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Climate change projections indicate increased precipitation in northern Europe, leading to increased inflow of allochthonous organic matter to aquatic systems. The food web responses are poorly known, and may differ depending on the trophic structure. We performed an experimental mesocosm study where effects of labile dissolved organic carbon (DOC) on two different pelagic food webs were investigated, one having zooplankton as highest trophic level and the other with planktivorous fish as top consumer. In both food webs, DOC caused higher bacterial production and lower food web efficiency, i.e., energy transfer efficiency from the base to the top of the food web. However, the top-level response to DOC addition differed in the zooplankton and the fish systems. The zooplankton production increased due to efficient channeling of energy via both the bacterial and the phytoplankton pathway, while the fish production decreased due to channeling of energy mainly via the longer and less efficient bacterial pathway. We conclude that the added DOC either acted as a subsidy by increasing the production of the top trophic level (mesozooplankton), or as a sink causing decreased top consumer production (planktivorous fish). [ABSTRACT FROM AUTHOR]

A fair and effective allocation of carbon quotas is crucial for China to achieve its "Double Carbon" goals and the effective operation of its carbon trading market. By constructing a differential game model, this study explored the effects of the technology spillovers and incremental costs of carbon transfers on the allocation of carbon quotas under centralised and decentralised decision-making scenarios with the purpose of maximizing social welfare. This paper proposes a cost-sharing contract to coordinate a supply chain for the loss of social welfare under decentralised decision-making. The results show that the effects of spillovers and incremental costs on carbon quota allocation depend upon the enterprises' abatement costs. The suppliers' carbon quotas are negatively correlated with the spillover effects. The incremental cost effects will be more pronounced for suppliers when their abatement costs are high and they could obtain more carbon quotas accordingly. When the manufacturer's abatement costs are low (high), its carbon quotas decrease (increase) with the spillover effects but increase (decrease) with the incremental costs. The cost-sharing contract achieves Pareto improvements based on improved social welfare and increased carbon quotas for both the manufacturer and supplier. Given the effects of carbon transfer on enterprises with different abatement costs, this paper can provide the government with a reference for designing an allocation mechanism for carbon quotas. [Display omitted] [ABSTRACT FROM AUTHOR]

Due to a considerable imbalance in the levels of social and economic development and urbanization in different regions of China, factors such as population, floor area, and building energy consumption have gradually undergone regional structural changes, and further show a specific center of gravity migration trend. The impact of this center of gravity migration on building carbon emissions deserves further exploration. Based on center of gravity model and comprehensive carbon emission reduction effect analysis model, this study depicts the center of gravity migration trajectory of China's population, floor area, building energy consumption, and elucidates the reduction effect of the center of gravity migration on building carbon emissions. Finally, the theoretical and essential reasons for the building carbon emission reduction effect are further discussed. The results showed that the center of gravity of China's population, floor area, building energy consumption, and building carbon emissions moved from north to south, with that for building energy consumption being most obvious (moved south by 1.22°). A total reduction of 32.7 million tCO 2 in building carbon emissions was facilitated by the southward migration of the three centers of gravity. This occurred essentially because the southward migration of the center of gravity led to relatively cleaner building energy consumption across the country, which in turn weakened the overall energy consumption intensity and carbon emission factor. This study expands and deepens the theoretical mechanism of building carbon emission reduction, and provides a decision-making basis for government policymakers to balance regional differences to formulate differentiated building carbon emission reduction strategies. [Display omitted] • Population, floor area, and building energy consumption centers of gravity gradually shifted from north to south. • Southward migration was particularly evident for the building energy consumption center of gravity. • Southward migration of the three centers of gravity could facilitate reductions in building carbon emissions. • Building carbon emission reduction is essentially caused by the weakening of energy intensity and carbon emission factor. [ABSTRACT FROM AUTHOR]

