Carbon Balance Research Articles

Spatiotemporal differentiation of carbon budget and balance zoning: Insights from the middle reaches of the Yangtze River Urban Agglomeration, China

Urbanization has substantially changed land use and led to local growth and an overall imbalance in carbon emissions. Scientific analysis of carbon emissions from land use (CELU) and exploration of carbon balance zoning can provide useful references for regional low-carbon land use management in urban agglomerations. This study analyzed the spatiotemporal dynamics of CELU based on land use and socioeconomic data, and utilizing the emission coefficient method. The economic contribution coefficient of carbon emissions (ECC) and Ecological Support Coefficient of carbon emissions (ESC) was used as the basis for developing carbon balance zoning, and the main function positioning of counties was used to combine with carbon balance zoning. Subsequently carbon balance partitions with determinants across 190 counties in the Middle Reaches of the Yangtze River Urban Agglomeration (MRYRUA) was obtained. We found that the net carbon emissions from land use in MRYRUA increased from 1.242 to 4.049 million tons, showing a clear upward trend. Notably, the Gini coefficients of carbon emissions and sinks of the MRYRUA were both higher than 0.4, and the pressure on the regional carbon balance intensified. In addition, based on the carbon balance analysis, MRYRUA was divided into five types: low-carbon economic zones, low-carbon optimization zones, carbon intensity control zones and high-carbon optimization zones. These zones were used to combine with the main function positioning, and finally got 11 types of zoning results. In response, this study proposes different low-carbon land-use optimization strategies based on the carbon budget and comprehensive development characteristics of different zones.

How and why do species break a developmental trade-off? Elucidating the association of trichomes and stomata across species.

Previous studies have suggested a trade-off between trichome density (Dt) and stomatal density (Ds) due to shared cell precursors. We clarified how, when, and why this developmental trade-off may be overcome across species. We derived equations to determine the developmental basis for Dt and Ds in trichome and stomatal indices (it and is) and the sizes of epidermal pavement cells (e), trichome bases (t), and stomata (s) and quantified the importance of these determinants of Dt and Ds for 78 California species. We compiled 17 previous studies of Dt-Ds relationships to determine the commonness of Dt-Ds associations. We modeled the consequences of different Dt-Ds associations for plant carbon balance. Our analyses showed that higher Dt was determined by higher it and lower e, and higher Ds by higher is and lower e. Across California species, positive Dt-Ds coordination arose due to it-is coordination and impacts of the variation in e. A Dt-Ds trade-off was found in only 30% of studies. Heuristic modeling showed that species sets would have the highest carbon balance with a positive or negative relationship or decoupling of Dt and Ds, depending on environmental conditions. Shared precursor cells of trichomes and stomata do not limit higher numbers of both cell types or drive a general Dt-Ds trade-off across species. This developmental flexibility across diverse species enables different Dt-Ds associations according to environmental pressures. Developmental trait analysis can clarify how contrasting trait associations would arise within and across species.

Reduction of an Ilmenite Concentrate by Using a Novel CO2/CH4 Thermal Plasma Torch

Plasma technology has emerged as a very helpful tool in a variety of sectors, notably metallurgy. Innovators and scientists are focused on the problem of finding a more ecologically friendly way of extracting titanium and iron metal from natural ilmenite concentrate for industrial applications. A direct current (DC) plasma torch operating at atmospheric pressure is used in this study to describe a decarbonization process for reducing an ilmenite concentrate. The plasma gases employed in this torch are CO2 and CH4. The molar ratio of the gases may be crucial for achieving a satisfactory reduction of the ilmenite concentrate. As a result, two molar ratios for CO2/CH4 have been chosen: 1:1 and 2:1. During torch operation, a thin layer of graphite is formed on the cathode to establish a protective barrier, prolonging the cathode’s life. The material was analyzed using X-ray diffraction (XRD) and scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS). The output gases were analyzed using mass spectrometry (MS). In addition, a thermodynamic analysis was performed to predict the development of thermodynamically stable phases. An economic assessment (including capital expenditures (CAPEX) and operating expenditures (OPEX)) and a carbon balance were developed with the feasibility of the piloting in mind.

