Mangroves are one of the most carbon‐dense forests on the Earth and have been highlighted as key ecosystems for climate change mitigation and adaptation. Hundreds of studies have investigated how ...mangroves fix, transform, store, and export carbon. Here, we review and synthesize the previously known and emerging carbon pathways in mangroves, including gains (woody biomass accumulation, deadwood accumulation, soil carbon sequestration, root and litterfall production), transformations (food web transfer through herbivory, decomposition), and losses (respiration as CO2 and CH4, litterfall export, particulate and dissolved carbon export). We then review the technologies available to measure carbon fluxes in mangroves, their potential, and their limitations. We also synthesize and compare mangrove net ecosystem productivity (NEP) with terrestrial forests. Finally, we update global estimates of carbon fluxes with the most current values of fluxes and global mangrove area. We found that the contributions of recently investigated fluxes, such as soil respiration as CH4, are minor (<1 Tg C year−1), while the contributions of deadwood accumulation, herbivory, and lateral export are significant (>35 Tg C year−1). Dissolved inorganic carbon exports are an order of magnitude higher than the other processes investigated and were highly variable, highlighting the need for further studies. Gross primary productivity (GPP) and ecosystem respiration (ER) per area of mangroves were within the same order of magnitude as terrestrial forests. However, ER/GPP was lower in mangroves, explaining their higher carbon sequestration. We estimate the global mean mangrove NEP of 109.1 Tg C year−1 (7.4 Mg C ha−1 year−1) or through a budget balance, accounting for lateral losses, a global mean of 66.6 Tg C year−1 (4.5 Mg C ha−1 year−1). Overall, mangroves are highly productive, and despite losses due to respiration and tidal exchange, they are significant carbon sinks.
Pools are common features of peatlands and can represent from 5 % to 50 % of
the peatland ecosystem's surface area. Pools play an important role in the
peatland carbon cycle by releasing carbon ...dioxide and methane to the
atmosphere. However, the origin of this carbon is not well constrained. A
hypothesis is that the majority of the carbon emitted from pools
predominantly originates from mineralized allochthonous (i.e.,
plant-derived) dissolved organic matter (DOM) from peat rather than in situ
primary production. To test this hypothesis, this study examined the origin,
composition, and degradability of DOM in peat porewater and pools of an
ombrotrophic boreal peatland in northeastern Quebec (Canada) for 2 years
over the growing season. The temporal evolution of dissolved organic carbon
(DOC) concentration, the optical properties, molecular composition
(THM-GC-MS), stable isotopic signature (δ13C-DOC), and
degradability of DOM were determined. This study demonstrates that DOM, in
both peat porewater and pools, presents a diverse composition and
constitutes highly dynamic components of peatland ecosystems. The molecular
and isotopic analyses showed that DOM in pools was derived from plants.
However, DOM compositions in the two environments were markedly different.
Peat porewater DOM was more aromatic, with a higher molecular weight and
DOC : DON (dissolved organic nitrogen) ratio compared to pools. The temporal dynamics of DOC concentration
and DOM composition also differed. In peat porewater, the DOC concentration
followed a strong seasonal increase, starting from 9 mg L−1 and reaching a plateau above 20 mg L−1 in summer and autumn. This was
explained by seasonal peatland vegetation productivity, which is greater
than microbial DOM degradation. In pools, DOC concentration also increased
but remained 2 times lower than in the peat porewaters at the end of the
growing season (∼ 10 mg L−1). Those differences might be
explained by a combination of physical, chemical, and biological factors.
The limited hydraulic conductivity in deeper peat horizons and associated
DOM residence time might have favored both DOM microbial transformation
within the peat and the interaction of DOM aromatic compounds with the peat
matrix, explaining part of the shift of DOM compositions between peat
porewater and pools. This study did not report any photolability of DOM and
only limited microbial degradability. Thus, it is likely that the DOM might
have been microbially transformed at the interface between peat and pools.
The combination of DOM quantitative and qualitative analyses presented in
this study demonstrates that most of the carbon present within and released
from the pools originates from peat vegetation. These results demonstrate
that pools represent a key component of the peatland ecosystem ecological
and biogeochemical functioning.