Mangroves are highly productive ecosystems that exhibit a diverse range of habitats, including tidal creeks and flats, forest gaps and interior forest with varying understory light intensity, tidal dynamics, geomorphological settings, and overall biological production. Within mangrove ecosystems, invertebrates and fish feed on heterogeneous food sources, the occurrence of which is unevenly distributed across the system. This provides a basis for testing models of carbon transfer across mangrove ecosystems. We hypothesized that the carbon transfer and assimilation by fish and invertebrates will vary across the different mangrove habitats and that such variations can be predicted by their stable isotope compositions. We analysed δ13C and δ15N signatures of consumers and their potential organic carbon sources across a tropical mangrove ecosystem in Vietnam. The δ13C values of crabs and snails significantly decreased from the tidal flat to interior forest, indicating that variations in carbon transfer and assimilation occurred at small scales <30 m. Reduced variation in δ13C of suspension-feeding bivalves suggested that tidal water was a vector for large-scale transport of carbon across the mangrove ecosystem. An analysis of co-variance using habitat as a fixed factor and feeding habit and movement capacity of consumers as co-variates indicated that habitat and feeding types were major features that affected the δ13C values of invertebrates and fish. The findings demonstrate that carbon transfer and assimilation across mangrove ecosystems occur as a diverse combination of small (<30 m) and large (>30 m) scale processes. [ABSTRACT FROM AUTHOR]

Generalist fishes commonly show intraspecific niche segregation along the littoral-pelagic resource axis in lakes. Recent studies have shown that the deep, cold and seemingly unproductive profundal zone can also offer underutilised resources and facilitate specialised individuals, and can contribute to lake food webs via methane-derived carbon pathways. Despite numerous examples from salmonid fish species, such intraspecific niche segregation along a littoral-profundal resource axis has not been reported in percids or other predominantly littoral benthivorous fishes., Here, we describe a case of ruffe ( Gymnocephalus cernua: Percidae) populations consisting of shallow- and deep-water dwelling individuals in two post-mining lakes in the northern Czech Republic. Results from stable isotope (δ15N and δ13C) mixing models indicated that littoral and profundal food resources dominated the long-term diets of ruffe individuals caught from shallow- and deep-water habitats, respectively. No similar niche segregation along the littoral-profundal gradient was observed in coexisting perch ( Perca fluviatilis: Percidae) which used more pelagic food than the benthivorous ruffe., The observed littoral-profundal niche segregation in ruffe was more pronounced in the macrophyte-rich and poorly oxygenated Lake Milada, where high habitat complexity and strong interspecific interactions in the littoral zone as well as the absence of competing fish species in the profundal zone likely promote narrow trophic niches of shallow- and deep-water dwelling ruffe, Our study provides novel evidence of littoral-profundal niche segregation in a predominantly benthivorous fish species. The results also show that intraspecific niche variation can be affected by lake ecosystem characteristics, in particular by the availability of and competition for littoral and profundal resources. Although more research is needed to confirm potential early divergence of shallow- and deep-water dwelling ruffe as well as cascading effects on lake ecosystem processes (e.g. nutrient cycling and competitive and predatory interactions), our study indicates that individual ruffe may show limited habitat and food-web coupling due to their restricted use of shallow or deep resources. [ABSTRACT FROM AUTHOR]

Despite an increasing number of experiments, no consensus has emerged on the effect of ocean acidification on plankton communities and carbon flow. During two experiments, performed in the Bay of Calvi (France, Corsica; summer 2012) and the Bay of Villefranche (France; winter 2013), nine off-shore mesocosms (∼50 m 3 ) were deployed among which three served as controls and six were enriched with CO 2 to reach partial pressure of CO 2 ( p CO 2 ) levels from 450 to 1350 μatm and 350–1250 μatm in the Bay of Calvi and the Bay of Villefranche, respectively. In each mesocosm, inorganic 13 C was added in order to follow carbon transfer from inorganic via bulk particulate organic carbon and phytoplankton to bacteria by means of biomarkers as well as to zooplankton and settling particles. Despite very low plankton biomasses, labelled carbon was clearly transferred through plankton communities. Incorporation rates in the various plankton compartments suggested a slow-growing community based on regenerated production in the Bay of Calvi while in the Bay of Villefranche, fast-growing species were clearly dominating community production at the start with a shift toward slow-growing species during the experiment due to nutrient limitation. Both bulk and group-specific productions rates did not respond to increasing p CO 2 levels. These experiments were the first conducted in the Mediterranean Sea under low nutrient concentrations and phytoplankton biomasses and suggest that ocean acidification may not significantly impact plankton carbon flows in low nutrient low chlorophyll (LNLC) areas. [ABSTRACT FROM AUTHOR]