Global carbon balance of the forest: satellite-based L-VOD results over the last decade

Monitoring forest carbon (C) stocks is essential to better assess their role in the global carbon balance, and to better model and predict long-term trends and inter-annual variability in atmospheric CO2 concentrations. On a national scale, national forest inventories (NFIs) can provide estimates of forest carbon stocks, but these estimates are only available in certain countries, are limited by time lags due to periodic revisits, and cannot provide spatially continuous mapping of forests. In this context, remote sensing offers many advantages for monitoring above-ground biomass (AGB) on a global scale with good spatial (50–100 m) and temporal (annual) resolutions. Remote sensing has been used for several decades to monitor vegetation. However, traditional methods of monitoring AGB using optical or microwave sensors are affected by saturation effects for moderately or densely vegetated canopies, limiting their performance. Low-frequency passive microwave remote sensing is less affected by these saturation effects: saturation only occurs at AGB levels of around 400 t/ha at L-band (frequency of around 1.4 GHz). Despite its coarse spatial resolution of the order of 25 km × 25 km, this method based on the L-VOD (vegetation optical depth at L-band) index has recently established itself as an essential approach for monitoring annual variations in forest AGB on a continental scale. Thus, L-VOD has been applied to forest monitoring in many continents and biomes: in the tropics (especially in the Amazon and Congo basins), in boreal regions (Siberia, Canada), in Europe, China, Australia, etc. However, no reference study has yet been published to analyze L-VOD in detail in terms of capabilities, validation and results. This paper fills this gap by presenting the physical principles of L-VOD calculation, analyzing the performance of L-VOD for monitoring AGB and reviewing the main applications of L-VOD for tracking the carbon balance of global vegetation over the last decade (2010–2019).

Short-term effect of the harvesting method on ecosystem carbon budget in hemiboreal Scots pine forest: Shelterwood cutting versus clear-cut

Shelterwood cutting (SC) has been highlighted as an alternative method to clear-cut (CC)-based even-aged forest management. However, compared to CC, the effect of SC on stand carbon (C) balance is still poorly understood at the ecosystem level. We examined the prompt effect of SC versus CC on ecosystem net primary production (NEP) on a short-term scale, using the C budgeting method combined with eddy covariance (EC) measurements in hemiboreal mature Scots pine stands.The early effect of SC on annual C budget after removing 30–40 % of the growing stock revealed diverse patterns in the studied stands; NEP varied from 0.62 to −1.3 t C ha−1 yr−1 for the C sink and the C source, respectively. However, C loss decreased already in the second post-thinning year and levelled out attaining −0.41 t C ha−1 yr−1, which is close to balance.Furthermore, C loss declined in the second post-harvesting year at the CC sites as a result of the increased production of the ground vegetation and the decreased soil heterotrophic respiration (Rh) flux. However, C loss from dry mesotrophic clear-cuts was almost −1.8 t C ha−1 yr−1 for both study sites. Since estimation of the individual C fluxes for C budgeting is associated with variability-induced errors, the estimated values of NEP contain uncertainties of various levels.The estimated annual cumulative Rh flux was significantly higher in the SC versus CC areas and the mean annual Rh values across the study sites were 3.57 ± 0.25 and 2.59 ± 0.09 t C ha−1 yr−1, respectively.Annual estimated NEE after SC was 1.8 ± 0.52 t C ha−1 yr−1, gross primary ecosystem production was 9.28 ± 0.97 and total ecosystem respiration was 7.47± 0.28 t C ha−1 yr−1. The discrepancy between the estimated values of NEE and NEP was 1.2 t C ha−1 yr−1.In the short term SC demonstrated some advantage over CC from the perspective of the C cycle, but the difference in NEP values between the SC and CC treatments was not convincingly overwhelming. Hence, SC allows to maintain the forest cover for a longer period and to avoid drastic changes in the landscape; still, after SC, C budget varied between the C sink and the C source.

