Net Production Research Articles

Analyzing the potential for Padina gymnospora cultivation in the coastal waters of St. Martin’s Island, Bay of Bengal, Bangladesh: Determining the fluctuations of physicochemical property across seasons and locations

Cultivating seaweed presents an opportunity to enhance the livelihoods of the inhabitants of St. Martin's Island inhabitants. This research investigates the suitability of the island's coastal waters for seaweed cultivation, taking into account variations in physicochemical factors in different seasons. The water temperature and salinity at various locations ranged from 24.22ºC to 27.64ºC and 23.8 to 33.76 psu, respectively. pH remained relatively constant throughout the year, fluctuating between 7.71 and 8.22. Dissolved oxygen levels were highest during the dry, cooler winter season (6.47±0.21 ppm) and lowest during the monsoon season (4.96±0.09 ppm). Electrical conductivity (EC) ranged from 39.00 mS/cm to 53.46 mS/cm, while total dissolved solids (TDS) varied between 20.35 and 27.90 g/l. Water clarity was at its peak during the dry, cooler winter season, averaging 4.14 meters. This investigation confirms the feasibility of year-round seaweed cultivation in the coastal waters around St. Martin's Island. In our study comparing cultivation methods for Padina gymnospora during the dry, cool winter season, the long-line approach resulted in a higher daily weight gain compared to the floating net method. This trend extended to growth rates by length, with the long-line method demonstrating a 5.09% daily growth and the floating net method showing 4.46%. However, net biomass production was 289.32 g/m² for the long-line method and 381.28 g/m² for the floating net method. Furthermore, the Cost-Benefit Ratio values for the long-line and floating net methods were 2.57 and 3.27, respectively. These findings affirm the viability of cultivating Padina gymnospora in coastal waters using the floating net method. Biodivers. Conserv. Bioresour. Manag. 2024, 10(1): 1-14

Net productivity of photosynthesis of bread wheat lines introduced from CIMMYT

The improvement of wheat through the hybridization of existing highly productive genotypes with genotypes resistant to abiotic and biotic factors, as well as the use of wild relatives of wheat in hybridization, has great potential. This contributes to increasing the climate resilience of wheat and its stable productivity. The 29thSAWYT (Semi-Arid Wheat Yield Trials) nursery introduced from CIMMYT includes spring bread wheat lines developed through complex hybridization. Wheat lines have a higher growth rate and net productivity of photosynthesis than the local variety of Gobustan. Keywords: Wheat, 29thSAWYT, crop growth rate, dry mass, leaf area, net productivity of photosynthesis

The impact of large-scale ecological restoration projects on trade-offs/synergies and clusters of ecosystem services

Understanding the relationships between ecosystem services (ES) and the factors driving their changes over long periods and multiple scales is key for landscape managers in decision-making. However, the widespread implementation of restoration programs has led to significant ES changes, with trade-offs across space and time that have been little explored empirically, making it challenging to provide effective experience for managers. We quantified changes and interactions among five ES across various stages of the Grain-to-Green Program in the eastern Loess Plateau, examining these dynamics at threefold spatial scales. We observed notable increases in soil retention and Net Ecosystem Production but declines in habitat quality and Landscape aesthetics under afforestation. Over time, and with more integrated restoration strategies, synergies between ES pairs weakened, and non-correlations (even trade-offs) increased. To avoid unnecessary trade-offs, we recommend incorporating socio-ecological factors driving ES changes and ES bundles, informed by empirical experience, into proactive spatial planning and environmental management strategies for multi-ES objectives. The temporal lags and spatial trade-offs highlighted by this study offer crucial insights for large-scale restoration programs worldwide.

