Carbon Sequestration In Wetlands Research Articles

Wetland Landscape Dynamics and Multi-Functional Assessment of Wuhan City, China

Under the dual pressures of rapid urbanization and intensifying global climate change, China has proposed governance policies aimed at promoting ecological urban construction. Wetland landscapes play a key role in sustaining human and social well-being. As a significant city in the middle reaches of the Yangtze River, Wuhan’s wetland resources play an irreplaceable role in maintaining the regional ecological balance and promoting sustainable economic and social development. However, urbanization poses a severe challenge to the ecological service functions of wetlands. Consequently, in this study, we analyzed the spatial–temporal evolution patterns of the sub-functional systems of carbon sequestration, biodiversity conservation, water yield, and water purification in five wetland types in Wuhan City from 2000 to 2020 by using the CASA model and InVEST model. Then, a wetland multi-functional assessment framework was constructed to quantify the comprehensive multi-function score. It is imperative to unravel the underlying mechanisms driving the changes in wetland functions and to explore the equilibrium point between wetland conservation and urban sustainable development. Our results show that the wetland area of Wuhan City decreased from 5077.33 km2 in 2000 to 4696.60 km2 in 2020, and the wetland multi-functions exhibited significant spatial heterogeneity from 2000 to 2020. Wetland carbon sequestration increased from 0.94 Tg in 2000 to 1.11 Tg in 2020. The wetland habitat quality declined from 0.13 in 2000 to 0.11 in 2020. The water production of the wetlands increased from 5.43 × 109 t in 2000 to 22.59 × 109 t in 2020. The wetland N loss decreased from 55,850.58 t in 2000 to 49,209.93 t in 2020. The highest multi-function score was in paddy fields, which increased from 0.41 ± 0.12 to 0.51 ± 0.12, followed by tidal flats, which increased from 0.39 ± 0.14 to 0.50 ± 0.16, and the lowest was rivers, which also increased from 0.33 ± 0.12 to 0.41 ± 0.14. The multi-function score was closely related to the wetland type and urban development direction over the past two decades, and it was negatively correlated with production and living density, providing new ideas for wetland ecological protection and construction in Wuhan City.

Improving Carbon Sequestration in Wetlands Using Native Poplar Genotypes for Reforestation Purposes

From the early 2000s, many forestation projects were carried out in the flooding areas of the Po River to preserve abandoned or damaged riverbanks and establish natural populations of Populus nigra L. for species conservation and future seed collection activities. Different clones of P. nigra, belonging to a collection of the Centre for Forestry and Wood (CREA-FL), were planted. The group named ‘POBIA’ comprises 35 selected clones chosen for their survival ability and fast growth. After plantation and a few essential cultural inputs, four establishments were left undisturbed. This study highlights the survival, growth, and performance results of the ‘POBIA’ group compared to other not-selected clones. The ‘POBIA’ clones showed a higher survival than the not-selected clones. Moreover, the ‘POBIA’ groups showed a significantly higher C sink performance in three of four establishments, reaching 278.6 t ha−1 of CO2 obtained in thirteen years in one site. The management of ‘POBIA’ clones in reforestation projects agrees with the EU recommendations for a vital ecosystem service.

Microorganisms Directly Affected Sediment Carbon–Nitrogen Coupling in Two Constructed Wetlands

