Plant Carbon Research Articles

Comprehensive analysis of greenhouse gas emissions and emission factors in a Korean domestic wastewater treatment plant: Insights into mechanisms and pathways for climate change mitigation

This study aimed to estimate greenhouse gas (GHG) emissions from the Daejeon wastewater treatment plant (WWTP) in South Korea and identify strategies for reducing its carbon footprint. Both the worksheet-based Carbon Footprint Calculation Tool and the Massflow3 simulator were used to calculate the total GHG emissions from the “D” WWTP and identify the main sources of emissions. The results revealed that electricity consumption contributed to 45 − 48 % of emissions, while direct emissions from N2O accounted for 35–38 % of the total emissions. Furthermore, it was discovered that the WWTP's GHG emissions were 33–57 % higher compared to European sewage treatment plants that had established GHG reduction programs. To decrease the plant's carbon footprint, recommendations include optimizing nitrogen removal rates while minimizing incomplete nitrification and controlling the air flow rate in the aeration tank. Additionally, there is an emphasize on the importance of establishing a strategy to reduce indirect GHG emissions resulting from power consumption. These findings have important implications for the policy and management of WWTPs, highlighting the potential environmental and economic benefits of GHG emissions reduction.

Lettuce tolerance to verticillium wilt after inoculation with Penicillium pinophilum and Rhizophagus intraradices

The ability to mitigate verticillium wilt is an important attribute of a biocontrol agent in terms of its global market potential. This study evaluated the protective effect of an arbuscular mycorrhizal (AM) fungus and an endophytic fungus (Penicillium pinophilum) inoculation against verticillium wilt in lettuce host. The seedlings in four treatment groups (control, AM, Penicillium, AM + Penicillium) were raised for six weeks in the presence or absence of the pathogen (Verticillium dahliae) in a growth chamber. The foliar disease incidence was evaluated and recorded as 37 %, 35 %, 3 %, and 14 % for Control, AM, Penicillium, and dual inoculated treatments, respectively. V. dahliae decreased the plant growth indices, carbon, and nitrogen contents in all groups, except in Penicillium treatment. Trace elements concentrations were reduced due to disease across board, but manganese (Mn) was modulated by the endophyte. R. intraradices and its co-inoculation with P. pinophilum did not confer protection to lettuce, despite having lower quantity of pathogen DNA in their stems than Control and Penicillium inoculated plants. In mitigating the negative effect of V. dahliae, aside in vivo pathogen antibiosis, the endophyte modulated reactive oxygen species, nitrogen, manganese, and improved host growth indices, thereby, gave the most effective bio-protection. However, its co-inoculation with the R. intraradices reduced its efficacy.

Effect of salinity on carbon sequestration in constructed wetlands and its functional mechanisms

Currently, many constructed wetlands (CWs) are facing the threat of salinization, but its effect on the carbon sequestration function of CWs is still unclear. In this study, three CWs with different salinities (i.e., control: C-CW; low salinity: LS-CW; high salinity: HS-CW) were conducted. Increased salinity significantly reduced the carbon sequestration in CWs. The highest carbon sequestration was observed in C-CW (5.1 ± 0.2 kg C·m−2·y-1), and the carbon sequestration capacity of plants was identified as the major influencing factor. The substrate carbon pool decreased with salinity since it altered plant carbon inputs, enzyme activities, and microbial community structure. However, the decrement in the carbon pool management index with salinity indicated that salinity could enhance carbon pool stability and subsequently reduce carbon emissions of CWs. These findings improve the understanding in relationships between salinity and carbon sequestration in CWs and provide theoretical support for the proper management of CWs.

Prebiotics: A Solution for Improving Plant Growth, Soil Health, and Carbon Sequestration?

