Earth system model (ESM). Important Findings Compared with baseline (1971–2005), the mean annual air temperature over Chinese grasslands increased by 2.5°C and 3.7°C under SWL1.5 and SWL2, respectively. The increase in temperature in the alpine meadow was higher than that in the temperate grassland under both SWL1.5 and SWL2. Precipitation was also shown an increasing trend under SWL2 over most of the Chinese grasslands. Strong increases in gross primary productivity (GPP) were simulated in the Chinese grasslands, and the mean annual GPP (GPPMA) increased by 19.32% and 43.62% under SWL1.5 and SWL2, respectively. The C storage increased by 0.64 Pg C and 1.37 Pg C under SWL1.5 and SWL2 for 50 years simulations. The GPPMA was 0.670.390.88 (0.82) (model meanminmax (this study)), 0.850.451.24 (0.97) and 0.940.611.30 (1.17) Pg C year−1 under baseline, SWL1.5 and SWL2 modeled by four CMIP5 ESMs (phase 5 of the Coupled Model Inter-comparison Project Earth System Models). In contrast, the mean annual net biome productivity was −18.55−40.374.47 (−3.61),18.65−2.0364.03 (10.29) and 24.158.3838.77 (24.93) Tg C year−1 under baseline, SWL1.5 and SWL2 modeled by the four CMIP5 ESMs. Our results indicated that the Chinese grasslands would have higher productivity than the baseline and can mitigate climate change through increased C sequestration under future global warming of 1.5°C and 2°C with the increase of precipitation and the global increase of atmospheric CO2 concentration.

scholarly journals Modelling microbial exchanges between forms of soil nitrogen in contrasting ecosystems

2014 ◽  
Vol 11 (4) ◽  
pp. 915-927 ◽  
Author(s):  
M. Pansu ◽  
D. Machado ◽  
P. Bottner ◽  
L. Sarmiento
Keyword(s):  
Organic Molecules ◽  
Dynamic Models ◽  
Global Scale ◽  
Plant Materials ◽  
C Storage ◽  
Exchange Processes ◽  
C Cycle ◽  
Plant Photosynthesis ◽  
C And N ◽  
A Chain

Abstract. Although nitrogen (N) is often combined with carbon (C) in organic molecules, C passes from the air to the soil through plant photosynthesis, whereas N passes from the soil to plants through a chain of microbial conversions. However, dynamic models do not fully consider the microorganisms at the centre of exchange processes between organic and mineral forms of N. This study monitored the transfer of 14C and 15N between plant materials, microorganisms, humified compartments, and inorganic forms in six very different ecosystems along an altitudinal transect. The microbial conversions of the 15N forms appear to be strongly linked to the previously modelled C cycle, and the same equations and parameters can be used to model both C and N cycles. The only difference is in the modelling of the flows between microbial and inorganic forms. The processes of mineralization and immobilization of N appear to be regulated by a two-way microbial exchange depending on the C : N ratios of microorganisms and available substrates. The MOMOS (Modelling of Organic Matter of Soils) model has already been validated for the C cycle and also appears to be valid for the prediction of microbial transformations of N forms. This study shows that the hypothesis of microbial homeostasis can give robust predictions at global scale. However, the microbial populations did not appear to always be independent of the external constraints. At some altitudes their C : N ratio could be better modelled as decreasing during incubation and increasing with increasing C storage in cold conditions. The ratio of potentially mineralizable-15N/inorganic-15N and the 15N stock in the plant debris and the microorganisms was modelled as increasing with altitude, whereas the 15N storage in stable humus was modelled as decreasing with altitude. This predicts that there is a risk that mineralization of organic reserves in cold areas may increase global warming.

scholarly journals Scotland's forgotten carbon: a national assessment of mid-latitude fjord sedimentary carbon stocks

2017 ◽  
Vol 14 (24) ◽  
pp. 5663-5674 ◽  
Author(s):  
Craig Smeaton ◽  
William E. N. Austin ◽  
Althea L. Davies ◽  
Agnes Baltzer ◽  
John A. Howe ◽  
...  
Keyword(s):  
Natural Capital ◽  
National Assessment ◽  
Long Term Storage ◽  
Climate Regulation ◽  
Coastal Marine ◽  
C Cycle ◽  
C Stocks ◽  
The Individual

Abstract. Fjords are recognised as hotspots for the burial and long-term storage of carbon (C) and potentially provide a significant climate regulation service over multiple timescales. Understanding the magnitude of marine sedimentary C stores and the processes which govern their development is fundamental to understanding the role of the coastal ocean in the global C cycle. In this study, we use the mid-latitude fjords of Scotland as a natural laboratory to further develop methods to quantify these marine sedimentary C stores on both the individual fjord and national scale. Targeted geophysical and geochemical analysis has allowed the quantification of sedimentary C stocks for a number of mid-latitude fjords and, coupled with upscaling techniques based on fjord classification, has generated the first full national sedimentary C inventory for a fjordic system. The sediments within these mid-latitude fjords hold 640.7 ± 46 Mt of C split between 295.6 ± 52 and 345.1 ± 39 Mt of organic and inorganic C, respectively. When compared, these marine mid-latitude sedimentary C stores are of similar magnitude to their terrestrial equivalents, with the exception of the Scottish peatlands, which hold significantly more C. However, when area-normalised comparisons are made, these mid-latitude fjords are significantly more effective as C stores than their terrestrial counterparts, including Scottish peatlands. The C held within Scotland's coastal marine sediments has been largely overlooked as a significant component of the nation's natural capital; such coastal C stores are likely to be key to understanding and constraining improved global C budgets.