Clarifying the carbon–nitrogen coupling pattern in wetlands is crucial for understanding the driving mechanism of wetland carbon sequestration. However, the impacts of plants and environmental factors on the coupling of carbon–nitrogen in wetland sediments are still unclear. Sediment samples from plant (Typha angustifolia and Phragmites australis)-covered habitats and bare land were collected in two constructed wetlands in northern China. The contents of different forms of carbon and nitrogen in sediments and plants, and the sediment microbial community were detected. It was found that the sediment carbon to nitrogen (C/N) ratios did not differ significantly in the bare sites of different wetlands, but did in the plant-covered sites, which highlighted the different role of plants in shifting the carbon–nitrogen coupling in different constructed wetlands. The effects of plants on the sediment carbon–nitrogen coupling differed in two constructed wetlands, so the structural equation model was used and found that sediment microorganisms directly affected sediment C/N ratios, while water and sediment physicochemical properties indirectly affected sediment C/N ratios by altering sediment microbial functions. Multiple linear regression models showed that water pH, sediment moisture content, water dissolved oxygen, and water depth had a greater influence on the carbon metabolism potential of the sediment microbial community, while sediment moisture content had the greatest impact on the sediment microbial nitrogen metabolism potential. The study indicates that variations in environmental conditions could alter the influence of plants on the carbon and nitrogen cycles of wetland sediments. Water environmental factors mainly affect microbial carbon metabolism functions, while soil physicochemical factors, especially water content, affect microbial carbon and nitrogen metabolism functions.

Response Mechanism of cbbM Carbon Sequestration Microbial Community Characteristics in Different Wetland Types in Qinghai Lake.

Carbon-sequestering microorganisms play an important role in the carbon cycle of wetland ecosystems. However, the response mechanism of carbon-sequestering microbial communities to wetland type changes and their relationship with soil carbon remain unclear. To explore these differences and identify the main influencing factors, this study selected marsh wetlands, river wetlands and lakeside wetlands around Qinghai Lake as research subjects. High-throughput sequencing was employed to analyze the functional gene cbbM of carbon-sequestering microorganisms. The results revealed that the alpha diversity of cbbM carbon-sequestering microorganisms mirrored the trend in total carbon content, with the highest diversity observed in marsh wetlands and the lowest in lakeside wetlands. The dominant bacterial phylum was Proteobacteria, with prevalent genera including Thiothrix, Acidithiobacillus, and Thiodictyon. Acidithiobacillus served as a biomarker in lakeside wetlands, while two other genera were indicative of marsh wetlands. The hierarchical partitioning analysis indicated that the diversity of cbbM carbon-fixing microorganisms was primarily influenced by the total nitrogen content, while the community structure was significantly affected by the soil total carbon content. Moreover, an increased soil temperature and humidity were found to favor the carbon fixation processes of Thiomicrospira, Thiomonas, Polaromonas, and Acidithiobacillus. In summary, changes in wetland types seriously affected the characteristics of cbbM carbon sequestration in microbial communities, and a warm and humid climate may be conducive to wetland carbon sequestration.

Wetlands harbor lactic acid-driven chain elongators.

Wetlands are globally significant carbon cycling hotspots that both sequester large amounts of CO2 as soil carbon as well as emit a third of all CH4 globally. Their outsized role in the global carbon cycle makes it critical to understand microbial processes contributing to carbon breakdown and storage in these ecosystems. Here, we confirm the presence of chain-elongating organisms in freshwater wetland soils. These organisms take small carbon compounds formed during the breakdown of biomass and turn them into larger compounds (six to eight carbon organic acids) that may potentially contribute to the formation of soil organic matter and long-term carbon storage. Moreover, we find that these chain-elongating organisms may be widely distributed in wetlands globally. Future work should identify these organisms' contribution to carbon cycling in wetlands and the potential role of the products they form in carbon sequestration in wetlands.

Distribution and correlation of iron oxidizers and carbon-fixing microbial communities in natural wetlands