The magnitudes of dissolved organic carbon (DOC) exports from boreal peatlands to streams through lateral subsurface flow vary during the ice-free season. Peatland water table depth and the ...alternation of low and high flow in peat-draining streams are thought to drive this DOC export variability. However, calculation of the specific DOC exports from a peatland can be challenging considering the multiple potential DOC sources within the catchment. A calculation approach based on the hydrological connectivity between the peat and the stream could help to solve this issue, which is the approach used in the present research. This study took place from June 2018 to October 2019 in a boreal catchment in northeastern Canada, with 76.7 % of the catchment being covered by ombrotrophic peatland. The objectives were to (1) establish relationships between DOC exports from a headwater stream and the peatland hydrology; (2) quantify, at the catchment scale, the amount of DOC laterally exported to the draining stream; and (3) define the patterns of DOC mobilization during high-river-flow events. At the peatland headwater stream outlet, the DOC concentrations were monitored at a high frequency (hourly) using a fluorescent dissolved organic matter (fDOM) sensor, a proxy for DOC concentration. Hydrological variables, such as stream outlet discharge and peatland water table depth (WTD), were continuously monitored at hourly intervals for 2 years. Our results highlight the direct and delayed control of subsurface flow from peat to the stream and associated DOC exports. Rain events raised the peatland WTD, which increased hydrological connectivity between the peatland and the stream. This led to increased stream discharge (Q) and a delayed DOC concentration increase, typical of lateral subsurface flow. The magnitude of the WTD increase played a crucial role in influencing the quantity of DOC exported. Based on the observations that the peatland is the most important contributor to DOC exports at the catchment scale and that other DOC sources were negligible during high-flow periods, we propose a new approach to estimate the specific DOC exports attributable to the peatland by distinguishing between the surfaces used for calculation during high-flow and low-flow periods. In 2018–2019, 92.6 % of DOC was exported during flood events despite the fact that these flood events accounted for 59.1 % of the period. In 2019–2020, 93.8 % of DOC was exported during flood events, which represented 44.1 % of the period. Our analysis of individual flood events revealed three types of events and DOC mobilization patterns. The first type is characterized by high rainfall, leading to an important WTD increase that favours the connection between the peatland and the stream and leading to high DOC exports. The second is characterized by a large WTD increase succeeding a previous event that had depleted DOC available to be transferred to the stream, leading to low DOC exports. The third type corresponds to low rainfall events with an insufficient WTD increase to reconnect the peatland and the stream, leading to low DOC exports. Our results suggest that DOC exports are sensitive to hydroclimatic conditions; moreover, flood events, changes in rainfall regime, ice-free season duration, and porewater temperature may affect the exported DOC and, consequently, partially offset the net carbon sequestration potential of peatlands.
We propose the modelling of elements of small dimensions (at least one dimension small by respect to the wavelength) in a planar circuit by a quasistatic approach, and the rest of the circuit by a ...rigorous integral method including sources. This mixed method is applied to the study of a MIM (Metal-Insulator-Metal) capacitor. Numerical results are in good agreement with experimental data.< >
Peatlands store organic carbon available for decomposition and transfer to neighboring water bodies, which can ultimately generate carbon dioxide (CO2) and methane (CH4) emissions. The objective of ...this study was to clarify the biogeochemical functioning of open‐water peatland pools and their influence on carbon budgets at the ecosystem and global scale. Continuously operated automated equipment and monthly manual measurements were used to describe the CO2 and CH4 dynamics in boreal ombrotrophic peatland pools and porewater (Québec, Canada) over the growing seasons 2019 and 2020. The peat porewater stable carbon isotope ratios (δ13C) for both CO2 (median δ13C‐CO2: −3.8‰) and CH4 (median δ13C‐CH4: −64.30‰) suggested that hydrogenotrophic methanogenesis was the predominant degradation pathway in peat. Open‐water pools were supersaturated in CO2 and CH4 and received most of these dissolved carbon greenhouse gases (C‐GHG) from peat porewater input. Throughout the growing season, higher CO2 concentrations and fluxes in pools were measured when the water table was low—suggesting a steady release of CO2 from deep peat porewater. Higher CH4 ebullition and diffusion occurred in August when bottom water and peat temperatures were the highest. While this study demonstrates that peatland pools are chimneys of CO2 and CH4 stored in peat, it also shows that the C‐GHG concentrations and flux rates in peat pools are comparable to other aquatic systems of the same size. Although peatlands are often considered uniform entities, our study highlights their biogeochemical heterogeneity, which, if considered, substantially influences their net carbon balance with the atmosphere.
Key Points
Peatland pools are supersaturated in CO2 and CH4 and represent net carbon greenhouse gas sources to the atmosphere
CO2 and CH4 concentrations and fluxes fluctuated over the seasons and were explained by water table level fluctuations and temperature changes
Net peatland carbon budgets must include open water surface emissions to avoid overestimating carbon removal from peatlands
Statistical postprocessing of medium-range weather forecasts is an important component of modern forecasting systems. Since the beginning of modern data science, numerous new postprocessing methods ...have been proposed, complementing an already very diverse field. However, one of the questions that frequently arises when considering different methods in the framework of implementing operational postprocessing is the relative performance of the methods for a given specific task. It is particularly challenging to find or construct a common comprehensive dataset that can be used to perform such comparisons. Here, we introduce the first version of EUPPBench (EUMETNET postprocessing benchmark), a dataset of time-aligned forecasts and observations, with the aim to facilitate and standardize this process. This dataset is publicly available at
https://github.com/EUPP-benchmark/climetlab-eumetnet-postprocessing-benchmark (31 December 2022) and on Zenodo (https://doi.org/10.5281/zenodo.7429236, Demaeyer, 2022b and
https://doi.org/10.5281/zenodo.7708362, Bhend et al., 2023). We provide examples showing how to download and use the data, we propose a set of evaluation methods, and we perform a first benchmark of several methods for the correction of 2 m temperature forecasts.