Soil fertility and productivity are severely impacted by exploitation and degradation processes. These threats, coupled with population growth and climatic changes, compel us to search for innovative agroecological solutions. Prebiotics, a type of soil biostimulant, are used to enhance soil conditions and plant growth and may play a role in carbon (C) sequestration. Two commercial prebiotics, K1® and NUTRIGEO L® (referred to as SPK and SPN, respectively), were assessed for their effects on agricultural soil cultivated with Zea mays L., compared to untreated soil or control (SP). Analyses were performed at two harvesting dates: three weeks (D1) and ten weeks (D2) after the application of prebiotics. Plant growth parameters and soil characteristics were measured, focusing on soil organic matter, soil bacterial and fungal communities, and plant root mycorrhization. Regarding physicochemical parameters, both prebiotic treatments increased soil electrical conductivity, cation exchange capacity, and soluble phosphorus (P) while decreasing nitrates. Meanwhile, the SPN treatment was distinct in elevating specific cationic minerals, such as calcium (Ca) and boron (B), at D2. At the microbial level, each prebiotic induced a unique shift in the indigenous bacterial and fungal communities’ abundance and diversity, evident at D2. Simultaneously, specific microbial taxa were recruited by each prebiotic treatment, such as Caulobacter, Sphingobium, and Massilia from bacteria and Mortierella globalpina and Schizothecium carpinicola from fungi in SPK as well as Chitinophaga, Neobacillus, and Rhizomicrobium from bacteria and Sordariomycetes and Mortierella minutissima from fungi in SPN. These biomarkers were identified as (a) saprotrophs, (b) plant growth-promoting bacteria and fungi, (c) endohyphal bacteria, and (d) endophytic and symbiotic microbiota. This result was reflected in the increase in glomalin content and mycorrhization rate in the treated soils, especially by SPN. We observed that these effects led to an increase in plant biomass (shoots by 19% and 22.8% and roots by 47.8% and 35.7% dry weights for SPK and SPN, respectively) and contributed to an increase in soil C content (organic C by 8.4% and total C by 8.9%), particularly with SPN treatment. In light of these findings, the use of prebiotics ten weeks after application not only increased plant growth by improving soil characteristics and shaping its native microbial community but also demonstrated the potential to enhance C sequestration.

The miRNA–mRNA regulatory networks of the response to NaHCO3 stress in industrial hemp (Cannabis sativa L.)

BackgroundIndustrial hemp is an important industrial crop and has strong resistance to saline-alkaline stress. However, research on the industrial hemp response to NaHCO3 stress is limited. Therefore, the response mechanisms of industrial hemp under NaHCO3 stress were analysed through miRNA–mRNA regulatory networks.ResultsSeedlings of two salt–alkali tolerant and sensitive varieties were cultured in a solution containing 100 mM NaHCO3 and randomly sampled at 0, 6, 12, and 24 h. With prolonged NaHCO3 stress, the seedlings gradually withered, and the contents of jasmonic acid, lignin, trehalose, soluble protein, peroxidase, and superoxide dismutase in the roots increased significantly. The abscisic acid content decreased and then gradually increased. Overall, 18,215 mRNAs and 74 miRNAs were identified as differentially expressed under NaHCO3 stress. The network showed that 230 miRNA–mRNA interactions involved 16 miRNAs and 179 mRNAs, including some key hub novel mRNAs of these crucial pathways. Carbon metabolism, starch, sucrose metabolism, plant hormone signal transduction, and the spliceosome (SPL) were crucial pathways in industrial hemp's response to NaHCO3 stress.ConclusionsIt is speculated that industrial hemp can regulate SPL pathway by upregulating miRNAs such as novel_miR_179 and novel_miR_75, thus affecting starch and sucrose metabolism, plant hormone signal transduction and carbon metabolism and improving key physiological indices such as jasmonic acid content, trehalose content, and peroxidase and superoxide dismutase activities under NaHCO3 stress.

The effect of plant growth regulators, carbon sources and gelling agent on the callus regeneration of Malaysian rice MR219 (Oryza sativa L.)

The development of a highly efficient tissue culture system for indica rice is crucial to speed up the implementation of gene editing in breeding programmes as well as to explore the roles of indica genes. However, because indica rice types are recalcitrant to in vitro response, there are only a few reports on the successful transformation process on indica rice due to recalcitrant response to in vitro response. The present study attempted to identify the effects of plant growth regulator (PGR), carbon sources and different concentrations of gelling agent on embryogenic callus induction and rice regeneration of Oryza sativa var MR219. The PGR used were 1 or 2 mg/L 6-benzylaminopurine (BAP) and 1-Naphthaleneacetic acid (NAA) and the carbon sources were 30 g/L sucrose and maltose. Three different gelling agent concentrations (3 mg/L, 6 mg/L or 9 mg/L) were evaluated. The highest frequency of friable callus induction (87%) was observed in callus induction media (CI) containing Murashige and Skoong media (MS) supplemented with 3 mg/L 2,4-dichlorophenoxy acetic acid (2,4-D) and 0.3 mg/L kinetin. Histological studies of the calli showed the presence of embryogenic calli with small intercellular spaces compared to non-embryogenic areas which developed on the hormone MS media. The highest regeneration frequency (50%) was achieved when friable calli were cultured on MS medium containing 3% sucrose, 1 mg/L BAP, and 1 mg/L NAA with 9% phytagel. The callus grown on sucrose media showed the highest number (66.13%) of albino plantlets, while the number of albino plantlets on maltose media was smaller (20%). In conclusion, this optimised mature embryo-derived callus of MR219 rice is responsive to regeneration and could be amenable to genetic transformation studies.