Most microaerophilic Fe(II)-oxidizing bacteria (mFeOB) belonging to the family Gallionellaceae are autotrophic microorganisms that can use inorganic carbon to drive carbon sequestration in wetlands. However, the relationship between microorganisms involved in Fe and C cycling is not well understood. Here, soil samples were collected from different wetlands to explore the distribution and correlation of Gallionella-related mFeOB and carbon-fixing microorganisms containing cbbL and cbbM genes. A significant positive correlation was found between the abundances of mFeOB and the cbbL gene, as well as a highly significant positive correlation between the abundances of mFeOB and the cbbM gene, indicating the distribution of mFeOB in co-occurrence with carbon-fixing microorganisms in wetlands. The mFeOB were mainly dominated by Sideroxydans lithotrophicus ES-1 and Gallionella capsiferriformans ES-2 in all wetland soils. The structures of the carbon-fixing microbial communities were similar in these wetlands, mainly consisting of Alphaproteobacteria, Betaproteobacteria, and Gammaproteobacteria. The extractable Fe(II) concentrations affected the community composition of mFeOB, resulting in a significant difference in the relative abundances of the dominant FeOB. The main factors affecting cbbL-related microbial communities were dissolved inorganic carbon and oxygen, soil redox potential, and sodium acetate-extracted Fe(II). The composition of cbbM-related microbial communities was mainly affected by acetate-extracted Fe(II) and soil redox potential. In addition, the positive correlation between these functional microorganisms suggests that they play a synergistic role in Fe(II) oxidation and carbon fixation in wetland soil ecosystems. Our results suggest a cryptic relationship between mFeOB and carbon-fixing microorganisms in wetlands and that the microbial community structure can be effectively altered by regulating their physicochemical properties, thus affecting the capacity of carbon sequestration.

Assessment of the impact of wetland changes on carbon storage in coastal urban agglomerations from 1990 to 2035 in support of SDG15.1

The quantitative assessment and spatial representation of wetland carbon storage, which play a critical role in the global carbon cycle and human production, can provide useful data and knowledge for decision-making in achieving sustainable development goals (SDGs). Currently, human activities and climate change impacts pose a challenge for the assessment of wetland carbon storage in coastal urban clusters. We proposed a “past-present-future” long time series refined wetland carbon storage assessment model using Guangxi Beibu Gulf (GBG) and Guangdong, Hong Kong, Macao and the Greater Bay Area (GBA) as the study area. The CLUE-S and InVEST models were coupled to conduct a comparative analysis of the spatial and temporal changes in wetland carbon storage and the spatial identification of damages from 1990 to 2035 and finally explore the sensitivity of wetland changes to carbon storage and quantitatively assess the SDG15.1 target. The results showed that (1) both urban clusters are characterized by many reservoirs/farming ponds, large river areas and few lakes. 1990–2035 rivers, shallow waters and mudflats have a decreasing trend to be distributed in the middle of their respective regions, mangroves are on an increasing trend, GBG is mainly distributed in the Maowei Sea and GBA is mainly distributed in Shenzhen Bay. (2) Wetland carbon storage of the two urban clusters show an overall fluctuating downward trend, with rivers, lakes and beaches all showing a downward trend. The multiyear average carbon storage of the GBG are 3.2 times higher than those of the GBA. In ecological protection scenario (EPS) policy planning, it is reasonable to help wetland carbon sequestration in coastal urban clusters. (3) The trend of wetland change from 1990 to 2020 was positive for carbon storage. The rate of recovery of wetland carbon stocks is lower in GBA than in GBG under the natural increase scenario (NIS) and the ecological protection scenario (EPS). The economic development scenario (EDS) contributes least to the realisation of SDG15.1 for the coastal urban agglomeration. The ecological protection scenario (EPS) contributes the most to the realisation of SDG15.1 for the coastal urban agglomeration.

Evolution Characteristics of Wetland Landscape Pattern and Its Impact on Carbon Sequestration in Wuhan from 2000 to 2020