To determine the longitudinal changes in body composition, physical capacities, and time and energy expenditure (EE) devoted to various activities in the course of a 9-month weight-reduction period.
...Longitudinal, clinical intervention including lifestyle education, moderate energy restriction, progressive training, and psychological follow-up.
A total of 27 (13 boys and 14 girls) severely obese adolescents (mean BMI: 33.9 kg/m2; 41.5% fat mass (FM)), aged 12-16 y.
Before the beginning and after the weight-reduction program, body composition was assessed by dual-energy X-ray absorptiometry (DXA), physical capacities by multistage treadmill test, and EE both by whole-body calorimetry and in free-living conditions using the heart rate-recording method. During 8 months of the weight-reduction period, type and duration of each activity were recorded using a daily controlled activity diary.
One boy resigned after 5 months. Body weight (BW) and FM decreased (-19 and -42%, respectively, P<0.001) both in boys and in girls, but fat-free mass (FFM) decreased only in girls (-6%, P<0.001). VO2max (l/min) did not vary significantly, but strength and fitness were improved (P<0.001). Time and EE spent at sedentary activities decreased significantly (P<0.001) to the benefit of moderate (recreational) activities and total physical activities (P<0.001) at the institution during the weekdays, and at home during the weekends and holidays.
The great BW and FM losses, preservation of FFM, and improvement of physical capacities of obese adolescents obtained under experimental conditions were associated with increases in leisure physical activities in free-living conditions at the expense of sleep and sedentary activities.
First‐order streams flowing through peatlands receive, carry and transform large amounts of organic carbon, methane (CH4) and carbon dioxide (CO2) but remain poorly documented. The objectives of this ...study were to (a) identify the origins of CO2 and CH4 (thereafter C‐GHG for carbon greenhouse gases) in a peatland headwater stream, (b) determine the environmental factors driving C‐GHG export and emissions, and (c) quantify C‐GHG losses from this system and discuss its implications. Data were collected from eight sampling sites along a 3 km boreal peatland headwater stream (Eastern Canada) over the growing seasons 2019 and 2020. The studied stream was oversaturated in pCO2 min: 2,044; max: 23,306 μatm and pCH4 14; 17,614 μatm. A mass balance model showed that ∼81% of in‐stream CO2 originated from porewater seepage while the remaining 17% and 2% originated from in‐stream productivity and methane oxidation, respectively. Porewater seepage was concluded to be the primary source of CH4. Seasonal dissolved C‐GHG concentrations were negatively correlated with the peatland water table depth, suggesting an active release of carbon‐rich peat porewater during the base flow. Nevertheless, greater C‐GHG losses occurred during stormflow periods which acted as pulses with most of the C‐GHG being shunted downstream. The sum of C‐GHG export and emissions at our site was 8.08 gC m−2 y−1 with 86% being released to the atmosphere and 14% being exported downstream. Our study demonstrates that peatland headwater streams act as large sources of C‐GHG and that precipitation events and topography control the magnitude of the fluxes.
Plain Language Summary
Headwater streams are the inceptive fragment of the river network where a substantial quantity of organic carbon is released from the surrounding substrate. This terrestrial organic carbon can also be transformed into greenhouse gases (GHGs) such as methane and carbon dioxide. In the stream, those GHG can be either consumed, emitted to the atmosphere, or exported downstream. However, the respective contribution of those pathways is unknown. We sampled a stream draining a rain‐fed peatland in Eastern Canada to describe and quantify its carbon GHG dynamics. We found higher concentrations in this stream than in most headwater streams but the total carbon emissions and export were comparable. Peatland streams typically have a low velocity and gentle slope which minimizes atmospheric gas release. We also found that concentrations were greater during the low flow period, potentially because carbon‐rich porewater was released from the peat. However, greater export was reported during the few days of intense rain. The significance of this work is that GHG in headwater streams are spatially and temporally variable and controlled by the surrounding ecosystems, the intensity of rain events and the stream morphology. The inclusion of this variability will improve regional and global carbon budget estimates.
Key Points
Porewater seepage accounted for 81% of the carbon dioxide (CO2) present in the stream, in‐stream production and methane (CH4) oxidation contributed to 17% and 2%
86.5% of the dissolved CO2 and CH4 was emitted to the atmosphere rather than exported downstream due to gases oversaturation and slow flow
46% of the CO2 and CH4 exported downstream occurred during the 10% period when water discharge rates were maximum, suggesting a pulse effect