Embodied carbon emissions have an important role in China's "dual carbon" target and carbon reduction policy. Our study applied a multiregional input–output (MRIO) model and structural decomposition analysis (SDA) to examine the spatiotemporal evolution and driving forces of embodied carbon emissions in the specific region of Shanxi Province, an energy-rich region in China, in the empirical study using MRIO data. First, we found that Shanxi had considerable net embodied carbon outflow in interprovincial trade, with outflow increasing from 216.18 Mt in 2012 to 221.60 Mt in 2017. Second, the main driving forces of embodied carbon outflow include technological level and trade demand. We then classified 29 sectors into six categories, including mainly developed, controlled, moderately guided, moderately controlled, cost guided, and maintained to describe the relationship between the net transfer of embodied carbon emissions and value added, and formulated proposed sectoral development policies. Third, the sectors with the highest net embodied carbon outflow include electricity and heat production and supply; metal smelting and rolling processing; and petroleum processing, coking, and nuclear fuel processing. We constructed a coupled relationship model to adjust the technology and scale of interprovincial trade to reduce carbon emissions with lower cost and higher equity. The results can be used as a reference for formulating carbon reduction policies in energy-rich regions. [Display omitted] • We calculate the amount of net embodied carbon transferred from Shanxi. • We estimate the sectors' embodied carbon emissions in inter-provincial trade. • Driving forces are decomposed of embodied carbon outflowed from Shanxi. • A classification model is constructed to identify sectoral characteristics. • The key sectors are identified and then trade relationships are adjusted. [ABSTRACT FROM AUTHOR]

[Display omitted] • Energy sharing and carbon transfer are considered. • Integrated energy system group is constructed by interconnected subsystems. • KDE and Wasserstein metric are combined to describe the fuzzy uncertainty set. • Two-stage distributionally robust optimization model is proposed. • The affinely adjustable policy is used to establish the correlation model. Due to the small scale and few functions of the single integrated energy system, the absorption capacity of wind turbine and photovoltaic is limited, the ability to cope with uncertainties is weak, and the space for optimal allocation of resources is limited. To solve the coordination problem of robustness, economy, environmental protection and efficiency, this paper forms an integrated energy system group (IESG) by means of energy sharing and carbon transfer, and innovatively proposes a two-stage distributionally robust optimization model (TSDRO) based on kernel density estimation (KDE) and Wasserstein metric. Firstly, the structure of IESG with carbon capture, utilization, and storage-power-to-gas (CCUS-P2G) system is introduced. Then, the nonparametric KDE method is applied to fit the probability density functions of the forecast power error of wind turbine and photovoltaic. Wasserstein metric is used to characterize the fuzzy uncertainty set of distributions. The cumulative distribution function of KDE is taken as the center, and the obtained distance is taken as the radius to form the Wasserstein ball of probability distribution. Based on affinely adjustable policy, a correlation model of real-time variables with respect to day-ahead variables is established. Finally, according to the dual theory and convex optimization theory, the TSDRO model is reformulated into a solvable model. The simulation results show that: (1) energy sharing and carbon transfer can improve the ability of IESG to cope with uncertainty and expand the boundary of resource optimal allocation, and the minimum expected operating cost under the worst distribution is $ 40,259.94. (2) CCUS-P2G system strengthens the synergistic relationship between electricity and carbon and reduces the carbon emission of the system by 128.2 t. (3) After testing, the results obtained by nonparametric KDE are closer to the true distribution and more objective. (4) The TSDRO model is data-driven and has the advantages of high solving efficiency and low decision-making conservatism. The solution time of the TSDRO model is 73.03 % less than that of the stochastic optimization model, and the operation cost is 1.69 % less than that of the robust optimization model, which achieves the balance of economy, robustness and environmental protection of IESG. [ABSTRACT FROM AUTHOR]