scholarly journals EMISIÓN DE METANO Y ÓXIDO NITROSO DE LOS SEDIMENTOS DE MANGLAR DE LA CIÉNAGA GRANDE DE SANTA MARTA, CARIBE COLOMBIANO

2016 ◽  
Vol 42 (1) ◽  
Author(s):  
Julián Mauricio Betancourt Portela ◽  
Juan Pablo Parra ◽  
Carlos Villamil
Keyword(s):  
Ghg Emissions ◽  
N2o Emissions ◽  
Mangrove Forests ◽  
Agricultural Systems ◽  
Release Rates ◽  
Mangrove Sediments ◽  
Ch4 And N2o ◽  
Magdalena River ◽  
Global Carbon

In Colombia there is little information on the role of mangroves in relation to greenhouse gases (GHG), their release rates under different environmental conditions, or their role in the global carbon cycle. For these reasons, in this study we evaluated the fluxes of CH4 and N2O, in four sectors of the Ciénaga Grande de Santa Marta (CGSM) with different degrees of conservation of mangrove forests, to determine their role as a source or sink of GHG. The fluxes were measured by the method of the static chambers and showed variations between 34.7-1179.7 and nd-31569.2 μg.m-2.h-1 for N2O and CH4, respectively, showing that mangrove sediments of CGSM are a net source of GHG, and furthermore are of the same magnitude as levels recorded world-wide in mangroves subjected to sewage input. Statistical analyses showed differences between sectors but not between climatic periods. N2O emissions were highest in the Agua Negras station (AN, 847.3 ± 265.7 μg.m-2.h-1), a locality in the process of natural regeneration with a direct influence from the Magdalena River and in Caño Dragado (CD, 438.7 ± 235.3 μg.m-2.h-1); while emissions were lower in the recovery sites Caño Grande (CG) and Rinconada (RIN), (104.7 ± 49.4 and 152.1 ± 36.0 μg.m-2.h-1, respectively). The highest CH4 emission was recorded in recovery sectors: CG and AN (9573.4 ± 8623.8 and 4328.2 ± 7569.5 μg.m-2.h-1, respectively). In terms of CO2-equivalent, N2O emissions account for over 50% of the total, and this has been documented for agricultural systems and constitutes evidence of deterioration of CD. A correlation analysis with environmental factors showed that N2O emissions vary inversely with salinity and positively with nitrites, suggesting production mainly via nitrification. Finally, a coarse estimation of GHG emissions per hectare indicated that, depending on the state of conservation or deterioration of the mangrove, emissions can vary from 10.2 to 27.1 tCO2-eq.ha-1.a-1.

scholarly journals Simultaneous high C fixation and high C emissions in <i>Sphagnum</i> mires

2015 ◽  
Vol 12 (15) ◽  
pp. 4739-4749 ◽  
Author(s):  
S. F. Harpenslager ◽  
G. van Dijk ◽  
S. Kosten ◽  
J. G. M. Roelofs ◽  
A. J. P. Smolders ◽  
...  
Keyword(s):  
C Sequestration ◽  
Water Infiltration ◽  
C Storage ◽  
Chemical Release ◽  
C Dynamics ◽  
C Cycle ◽  
C Stocks ◽  
Recalcitrant Organic Matter ◽  
Bare Peat ◽  
Floating Peat

Abstract. Peatlands play an important role in the global carbon (C) cycle due to their large C storage potential. Their C sequestration rates, however, highly vary depending on climatic and geohydrological conditions. Transitional mires are often characterised by floating peat with infiltration of buffered groundwater or surface water. Sphagnum mosses grow on top, producing recalcitrant organic matter and fuelling large C stocks. As Sphagnum species strongly differ in their tolerance to the higher pH in these mires, their species composition can be expected to influence C dynamics in transitional mires. We therefore experimentally determined growth and net C sequestration rates for four different Sphagnum species (Sphagnum squarrosum, S. palustre, S. fallax and S. magellanicum) in aquaria, with floating peat influenced by the infiltration of buffered water. Surprisingly, even though the first three species increased their biomass, the moss-covered peat still showed a net efflux of CO2 that was up to 3 times higher than that of bare peat. This species-dependent C release could be explained by Sphagnum's active lowering of the pH, which triggers the chemical release of CO2 from bicarbonate. Our results clearly illustrate that high Sphagnum biomass production may still coincide with high C emission. These counterintuitive C dynamics in mire succession seem to be the result of both species- and biomass-dependent acidification and buffered water infiltration. Together, these processes can explain part of the large variation in C fluxes (ranging from C sequestration to C release) reported for pristine mires in the literature.

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