The wetland ecosystem is an important organic carbon pool on earth, and rich carbon storage and high carbon density are present in wetland vegetation and soil. However, large areas of wetlands have been drained, the area of wetlands has shrunk, and the degree of fragmentation has intensified due to rapid urbanization in the past 20 years. Enhancing ecological carbon sequestration capacity is a key task of carbon peaking and neutrality, and studying the carbon sequestration function of urban wetland is urgently needed. In this work, the wetland in Wuhan was taken as the main research object. The landscape pattern index of Wuhan wetland was calculated and the evolution characteristics of landscape pattern were analyzed using the remote sensing image interpretation data from 2000 to 2020. CASA model was used to estimate the carbon sequestration of wetlands and explore the spatial and temporal distribution pattern of carbon sequestration. Spearman correlation was used to study the effects of different landscape pattern parameters on carbon sequestration. Results indicate the following: (1) From 2000 to 2020, the total wetland area in Wuhan has been reduced by 158.99 km2, among which the area of lakes, reservoirs and marshes decreased by 60.65 km2, 55.51 km2 and 41.77 km2, respectively. The density of wetland patches and the degree of fragmentation and irregularity increased, and the LPI, aggregation degree and diversity decreased. (2) In the past 20 years, the total carbon sequestration amount of wetland in Wuhan first decreased and then increased, among which the carbon sequestration in wetland was the lowest in 2010 (571,900 t). The amount of carbon sequestration in 2020 was the same as that in 2000, reaching 800,000 t. (3) A larger wetland area means more concentrated and denser distribution, more complex shape, more diverse type, and stronger carbon sequestration capacity for Wuhan wetland. On the contrary, the distribution of wetlands becomes more fragmented and regular, and the disordered planning leads to the reduction in wetland types in a unit area, which will decrease the carbon sink capacity of urban wetlands.

Aboveground biomass of marshes in Northeast China: Spatial pattern and annual changes responding to climate change

Examining vegetation aboveground biomass (AGB) changes is important to understanding wetland carbon sequestration. Here, we combined the field-measured AGB data (458 samples) from 2009 to 2021, moderate resolution imaging spectroradiometer reflectance products, and climatic data to reveal the AGB variations of marshes in Northeast China by comparing various models driven by different indicators. The results indicated that random forest model driven by six vegetation indices, land surface temperature, and land surface water index achieved accurate marsh AGB estimation with R2 being 0.78 and relative error being 16.71%. The mean marsh AGB in Northeast China from 2000 to 2021 was 682.89 ± 31.69 g·m−2, which generally increased from north to south in space. Temporally, annual marsh AGB declined slowly at a rate of 3.45 g·m−2·year−1 during the past 21 years driven mainly by the decrease in summer mean temperature that was characterized by a significantly positive correlation between them. Nevertheless, we highlighted that the temporal changes of marsh AGB spatially varied in response to inconsistent climate change, thus place-based measures are required for sustainable management of marshes.

Hydrologic-induced concentrated soil nutrients and improved plant growth increased carbon storage in a floodplain wetland over wet-dry alternating zones

Hydrological gradient variations in wetlands have a vital impact on wetland carbon storage. However, the mechanisms by which hydrological gradient variations affect biomass and carbon storage by regulating the soil nutrient contents and plant diversity remain unclear. This study attempted to explore these influencing mechanisms by studying the relationships between hydrological gradient variations and carbon storage in wetlands. The results showed that the average nutrient content, plant biomass and soil carbon content values in the high-frequency wet-dry alternating zones (HFWA, zones where the frequency of water level occurs between −25 cm and 25 cm greater than 0.5) were 1.4 times, 2.3 times and 0.43 higher, respectively, than those in the low-frequency wet-dry alternating zones (LFWA, zones where the frequency of water level occurs between −25 cm and 25 cm less than 0.3). These results indicated that the HFWA zones had higher soil nutrients, higher plant dominance, higher biomass and higher soil carbon contents than the LFWA zones. The structural equation model revealed a significant positive correlation between wet-dry alternations and the soil nutrient-plant biomass-soil carbon relation in wetlands. Moreover, there was also a significant positive correlation between wet-dry alternations and the plant dominance-plant biomass-soil carbon relation in wetlands. This implied that the concentrated effect of HFWA on soil nutrients promotes plant growth, enhances plant dominance, promotes plant productivity, and enhances the capacities of plants to input carbon to the soil, thereby increasing the soil carbon content. This study closely linked wetland hydrological gradients, plant biodiversity and wetland carbon sequestration and profoundly revealed the mechanisms by which hydrological gradients in wetlands regulate the concentrations of nutrient elements, thereby affecting vegetation growth and carbon sequestration; these results could provide a new cognitive basis for understanding the coupling of carbon and water.