In this paper, an environmentally extended multi-regional input-output model is applied to calculate the exported production CO 2 emissions and the imported consumption CO 2 emissions of 14 major economies in 2009. In particular, a carbon flow chart is drawn to depict the embodied CO 2 emissions transfer between each economies. The main findings are obtained as follows: (1) More than one fifth of China's production-based CO 2 exports were driven by the final demand of the US; in return, there were 8.30% of the production-based CO 2 exports of the US flowed into China. (2) The CO 2 trade flows between the US and Canada were very strong, with 12.53% of the CO 2 exports of the US flowing to Canada and 52.92% of Canada's CO 2 exports flowing to the US. (3) The consumption-based CO 2 imports of the US, Japan and Australia were similar, with the contribution from China being over one third. (4) The source structure of China's CO 2 imports was relatively average, with the CO 2 flows from Japan, South Korea, Russia, Chinese Taiwan and the US all accounting for a share of less than 10%. The findings would be of great significance to undertake targeted climate policies. [ABSTRACT FROM AUTHOR]

The Norris Geyser Basin in Yellowstone National Park contains a large number of hydrothermal systems, which host microbial populations supported by primary productivity associated with a suite of chemolithotrophic metabolisms. We demonstrate that Metallosphaera yellowstonensis MK1, a facultative autotrophic archaeon isolated from a hyperthermal acidic hydrous ferric oxide (HFO) spring in Norris Geyser Basin, excretes formaldehyde during autotrophic growth. To determine the fate of formaldehyde in this low organic carbon environment, we incubated native microbial mat (containing M. yellowstonensis) from a HFO spring with C-formaldehyde. Isotopic analysis of incubation-derived CO and biomass showed that formaldehyde was both oxidized and assimilated by members of the community. Autotrophy, formaldehyde oxidation, and formaldehyde assimilation displayed different sensitivities to chemical inhibitors, suggesting that distinct sub-populations in the mat selectively perform these functions. Our results demonstrate that electrons originally resulting from iron oxidation can energetically fuel autotrophic carbon fixation and associated formaldehyde excretion, and that formaldehyde is both oxidized and assimilated by different organisms within the native microbial community. Thus, formaldehyde can effectively act as a carbon and electron shuttle connecting the autotrophic, iron oxidizing members with associated heterotrophic members in the HFO community. [ABSTRACT FROM AUTHOR]

Potassium (K) is an important limiting factor of tree growth, but little is known of the effects of K supply on the long-distance transport of photosynthetic carbon (C) in the phloem and of the interaction between K fertilization and drought. We pulselabelled 2-year-old Eucalyptus grandis L. trees grown in a field trial combining K fertilization (+K and -K) and throughfall exclusion (+W and -W), and we estimated the velocity of C transfer by comparing time lags between the uptake of 13CO2 and its recovery in trunk CO2 efflux recorded at different heights. We also analysed the dynamics of the labelled photosynthates recovered in the foliage and in the phloem sap (inner bark extract). The mean residence time of labelled C in the foliage was short (21-31 h). The time series of 13C in excess in the foliage was affected by the level of fertilization, whereas the effect of throughfall exclusion was not significant. The velocity of C transfer in the trunk (0.20-0.82 m h-1) was twice as high in +K trees than in -K trees, with no significant effect of throughfall exclusion except for one +K -W tree labelled in the middle of the drought season that was exposed to a more pronounced water stress (midday leaf water potential of -2.2 MPa). Our results suggest that besides reductions in photosynthetic C supply and in C demand by sink organs, the lower velocity under K deficiency is due to a lower cross-sectional area of the sieve tubes, whereas an increase in phloem sap viscosity is more likely limiting phloem transport under drought. In all treatments, 10 times less 13C was recovered in inner bark extracts at the bottom of the trunk when compared with the base of the crown, suggesting that a large part of the labelled assimilates has been exported out of the phloem and replaced by unlabelled C. This supports the 'leakage-retrieval mechanism' that may play a role in maintaining the pressure gradient between source and sink organs required to sustain high velocity of phloem transport in tall trees. [ABSTRACT FROM AUTHOR]