Impacts of wildfires on boreal forest ecosystem carbon dynamics from 1986 to 2020

Abstract Wildfires significantly change boreal forest ecosystem carbon balance through both direct combustion and post-fire carbon dynamics. Affected vegetation influences soil thermal regime and carbon cycling by impacting the surface energy balance of boreal forests. This study uses a process-based biogeochemistry model to quantify carbon budget of North American boreal forests during 1986-2020 based on satellite-derived burn severity data. During the study period, burn severity generally increases. Fires remove ecosystem carbon of 2.4 Pg C and reduce net ecosystem production (NEP) from 32.6 to 0.8 Tg C/year, making the forest ecosystems lose 3.5 Pg C, shifting a carbon sink to a source. The canopy’s cooling effect leads to lower soil temperature and lower net primary production due to lower nitrogen mineralization and uptake. Post-fire NEP decreases from 1.6 to 0.8 Tg C/year. This reduction accounts for 50% of the simulated NEP when the effects of fire-affected canopy are not considered. Our study highlights the importance of wildfires and their induced-canopy changes in soil thermal and ecosystem carbon dynamics of boreal forests.

Climate-regulation of organic carbon export in erosive mountain settings: A case study from Taiwan since the last glacial maximum

The balance between the burial of biospheric organic carbon (OCbio) in the ocean and the oxidation of rock-derived organic carbon across landscapes (OCpetro) helps to regulate atmospheric CO2 and O2 over geological time. However, we lack reconstructions of these processes over the timescales necessary to properly understand the drivers and feedbacks operating. Here we use a sediment core from the Zhuoshui River delta in Taiwan, which receives sediments from a rapidly uplifting and eroding catchment, to reconstruct the variations in OC content and radiocarbon composition since the Last Glacial Maximum (LGM). We find that the export of OCbio and the oxidation of OCpetro are both modulated by climate-driven changes in physical erosion and temperature. During cold and dry periods, such as the LGM and the Younger Dryas (YD), shallow erosion and low temperature enhanced the preservation of OCbio in the biosphere in catchment, while deep erosion and high temperature during warm and wet periods, such as the Holocene, favored the dilution and degradation of OCbio. The weathering intensity of OCpetro (ω) was inversely related to physical erosion, suggesting a lower intensity of oxidation during the Holocene period while the overall oxidation flux was enhanced. This suggests that the degree of weathering was primarily controlled by physical erosion. We propose a proxy to estimate the ratio of fluxes of OCbio export and OCpetro oxidation, and show that the net balance between these two processes shifted from a carbon sink during the late deglacial period to a carbon source during the mid-late Holocene. Our study reveals that with CO2 rise, a warmer and wetter climate would promote the exposure and oxidation of OCpetro by erosion in this mountain range, leading the organic carbon balance towards a CO2 source to the atmosphere.

Nitrided Copper-Iron Composite Oxides Derived from Layered Double Hydroxides for Enhanced Carbon Dioxide Electroreduction to Methane and Formic Acid

The reduction of carbon dioxide to valuable chemical products is a promising solution to address carbon balance and energy issues. Herein, amorphous nitrided copper-iron oxides are prepared by gas-phase nitriding of CuFe-layered double hydroxide precursors with urea as nitrogen source. Amorphous materials are more likely to generate defect vacancies during the reaction process, and these vacancies can function as active sites for catalytic reactions. Therefore, the obtained materials show high activity for CO2 electroreduction to methane and formic acid, achieving a total Faraday efficiency of 74.7% at −0.7 V vs RHE and exhibiting a continuous 10 h durability in the H-cell. The uniformly distributed Cu+ sites act as active sites by losing electrons to activate CO2. During the CO2 electroreduction, CO2 is converted to *COOH via proton-electron coupling, *COOH combines directly with a proton in solution to produce the HCOOH product, and the other part of *COOH undergoes a protonated dehydration process to form the *CHO intermediate which dehydrates again to form CH4. This study provides a new approach for designing CO2 electroreduction catalysts.

Assessment of the Potential Contribution of the Urban Green System to the Carbon Balance of Cities

Reducing greenhouse gas emissions is a crucial challenge in urban areas characterized by high energy consumption and reduced exposure to nature. In this context, the urban green system could play a pivotal role. In the literature, scholars have analyzed both the ability of species-specific and layout-specific green infrastructure to increase carbon sequestration and the best location sites for new green infrastructure to increase the provision of overall ecosystem services. There is a lack of studies helping green urban planners and designers choose where and which green infrastructure to implement based on vegetation species-specific performance and the local carbon emissions of city components. This paper uses tree inventory data from a medium-sized city in central Italy (Perugia) to develop a spatial analysis of urban park performance in carbon sequestration. Then, the method evaluates the carbon emission of a public city building to generate a spatialized balance between building demand and tree supply to support local decisions about the best locations for new green infrastructure and the choice between species. The paper contributes to GIS-based tools that vary the recommended location sites and species for new green infrastructure based on the demanded ecosystem service.