The decomposition process and nutrient release of invasive plant litter regulated by nutrient enrichment and water level change.

Wetlands are vulnerable to plant invasions and the decomposition of invasive plant litter could make impacts on the ecosystem services of wetlands including nutrient cycle and carbon sequestration. However, few studies have explored the effects of nutrient enrichment and water level change on the decomposition of invasive plant litter. In this study, we conducted a control experiment using the litterbag method to compare the decomposition rates and nutrient release in the litter of an invasive plant Alternanthera philoxeroides in three water levels and two nutrient enrichment treatments. This study found that the water level change and nutrient enrichment showed significant effects on the litter decomposition and nutrient dynamic of A. philoxeroides. The increase of water level significantly reduced the decomposition rate and nutrient release of litter in the nutrient control treatment, whereas no clear relationship was observed in the nutrient enrichment treatment, indicating that the effect of water level change on litter decomposition might be affected by nutrient enrichment. At the late stage of decomposition, the increase of phosphorus (P) concentration and the decrease of the ratio of carbon to P suggested that the decomposition of invasive plant litter was limited by P. Our results suggest that controlling P enrichment in water bodies is essential for the management of invasive plant and carbon sequestration of wetlands. In addition, the new index we proposed could provide a basis for quantifying the impact of invasive plant litter decomposition on carbon cycle in wetlands.

Conceptual Model of Ecosystem Service Flows from Carbon Dioxide to Blue Carbon in Coastal Wetlands: An Empirical Study Based on Yancheng, China

Large amounts of blue carbon exist in the ecosystems of coastal wetlands. Accurate calculations of the stocks and economic value of blue carbon in various plant communities can facilitate vegetation rehabilitation. Based on this objective, first, a blue carbon estimation model was constructed by combining a Carnegie-Ames-Stanford Approach (CASA) model, and second, the distribution pattern of blue carbon and flow direction of ecosystem services (carbon sequestration) in a coastal wetland in China was analyzed utilizing a combination of field surveys, remote sensing data, and laboratory analysis techniques. Finally, the wetland carbon sequestration value and its income-expenditure status were measured using the carbon tax method. The results show that the aboveground net primary productivity of coastal wetland vegetation exhibits a non-zonal distribution in the south-north direction, whereas it presented a three-level gradient distribution, characterized as “low (200–300 g/m2∙y)–intermediate (300–400 g/m2∙y)–high (400–500 g/m2∙y)”, in the east-west direction. The accumulation of carbon gradually increased from the ground surface to the underground (litter < underground roots < soil) in Spartina alterniflora and Phragmites australis. On the type scale, Spartina alterniflora and Phragmites australis wetlands were of the “blue carbon” net outflow type (supply type), with mean annual outflow carbon sequestration values of 3272.3 $/ha and 40.9 $/ha, respectively. The Suaeda glauca wetland was of the “blue carbon” net inflow type (benefit type), with a mean annual inflow carbon sequestration value of 190.7 $/ha.

Vegetation Carbon Sequestration Mapping in Herbaceous Wetlands by Using a MODIS EVI Time-Series Data Set: A Case in Poyang Lake Wetland, China