The carbon balance of plants: economics, optimization, and trait spectra in a historical perspective.

Over fifty years have passed since the publication of Harold Mooney's formative paper, "The Carbon Balance of Plants" on pages 315-346 of Volume 3 (1972) of Annual Review of Ecology and Systematics. Arguably, the conceptual framework presented in that paper, and the work by Mooney and his students leading up to the paper, provided the foundational principles from which core disciplines emerged in plant economic theory, functional trait theory and, more generally, plant physiological ecology. Here, we revisit the primary impacts of those early discoveries to understand how researchers constructed major concepts in our understanding of plant adaptations, and where those concepts are likely to take us in the near future. The discipline of functional trait ecology, which is rooted in the principles of evolutionary and economic optimization, has captured the imagination of the plant physiological ecology research community, though its emphasis has shifted toward predicting species distributions and ecological roles across resource gradients. In the face of 'big-data' research pursuits that are revealing trait expression patterns at the cellular level and mass and energy exchange patterns at the planetary scale, an opportunity exists to reconnect the principles of plant carbon balance and evolutionary optimization with trait origins at the genetic and cellular scales and trait impacts at the global scale.

Fate of trimethoprim, sulfamethoxazole and caffeine after hydrothermal regeneration of activated carbon

Emerging contaminants are found in all parts of our environment. Adsorption of these contaminants by activated carbon in water treatment plants is well-known; however, a problem resides in the handling of the spent adsorbents. As current regenerative technologies are expensive, the adsorbents are often destructed or landfilled. Here, we examine a novel regeneration method for the used adsorbents with subcritical water – i.e., hydrothermal treatment. The degradation of three well-known emerging contaminants – caffeine, trimethoprim and sulfamethoxazole – was studied with regard to processing temperature (160–280 °C), concentration (2 and 20 mg/L), and the impact of adsorbents. In addition to trimethoprim in the mix at 20 mg/L, the other contaminants were entirely degraded at 280 °C. To obtain insight into transformation products formed during hydrothermal regeneration, we performed non-target and targeted analyses with LC-MS-QTOF using two types of columns, C18 and ZIC-HILIC. This approach ensured a wide range of hydrophilicities. Results showed more transformation products for trimethoprim (20) compared to sulfamethoxazole and caffeine (4). To assess the regeneration efficiencies of the activated carbons, we conducted three cycles of regeneration at 280 °C and between 61 and 120 % degradation was achieved. Moreover, only two transformation products were detected and readsorbed on the adsorbent after regeneration. Hydrothermal regeneration efficiently degraded the target emerging contaminants, suggesting a potential approach for enabling alternative, sequential uses for regenerated activated carbon.

Convergence points of optimal herbage accumulation and intake rate by sheep grazing tall fescue

AbstractPasture management oriented towards sustainable intensification and stability of yield must consider the ideal balance between the mass of leaves removed by grazing and the mass left as residual. The former supports high animal production and the later supports an optimum soil–plant carbon balance. This study aimed to evaluate the optimal herbage level from both plant and animal perspectives, through the adjustment of instantaneous herbage accumulation rate as estimated by the Gompertz curve model and short‐term intake rate of sheep. Weekly tall fescue (Schedonorus arundinaceus) herbage accumulation was measured during seven growth periods with initiation dates in October, November and December 2015, and March, April, August and September 2016 and with the initiation dates arranged in a randomized complete block design with four replicates. Total herbage mass, leaf lamina mass, pseudo‐stem + sheath mass, senescent mass, and sward surface height were measured each week. The results demonstrated that a pre‐grazing sward surface height of 22.3 cm of tall fescue promoted the maximum short‐term intake rate of sheep and the optimum herbage accumulation rate in the spring and autumn periods. In general, the convergent point occurred after the maximum instantaneous leaf lamina accumulation rate and before the maximum instantaneous accumulation rate of pseudo‐stem + sheath and senescent material. We suggest the existence of a convergent point in which both primary and secondary production of pastoral ecosystems could be fostered.