Cultivated Grassland Types Differently Affected Carbon Flux Downstream of the Yellow River

Cultivated Grassland Types Differently Affected Carbon Flux Downstream of the Yellow River

Tracking Land-use Trajectory and Other Potential Drivers to Uncover the Dynamics of Carbon Stocks of Terrestrial Ecosystem in the Songnen Plain

Land-use change is an important factor affecting terrestrial carbon balance, and it is crucial to explore the response of terrestrial carbon stocks to land-use change, especially in the Songnen Plain, which faces a fierce conflict between the rapid growth of production activities and ecosystem degradation. In this study, we measured soil organic carbon and vegetation biocarbon stocks in the Songnen Plain based on IPCC-recommended methodologies, and explored the characteristics of carbon stock changes in land-use trajectories, land-use drivers, and specific land-use change scenarios (cropland cultivation, returning cropland to forests, the expansion of land for construction, deforestation, greening, and land degradation). The results showed that soil organic carbon stock in the Songnen Plain decreased by 1.63 × 105 t, and vegetation biocarbon stock increased by 2.10 × 107 t from 2005 to 2020. Human factors and natural factors jointly contributed to the land-use change, but the extent of the role of human factors was greater than that of natural factors. The increase in land-use trajectory led to the decrease in soil organic carbon stock and the increase in vegetation biocarbon stock. There was no difference in the effects of human-induced and natural-induced land-use changes on vegetation biocarbon stocks, but the effects on soil organic carbon stocks were diametrically opposite, increasing by 43.27 t/km2 and decreasing by 182.02 t/km2, respectively. The reclamation of arable land, returning cropland to forests, and greening led to a net increase in terrestrial carbon stocks (+813,291.84 t), whereas land degradation, deforestation, and land-use expansion led to a decrease in terrestrial carbon stocks (−460,710.2 t). The results of this study can provide a reference for the adjustment of land-use structure and the increase in terrestrial carbon stock in the Songnen Plain.

Carbon storage in a dry Miombo woodland area in Tanzania

A persistent need exists, both politically and academically, for knowledge on carbon storage and sequestration potentials of forest ecosystems and their contributions to the global carbon balance. This study assessed carbon stocks of a 6 065 ha dry Miombo woodland site in Iringa Rural district, Tanzania. The carbon stock for each of the six pools: trees, shrubs, deadwood, herbaceous vegetation (grass and herbs), surface litter and soil were estimated. Assuming a 50% carbon share of biomass, the results showed that the aboveground carbon stocks were: 24.71 Mg C ha−1 for trees; 10.88 Mg C ha−1 for shrubs; 0.54 Mg C ha−1 for deadwood; 0.58 Mg C ha−1 for herbaceous vegetation; and 2.47 Mg C ha−1 for surface litter. Soil carbon was estimated separately for two depth ranges: 0–15 cm and 15–30 cm below the surface. These soil strata contributed 21.24 Mg C ha−1 and 8.22 Mg C ha−1 respectively. The total carbon (C) stock of the six pools was 68.64 Mg C ha−1. Considering the vast area covered by dry Miombo woodlands in Tanzania and in 10 other countries in south-eastern Africa, the carbon stock of these ecosystems is clearly tremendous, underscoring the importance of conserving them.

