Carbon Accumulation Rates Research Articles

Net primary productivity of paleo-peatlands linked to deep-time glacial periods in the late Carboniferous and early Permian icehouse interval

Peatlands, an important organic carbon reservoir, play a crucial role in the global carbon cycle. The carbon accumulation of peatlands, reflected by net primary productivity (NPP), can have an impact on global carbon cycling and climate change. The late Carboniferous - early Permian is an icehouse period, during which numerous thick coal beds were accumulated in the North China Block (NCB) located within a low-latitude area, providing an opportunity for studying the carbon cycling under the glacial and interglacial climates. In this study, spectral analysis was performed on the natural gamma-ray (GR) logs of the Benxi, Taiyuan and Shanxi formations of the late Carboniferous to early Permian in a borehole section located within the Ordos Basin in western NCB. Cyclic signals related to astronomical orbital parameters were identified, including long eccentricity (~405 kyr), short eccentricity (~125 kyr and ~ 95 kyr), and obliquity (~35.5kyr). A floating astronomical time scale was established by using the long eccentricity signal, and this time scale was further used to constrain the durations of the accumulation of coal-forming paleo-peatlands. The paleo-peatland for the C8 + 9 coal seam (9 m thick) of the Taiyuan Formation lasted approximately 203 kyr, and the paleo-peatland for the C5 coal seam (4 m thick) of the Shanxi Formation lasted approximately 46 kyr. Using this timeframe and an estimation of carbon loss during coalification, the carbon accumulation rates of the late Carboniferous - early Permian low-latitude peatlands are calculated to be 104.7 ± 14.9 g·C·m−2·a−1for the C8+9 coal seam and 192.6 ± 11.6 g·C·m−2·a−1for the C5 coal seam. The NPP of the paleo-peatlands, which deducts a part of carbon loss caused by the loss of CO2 and CH4, can be calculated from the carbon accumulation rates. The calculated average NPP of the paleo-peatlands for the C8+9 seam was 199 ± 28 g·C·m−2·a−1, and that of the C5 seam was 366 ± 22 g·C·m−2·a−1. In combination of the absolute time scale calibrated by high-precision UPb dates from Palougou section in western NCB, the depositional time of the investigated strata was constrained to be from 300.1 ± 0.5 Ma to 294.3 ± 0.5 Ma. The coal seams of the late Carboniferous to early Permian in the NCB corresponds to interglacial interval around ~298 Ma. The peatland with a lower NPP corresponds to the warming stage and the peatland with a higher NPP corresponds to the cooling stage. This implies that a lower NPP of paleo-peatland tend to be less efficient in carbon storage, and could not reduce the atmospheric CO2 substantially. In contrast, a higher NPP of paleo-peatland tend to accelerate carbon fixation, leading to temperature decrease and the termination of interglacial interval in early Permian. The results of this study could provide insights into the relationship between the development of paleo-peatlands and the record of the paleoclimates during the same period, and could be helpful for the prediction of future climate change.

Carbon sequestration in a typical mountain lake associated with earthquakes, floods, droughts, and human activities in southern Altay during the late Holocene

Lakes, being key regulators of atmospheric carbon dioxide (CO2), have not yet been intensively explored in the carbon cycle. This study provides an attempt to investigate how carbon sequestration in mountain lakes responds to seismic activities, extreme climate events and human disturbance. The new data of grain-size end members (EMs), TN contents, C/N, concentrations of algal spores, and P and Mn contents, in addition to previously published data of TOC and Ca contents, Zr/Rb, Rb/Sr, and land-pollen assemblages of a well-dated sediment core from Yileimu Lake, depicted a more detailed history of environmental evolution in the region. A great earthquake happened in southern Altay at ∼ 3500 cal yr BP that triggered extensive landslides around the lake, and then frequent floods eroded the catchment between ∼ 3500 and 2300 cal yr BP, subsequently severe drought events occurred within the period of 2300–1000 cal yr BP, finally agricultural and pastoral activities intensified within the last 1000 yrs. Organic carbon accumulation rate (OCAR) in Yileimu Lake was extremely high (an underestimated value of ∼ 370 g m–2 yr–1) during the earthquake event, in response to the rapid accumulation of landslide materials. Regional comparison revealed that summer temperature was unexpected to have determined the OCAR during both flood and drought events (average 4.07 and 3.64 g m–2 yr–1, respectively), because it dominated the production of land- and aquatic plants. Human activities increased the OCAR prominently (averages 6.26 g m–2 yr–1) via changing sediment production and vegetation planting, which decoupled the OCAR from climate factors. These data imply that carbon sequestration in lakes from mountain areas where temperature adversity stress dominated vegetation growth would have the potential to increase under anthropogenic warming. In addition, seismically induced carbon sequestration in lakes from tectonically active regions cannot be ignored.