Responses of plant carbon and nitrogen assimilations to nitrogen addition in a subtropical forest: Canopy addition vs. understory addition

The global atmospheric nitrogen (N) deposition has intensified in recent years, resulting in a complex impact on forest ecosystems. This study investigated the effects of canopy (CAN) and understory additions of N (UAN) on leaf carbon (C) and N assimilations, as well as growth parameters of representative woody plant species in an evergreen broad-leaved forest, i.e. Castanea henryi, Schefflera heptaphylla, Blastus cochinchinensis, and Lasianthus chinensis. The results showed that leaf N assimilation key enzyme nitrate reductase (NR) activities of B. cochinchinensis and S. heptaphylla were significantly decreased by UAN, and were significantly decreased by CAN for C. henryi. CAN significantly decreased the nitrite reductase activity of C. henryi, while significantly increased that of L. chinensis. However, the Amax values of each woody species were not significantly different among control (CK), CAN, and UAN. Community surveys demonstrated that CAN and UAN inhibited the growth (diameter at breast height, height, or crown width) of the representative large tree, C. henryi, while promoting the growths of understory woody species (B. cochinchinensis and L. chinensis). Overall, N addition was found to change the physiological processes of N and C metabolisms of the dominant woody species in an evergreen broad-leaved forest. The community of subtropical evergreen broad-leaved forests may further decline and its C fixation capacity may be detrimentally changed under N deposition in the future.

The impact of external plant carbon sources on nitrogen removal and microbial community structure in vertical flow constructed wetlands

The present study was developed to explore nitrogen removal performance and associated microbial mechanisms of action in vertical flow constructed wetlands (VFCWs) when using external carbon sources. These analyses ultimately revealed that alkali-soaked Phragmites australis (P. australis) could serve as an effective plant carbon source, exhibiting the lower levels of total nitrogen (TN) release and the highest chemical oxygen demand (COD) of all tested carbon sources. Nitrogen removal efficiency improved following the addition of plant carbon sources, and under carbon/nitrogen (C/N) rations of 2, 4, 5, and 7, the VFCW system was able to remove 43.69%–75.76% TN, with the highest removal rate being observed at a C/N of 5. The abundance of denitrifying microorganisms such as Thiobaillus and Halomonas were also more enriched in VFCW1 than VFCW0, with stronger correlations in the microbial network community. A qPCR approach was used to analyze functional genes involved in denitrification, revealing that the addition of plant carbon sources was associated with increases in total gene abundance and the abundance of the denitrifying gene nirS, whereas no corresponding increase in amoA or nxrA abundance was observed. Higher total gene, amoA, and nxrA abundance were observed in the upper levels of these VFCW systems as compared to the lower layers, whereas nirS exhibited the opposite abundance pattern. Overall, these findings suggested that short-range denitrification is likely to be the primary denitrification process active in this VFCW system.

Source‐sink patterns on coffee trees related to annual climate variability: An approach through stable isotopes analysis

AbstractStable isotopic determination constitutes a useful tool to identify the processes that control the dynamics of the carbon and nitrogen flow in plants, unravelling the mechanisms of their differential investment under different environments. This work aimed to evaluate the spatiotemporal variation of source‐sink patterns of coffee trees under field conditions in response to climatic conditions through the assessment of stable isotopes. For this purpose, stems, leaves, and fruit samples from coffee trees were collected following a temporal pattern based on the region's climatic characteristics and the plant's phenology and a spatial pattern considering different parts of the canopy. The carbon and nitrogen percentage content, the C/N ratio, and the carbon and nitrogen isotopic compositions (δ13C and δ15N) were determined for all samples. The basal portion of the orthotropic branch was also considered for the isotopic analysis of the tree's growth rings. The results obtained were correlated with the climatic variables of the region through a Pearson correlation analysis (p < .05). Coffee plants showed traditional δ13C values of C3 plants. Temporal δ13C variation was associated with the different growth rates between phenological stages and the use of substrates produced at different times under different environmental conditions leading to differences in photosynthetic discrimination. Spatial δ13C variation was observed with heterotrophic tissues isotopically heavier than leaves, with a significant decrease trend in δ13C values from the top (upper third) to the bottom (lower third), associated with ecophysiological differences between the canopy, isotopic fractionation processes downstream of photosynthetic carbon discrimination, and the fixation of C from other pools. Temporal δ15N variation was associated with the precipitation rates in the region and the fertilization distribution across the tree, while the spatial variation was with the plant's nitrogen assimilation and translocation patterns. The tree growth rings isotopic analyses showed isotopic differences between growth rings of the same plant addressed by the climatic conditions, with precipitation being the primary climatic determinant influencing the fixation and discrimination against 13C. Our results highlight the importance of using stable isotope analysis as a reference point for coffee ecophysiological studies to characterize how the temporal and spatial patterns of δ13C and δ15N emerge and signal the influence of climate on the source‐sink relationship of coffee trees under field conditions.