Non-structural carbohydrate concentrations in tree organs vary across biomes and leaf habits, but are independent of the fast-slow plant economic spectrum

Carbohydrate reserves play a vital role in plant survival during periods of negative carbon balance. Under a carbon-limited scenario, we expect a trade-offs between carbon allocation to growth, reserves, and defense. A resulting hypothesis is that carbon allocation to reserves exhibits a coordinated variation with functional traits associated with the ‘fast-slow’ plant economics spectrum. We tested the relationship between non-structural carbohydrates (NSC) of tree organs and functional traits using 61 angiosperm tree species from temperate and tropical forests with phylogenetic hierarchical Bayesian models. Our results provide evidence that NSC concentrations in stems and branches are decoupled from plant functional traits. while those in roots are weakly coupled with plant functional traits. In contrast, we found that variation between NSC concentrations in leaves and the fast-slow trait spectrum was coordinated, as species with higher leaf NSC had trait values associated with resource conservative species, such as lower SLA, leaf N, and leaf P. We also detected a small effect of leaf habit on the variation of NSC concentrations in branches and roots. Efforts to predict the response of ecosystems to global change will need to integrate a suite of plant traits, such as NSC concentrations in woody organs, that are independent of the ‘fast-slow’ plant economics spectrum and that capture how species respond to a broad range of global change drivers.

Phenology response of subtropical Chinese fir (Cunninghamia lanceolata) to soil warming, precipitation exclusion and their interaction

Plant phenology plays an important role in nutrient cycling and carbon balance in forest ecosystems, but its response to the interaction of global warming and precipitation reduction remains unclear. In this study, an experiment with factorial soil warming (ambient, ambient +5 °C) and precipitation exclusion (ambient, ambient −50 %) was conducted in a subtropical Chinese fir (Cunninghamia lanceolata) plantation. We investigated the effects of soil warming, precipitation exclusion, and their interactions on Chinese fir phenology involving the timing of tree height and fine root growth. In the meantime, the impact of tree height growth and related climatic factors on fine root production was also assessed. The results showed that: (1) more variable phenology responses were observed in fine root growth than in tree height growth to the climatic treatments; the duration of fine root growth and tree height growth was significantly reduced by the precipitation exclusion and warming treatment, respectively; phenology differences of fine roots and tree heights exerted by the solo warming and precipitation exclusion treatment were further enlarged by the combined treatment; and despite the greater inter-annual phenology stability of tree height growth than fine roots, both of them showed insignificant response to all the climate treatments; (2) asynchrony of phenology between tree height and fine root growth was significantly extended by solo warming and precipitation exclusion treatments, and further extended by the combined treatment; (3) fine root production was significantly and positively correlated with atmospheric, and soil temperature, and tree height growth as well, which was altered by warming and precipitation exclusion treatments. Our results demonstrated that climatic changes significantly and differently enlarge phenology differences for both above and below ground plant components, extend the phenology asynchrony between above and below ground, and also reveal the sensitive and variable nature of root phenology. Overall, these phenology responses to climatic change may contribute to weaken the close link between fine root production and tree height growth, which may result in mismatch between nutrient demand and supply timing in Chinese fir plantation.

Contrasted effects of shade tree legumes on soil organic carbon stock and carbon balance in 20-year cacao agroforestry, Ivory Coast

Cacao–based agroforestry systems are promoted as adaptation and mitigation solutions for cacao production and carbon sequestration. Based on a 20-year experiment, we assessed the impact of associated shade tree legume (ATL), Albizia lebbeck and Acacia mangium on the total carbon stock (in soil at 60 cm depth + tree biomass + litter) of cacao stands. This study included cacao systems shaded with either A. lebbeck (Cacao-Alb) or A. mangium (Cacao-Aca) and full-sun cacao stands (Control). Soil organic carbon (SOC) contents (up to 60 cm deep) were estimated by a calibrated near-infrared spectroscopy model. Total tree biomasses were estimated using allometric equations. Leaf litter was sampled from 1-m2 quadrats. Compared to Control, Cacao-Aca had a significant negative impact on the carbon stock in the cacao biomass (−47%) as well and in the soil at depths of 10 cm (−23%), 30 cm (−21%) and 60 cm (−12%). In contrast, Cacao-Alb had a nonsignificant effect on carbon storage in the cacao biomass, whereas it generally had a positive influence on the SOC stock regardless of depth, i.e., +6% at the 0–10 cm depth, +7% at 0–30 cm, +20% at 30–60 cm and + 11% at 0–60 cm. Cacao-Aca had a significant positive impact (+71%) on the total carbon stock per hectare. The increase in Cacao-Alb relative to that in the Control reached +38%, but the difference was not significant. These contrasting results between the two tree legume species could be explained by the high-quality litter, reflected by the lower C/N and C/P ratios produced by A. lebbeck, and the greater negative impact of A. mangium on cacao biomass. The main finding of this study is that the impact of intercropping cacao with shade tree legumes on the stand-level total carbon stock depends on the ATL species.