Environmental changes and human impacts over the past 1200 years: Evidence from high-resolution pollen records from peat in the Yunnan-Guizhou Plateau, Southwest China

Over the past millennium, the understanding of vegetation and climate changes in mountainous regions, driven by both natural and anthropogenic forces, remains unclear. In this study, we provide a high-resolution vegetation record spanning the past 1200 years from a subalpine peatland in the Niangniang Mountains, southwestern China. By analyzing pollen, charcoal, and loss-on-ignition from the peat sediment, we elucidate the interactions between vegetation, fire, and human impact. Our findings reveal that before 1150 CE, the mountains were covered with dense broadleaf forests and experienced minimal human activity. Natural forcings, primarily climatic conditions, drove vegetation succession and forest fires. After 1150 CE, the Human Influence Index (HII) increased sharply, coinciding with a rise in cereal-type pollen. Significant agricultural activities in the southwestern mountainous regions of China began after 1150 CE, which is later than those in the low-altitude lake basins of southwestern China. During the Medieval Climate Anomaly (MCA, 836–1400 CE), the Niangniang Mountains were characterized by warm and humid climatic conditions, a stable forested landscape, and a high peat carbon accumulation rate. Although human activities increased markedly during this period, the arbors did not undergo notable changes, and climate forcings continued to have a greater impact on vegetation than anthropogenic forcings. During the Little Ice Age (LIA, 1400–1900 CE), the regional vegetation landscape transitioned from dense forests to open grasslands as climate conditions became cold and dry, reducing peat carbon accumulation rate. This period also saw increased forest fires and significant human-driven deforestation, with anthropogenic forcings becoming dominant. After 1900 CE, vegetation changes were increasingly influenced by government policies. Comparison with major climate forcings and spectrum analysis have shown that variations in monsoon intensity, regulated by solar and volcanic activity, have influenced the climate and peat depositional environment in the Niangniang Mountains. Our research offers meaningful insights into forest conservation in the mountainous regions of the Yunnan-Guizhou Plateau.

CARBON SEQUESTRATION IN A KARST MIRE OF THE MORDOVIAN RESERVE DURING THE LATE HOLOCENE

The article presents the results of the study of carbon accumulation over the past 3000 years in the Stol-bovoye karst mire located within the Smidovich Mordovian State Nature Reserve on the southern border of the coniferous-deciduous forests of the East European Plain. Minerothrophic (sedge, wood-sedge, grass) and mesotrophic (Sphagnum, grass-Sphagnum, sedge-Sphagnum, cotton grass) types of peat are present in the peat deposits of the Stolbovoye mire. The mire is at the mesotrophic stage of development. The content of organic carbon varies from 37,2 to 53,4% (49,7% on average). The nitrogen content in peat shows significantly higher variations along the core compared to organic carbon, i. e. from 1,1 to 2,6% (the average value is 1,9%). The total carbon pool in the Stolbovoye mire is about 6,7 kg/m2. The data obtained showed that a fast-growing peatland is capable to sequester large amounts of atmospheric carbon. The carbon accumulation rate in the studied peatland varies from 32,0 to 158,4 g C/m2/yr, with an average of 68,9 g C/m2/yr, which is significantly higher than the average carbon accumulation rates in different types of peatlands during the Holocene. A relationship between carbon accumulation rate and climatic changes over the past 3000 years was not revealed. A significant increase in the rate of carbon accumulation at a depth of 60 cm (480 cal. years BP) could be associated with the high productivity of vascular plants even at higher levels of mineralization/humification of their residues.