Plant Diversity, Aboveground Biomass and Carbon Stock in an Isolated Tropical Sub Montane Forest in Sri Lanka

This study was conducted at Rilagala conservation forest, Nawalapitiya to assess and compare the plant diversity, above ground biomass and carbon stock in the periphery and interior of an isolated sub montane forest in Sri Lanka. All trees above 5 cm Diameter at Breast Height (DBH) in eleven randomly demarcated 25 m × 25 m plots were recorded. Distance up to 100 m from the forest boundary considered as the periphery (8 plots) and over 200 m as the core (3 plots). A total of 1,583 trees belonging to 29 species were recorded and aboveground biomass (AGB) and carbon stocks were calculated using allometric equations. The tree diversity of each plot was calculated using the Shannon diversity index (H’). Results were statistically analysed using single factor ANOVA. The species richness and H’ were the highest at the periphery (n=23, H’= 2.55) while the lowest at forest interior (n=11, H’= 1.97). The highest tree density was recorded at periphery (2,992 trees ha-1) and it decreased to 1,408 trees ha-1 towards the core. The average DBH was 8.5 ± 3.33 cm and it increased towards the forest interior (9.7 ± 4.51 cm) from the periphery (7.2 ± 3.74 cm). Estimated aboveground biomass ranged from 63.99 - 108.13 Mg ha-1 with a mean of 82.53 ± 14.39 Mg ha-1. The above ground C stock was estimated from 31.99 - 54.07 Mg ha-1 with a mean of 41.26 ± 7.2 Mg ha-1. However, there was no significant difference between forest periphery and core in variables, except species richness (p<0.05). The study revealed that the diversity and density of trees decreased towards the forest interior and vice versa was recorded for DBH, AGB and carbon stock. The study highlights the importance of conserving isolated tropical sub montane forest patches for carbon sequestration.

Fine-Root C:N:P Stoichiometry and Its Driving Factors Are Different between Arbuscular and Ectomycorrhizal Plants in China

Fine roots are essential for terrestrial biogeochemical cycles. Mycorrhizal fungi’s functions in regulating the uptake of carbon (C), nitrogen (N), and phosphorus (P) in plants are increasingly being recognized. However, the influence of mycorrhizae on Chinese plants’ fine-root stoichiometry has not been considered. Herein, 772 plants with identified mycorrhizal types were divided into arbuscular mycorrhizal (AM) and ectomycorrhizal (ECM) types to investigate the differences in their fine-root stoichiometry and their driving factors. The results showed that the AM and ECM fine-root stoichiometries were significantly different (p < 0.001; p < 0.05). The AM plants’ fine-root stoichiometry was mainly affected by the soil environment (8.76–90.12%), while ECM plants were more sensitive to climatic factors (23.51–52.41%). Further analysis showed that the mean annual temperature (MAT) was significantly correlated with AM plants’ fine-root C and P and ECM plants’ fine-root N and P. Mean annual precipitation (MAP) was significantly correlated with all AM plants’ fine-root elements (p < 0.01) but was only negatively correlated with ECM fine-root P. It was concluded that the mycorrhizal type affects the response of the fine-root stoichiometry to climate and soil variations. Therefore, the mycorrhizal effect deserves attention when studying the relationship between plant nutrient uptake and environmental changes.

Aquatic plant wax hydrogen and carbon isotopes in Greenland lakes record shifts in methane cycling during past Holocene warming.