Temporal and Spatial Changes and Driving Forces of Carbon Stocks and Net Ecosystem Productivity: A Case Study of Zoige County, Sichuan Province, China

Temporal and Spatial Changes and Driving Forces of Carbon Stocks and Net Ecosystem Productivity: A Case Study of Zoige County, Sichuan Province, China

Functional genes and microorganisms controlling in situ methylmercury production and degradation in marine sediments: A case study in the Eastern China Coastal Seas

Dominant microorganisms and functional genes, including hgcA, hgcB, merA, and merB, have been identified to be responsible for mercury (Hg) methylation or methylmercury (MeHg) demethylation. However, their in situ correlation with MeHg levels and the processes of Hg methylation and MeHg demethylation in coastal areas remains poorly understood. In this study, four functional genes related to Hg methylation and MeHg demethylation (hgcA, hgcB, merA, and merB) were all detected in the sediments of the Eastern China Coastal Seas (ECCSs) (representative coastal seas highly affected by human activities) using metagenomic approaches. HgcA was identified to be the key gene controlling the in situ net production of MeHg in the ECCSs. Based on metagenomic analysis and incubation experiments, sulfate-reducing bacteria were identified as the dominant microorganisms controlling Hg methylation in the ECCSs. In addition, hgcA gene was positively correlated with the MeHg content and Hg methylation rates, highlighting the potential roles of Hg methylation genes and microorganisms influenced by sediment physicochemical properties in MeHg cycling in the ECCSs. These findings highlighted the necessity of conducting similar studies in other natural systems for elucidating the molecular mechanisms underlying MeHg production in aquatic environments.

Climate interacts with the trait structure of tree communities to influence forest productivity

Abstract Tree functional diversity can increase forest productivity by enhancing species interactions and providing greater growth stability. However, very few studies have examined the influence of tree community trait structure on survivor growth, recruitment and mortality simultaneously, which are the main drivers of forest population dynamics. Here, we explore the interactions among functional diversity, productivity and climate to investigate the role of the trait structure of communities on forest productivity and to determine under what circumstances functional diversity should be promoted to ensure forest adaptive capacity under future climate. Using random‐forest modelling and a network of permanent sample plots covering a broad gradient of climatic conditions, we isolated the effects of functional diversity—described as the distribution of trait values in a community—and climate variables on net forest productivity (NFP), survivor growth, recruitment and mortality. Based on our findings, community‐level trait structure affects forest productivity in different ways. NFP was influenced by three traits from three different plant strategy dimensions, whereas survivor growth and recruitment were strongly correlated with leaf and resource acquisition traits, and tree mortality with a mix of traits reflecting various plant strategies. We also observed climate interactions with the functional trait structure of tree communities. For instance, we observed an interaction between drought tolerance and mean annual temperature: At low temperatures, NFP biomass accumulation increased with the value of the drought tolerance trait; however, at higher temperatures, the opposite pattern was observed. However, we found contrasting patterns of population response to climate variability, depending on their functional diversity. Greater functional diversity does not necessarily increase biomass accumulation under different climatic conditions. Synthesis. As all components of forest productivity contribute to NFP, studies on forest productivity should consider not only survivor growth but also recruitment and mortality. Each component responds differently in terms of biomass changes in climatic variation, according to the trait structure of tree communities. This study provides a framework to identify the trait structure that should be targeted under different climate scenarios to anticipate change and help strengthen forest response capacity to climate change.

Moisture contents regulate peat water-leachable concentrations of methylmercury, inorganic mercury, and dissolved organic matter from boreal peat soils

Boreal peatlands are “hotspots” of net methylmercury (MeHg) production and may become drier in the future due to climate change. This study investigates a critical gap by analyzing the nuanced relationship between soil moisture content and the release of MeHg, inorganic mercury (IHg), sulfate (SO42-), and dissolved organic matter (DOM) in a laboratory incubation of boreal peat soils. Dried peat soils exhibited heightened releases of IHg, MeHg, and SO42- during re-wetting events. Both dried and saturated peat soils released more DOM than moist peat soils during re-wetting events, and DOM released from dried soils had higher bioaccessibility than that from the saturated soils (p<0.05). There was an equilibrium of IHg concentrations between peat soils and pore waters, but long-term severe drought may disrupt this equilibrium and then release more IHg to pore waters during re-wetting events. Contrary to expectations, positive relationships between IHg concentrations and SUVA254 did not exist in all treatments. MeHg and SO42- were depleted quickly because there was no external input of Hg and SO42- to this static system. More bioaccessible DOM than aromatic DOM was released from peat soils with different soil moisture contents after 32 weeks during the re-wetting event (p<0.05). These results imply that re-wetting of peat soils after droughts can increase the release of MeHg from peat soils and may also increase net MeHg production due to the release of SO42- and bioaccessible DOM from peat soils, reshaping our understanding of soil moisture's role in mercury dynamics. This novel insight into soil moisture and MeHg dynamics carries significant implications for mitigating mercury contamination in aquatic ecosystems.