Blue Carbon Assessment in the Salt Marshes of the Venice Lagoon: Dimensions, Variability and Influence of Storm‐Surge Regulation

AbstractSalt marshes are intertidal coastal ecosystems shaped by complex feedbacks between hydrodynamic, morphological, and biological processes. These crucial yet endangered environments provide a diverse range of ecosystem services but are globally subjected to high anthropogenic pressures, while being severely exposed to climate change impacts. The importance of salt marshes as “blue carbon” sinks, deriving from their primary production coupled with rapid surface accretion, has been increasingly recognized within the framework of climate mitigation strategies. However, large uncertainties remain in salt marsh carbon stock and sequestration estimation. In order to provide further knowledge in salt marsh carbon assessment and investigate marsh carbon pool response to management actions, we analyzed organic matter content in salt marsh soils of the Venice Lagoon (Italy) from 60 sediment cores to the depth of 1 m and estimated organic carbon stock and accumulation rates in different areas. Organic carbon stocks and accumulation rates were highly variable in different marshes, being affected by organic and inorganic inputs and preservation conditions. Our estimates suggest that the studied marshes store 17,108 ± 5,757 tons of carbon per square kilometer in top 1‐m of soil and can accumulate 85 ± 25 tons of carbon per square kilometer per year. However, flood regulation may reduce the annual marsh CO2 sequestration potential by more than 30%. Our results contribute valuable information for regional carbon assessments, reinforcing the need for integrated coastal management policies to preserve the ecosystem services of coastal environments, and underscore the importance of considering local variability and methodological variations.

Soil Formation on Loamy Deposits in Technogenic Landscapes of the Taiga Zone in the North-Eastern Part of European Russia

The paper highlights the influence of moisture on the soil formation process on loamy deposits during the primary vegetation succession. The study was carried out in the north-eastern part of European Russia (Komi Republic) in the middle taiga subzone. The authors analyzed young soils on the territory of a quarry for extraction of loamy grounds and background soils in the vicinity of it. Planting the Siberian spruce cultures on the territory of the quarry activated formation of the tree layer and thereby accelerated formation of the zonal type soils. The third succession decade in drained conditions saw formation of organic soil horizons (litters), a decrease in soil density in the upper profile part, a tendency to redistribute and differentiate the silty fraction by one-and-a-half oxides, indicating the beginning of selective podzolization. The rise in soil moisture content increased conservation of organic residues (peat formation) and made gley formation active. The quarry soils, like background soils, increased in acidity, carbon and nitrogen reserves along with the soil moisture content increase. In automorphic soil formation conditions, the rate of organic carbon accumulation in the upper 0–20-cm layer is 0.4 t· ha–1·year1; the excessive soil moisture content further increased it (1.0–1.2 t·ha–1·year1). The reserves of Corg in the upper 20-cm soil layer of young soils are by 2–4 times less than those in background soils.

Re-organization of Pacific overturning circulation across the Miocene Climate Optimum

The response of the ocean overturning circulation to global warming remains controversial. Here, we integrate a multiproxy record from International Ocean Discovery Program Site U1490 in the western equatorial Pacific with published data from the Pacific, Southern and Indian Oceans to investigate the evolution of deep water circulation during the Miocene Climate Optimum (MCO) and Middle Miocene Climate Transition (MMCT). We find that the northward export of southern-sourced deep waters was closely tied to high-latitude climate and Antarctic ice cover variations. Global warming during the MCO drove a progressive decrease in carbonate ion concentration and density stratification, shifting the overturning from intermediate to deeper waters. In the western equatorial Pacific, carbonate dissolution was compensated by increased pelagic productivity, resulting in overall elevated carbonate accumulation rates after ~16 Ma. Stepwise global cooling and Antarctic glacial expansion during the MMCT promoted a gradual improvement in carbonate preservation and the initiation of a near-modern Pacific overturning circulation. We infer that changes in the latitudinal thermal gradient and in Southern Ocean zonal wind stress and upper ocean stratification drove radically different modes of deep water formation and overturning across the MCO and MMCT.