Predicting changes to methane cycling in Arctic lakes is of global concern in a warming world but records constraining lake methane dynamics with past warming are rare. Here, we demonstrate that the hydrogen isotopic composition (δ2H) of mid-chain waxes derived from aquatic moss clearly decouples from precipitation during past Holocene warmth and instead records incorporation of methane in plant biomass. Trends in δ2Hmoss and δ13Cmoss values point to widespread Middle Holocene (11,700 to 4200 years ago) shifts in lake methane cycling across Greenland during millennia of elevated summer temperatures, heightened productivity, and lowered hypolimnetic oxygen. These data reveal ongoing warming may lead to increases in methane-derived C in many Arctic lakes, including lakes where methane is not a major component of the C cycle today. This work highlights a previously unrecognized mechanism influencing δ2H values of mid-chain wax and draws attention to the unquantified role of common aquatic mosses as a potentially important sink of lake methane across the Arctic.

Differences in background environment and fertilization method mediate plant response to nitrogen fertilization in alpine grasslands on the Qinghai-Tibetan Plateau

Grassland degradation threatens ecosystem function and livestock production, partly induced by soil nutrient deficiency due to the lack of nutrient return to soils, which is largely ascribed to the intense grazing activities. Therefore, nitrogen (N) fertilization has been widely adopted to restore degraded Qinghai-Tibetan Plateau (QTP) grasslands. Despite numerous field manipulation studies investigating its effects on alpine grasslands, the patterns and thresholds of plant response to N fertilization remain unclear, thus hindering the prediction of its influences on the regional scale. Here, we established a random forest model to predict N fertilization effects on plant productivity based on a meta-analysis synthesizing 88 publications in QTP grasslands. Our results showed that N fertilization increased the aboveground biomass (AGB) by 46.51 %, varying wildly among plant functional groups. The positive fertilization effects intensified when the N fertilization rate increased to 272 kg ha−1 yr−1, and decreased after three years of continuous fertilization. These effects were more substantial when applying ammonium nitrate compared to urea. Further, a machine learning model was used to predict plant productivity response to N fertilization. The total explained variance and mean squared residuals ranged from 49.41 to 75.13 % and 0.011–0.058, respectively, both being the highest for grasses. The crucial predictors were identified as climatic and geographic factors, background AGB without N fertilization, and fertilization methods (i.e., rate, form, and duration). These predictors with easy access contributed 62.47 % of the prediction power of grasses' response, thus enhancing the generalizability and replicability of our model. Notably, if 30 % of yak dung is returned to soils on the QTP, the grassland productivity and plant carbon pool are predicted to increase by 5.90–6.51 % and 9.35–10.31 g C m−2 yr −1, respectively. Overall, the predictions of this study based on literature synthesis enhance our understanding of plant responses to N fertilization in QTP grasslands, thereby providing helpful information for grassland management policies.Conflict of interest: The authors declare no conflict of interest.

Plant carbon removal affects monthly temperature sensitivity of soil respiration during growing season in three typical plantations in the Loess Hilly Region, China

The temperature sensitivity of soil respiration (Q10) is primarily related to annual climate parameters and soil properties in regional models. Changes in climate and soil properties influence plant carbon (C) inputs, which in turn alter Q10 during the growing season. However, the magnitude of this influence remains uncertain. Herein, using meteorological data from small stations and field experiments across three plantations (Robinia pseudoacacia, Caragana korshinskii, and Bothriochloa ischaemum), we investigated the variations in Q10 with respect to the following four treatments: litter removal, root trenching, root trenching and litter removal, and a control group, for 6 months. We found that R. pseudoacacia had the highest relative contribution to atmospheric C release, followed by C. korshinskii, and then B. ischaemum. The Q10 components were month-dependent under C remove in three typical plantations. Litter removal significantly reduced Q10, but the effect of root trenching differed according to the plantation. The variations of Q10 with C removal were primarily controlled by interacting air temperature, air pressure, potential hydrogen, root C, root biomass, soil organic C, and relative humidity, explaining the variations of 81.29–99.33 % (R. pseudoacacia plantation), 89.1–99.76 % (C. korshinskii plantation), and 99.34–99.74 % (B. ischaemum) of the variation in Q10; among them, the cumulative contribution of climate (soil temperature, air pressure, and relative humidity), plants (root C and root biomass), and soil properties (potential hydrogen and soil organic C) accounted for 34.84 %–61.93 %, 12.15 %–32.75 %, and 8.07 %–32.11 %, respectively. These findings demonstrate that C removal variations influenced the Q10, whereas Q10 was also month-dependent. Overall, we recommend that the role of Q10 in the growing season should carefully consider C removal into the soil to improve the biosphere–atmosphere C exchange model in the context of climate change.