Post-windthrow differences of carbon and water fluxes between managed and unmanaged Norway spruce stands

Windthrow is a major forest disturbance source in Europe. The impact of management (salvage logging) and no-management (deadwood left in ecosystem) treatments on carbon and water fluxes of Norway spruce stand affected by windthrow were analysed. The net ecosystem production (NEP), gross primary production (GPP), ecosystem respiration (Reco) and evapotranspiration (ET) were measured with eddy-covariance tower during 2019–2022 period. Additional chamber gas-exchange measurements, and vegetation inventory were performed. The unmanaged site had greater vegetation diversity and plant abundance, with higher leaf area index (LAI). The managed site showed overall higher NEP, lower GPP, lower Reco, lower GPP based water-use efficiency (WUEGPP), but higher NEP based WUENEP, compared with unmanaged site. The ET showed no clear trend between the two treatments. The higher GPP of unmanaged site can be linked to greater abundance of herbaceous species, which showed significantly higher photosynthetic capacity than the tree species. Moreover, the higher WUEGPP of unmanaged site can be affected also by the higher LAI of the unmanaged site. Nevertheless, if the Reco is accounted for in WUENEP, the differences between sites are reversed and the unmanaged site had lower WUENEP compared to the managed site. The option to leave the disturbed site without management leads to more productive ecosystem (GPP), with greater species diversity and abundance, but also with greater Reco and lower WUENEP. The discrepancy between WUEGPP and WUENEP suggests that studies analysing natural ecosystems affected by disturbances should use WUENEP to account for Reco carbon losses and avoid mis-interpreting the ecosystem carbon-water balance with WUEGPP.

Innovative biorefinery approaches for upcycling of post-consumer food waste in a circular bioeconomy context

Owing to the significant amounts produced each year, food waste is a critical issue that affects the economy, society, and environment. An estimated US$ 1 trillion food is wasted annually because of the supply chain and harvesting processes, which lose around one-third of the net production. This significant loss has sparked global concern, there is an urgent need for sustainable approaches to reduce food waste or to propose an economical route for its utilization. Major concerns associated with its improper management include environmental degradation and the exacerbation of greenhouse gases. This review provides a comprehensive understanding of the recent advances in measures to minimize food waste (FW) and its chemical and biotransformation into valuable products. Food waste comprises mainly carbohydrates, proteins, and oils; the former two components are commonly used as microbial feedstock, leaving behind the residual oil fraction which poses a greater environmental risk. Microbial transformation of these hydrophobic materials present in food waste into value-added products proves to be a sustainable and economical strategy. Thus, this study proposes an integrated biorefinery strategy for holistic valorization of FW, whereby all its components were used to produce value-added compounds such as biofuels, bioplastics, nutraceuticals, and biomaterials using microbial biocatalysis. Compared to conventional methods, an integrated biorefinery will be more sustainable and uplift the microbial processes by switching from ‘pure’ to food waste-derived substrates and thereby pave ways to achieve ‘green’ transition.