Anthropogenic and climatic impacts on historic sediment, carbon, and phosphorus accumulation rates using 210Pbex and 137Cs in a sub-watershed linked to Zarivar Lake, Iran

To estimate a watershed’s response to climate change, it is crucial to understand how human activities and climatic extremes have interacted over time. Over the last century, the Zarivar Lake watershed, Iran, has been subjected to various anthropogenic activates, including deforestation and inappropriate land-management practices alongside the implementation of conservation measures like check dams. To understand the effects of these changes on the magnitude of sediment, organic carbon (OC), and phosphorus supplies in a small sub-watershed connected to the lake over the last century, a lake sediment core was dated using 210Pbex and 137Cs as geochronometers. The average mass accumulation rate (MAR), organic carbon accumulation rates (OCAR), and particulate phosphorus accumulation rates (PPAR) of the sediment core were determined to be 6498 ± 2475, 205 ± 85, and 8.9 ± 3.3 g m−2 year−1, respectively. Between the late 1970s and early 1980s, accumulation rates were significantly higher than their averages at 7940 ± 3120, 220 ± 60, and 12.0 ± 2.8 g m−2 year−1 respectively. During this period, the watershed underwent extensive deforestation (12%) on steep slopes, coinciding with higher mean annual precipitations (more than double). Conversely, after 2009, when check dams were installed in the sub-watershed, the sediment load to the lake became negligible. The results of this research indicate that anthropogenic activities had a pronounced effect on MAR, OCAR, and PPAR, causing them to fluctuate from negligible amounts to values twice the averages over the last century, amplified by climatic factors. These results imply that implementing climate-smart watershed management strategies, such as constructing additional check dams and terraces, reinforcing restrictions on deforestation, and minimum tillage practices, can facilitate protection of lacustrine ecosystems under accelerating climate change conditions.Graphical

Spatial variability in blue carbon storage and sequestration of seagrass meadows in southern China

Although seagrass meadows are intense carbon sinks, information on the regional variability in seagrass blue carbon stocks and carbon sequestration remains limited. We estimated the organic carbon (Corg) stocks and carbon accumulation rates (CAR) of seven seagrass meadows along the subtropical coast of China's Zhanjiang City and analyzed the driving factors of variability in sediment Corg stocks in three seagrass meadows. Results showed that most Corg (99.83 %) was stored in the sediments, and the contribution of living biomass was minor. The average Corg stocks of living biomass and sediments across all sites were 0.04 ± 0.01 and 42.03 ± 25.07 Mg C ha−1, respectively, which were significantly lower than the world average (2.52 ± 0.48 and 194.2 Mg C ha−1). The sediment Corg stocks of the upper 1 m ranged from 24.26 to 157.12 Mg C ha−1 with substantial variability among sites: Liusha Bay (64.93 ± 22.31 Mg C ha−1) > Donghai Island (33.8 ± 10.65 Mg C ha−1) > Dongshen Ferry (27.35 ± 4.15 Mg C ha−1). The average sediment CAR was 53.47 g C m−2 yr−1, and the total CAR of 864.18 ha seagrass meadows was 260.76 ± 4.86 Mg C yr−1 in these studied sites. Physicochemical factors, such as high moisture content, salinity, CaCO3 content, and low dry bulk density, jointly inhibited the mineralization rate of Corg in sediments. Our study provides data from understudied regions to a growing dataset on seagrass carbon stocks and sequestration rates and highlights the significance of local and regional differences in seagrass blue carbon storage to accurately assess the climate change mitigation potential of seagrass ecosystems.

Effects of land reclamation on peatland carbon stability in Sanjiang Plain (Northeast China) over the last century

Peatlands store vast amounts of soil carbon and the stability of this carbon pool plays a crucial role in the carbon dynamics under global change. In the Sanjiang Plain, one of the important peatlands distributed region in China, peatlands were seriously affected by the regional land reclamation during the last century. While, there is a scarcity of data evaluating the impact of land reclamation on peatland carbon stability. Here, based on 210Pb dating of the Shenjiadian (SJD) peatland, we reconstructed historical variations in peatland carbon stability and assessed its response on regional land reclamation over the last century in the Sanjiang Plain. The results showed that the highest aromatic content (25.2 ± 0.7 %) and the lowest carbohydrate content (34.7 ± 2.5 %) occurred between 1950 and 1980, coinciding with the period of extensive second land reclamation in the Sanjiang Plain. The increase in regional human activities led to greater accumulation of pyrogenic carbon in the peatland, enhancing carbon stability in the 1950 s. However, as farmland area continued to grow in the 1960 s, local fires caused by agricultural activities led to more frequent peat fires, promoting the accumulation of herbaceous litter in the peatland, which decreased the stability of the peatland carbon pool but increased carbon accumulation rates. With the proportion of shrub litter increasing and regional land reclamation weakening after 1980, the accumulation of shrub litters has increased both carbon stability and carbon accumulation rates in the studied peatland, particularly after 2000.