The Belt and Road Initiative was proposed by China in 2013 to promote the interconnected development and prosperity of all participating countries. In the context of global response to climate change, understanding the embodied carbon transfer change along economic trade before and after the Belt and Road Initiative is essential to reduce carbon overall emission. In this paper, we used a multi-regional input-output model to study the embodied carbon transfer in trade between the Belt and Road countries that have signed cooperation documents with China from 2004 to 2017. The results showed that from 2004 to 2017, the growth rate that China's carbon emissions imported from other Belt and Road Initiative countries was about 1.9 times that of its exports. From 2004 to 2017, the proportion of China's carbon imports from other Belt and Road countries in China's total carbon imports increased from 3.41% to 3.73%, and exports decreased from 6.52% to 6.03%. In both 2004 and 2017, Electricity, Gas and Water sector, Heavy Industry sector, Transport sector were the three largest carbon transfer sectors in China's multilateral trade. In 2017, the embodied carbon transfer by multilateral trade among other Belt and Road countries except China increased by 15.53% compared with 2004. By comparing the characteristics of carbon transfer between China and the Belt and Road countries from 2004 to 2017, this study will provide insights for carbon emission reduction policy setting of Belt and Road Initiative countries. • We took countries that have signed documents with China as research objects. • MRIO model was used to analyze the carbon transfer change from 2004 to 2017. • The embodied carbon transfer in 2017 of BRI increased by 15.53% compared with 2004. • The growth rate of China's carbon imports from BRI was 1.9 times that of exports. [ABSTRACT FROM AUTHOR]

The mismatch between carbon transfer and economic benefits embodied in inter-provincial trade generates carbon inequality among provinces. Exacerbating carbon inequality would diminish the effectiveness of carbon policy, thereby challenging the realization of carbon neutrality target in China. Combining the network analysis and multi-regional input-output (MRIO) analysis, this paper depicted the unbalanced relationship between carbon transfer and value-added flow embodied in inter-provincial trade of China during 2012–2017 to shed light on the evolution features of trade-attributed carbon inequality from a multi-dimensional perspective. The research findings reveal that the carbon inequality embodied in inter-provincial trade of China has increased significantly during the study period, as the coefficient of structural equivalence between carbon transfer network and value-added transfer network decreased from 0.772 in 2012 to 0.634 in 2017. Different environmental regulation intensities and economic development levels among provinces are the main factors triggering the trade-attributed carbon inequality. During the surveyed years, some provinces such as Beijing, Tianjin, and Jiangsu have changed their roles from the drivers of carbon inequality to the leaders of green trade. Whilst some provinces located in the Northwest China which include Ningxia, Gansu, and Inner Mongolia are still placed in inferior positions in trade, and remain as the victims suffering from carbon inequality. The detected provincial communities present geographic adhesiveness and they are basically consistent with national urban agglomeration development planning. The research findings urge the need to shift from local carbon reduction to collective governance of carbon reduction, and provide supportive references for Chinese governments to develop integrated solutions and tailor-made policies towards equitable and sustainable development. • Network analysis is applied to unfold the evolution of trade-attributed carbon inequality. • The trade-attributed carbon inequality of China has increased significantly during 2012–2017. • Environmental regulation and economic development are the main factors of the carbon inequality. • Some provinces (Beijing, etc.) changed roles from drivers of carbon inequality to leaders of green trade. • Some provinces (Ningxia, etc.) remain as the victims suffering from carbon inequality. [ABSTRACT FROM AUTHOR]

The use of stable-isotope probing (SIP) allows tracing specific labeled substrates into fungi leading to a better understanding of their role in biogeochemical cycles and their relationship with their environment. Stable isotope probing combined with ribosomal RNA molecule, conserved in the three kingdoms of life, and messenger RNA analysis permits the linkage of diversity and function. Here, we describe two methods designed to investigate the interactions between plants and their associated mycorrhizal compartment by tracing carbon flux from the host plant to its symbionts., (© 2023. The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature.)

We conducted an in situ C pulse-labeling experiment from July to September 2011, involving three land use types: native alpine meadow with winter grazing (native meadow), cultivated perennial Elymus nutans (perennial grass), and annual Avena sativa (annual grass) pastures in the Qinghai-Tibetan Plateau. Thirty-two days after labeling, 32, 23, and 43 % of recovered C of native meadow, perennial grass, and annual grass, respectively, were released by shoot respiration, and 43, 34, and 22 % were allocated to belowground C pools. About half of C allocated to belowground C pools was released by soil respiration. Mean residence time of net assimilate C in this ecosystem was 67, 118, and 43 days for native meadow, perennial grass, and annual grass, respectively. Our results imply that species abundance and root/shoot ratio are the major controlling factors of soil C stocks in high-altitude grassland ecosystems, explaining 35 and 73 %, respectively. We suggest that conversion to monoculture for food production on the Qinghai-Tibetan Plateau may deteriorate soil health through rapid loss of soil organic C. The main cause of C transfer reduction after conversion to monoculture is the change in species richness and root/shoot ratio. Together with previous research studies, our results also support the finding that moderate grazing benefits grassland C transfer and stock, owing to higher species richness and root/shoot ratio. [ABSTRACT FROM AUTHOR]