Numerical Investigation of Combustion Characteristics in a Binary Fuel Blend of C &lt;sub&gt;8&lt;/sub&gt; H &lt;sub&gt;18&lt;/sub&gt; and H &lt;sub&gt;2&lt;/sub&gt;

&lt;div&gt;The escalating energy demand in today’s world has amplified exhaust emissions, contributing significantly to climate change. One viable solution to mitigate carbon dioxide emissions is the utilization of hydrogen alongside gasoline in internal combustion engines. In pursuit of this objective, combustion characteristics of iso-octane/hydrogen/air mixtures are numerically investigated to determine the impact of hydrogen enrichment. Simulations are conducted at 400 K over a wide range of equivalence ratio 0.7 ≤ Ф ≤ 1.4 and pressure 1–10 atm. Adiabatic flame temperature, thermal diffusivity, laminar burning velocity, and chemical participation are assessed by varying hydrogen concentration from 0 to 90% of fuel molar fraction. As a result of changes in thermal properties and chemical participation, it is noticed that the laminar burning velocity (LBV) increases with higher hydrogen concentration and decreases as pressure increases. Chemical participation and mass diffusion were found to be the main contributors to the LBV increase in binary fuel blends. To circumvent NO&lt;sub&gt;X&lt;/sub&gt; formation, a binary fuel blend at Ф = 0.7 and 80% H&lt;sub&gt;2&lt;/sub&gt; is selected to increase combustion intensity while maintaining a relatively low flame temperature and retaining 85% of energy density by volume. It is noted that the concentration of H, O, and OH radicals increase with hydrogen enrichment. Furthermore, the analysis revealed that the LBV increases linearly with the peak mole fraction of radicals. Key reactions are identified through sensitivity analysis and net reaction rates. A significant increase in net reaction rate is observed for H&lt;sub&gt;2&lt;/sub&gt; + O &amp;lt;=&amp;gt; H + OH and H&lt;sub&gt;2&lt;/sub&gt; + OH &amp;lt;=&amp;gt; H + H&lt;sub&gt;2&lt;/sub&gt;O, which in turn increases the pool of radicals. This is evident by the increase in the net production rate of H, O, and OH radicals.&lt;/div&gt;

Water column oxygenation by Posidonia oceanica seagrass meadows in coastal areas: A modelling approach

BackgroundSeagrass meadows are among the most abundant marine coastal ecosystems in the world. The wide variety of species, a worldwide distribution with overall high abundance, and especially their high productivity make them a plausible nature-based blue carbon solution to mitigate atmospheric CO2 levels. In the Mediterranean Basin, the endemic angiosperm Posidonia oceanica plays a remarkable role as a marine habitat provider in shallow waters through its vertical growth and as a carbon sink storing allochthonous carbon and biomass underneath the meadows. ObjectivesHere, we assess the capacity of a pristine meadow to oxygenate the water column in the coastal area of the Balearic Islands through an evaluation of the metabolic rates in the benthic compartment as well as the resulting oxygen concentrations in the pelagic compartment. MethodsGross primary production (GPP), respiration (R), and net community production (NCP) are determined from dissolved oxygen (DO) measurements using two different calculation methods: a model developed for this purpose is used for data obtained from water column sensors and benthic multiparametric sensors, whereas the mass balance of measured DO is used to calculate the metabolic rates inside benthic chambers. ResultsThe meadow at our study site was characterised as a net autotrophic ecosystem throughout the year. Oxygen productivity was significantly higher in the benthic compartment than in the water column and followed clear seasonal patterns, with enhanced productivity during spring. NoveltyThis work shows the key role of a healthy Posidonia oceanica ecosystem as a water column oxygenator by comparing primary production using three different sampling strategies. The potential of the seagrass as climate change mitigator and its importance for the Mediterranean coasts should be considered in future coastal planning strategies.