The carbon sequestration capacity of wetland vegetation determines carbon stocks and changes in wetlands. However, modeling vegetation carbon sequestration of herbaceous wetlands is still problematic due to complex hydroecological processes and rapidly changing biomass carbon stocks. Theoretically, a vegetation index (VI) time series can retrieve the dynamic of biomass carbon stocks and could be used to calculate the cumulative composite of biomass carbon stocks during a given interval, i.e., vegetation carbon sequestration. Hence, we explored the potential for mapping vegetation carbon sequestration in herbaceous wetlands in this study by using a combination of remotely sensed VI time series and field observation data. This method was exemplarily applied for Poyang Lake wetland in 2016 by using a 16-day Moderate Resolution Imaging Spectroradiometer (MODIS) enhanced vegetation index (EVI) time series. Results show that the vegetation carbon sequestration in this area was in the range of 193–1221 g C m−2 year−1 with a mean of 401 g C m−2 year−1 and a standard deviation of 172 g C m−2 year−1 in 2016. The approach has wider spatial applicability in wetlands than the currently used global map of vegetation production (MOD17A3) because our carbon estimation in areas depicted by ‘no data’ in the MOD17A3 product is considerable, which accounts for 91.2–91.5% of the total vegetation carbon sequestration of the wetland. Thus, we determined that VI time series data shows great potential for estimating vegetation carbon sequestration in herbaceous wetlands, especially with the continuously improving quality and frequency of satellite VI images.

Carbon sequestration and storage in Norwegian Arctic coastal wetlands: Impacts of climate change

Coastal wetlands contain some of the largest stores of pedologic and biotic carbon pools, and climate change is likely to influence the ability of these ecosystems to sequester carbon. Recent studies have attempted to provide data on carbon sequestration in both temperate and tropical coastal wetlands. Alteration of Arctic wetland carbon sequestration rates is also likely where coastal forcing mechanisms interact directly with these coastal systems. At present there are no data available to provide a detailed understanding of present day and historical carbon sequestration rates within Arctic coastal wetlands.In order to address this knowledge gap, rates of carbon sequestration were assessed within five Arctic coastal wetland sites in Norway. This was undertaken using radiometric dating techniques (210Pb and 137Cs) to establish a geochronology for recent wetland development, and soil carbon stocks were estimated from cores.Average carbon sequestration rates were varied, both between sites and over time, ranging between 19 and 603 g C m2 y−1, and these were correlated with increases in the length of the growing season. Stocks ranged between 3.67 and 13.79 Mg C ha−1, which is very low compared with global average estimations for similar coastal systems, e.g. 250 Mg C ha−1 for temperate salt marshes, 280 Mg C ha−1 for mangroves, and 140 Mg C ha−1 for seagrasses. This is most likely due to isostatic uplift and sediment accretion historically outpacing sea level rise, which results in wetland progradation and thus a continuous formation of new marsh with thin organic soil horizons. However, with increasing rates of sea level rise it is uncertain whether this trend is set to continue or be reversed.

Reducing Emissions From Degraded Floodplain Wetlands

Freshwater wetlands are significant carbon sinks, however, altering a wetland’s hydrology can reduce its ability to sequester carbon and may lead to the release of previously stored soil carbon. Rehabilitating a wetland’s water table has the potential to restore the natural process of wetland soil carbon sequestration and storage. Further, little is known about the role of microbial communities that mediate carbon cycling during wetland rehabilitation practices. Here, we examined the carbon emissions and microbial community diversity during a wetland rehabilitation process known as ‘environmental watering’ (rewetting) in an Australian, semi-arid freshwater floodplain wetland. By monitoring carbon dioxide (CO2) and methane (CH4) emissions during dry and wet phases of an environmental watering event, we determined that adding water to a degraded semi-arid floodplain wetland reduces carbon emissions by 28-84%. The watering event increased anoxic levels and plant growth in the aquatic zone of the wetland, which may correlate with lower carbon emissions during and after environmental watering due to lower anaerobic microbial decomposition processes and higher CO2 sequestration by vegetation. During the watering event, areas with higher inundation had lower CO2 emissions (5.15 ± 2.50 g CO2 m-2 d-1) compared to fringe areas surrounding the wetland (11.89 ± 4.25 g CO2 m-2 d-1). CH4 flux was inversely correlated with CO2 emissions during inundation periods, showing a 38% (0.013 ± 0.061 g CO2-e m-2 d-1) increase when water was present in the wetland. During the dry phases of environmental watering, there was CH4 uptake within the fringe and aquatic zones (-0.013 ± 0.063 g CO2-e m-2 d-1). A clear succession of soil microbial community was observed during the dry-wet phases of the environmental watering process. This suggests that wetland hydrology plays a large role in the microbial community structure of these wetland ecosystems, and is consequently linked to CO2 and CH4 emissions. Overall, the total carbon emissions (CO2 + CH4) were reduced within the wetland during and after the environmental watering event, due to increasing vegetative growth and subsequent CO2 sequestration. We recommend environmental watering practices in this degraded arid wetland ecosystem to improve conditions for wetland carbon sequestration and storage.