Based on the gross trade accounting method and WIOD data, this paper quantifies the global carbon transfer from 2000 to 2014. The social network analysis and temporal exponential random graph model (TERGM) are employed to investigate the structural change and influencing factors of global carbon transfer network from a global value chains (GVCs) perspective. Results show that the deepening of the GVC division connection has enhanced the relations in global carbon transfer network, and the low reciprocity and high disassortativity lie in the difference in GVC division positions among economies. Block model analysis manifests that Plate Ⅱ acts as the engine plate in the network which consists of China and the other four economies. The GVC division connection and relative GVC division position significantly facilitate the formation of carbon emission transfer relations. Moreover, economies' attribute effects and endogenous network structure effects are non-negligible important determinants of network formation. [Display omitted] • Structural change of global carbon transfer network derives from the GVC division. • Global carbon transfer network has low reciprocity and high disassortativity. • Plate Ⅱ composed of China and the other four economies is the engine plate. • Temporal exponential random graph model is used to analyze the influencing factors. • GVC division connection and relative division position boot the network formation. [ABSTRACT FROM AUTHOR]

Aluminum is the second most used metal after iron and steel worldwide, and its production is highly energy-intensive. It's increasingly important to focus on carbon reduction in the aluminum industry. The global aluminum cycle depends on international trade with great influence on the carbon distribution, but few studies have analyzed the aluminum industry from the perspective of carbon transfer. We analyze global carbon emissions and transfers from aluminum production, consumption, and trade from 2000 to 2018 to reveal the carbon distribution across regions and countries. The results show that 1) the aluminum trade carbon transfer increased from 99 to 114 Mt, mainly from resource-rich Oceania and Africa to faster-developing or developed regions such as Asia, Europe and North America, with a high degree of industrial concentration; 2) the carbon emissions of aluminum production increased from 363 to 1005 Mt, with China accounting for the largest share; 3) different countries had different consumption structure, and the northern hemisphere as the main consumption region has greater potential for recycling and emission reduction. There is a long way to go for the aluminum industry toward its low-carbon transition, and this study will provide important insights into carbon reduction in the global aluminum industry. • Global carbon emission and transfer of aluminum through production, consumption, and trade. • Alumina and primary aluminum account for more than 90% process emissions. • Carbon transfer in aluminum trade shows a trend from resource-rich South to developing or developed North. • Energy consumption for aluminum production varies significantly in different regions. [ABSTRACT FROM AUTHOR]

Globally, China ranks first in terms of total carbon dioxide emission, one-third of which is caused by carbon transfer, which is a prerequisite for carbon reduction. Studies have ignored the path comparison and influencing factors of industrial transfer and carbon transfer. This study employed the multiregional input–output (MRIO) model to investigate the evolution trend of carbon transfer in 2002, 2007, 2012, and 2017. The study compares the consistency of the path of interprovincial industrial transfer and carbon transfer. The impact of environmental regulation, industrial structure, energy intensity, and urbanization on carbon transfer is investigated using the multiscale geographically weighted regression (MGWR) model. The results demonstrate that the path of industrial transfer and carbon transfer is similar but not wholly coupled, indicating that industrial transfer is the key factor that causes carbon transfer. Environmental regulation has a negative impact on carbon transfer, and the impact on the eastern region is higher than that on the central and western regions. Urbanization has a negative impact on carbon transfer, and the degree of impact gradually decreases. The industrial structure has a significant and positive influence on carbon transfer, and the influence coefficient gradually increases. In 2002, energy intensity played a negative role in carbon transfer; however, it had a positive effect on carbon transfer in 2007, 2012, and 2017. • This study measures the path and influencing factors of carbon transfer. • ER and URB have negative effects on carbon transfer. • IS and EI play a positive role in carbon transfer and continue to deepen. • ER and EI affect underdeveloped areas and IS and URB impact on the eastern regions. [ABSTRACT FROM AUTHOR]