Organic carbon sink dynamics and carbon sink-source balance in global lakes during the Anthropocene

The carbon burial and greenhouse gas emissions of lakes are pivotal in the global carbon cycle to offset or accelerate global warming. However, their balance or the magnitude of anthropogenic increase of carbon burial remains uncertain in global lakes. Here, we quantified the carbon sink dynamics and the sink-source balance in global lakes with effect-size metrics, that is, the log-response ratio of organic carbon burial between post-1950 and pre-1900 periods and the carbon balance ratio between carbon burial and greenhouse gas emissions, respectively. The organic carbon burial ratios revealed an average increase of 2.45 times in carbon burial rates during the Anthropocene, while the carbon balance ratios were negative in 82.68% of lakes, indicating that most lakes had lower burial rates than emission rates and acted as carbon sources rather than carbon sinks. The organic carbon burial ratios exhibited a significantly decreasing latitudinal trend and were mainly influenced by lake's trophic state with the explained variation of 44.79%. They were also indirectly influenced by climate, lake morphometry and catchment properties through their interactions with the lake's trophic state. The carbon balance ratios, however, showed a nonsignificant latitudinal trend. They were primarily affected by lake catchment properties with the explained variation of 26.21% and were also indirectly affected by climate variables via the interactions with catchment properties. Overall, our study highlights that human activities such as lake eutrophication and catchment changes have altered the carbon sink and source in global lakes during the Anthropocene, and are essential drivers for future evaluations of lake carbon budgets.

Water, energy and environment nexus: Quantitative assessment for integrated power plants with renewable energy

The population increase and the demand for water and energy, accompanied by the implications of environment pollution for natural and human resources, indicate the critical necessity for a coherent movement towards nexus between water, energy, and environment. Due to the fact that power generation industry is responsible for a significant proportion of water and fuel consumption and Carbon dioxide emissions within the world, in this research, the application of the hybrid renewable system in a thermal power plant has been assessed based on the approach of analyzing the link between energy, water and environment. The design of the solar system and the assessment of carbon balance during the power plant lifetime have been conducted in PVsyst application in 2022. Moreover, ReCipe environmental model has been used for assessing the effect of decrease in carbon emission on the ecosystem. The findings of the research indicate that the replacement of at least 2 % of the nominal capacity of the fossil fuel power plant with the renewable one, prevents the emission of 1431.28 tons of carbon dioxide yearly. This amount equals to 380.34 cubic meters of reserve in fossil fuel consumption and 391.73 tons of crude oil. The results also showed that in addition to preserving natural resources, the hybrid cycle design leads to significant water demand reduction which equals to 3842 cubic meters with the capacity to supply underground water sources. Due to the interests of preserving water and energy resources and decreasing carbon emission in power plant industry, within the framework of nexus approach, management of energy supply by replacing resources and using water and heat recovery technologies and application of energy demand management policies based on energy efficiency and environmental implications is recommended.

Elucidating the role of ferric chloride on carbon capture from low-strength municipal wastewater in high-rate activated sludge process: Parameter optimization and crucial mechanism

To enhance organics capture efficiency from low-strength municipal wastewater of China, FeCl3 enhanced high-rate activated sludge (FC-HRAS) process was established in this work. Effects of sludge concentration and FeCl3 dosage on carbon capture in FC-HRAS were investigated. The optimum sludge concentration of 2.0 g/L and FeCl3 dosage of 30 mg Fe/L were obtained, with total COD removal efficiency of 76.8%. Carbon balance analysis showed that FC-HRAS increased organics capture proportion by 91.8% while reducing loss from oxidative metabolism compared to HRAS. The potential mechanism of enhanced carbon capture for FC-HRAS was further explored. Adding Fe(III) caused coagulation of organics by increasing the Zeta potential in wastewater. Impacted by charge neutralization “compression” and coagulation floc “encirclement”, sludge particle sizes decreased, leading to increases of internal surface area and adsorption site of sludge for binding with bacteria; it facilitated the biological flocculation of FC-HRAS. Meanwhile, Fe(III) binding with proteins in EPS induced formation of “protein shell – β polysaccharides kernel” sludge structure and reduction of sludge negative charge, which intensified sludge stability and agglomeration. These factors explained the increase in organics capture proportion. The decrease in metabolism loss of organics could be attributed to the increase in organics transfer resistance in sludge EPS and selective elimination of heteromorphic bacteria (e.g., denitrifiers) in sludge. This work provided guidance for energy-neutral and cost-saving wastewater treatment in China.