Idiosyncratic phenology of greenhouse gas emissions in a Mediterranean reservoir

AbstractExtreme hydrological and thermal regimes characterize the Mediterranean zone and can influence the phenology of greenhouse gas (GHG) emissions in reservoirs. Our study examined the seasonal changes in GHG emissions of a shallow, eutrophic, hardwater reservoir in Spain. We observed distinctive seasonal patterns for each gas. CH4 emissions substantially increased during stratification, influenced predominantly by the increase in water temperature, net ecosystem production, and the decline in reservoir mean depth. N2O emissions mirrored CH4's seasonal trend, significantly correlating to water temperature, wind speed, and gross primary production. Conversely, CO2 emissions decreased during stratification and displayed a quadratic, rather than a linear relationship with water temperature—an unexpected deviation from CH4 and N2O emission patterns—likely associated with photosynthetic uptake of bicarbonate and formation of intracellular calcite that might be exported to sediments. This investigation highlights the imperative of integrating these idiosyncratic patterns into GHG emissions models, enhancing their predictive power.

Spatial and temporal divergence and driving mechanisms of carbon sinks in terrestrial ecosystems in the middle reaches of the Yangtze River urban agglomerations during 2008–2020

Urban cluster carbon sinks are key parts of the terrestrial carbon cycle, and play an important role in global climate change. Based on the inversion results of net ecosystem productivity (NEP) in Middle Reaches of the Yangtze River Urban Agglomeration (MRYRUA), this study considered the influence of both natural environmental and socioeconomic factors on NEP, and investigated the driving mechanism of carbon sink emphasizing spatial and temporal heterogeneity by the geographically and temporally weighted regression model (GTWR). Results demonstrated that (1) During 2008–2020, the annual average NEP was positive in MRYRUA, and the carbon sink effect of terrestrial ecosystem increased. (2) In MRYRUA, Precipitation and DEM were positively correlated with carbon sinks, opposite for temperature, percentage of water areas and population density. (3) During the study period, the influence of natural environmental factors, such as temperature and precipitation on NEP grew gradually weaker, whereas that of socioeconomic factors increased. The influence of urbanization rate, night lights index and factors of industrial structure changed from negative to positive, while percentage of built-up area had an increasing negative effect on NEP. Based on the conclusions above, this study proposed differentiated policy implications, including improving vegetation hydrothermal environment, controlling urban expansion and accelerating industrial transformation. It would provide empirical inspiration for attaining peak carbon, carbon neutrality, and sustainable development goals.

Dietary acid load and risk of diminished ovarian reserve: a case-control study

BackgroundThe epidemiologic evidence on the association between acid load potential of diet and the risk of diminished ovarian reserve (DOR) is scarce. We aim to explore the possible relationship between dietary acid load (DAL), markers of ovarian reserve and DOR risk in a case-control study.Methods370 women (120 women with DOR and 250 women with normal ovarian reserve as controls), matched by age and BMI, were recruited. Dietary intake was obtained using a validated 80-item semi-quantitative food frequency questionnaire (FFQ). The DAL scores including the potential renal acid load (PRAL) and net endogenous acid production (NEAP) were calculated based on nutrients intake. NEAP and PRAL scores were categorized by quartiles based on the distribution of controls. Antral follicle count (AFC), serum antimullerian hormone (AMH) and anthropometric indices were measured. Logistic regression models were used to estimate multivariable odds ratio (OR) of DOR across quartiles of NEAP and PRAL scores.ResultsFollowing increase in PRAL and NEAP scores, serum AMH significantly decreased in women with DOR. Also, AFC count had a significant decrease following increase in PRAL score (P = 0.045). After adjustment for multiple confounding variables, participants in the top quartile of PRAL had increased OR for DOR (OR: 1.26; 95%CI: 1.08–1.42, P = 0.254).ConclusionDiets with high acid-forming potential may negatively affect ovarian reserve in women with DOR. Also, high DAL may increase the risk of DOR. The association between DAL and markers of ovarian reserve should be explored in prospective studies and clinical trials.