Simultaneous onboard analysis of seawater dissolved inorganic carbon (DIC) concentration and stable isotope ratio (δ13C‐DIC)

AbstractDissolved inorganic carbon (DIC) and its stable carbon isotope (δ13C‐DIC) are valuable parameters for studying the aquatic carbon cycle and quantifying ocean anthropogenic carbon accumulation rates. However, the potential of this coupled pair is underexploited as only 15% or less of cruise samples have been analyzed for δ13C‐DIC because the traditional isotope analysis is labor‐intensive and restricted to onshore laboratories. Here, we improved the analytical precision and reported the protocol of an automated, efficient, and high‐precision method for ship‐based DIC and δ13C‐DIC analysis based on cavity ring‐down spectroscopy (CRDS). We also introduced a set of stable in‐house standards to ensure accurate and consistent DIC and δ13C‐DIC measurements, especially on prolonged cruises. With this method, we analyzed over 1600 discrete seawater samples over a 40‐d cruise along the North American eastern ocean margin in summer 2022, representing the first effort to collect a large dataset of δ13C‐DIC onboard of any oceanographic expedition. We evaluated the method's uncertainty, which was 1.2 μmol kg−1 for the DIC concentration and 0.03‰ for the δ13C‐DIC value (1σ). An interlaboratory comparison of onboard DIC concentration analysis revealed an average offset of 2.0 ± 3.8 μmol kg−1 between CRDS and the coulometry‐based results. The cross‐validation of δ13C‐DIC in the deep‐ocean data exhibited a mean difference of only −0.03‰ ± 0.07‰, emphasizing the consistency with historical data. Potential applications in aquatic biogeochemistry are discussed.

Impact of paleohydrological conditions on wetland organic carbon accumulation in the monsoon-arid transition zone of North China during the Holocene

Wetlands rich in carbon are important ecosystems for storing organic carbon, with their carbon storage capacity closely linked to water levels. Therefore, it is valuable to explore the relation between paleohydrological conditions and the organic carbon accumulation in carbon-rich deposits. This study examined the total organic carbon concentration and the molecular and carbon isotope compositions of n-alkanes in Ganhai, a dried up lake located in a region transitioning from a monsoon to an arid climate in north China. The results showed that the apparent carbon accumulation rates (CAR) increased as the East Asian summer monsoon intensified (averaged at 26.5 g C m−2 yr−1, 1 σ = 8.6), but decreased when precipitation levels peaked (averaged at 15.8 g C m−2 yr−1, 1 σ = 2.2). The above relation between precipitation and CAR in Ganhai is supported by the correlation analysis (r = −0.35, p = 0.003). This suggests a threshold relation between wetland carbon accumulation and precipitation in this region. The output of a Bayesian multi-source mixing model, based on the molecular and carbon isotope compositions of long-chain n-alkanes, underscores the significant role of aquatic plants in influencing carbon accumulation in Ganhai during the mid-Holocene, with submersed plants dominating during high CAR periods and floating plants being more prevalent during peak precipitation. The study emphasizes the importance of understanding the hydrological threshold for carbon sequestration and vegetation restoration in carbon-rich wetlands.

Assessing methane emissions and soil carbon stocks in the Camargue coastal wetlands: Management implications for climate change regulation