Indonesia's contribution to global carbon flows: Which sectors are most responsible for the emissions embodied in trade?

Motivated by recent developments in global carbon policies, such as the carbon border adjustment mechanism (CBAM) in Europe and carbon pricing in Indonesia, this paper elaborates on CO2 emissions embodied in products entering and leaving Indonesia and identifies carbon-intensive sectors responsible for carbon leakage. This was performed by using global multi-regional input-output analysis and consumption-based accounting (CBA) - production-based accounting (PBA) ratio. In 2016, the annual CO2 emissions embodied in Indonesia's exports and imports were 114 and 95 Mt. CO2, respectively. Considering final demand only, these values reduce to 32 and 22 Mt. CO2 or 0.9 and 0.6 % of total CO2 emissions in global trade, respectively. The electrical and machinery sector makes up the most CO2 emissions in Indonesian exports. In terms of per USD, metal products and petroleum, chemical and non-metallic mineral products are among the most carbon-intensive sectors, thus likely to be affected by the CBAM policy. Furthermore, Indonesia's emissions under CBA were slightly lower than PBA, indicating that minor carbon leakage occurred in 2016, but this is subject to uncertainty. Assessing the relative CO2 emissions of various economic sectors is suitable for manufacturing goods whose processes are typically dominated by fossil combustion. However, this is not the case for the agriculture sector as its carbon footprint values are underestimated due to the exclusion of land use, land use change, and forestry emissions. Overall, our findings can serve as a baseline to further explore how a transition towards a low-carbon economy in Indonesia could improve global-trade carbon balances.

Allometric relationships and trade-offs in 11 common Mediterranean-climate grasses.

Biomass allocation in plants is the foundation for understanding dynamics in ecosystem carbon balance, species competition, and plant-environment interactions. However, existing work on plant allometry has mainly focused on trees, with fewer studies having developed allometric equations for grasses. Grasses with different life histories can vary in their carbon investment by prioritizing the growth of specific organs to survive, outcompete co-occurring plants, and ensure population persistence. Further, because grasses are important fuels for wildfire, the lack of grass allocation data adds uncertainty to process-based models that relate plant physiology to wildfire dynamics. To fill this gap, we conducted a greenhouse experiment with 11 common California grasses varying in photosynthetic pathway and growth form. We measured plant sizes and harvested above- and belowground biomass throughout the life cycle of annual species, while for the establishment stage of perennial grasses to quantify allometric relationships for leaf, stem, and root biomass, as well as plant height and canopy area. We used basal diameter as a reference measure of plant size. Overall, basal diameter is the best predictor for leaf and stem biomass, height, and canopy area. Including height as another predictor can improve model accuracy in predicting leaf and stem biomass and canopy area. Fine root biomass is a function of leaf biomass alone. Species vary in their allometric relationships, with most variation occurring for plant height, canopy area, and stem biomass. We further explored potential trade-offs in biomass allocation across species between leaf and fine root, leaf and stem, and allocation to reproduction. Consistent with our expectation, we found that fast-growing plants allocated a greater fraction to reproduction. Additionally, plant height and specific leaf area negatively influenced the leaf-to-stem ratio. However, contrary to our hypothesis, there were no differences in root-to-leaf ratio between perennial and annual or C4 and C3 plants. Our study provides species-specific and functional-type-specific allometry equations for both above- and belowground organs of 11 common California grass species, enabling nondestructive biomass assessment in California grasslands. These allometric relationships and trade-offs in carbon allocation across species can improve ecosystem model predictions of grassland species interactions and environmental responses through differences in morphology.