Soil environmental anomalies dominate the responses of net ecosystem productivity to heatwaves in three Mongolian grasslands

Climate change is causing more frequent and intense heatwaves. Therefore, it is important to understand how heatwaves affect the terrestrial carbon cycle, especially in grasslands, which are especially susceptible to climate extremes. This study assessed the impact of naturally occurring, simultaneous short-term heatwaves on CO2 fluxes in three ecosystems on the Mongolia Plateau: meadow steppe (MDW), typical steppe (TPL), and shrub-grassland (SHB). During three heatwaves, net ecosystem productivity (NEP) was reduced by 86 %, 178 %, and 172 % at MDW, TPL, and SHB, respectively. The changes in ecosystem respiration, gross primary production, evapotranspiration, and water use efficiency were divergent, indicating the mechanisms underlying the observed NEP decreases among the sites. The impact of the heatwave in MDW was mitigated by the high soil water content, which enhanced evapotranspiration and subsequent cooling effects. However, at TPL, insufficient soil water led to combined thermal and drought stress and low resilience. At SHB, the ecosystem's low tolerance to an August heatwave was heavily influenced by species phenology, as it coincided with the key phenological growing phase of plants. The potential key mechanism of divergent NEP response to heatwaves lies in the divergent stability and varying importance of environmental factors, combined with the specific sensitivity of NEP to each factor in ecosystems. Furthermore, our findings suggest that anomalies in soil environment, rather than atmospheric anomalies, are the primary determinants of NEP anomalies during heatwaves. This challenges the conventional understanding of heatwaves as a discrete and ephemeral periods of high air temperatures. Instead, heatwaves should be viewed as chronologically variable, compound, and time-sensitive environmental stressors. The ultimate impact of heatwaves on ecosystems is co-determined by a complex interplay of environmental, biological, and heatwave features.

Machine learning-based optimization and 4E analysis of renewable-based polygeneration system by integration of GT-SRC-ORC-SOFC-PEME-MED-RO using multi-objective grey wolf optimization algorithm and neural networks

This study introduces a new solar-methane-driven setup that recovers waste heat from flue gases to produce electricity, hydrogen, oxygen, fresh water (FW), and domestic hot water (DHW) while reducing the environmental impact of gas turbines. This integration includes the Brayton cycle and solid oxide fuel cell as motive cycles, the steam and organic Rankine cycle, a parabolic trough solar collector (PTC), a proton exchange membrane electrolyzer, multi-effect distillation, and reverse osmosis. Using Engineering Equation Solver software, analyses in energy, exergy, exergoeconomic, and exergoenvironment (4E) are conducted to identify critical system evaluation parameters in thermodynamics, economics, and the environment. Additionally, the proposed system is optimized using an artificial neural network and the multi-objective grey wolf optimizer algorithm, utilizing decision variables identified through sensitivity analysis to enhance system performance. The results of six-objective optimization show energy and exergy efficiencies at 49.48 % and 47.21 %, with a net power production of 133 MW and a total cost rate of $7903/h. Among all the components, the combustion chamber and PTC have the maximum exergy destruction, with values of 58.87 MW and 17.29 MW, respectively. Also, hydrogen, FW, and DHW production rates are 201.6 kg/h, 43.88 kg/s, and 40.98 kg/s, respectively. Moreover, the costs of hydrogen, FW, and DHW are $953.64/h, $57.35/h, and $82.48/h, respectively. Finally, Bloemfontein, Las Vegas, and Tunis are the most favorable regions economically, with a low levelized cost of electricity of $0.05931, $0.06006, and $0.05932 per kWh, along with payback periods of 0.6144, 0.5524, and 1.069 years, respectively.

A new method of estimating carbon sequestration and its efficiency in coastal waters