Coastal wetlands are crucial in climate change regulation due to their capacity to act as either sinks or sources of carbon, resulting from the balance between greenhouse gas (GHG) emissions, mainly methane (CH4), and soil carbon sequestration. Despite the paramount role of wetlands in climate regulation few studies investigate both aspects. The Camargue is one of the largest wetlands in Europe, yet the ways in which environmental and anthropic factors drive carbon dynamics remain poorly studied. We examined GHG emissions and soil organic carbon (SOC) stocks and accumulation rates in twelve representative wetlands, including two rice fields, to gain insights into the carbon dynamics and how it is influenced by hydrology and salinity. Mean CH4 rates ranged between – 87.0 and 131.0 mg m−2 h−1and the main drivers were water conductivity and redox, water table depth and soil temperature. High emission rates were restricted to freshwater conditions during summer flooding periods whereas they were low in wetlands subjected to summer drought and water conductivity higher than 10 mS cm−1. Nitrous oxide emissions were low, ranging from – 0.5 to 0.9 mg N2O m−2 h−1. The SOC stocks in the upper meter ranged from 17 to 90 Mg OC ha−1. Our research highlights the critical role of low-saline wetlands in carbon budgeting which potentially are large sources of CH4 but also contain the largest SOC stocks in the Camargue. Natural hydroperiods, involving summer drought, can maintain them as carbon sinks, but altered hydrology can transform them into sources. Artificial freshwater supply during summer leads to substantial CH4 emissions, offsetting their SOC accumulation rates. In conclusion, we advocate for readjusting the altered hydrology in marshes and for the search of management compromises to ensure the compatibility of economic and leisure activities with the preservation of the inherent climate-regulating capacity of coastal wetlands.

Quantifying growth, erosion and dislodgement rates of farmed kelp (Saccharina latissima) to examine the carbon sequestration potential of temperate seaweed farming

Seaweed cultivation, including kelp species, is rapidly expanding in many regions. A widely assumed co-benefit of seaweed farming is increased local carbon sequestration rates (thereby contributing to climate change mitigation), although direct field-based measurements of carbon assimilation and release are largely lacking. We quantified growth, erosion and dislodgement rates of farmed Saccharina latissima in Porthallow Bay (Cornwall, UK) throughout a typical cultivation season to provide insights into the carbon sequestration potential of small-scale kelp farms. Blade elongation rates increased from ~ 1.3 cm day−1 to ~ 2.3 cm day−1 in March–April, before declining to 1.4 cm day−1 by May. Meanwhile, erosion rates remained low, ranging from ~ 0.5 to ~ 0.8 cm day−1. Dislodgement rates decreased from 20% of plants in January–February to 5% in April–May. Rates of carbon accumulation and loss increased from January to May, related to an increase in standing stock. Conservative first-order estimates suggest that the farm captures 0.14 t C ha−1 y−1, of which up to 70% is released into the environment as particulate organic carbon. Based on previous estimates of carbon burial and storage rates, the farm may sequester 0.05 t CO2e ha−1 y−1. These values suggest that scaling-up European kelp farming should be motivated by other co-benefits, such as low-carbon product alternatives, job creation and potential biodiversity gains, and not be solely driven by a perceived meaningful increase in carbon sequestration. Importantly, further information needs to be obtained from a variety of cultivation sites to develop a better understanding of carbon dynamics associated with kelp farms.

Maximizing tree carbon in croplands and grazing lands while sustaining yields

BackgroundIntegrating trees into agricultural landscapes can provide climate mitigation and improves soil fertility, biodiversity habitat, water quality, water flow, and human health, but these benefits must be achieved without reducing agriculture yields. Prior estimates of carbon dioxide (CO2) removal potential from increasing tree cover in agriculture assumed a moderate level of woody biomass can be integrated without reducing agricultural production. Instead, we used a Delphi expert elicitation to estimate maximum tree covers for 53 regional cropping and grazing system categories while safeguarding agricultural yields. Comparing these values to baselines and applying spatially explicit tree carbon accumulation rates, we develop global maps of the additional CO2 removal potential of Tree Cover in Agriculture. We present here the first global spatially explicit datasets calibrated to regional grazing and croplands, estimating opportunities to increase tree cover without reducing yields, therefore avoiding a major cost barrier to restoration: the opportunity cost of CO2 removal at the expense of agriculture yields.ResultsThe global estimated maximum technical CO2 removal potential is split between croplands (1.86 PgCO2 yr− 1) and grazing lands (1.45 PgCO2 yr− 1), with large variances. Tropical/subtropical biomes account for 54% of cropland (2.82 MgCO2 ha− 1 yr− 1, SD = 0.45) and 73% of grazing land potential (1.54 MgCO2 ha− 1 yr− 1, SD = 0.47). Potentials seem to be driven by two characteristics: the opportunity for increase in tree cover and bioclimatic factors affecting CO2 removal rates.ConclusionsWe find that increasing tree cover in 2.6 billion hectares of agricultural landscapes may remove up to 3.3 billion tons of CO2 per year – more than the global annual emissions from cars. These Natural Climate Solutions could achieve the Bonn Challenge and add 793 million trees to agricultural landscapes. This is significant for global climate mitigation efforts because it represents a large, relatively inexpensive, additional CO2 removal opportunity that works within agricultural landscapes and has low economic and social barriers to rapid global scaling. There is an urgent need for policy and incentive systems to encourage the adoption of these practices.