Measurement and economic valuation of carbon sequestration in Nova Scotian wetlands

Carbon sequestration and methane flux in wetlands in Nova Scotia are measured. The social benefits associated with carbon storage are estimated using the net sequestration rate and estimates of the social cost of carbon from the Dynamic Integrated model of Climate and the Economy (DICE model). The net benefits of restoring wetlands in agricultural cropland are estimated based on these values and costs of restoration from the literature. The aim is to put a value on wetlands in Nova Scotia using original data rather than benefit transfers from other regions, thereby informing policy aimed at wetlands management in the region. Based on the results of this study, wetlands in Nova Scotia sequester 6.45 tCO2eha−1 yr−1 on average, and release 1.46 tCO2e ha−1 yr−1 as methane. The total benefits of carbon sequestration in wetlands in Nova Scotia are roughly $124–$373 ha−1 yr−1, and range from $5105 to $39,795 ha−1 in total. The social benefit of wetlands in terms of carbon sequestration is as high as $9.66 billion in Nova Scotia. Results indicate that protection of existing wetlands can be warranted on economic grounds. On average, it is not optimal to create wetlands for carbon sequestration, although it may be economically viable to target wetlands that are particularly productive in terms of storing CO2. It may also be viable to restore wetlands if ecosystem services are considered along with carbon sequestration.

Soil organic carbon pool and chemical composition under different types of land use in wetland: Implication for carbon sequestration in wetlands

This study was conducted to understand how different wetland vegetation-land use types influenced the storage and stability of soil organic carbon (SOC) in surface soils. We determined the concentration and chemical composition of SOC in both density (including light fraction organic carbon (LFOC) and heavy fraction organic carbon (HFOC)) and particle size fractions (including <2μm, 2-63μm, 63-200μm and 200-2000μm) in four wetland land use types covered with different vegetation: lake-sedge, reed, willow and poplar wetlands. Results showed that the concentrations and stock of SOC and LFOC in willow and poplar wetlands were significantly higher than those in lake-sedge and reed. However, a higher proportion of alkyl-C and a lower proportion of O-alkyl-C were observed in lake-sedge and reed wetlands than in willow and poplar, suggesting that accumulated C in willow and poplar wetlands was less stable than that in lake-sedge and reed. For all particle-size fractions except the silt (2-63μm), the SOC concentrations were highest in willow and lowest in reed wetland surface soils, while their alkyl-C/O-alkyl-C (A/O-A) and hydrophobic-C/hydrophilic-C ratios progressively decreased from lake-sedge and reed wetland surface soils to poplar and willow surface soils. Moreover, the ratios of A/O-A and hydrophobic-C/hydrophilic-C in surface soils generally decreased with increasing concentrations of SOC in particle-size fractions, with these stability indexes being lowest in the largest particle-size fraction. These results indicate that the wetland vegetation-land use types that could incorporate more C into finer particle-size fractions had a greater potential for sequestering more stable C in such wetland ecosystems. Different wetland vegetation-land use types resulted in significant changes in the concentration and chemical structure of SOC, which could affect soil C sequestration and dynamics, C cycling in wetland ecosystems. Although both willow and poplar forests could increase SOC stock, the stability of SOC in willow wetland was higher. Therefore, on balance (stock and stability) the land use of wetland for willow forest could be a more promising way for enhancing soil C sequestration in wetlands.