The biological pump (BP) in oceans refers to the fraction of phytoplankton organic matter sinking out of the euphotic zone (surface layer) into below the pycnocline layer (bottom layer) in the water column. Currently, sediment traps are commonly used to estimate organic settlement and carbon sequestration in open oceans, but the installation of the sediment traps in the ocean requires special efforts, let alone the temporal and spatial discordance of particle sinking trajectory from the surface to the bottom. Net community production is used only for the euphotic zone. Thus, there has been a lack of a simple method to estimate the export flux of organic carbon from the surface to bottom layer and to quantify BP efficiency in the coastal areas. In this study, we develop a conceptual model to illustrate carbon sequestration processes from the surface to the pycnocline layer and the bottom layer. The idea is to examine an increase (the release) in dissolved inorganic carbon (DIC) and organic carbon (DOC) in the bottom layer. Based on this model, a new method was developed to estimate carbon sequestration (CS) and carbon sequestration efficiency (CSE). Two cruises in May and August in 2016 were conducted to establish a three-end-member mixing model of θ-S which is used to estimate biologically mediated DIC (ΔDIC = DICin-situ-DICmixed) in relation to the conservative mixing of DIC. Based on the density gradient threshold of 0.03 kg m-3m-1, the water column is separated into the surface mixed layer, the pycnocline layer and bottom layer and integrated ΔDIC (IntΔDIC) in the three layers are estimated. The same approach is applied to dissolved organic carbon (DOC) data which are used to make the same calculation with the mixing model to obtain the sequestrated DOC mass in the bottom layer. Carbon uptake and carbon sequestration (CS) can be calculated as the integrated ΔDIC in the surface mixed layer and bottom layers, respectively. Carbon sequestration efficiency (CSE), which is defined as sum of bottom layer Int ΔDIC + Int ΔDOC divided by the whole water column integrated ΔDIC can also be calculated. The results showed that during algal blooms driven by abundant nutrients from the Pearl River Estuarine water in May, little sinking carbon was observed due to the absence of the bottom layer, resulting in low CSE. In contrast, in August, even no significant algal bloom occurred, the strengthened water stratification, lead to a substantial increase in the CS(449.49 ± 366.14 mmol C m-2), leading to an increased CSE to a range of 0 ∼ 92.79 % (average 60.55 ± 25.07 %). The carbon sequestration rate was 55.61 ± 45.30 mg C m-2 d-1. The new method, based on vertical changes of DIC and DOC due to biological uptake or release in relation to the conservative mixing of water masses, provides an easy and direct tool to estimate carbon sequestration and carbon sequestration efficiency in the stratified water column in coastal waters.

Stepwise Calibration of Age‐Dependent Biomass in the Integrated Biosphere Simulator (IBIS) Model

AbstractMany land surface models (LSMs) assume a steady‐state assumption (SS) for forest growth, leading to an overestimation of biomass in young forests. Parameters inversion under SS will potentially result in biased carbon fluxes and stocks in a transient simulation. Incorporating age‐dependent biomass into LSMs can simulate real disequilibrium states, enabling the model to simulate forest growth from planting to its current age, and improving the biased post‐calibration parameters. In this study, we developed a stepwise optimization framework that first calibrates “fast” light‐controlled CO2 fluxes (gross primary productivity, GPP), then leaf area index (LAI), and finally “slow” growth‐controlled biomass using the Global LAnd Surface Satellite (GLASS) GPP and LAI products, and age‐dependent biomass curves for the 25 forests. To reduce the computation time, we used a machine learning‐based model to surrogate the complex integrated biosphere simulator LSM during calibration. Our calibrated model led to an error reduction in GPP, LAI, and biomass by 28.5%, 35.3% and 74.6%, respectively. When compared with net biome productivity (NBP) using no‐age‐calibrated parameters, our age‐calibrated parameters increased NBP by an average of 50 gC m−2 yr−1 across all forests, especially in the boreal needleleaf evergreen forests, the NBP increased by 118 gC m−2 yr−1 on average, increasing the estimate of the carbon sink in young forests. Our work highlights the importance of including forest age in LSMs, and provides a novel framework for better calibrating LSMs using constraints from multiple satellite products at a global scale.