Soil and foliar Si fertilization alters elemental stoichiometry and increases yield of sugarcane cultivars

Silicon (Si) fertilization is widely recognized to improve the development of crops, especially in tropical soils and cultivation under dryland management. Herein, our working hypothesis was that Si stoichiometry favors the efficient use of carbon (C), nitrogen (N), and phosphorus (P) in sugarcane plants. Therefore, a field experiment was carried out using a 3 × 3 factorial scheme consisting of three cultivars (RB92579, RB021754 and RB036066) and three forms of Si application (control without Si; sodium silicate spray at 40 mmol L−1 in soil during planting; sodium silicate spray at 40 mmol L−1 on leaves at 75 days after emergence). All Si fertilizations altered the elemental C and P stoichiometry and sugarcane yield, but silicon-induced responses varied depending on sugarcane cultivar and application method. The most prominent impacts were found in the leaf Si-sprayed RB92579 cultivar, with a significant increase of 7.0% (11 Mg ha−1) in stalk yield, 9.0% (12 Mg ha−1) in total recoverable sugar, and 20% (4 Mg ha−1) in sugar yield compared to the Si-without control. In conclusion, our findings clearly show that silicon soil and foliar fertilization alter C:N:P stoichiometry by enhancing the efficiency of carbon and phosphorus utilization, leading to improved sugarcane production and industrial quality.

Critical review of nuclear power plant carbon emissions

Nuclear power plays a crucial role in achieving the target of carbon neutrality to build a sustainable society. However, it is not “carbon-free” when considering its entire life cycle. Therefore, accurate accounting and monitoring of its generated carbon emissions are required to avoid miscalculations of nuclear energy as a clean energy source. In this study, the life-cycle carbon emissions of nuclear power plants (NPPs) with different reactor types are reviewed. In addition to the characteristic differences among different reactors, disparities in the review results originate from the varying emissions at the respective stages of the nuclear fuel cycle, technology choices at each stage and accounting methods and boundaries. The carbon emissions resulting from NPP construction and operation are underestimated due to the limited data and methods, which creates uncertainty in the evaluation of NPP carbon emissions. An integrated framework for carbon emissions accounting considering the construction and operation of NPPs (CACO-NPP) is proposed. This integrated framework aims to improve the accounting accuracy for carbon emissions originating from NPPs. An emerging Generation III NPP with the latest technology, HPR1000 (an advanced pressurized water reactor), was adopted as a case study. The results show that the total emissions resulting from vegetation loss, equipment manufacturing and labor input during construction and operation are 1232.91 Gg CO2 with a carbon intensity of 1.31 g CO2/kWh, indicating the notable mitigation capability of Generation III NPPs. By combining the maturity of HPR1000 technology with successive design improvements, the carbon emissions of such reactor types could be further reduced. This development is very important for realizing China’s carbon neutrality target.

Vascular optimality dictates plant morphology away from Leonardo’s rule

Metabolic scaling theory (MST) provides an understanding of scaling in organismal morphology. Empirical data on the apparently universal pattern of tip-to-base conduit widening across vascular plants motivate a set of generalized MST (gMST) relationships allowing for variable rates of conduit coalescence and taper and a transition between transport and diffusive domains. Our model, with coalescence limited to the distalmost part of the conductive system, reconciles previous MST-based models and extends their applicability to the entire plant. We derive an inverse relationship between stem volume taper and conduit widening, which implies that plant morphology is dictated by vascular optimality and not the assumption of constant sapwood area across all branching levels, contradicting Leonardo's rule. Thus, energy efficiency controls conduit coalescence rate, lowering the carbon cost needed to sustain the vascular network. Our model shows that as a plant grows taller, it must increase conduit widening and coalescence, which may make it more vulnerable to drought. We calculated how our gMST model implies a lower carbon cost to sustain a similar network compared to previous MST-based models. We also show that gMST predicts the cross-sectional area of vessels and their frequency along the relative length better than previous MST models for a range of plant types. We encourage further research obtaining data that would allow testing other gMST predictions that remain unconfirmed empirically, such as conduit coalescence rate in stems. The premise of energy efficiency can potentially become instrumental to our understanding of plant carbon allocation.