Spatiotemporal variation of sterols in sediment as markers of primary production and ocean sewage dumping in the southwestern East Sea (Japan Sea)

The sedimentation of organic carbon in the Ulleung Basin, in the southwestern East Sea (Japan Sea) was investigated using radiocarbon and sterols. The accumulation rates of organic carbon and the contents of brassicasterol and dinosterol were higher on the slope than in the central basin, reflecting the surface water productivity, whereas cholesterol showed similar or higher contents in the central basin. The coprostanol concentration in surface sediments reflected the dispersion of sewage dumped in this region. The vertical distribution showed that the coprostanol concentration was the highest in the top 5-cm layer near the Korea Strait, close to one of the two dumping sites. A high coprostanol concentration was also found near the coast further north, where the content peaked at ∼10 cm depth. The vertical distribution of coprostanol helped to estimate the sediment accumulation rate at sites where radiocarbon gradient was too small or the values were too variable.

Mountain Peatlands and Drought: Carbon Cycling in the Pyrenees Amidst Global Climate Change

AbstractThis study provides a multi‐year (2017–2022) Net Ecosystem Carbon Balance (NECB) of a Pyrenean mountainous peatland through the integration of field data, satellite imagery, and statistical modeling. Fluvial organic carbon export was measured at 30 min frequency, while gaseous (CO2 and CH4) exchanges were measured monthly using closed chambers. These measurements were combined with Sentinel‐2 derived chlorophyll index and in situ high frequency (1 hr) measurements of key environmental variables such as air temperature, photosynthetically active radiation, and water table level, to develop hourly gaseous carbon flux models (R2 = 0.69 for GPP, R2 = 0.84 for ER, R2 = 0.59 for CH4). Over the 2017–2022 period, modeled average GPP (610 ± 39 gC.m−2.year−1) and ER (641 ± 59 gC.m−2.year−1) showed that the peatland acted as a weak source of CO2 to the atmosphere, releasing 31 ± 73 gC.m−2.year−1. Considering fluvial carbon export and CH4 exchanges, the loss of carbon from the peatland increased to 55 ± 73 gC.m−2.year−1. Dissolved organic carbon constituted 8%–106% of the NECB. The estimated long‐term organic accumulation rate indicated a steady carbon accumulation rate of 16.4 gC.m−2.year−1, contrasting with the contemporary NECB, suggesting a recent shift in ecosystem functioning from a carbon sink to a source. The study underscores the role of water availability and air temperature through a drought index (DI), in shaping the NECB. The DI correlated significantly with annual carbon gaseous fluxes, except for 2022, marked by an intense drought. During this year the peatland became a large source of carbon (189 gC.m−2.year−1) to the atmosphere.

Influence of changing water mass circulation on detrital component and carbon burial of late Pleistocene and Holocene sediments in the eastern-central Mid-Adriatic deep

A sediment core was retrieved in the eastern-central Mid-Adriatic Deep (MAD) to study the changes in the water mass circulation and their effect on carbon burial efficiency and the provenance of a detrital sediment component. An age-depth model of the sediment core POS-514-40-11 is based on radiocarbon dating and tephrochronology. Two tephra were correlated to the Neapolitan Yellow Tuff and Pomici di Mercato eruptions, extending the previously known distribution of Pomici di Mercato tephra. Based on the analysis of heavy mineral (HM) assemblages throughout the core, for the first time the occurrence of Eastern Adriatic current (EAC) was estimated at ca. 15 ka BP, i.e., at the beginning of the post last glacial maximum (LGM) transgression. During the late Pleistocene, the detrital component was dominated by Paleo-Po river sediments, which gradually shifted toward the Albanian province as a basin-wide counterclockwise circulation was established. Mass accumulation rates of organic carbon (OC), stable isotopes of carbon (δ 13C) and nitrogen (δ 15N) as well as C/N ratios, showed that carbon burial was affected by sea level rise and climatic changes. Climatic effects are observed during cold periods i.e., the Younger Dryas and the 8.4–7.9 ka cold period when terrestrial OC was dominant. In the latter case dominance of terrestrial carbon was due to the North Adriatic dense water (NAddW) influence. On the other hand, sea level rise increased MAD distance from the main river mouths/deltas, resulting in decreased influx of terrestrial organic carbon and lower accumulation rates of organic carbon in general. This reconstruction of the oceanographic setting is valuable considering that the Adriatic Sea is one of the key locations for the formation of DW and thus affects the overall Mediterranean circulation.