The impact of spongy moth (Lymantria dispar dispar) defoliation on carbon balance of a temperate deciduous forest in North America

Temperate deciduous forests are an important contributor to the global carbon (C) sink. However, changes in environmental conditions and natural disturbances such as insect infestations can impact carbon sequestration capabilities of these forests. While, insect infestations are expected to increase in warmer future climates, there is a lack of knowledge on the quantitative impact of these natural disturbances on the carbon balance of temperate deciduous forests. In 2021, a record-breaking defoliation, caused by the spongy moth (Lymantria dispar dispar (LDD), formerly knows as the gypsy moth) occurred in eastern North America. In this study, we assess the impact of this spongy moth defoliation on carbon uptake in a mature oak-dominated temperate forest in the Great Lakes region in Canada, using eddy covariance flux data from 2012 to 2022. Study results showed that the forest was a large C sink with mean annual net ecosystem productivity (NEP) of 207 ± 77 g C m–2 yr−1 from 2012 to 2022, excluding 2021, which experienced the infestation. Over this period mean annual gross ecosystem productivity (GEP) was 1,398 ± 137 g C m–2 yr−1, while ecosystem respiration (RE) was 1,209 ± 139 g C m–2 yr−1. However, in 2021 due to defoliation in the early growing season, annual GEP of the forest declined to 959 g C m–2 yr−1, while annual RE increased to 1,345 g C m–2 yr−1 causing the forest to become a large source of C with annual NEP of -351 g C m–2 yr−1. The forest showed a rapid recovery from this major disturbance event, with annual GEP, RE, and NEP values of 1,671, 1,287, and 298 g C m–2 yr−1, respectively in 2022 indicating that the forest was once again a large C sink. This study demonstrates that major transient natural disturbances under changing climate can have a significant impact on forest C dynamics. The extent to which North American temperate forests will remain a major C sink will depend on the severity and intensity of these disturbance events and the rate of recovery of forests following disturbances. Lay abstractTemperate deciduous forests play an important role in carbon sequestration from the atmosphere. However, the impact of climate change, extreme weather, and disturbance events can alter the extent to which these forests sequester carbon, in some cases shifting their role from being a carbon sink to becoming a carbon source to the atmosphere. In 2021, a spongy moth infestation severely defoliated a mature oak-dominated temperate forest north of Lake Erie, Ontario, Canada, turning the forest from a 10-year mean carbon sink of about 2 tons of carbon per hectare to a carbon source of about 3.5 tons of carbon per hectare. Our analysis indicates that meteorological conditions during the early growing season might have influenced the severity of this infestation. Specifically, the prevalence of dry and warm weather conditions enabled the moth to survive and thrive longer. This study shows the significant influence of natural disturbances on forest carbon dynamics as temperatures continue to rise due to climate change. The future role forests play in carbon sequestration will be determined by the severity of disturbance events and the effectiveness of forests to recover in the aftermath of these events.

High Abundances and Expression Levels of Atypical, Non‐Denitrifier N2O Reductases Drive Strong Microbial N2O Consumption Rates in a Minimally Impacted Mangrove Stand

AbstractKnowledge of the ecological mechanisms governing N2O cycling in marine sediments lags that of water columns and terrestrial soils, leaving much to be learned about how microbial community dynamics relate to variability in sediment N2O fluxes. The present study assesses these relationships across two distinct environments by focusing on the community structure and activity of N2O reducing microorganisms. The N2O sink capacity of minimally impacted Bermudian mangrove sediments was first estimated using trace‐level microsensors and profile interpretation modeling. Molecular data obtained from these sediments were then compared with those from the Northeast Subarctic Pacific (NESAP) outer continental margin, where previous measurements suggest considerable N2O effluxes. Net N2O uptake was observed for mangrove sediments under ambient and elevated dissolved inorganic nitrogen concentrations (−0.22 ± 0.15 to −0.30 ± 0.26 μmol N2O m−2 d−1), suggesting the microbial potential for N2O consumption exceeded the potential for production via combined nitrification and denitrification. Targeting of bacterial nosZI and nosII gene clusters for quantification using qPCR indicated higher abundance and expression of non‐denitrifier nosZII genes in mangrove sediments demonstrating net N2O uptake. Net N2O production in NESAP sediments was associated with higher abundance and expression of nosZI genes associated with canonical denitrifiers. These results suggest that organisms possessing atypical nosZII genes may act as important N2O scavengers in low‐nitrogen coastal sediments.