Environmental factors and physiological controls on photosynthesis influence the carbon isotopic signature of ecosystem respiration. Many ecosystem studies have used stable carbon isotopes to investigate environmental controls on plant carbon transfer from above- to belowground. However, a clear understanding of the internal mechanisms underlying time-lagged responses of carbon isotopic signatures in ecosystem respiration to environmental changes is still lacking. This study addressed plant physiological controls on the transfer time of recently assimilated carbon from assimilation to respiration. We produced a set of six wheat plants with varying physiological characteristics, by growing them under a wide range of nitrogen supply and soil water content levels under standardised conditions. The plants were pulse-labelled with [sup 13]C-CO[sub 2], and the isotopic signature of CO[sub 2] respired in the dark by plants and soil was monitored continuously over two days. Stomatal conductance (g[sub s]) was strongly related to the rate of transfer of recently assimilated carbon belowground. The higher g[sub s], the faster newly assimilated carbon was allocated belowground and the faster it was respired in the soil. Our results suggest that carbon sink strength of plant tissues may be a major driver of transfer velocity of recently assimilated carbon to plant respiratory tissues and soil respiration. [ABSTRACT FROM AUTHOR]

Abstract: Rocks below the brittle-ductile transition can deform viscously and compact while fluid percolates through (two-phase solid–fluid flow). We investigate chemical reaction systematics during two-phase flow using one-dimensional numerical models in which reactive H2O–CO2 fluid ascends down-temperature toward the surface, driving the retrograde reaction: . The reaction progress is compared to that predicted by fluid–rock reaction during “standard” Darcian flow. A range of layer thicknesses (km-scale) in one- and two-layer systems were investigated at pressure–temperature conditions below the brittle-ductile transition corresponding to ∼13–20 km depth. Model porosity waves of wavelength ∼5 km were generated repeatedly at the base of the flow region using a solitary wave solution with a prescribed initial wave amplitude A = (maximum porosity)/(background porosity of ). Simulation of reaction progress and carbon transfer for the Darcian flow model and for porosity wave transport with , 2.5 and 1.25 yield the following results. First, the overall reaction progress in the two fluid transport models is mainly controlled by the time-integrated fluid flux, and is not strongly dependent on the flow regime. The implication is that the fluid pressure gradient anomalies in the regional-scale porosity waves modeled herein play a negligible role in driving reaction progress. Second, although there are high fluid velocities and thus strong advection in large amplitude porosity waves, the kinetic parameters adopted from experiments predict that the fluid compositions approach local fluid–rock equilibrium in both transport models. Third, regional-scale carbonate-bearing rock layers may be substantial sinks for carbon in ascending fluids if sufficient porosity and permeability can be maintained during reaction. Finally, typical models of retrograde reactions predict that porosity ultimately becomes clogged and, thus, fluid flow is hindered. However, porosity wave transport provides a potential mechanism for creating new porosity to sustain fluid flow during retrogression. [Copyright &y& Elsevier]

Abstract: The decomposition rate of litter mixtures can differ from that expected on the basis of the decomposition rate of the individual components. This difference may be linked to nitrogen (N) transfer from high-N to low-N components. Transfer of N is probably also associated with transfer of C, but the extent and direction of this C transfer are unknown. This study examined transfer and loss in laboratory microcosms of C and N from two mixed litter species (Scots pine, Pinus sylvestris L. and maize, Zea mays L.), which have natural isotopic differences in 13C. Half the material was 15N-labelled and the plants were fertilised or unfertilised. Substantial bidirectional transfer of C and N occurred between the litters, with net transfer of C from pine to maize litter and net transfer of N from high-N to low-N litter. Mixtures of fertilised and unfertilised plant litter showed higher than expected C losses and net transfer of N. Mixtures with litters from the same fertilisation treatment had small or insignificant net transfer of N and their C losses did not differ from values estimated using the decomposition rates of the pure litters. [Copyright &y& Elsevier]