Holocene history of the Kungur forest-steppe (cis-Urals, European Russia): case study Uinskoe mire

The formation and development of the Kungur forest-steppe has been a controversial topic for almost 150 years due to its location within the belt of hemiboreal forests in the pre-Urals of European Russia. To further the knowledge on its manmade versus natural origin we conducted a palaeoecological study reconstructing the regional vegetation history in the Mid-Kama region as well as local bog development and additional archaeobotanical studies nearby. Detailed loss-on-ignition analysis, peat properties and high resolution radiocarbon dating were carried out to obtain long-term carbon accumulation rate estimates. The data document the presence of the pine-dominated forest-steppe with spruce and birch during the major part of the Holocene (∼9.7–5.5 ka) and the development of the modern hemiboreal forests from 5.5 ka onwards. Since 3.5 ka, the hemiboreal forests were increasingly influenced by human action, corresponding to the development of local archaeological cultures. The earliest human impact is observed during the Garinskaya culture (4.5–3.5 ka). It increased during the Early Iron Age with the Ananyino (2.8–2.2 ka) and Glyadenovo (2.2–1.6 ka) cultures and during the Medieval with the Nevolino culture (1.6–1.1 ka). Archaeobotanical data reveal consumption of Triticum aestivum and T. aestivum/spelta by bearers of the Nevolino culture as well as a local cultivation of emmer. The formation of the recent Pinus-Betula forest-steppe took place in the last 300 years during the Russian colonisation. In conclusion, continental and warm climatic conditions as well as fire activities were maintaining semi-open landscapes of the forest-steppe during the Early and Middle Holocene, while land use became the dominant factor since 3.5 ka.

Extensive carbon cycle between peatland and vegetation: Insights from high net primary productivity of the Middle Jurassic in northwestern China

Peatlands have obvious carbon storage capacity and are crucial in mitigating global climate change. As the end-product of peatlands, coals have preserved a large amount of palaeoenvironmental information. The carbon accumulation rate and the net primary productivity (NPP) of coal-forming peatlands can be used as proxies for recovering palaeoenvironments. A super-thick coal seam (42°35′N, 91°25′E) was developed in the Middle Jurassic Xishanyao Formation in the Shaerhu coalfield in the southern margin of the Tuha (Turpan-Hami) Basin, northwestern China. In this study, we use the time series analysis to identify the periods of Milankovitch orbital cycles in the Gamma-ray curve of this super-thick (124.85 m) coal and then use the obtained cycle periods of 405 ka, 173 ka, 44 ka, 37.6 ka, 22.5 ka to calculate the timeframe of the coal-forming peatlands which ranges from 2703.44 to 2975.11 ka. Considering that the carbon content of the coal seam is 78.32% and the carbon loss during the coalification is about 25.80%, the carbon accumulation rate of the targeted coal seam is estimated to be 58.47–64.34 g C/m2·a, and the NPP is estimated to be 252.28–277.63 g C/m2·a. The main palaeoenvironmental factors controlling the NPP of peatlands are CO2 content, palaeolatitude and palaeotemperature. The reduced NPP values of the palaeo-peatlands in the Shaerhu coalfield can be attributed to the mid-palaeolatitude and/or too low atmospheric CO2 contents. To a certain extent, the NPP of palaeo-peatlands reflects the changes in atmospheric CO2, which can further reveal the dynamic response of the global carbon cycle to climate change. Therefore, predicting the level of NPP in the Middle Jurassic and studying the final destination of carbon in the ecosystem are beneficial to understanding the coal-forming process and palaeoenvironment.