Heterogeneity of water quality signature and feedbacks to carbon sequestration in wetlands across some districts of West Bengal, India

Abstract Water quality measurements can indicate carbon status or algal biomass. Microalgae have an excellent ability to utilize all forms of dissolved inorganic carbon at different pH conditions. Water quality signature (WQS) using three different expressions with (i) pH; (ii) total alkalinity, hardness and total dissolved solids; and (iii) nitrate and conductivity of water was assessed in 32 wetlands distributed across 5 districts of West Bengal, India. Two zones were clearly discernible: coldwater (15–23 °C) high-altitude lakes in Darjeeling, and tropical (31–32 °C) low-altitude wetlands. Multivariate analysis of the Akaike information criterion (ACI) model revealed location-specific variability of agro-climatic and biogeochemical interactions. Dissolved inorganic carbon and inorganic nitrogen appeared to be important in regulating the phytocarbon content of microalgae. The wetlands located in the Gangetic alluvial tropical or semi-coastal areas (Hooghly, 24-Parganas, Nadia, Midnapore) were alkaline (pH = 7.52–7.97) where half-bound carbon dioxide comprised the major component (18–26%) of total inorganic carbon, with moderate to eutrophic (PO4-P− 0.16–0.23 mg/l) states which have a negative feedback to global warming. The heterogeneity of measured water quality signature consolidated the sanative nature of wetlands for their complex functional attributes with agro-climatic, biogeochemical and soil-water-biological interactions.

Carbon Sequestration Potential of Macrophytes and Seasonal Carbon Input Assessment into the Hokersar Wetland, Kashmir

Wetlands are the most effective terrestrial carbon sinks as their vegetation has high gross primary productivity. Species specific efficiency of wetland macrophytes for sequestering carbon, however, has not been studied well. This study highlights the carbon sequestration efficiency of twelve abundant macrophytes in Hokersar Wetland, Kashmir, India. The total dry biomass and the carbon (C) content were higher in post-summer than summer and winter seasons. In the selected macrophytes, C content was higher in the above-ground (AG) component than in the below-ground (BG) one. Among the twelve species studied, the C in the total dry biomass of Phragmites australis was highest followed by Sparganium erectum and Typha angustata. It was estimated that a total amount of carbon sequestered by twelve macrophytes was 0.85 Kg C m−2 yr.−1 of which marginal emergent macrophytes sequestered 0.73 Kg m−2 yr.−1, rooted floating types 0.08 Kg m−2 yr.−1 and submerged macrophytic species 0.042 Kg m−2 yr.−1 in Hokersar wetland ecosystem. This study will be helpful to refine our understanding about the role of macrophytes in carbon sequestration of wetlands and could also be explored in earning carbon credits in the global carbon market.

Operationalizing Blue Carbon in the Mission-Aransas National Estuarine Research Reserve, Texas

Recently, greater interest in the resilience of coastal habitat ecosystem services in the northern Gulf of Mexico has emerged due in part to an expansion of mangroves into areas previously dominated by salt marshes. To operationalize coastal wetland ecosystem services for decision-making, there is a need to clarify how salt marshes and mangroves function in this region. The goal of this research is to operationalize blue carbon (carbon stored in coastal habitats) within the Mission-Aransas National Estuarine Research Reserve, TX by documenting what we know about blue carbon within the study area, identifying data gaps and future research needs, and using available knowledge to inform management and decision-making within the Reserve. Our research shows that there is a lack of data within the Reserve on mangrove aboveground biomass, belowground biomass and soil carbon and on salt marsh soil carbon. There is also a dearth of information on wetland carbon sequestration and emission rates within the Reserve, making it challenging to inform management and develop a market for blue carbon.