Intercropping with aerobic rice or arbuscular mycorrhizal fungi (AMF) colonization alleviated watermelon wilt disease, which is likely attributed to rice root exudates or AMF depressing watermelon wilt pathogen. However, it is unclear whether rice root exudates transfers to watermelon rhizosphere soil and whether AMF affects the transfer of rice root exudates to watermelon rhizosphere soil. A rhizobox experiment, with aerobic rice under CO, was conducted to investigate the effect of AMF colonization on carbon (C) transfer from rice to watermelon and on phosphorus (P) uptake by both watermelon and rice. The rhizobox was separated into labelling side (L side) and sampling side (S side) by inserting nylon mesh in the middle of the box. The L side was planted with aerobic rice, and the S side was aerobic rice (monocropping) or watermelon (intercropping). When CO was added to rice canopy at the L side, C activities of rice roots and rhizosphere soils in the L side were increased by intercropping with watermelon or AMF colonization. The C was detected in roots and rhizosphere soils of rice and watermelon in the S side, but no differences were found among different treatments. C activities in leaves were improved by AMF inoculation in the S side, regardless of rice or watermelon. Mycorrhizal colonization stimulated P absorption and translocation to rice in intercropping system. These findings suggest that AMF colonization could increase C transfer from rice to watermelon while intercropping with watermelon could promote AMF colonization and P uptake by rice. [ABSTRACT FROM AUTHOR]

Carbonate rock outcrops cover 9%-16% of the continental area and are the principal source of the dissolved inorganic carbon (DIC) transferred by rivers to the oceans, a consequence their dissolution. Current estimations suggest that the flux falls between 0.1-0.6 PgC/a. Taking the intermediate value (0.3 PgC/a), it is equal to 18% of current estimates of the terrestrial vegetation net carbon sink and 38% of the soil carbon sink. In China, the carbon flux from carbonate rock dissolution is estimated to be 0.016 PgC/a, which accounts for 21%, 87.5%-150% and 2.3 times of the forest, shrub and grassland net carbon sinks respectively, as well as 23%-40% of the soil carbon sink flux. Carbonate dissolution is sensitive to environmental and climatic changes, the rate being closely correlated with precipitation, temperature, also with soil and vegetation cover. HCO-3 in the water is affected by hydrophyte photosynthesis, resulting in part of the HCO-3 being converted into DOC and POC, which may enhance the potential of carbon sequestration by carbonate rock dissolution. The possible turnover time of this carbon is roughly equal to that of the sea water cycle (2000a). The uptake of atmospheric/soil CO2 by carbonate rock dissolution thus plays an important role in the global carbon cycle, being one of the most important sinks. A major research need is to better evaluate the net effect of this sink in comparison to an oceanic source from carbonate mineral precipitation. [ABSTRACT FROM AUTHOR]

Abstract: Mycorrhizal networks, defined as a common mycorrhizal mycelium linking the roots of at least two plants, occur in all major terrestrial ecosystems. This review discusses the recent progress and challenges in our understanding of the characteristics, functions, ecology and models of mycorrhizal networks, with the goal of encouraging future research to improve our understanding of their ecology, adaptability and evolution. We focus on four themes in the recent literature: (1) the physical, physiological and molecular evidence for the existence of mycorrhizal networks, as well as the genetic characteristics and topology of networks in natural ecosystems; (2) the types, amounts and mechanisms of interplant material transfer (including carbon, nutrients, water, defence signals and allelochemicals) in autotrophic, mycoheterotrophic or partial mycoheterotrophic plants, with particular focus on carbon transfer; (3) the influence of mycorrhizal networks on plant establishment, survival and growth, and the implications for community diversity or stability in response to environmental stress; and (4) insights into emerging methods for modelling the spatial configuration and temporal dynamics of mycorrhizal networks, including the inclusion of mycorrhizal networks in conceptual models of complex adaptive systems. We suggest that mycorrhizal networks are fundamental agents of complex adaptive systems (ecosystems) because they provide avenues for feedbacks and cross-scale interactions that lead to self-organization and emergent properties in ecosystems. We have found that research in the genetics of mycorrhizal networks has accelerated rapidly in the past 5 y with increasing resolution and throughput of molecular tools, but there still remains a large gap between understanding genes and understanding the physiology, ecology and evolution of mycorrhizal networks in our changing environment. There is now enormous and exciting potential for mycorrhizal researchers to address these higher level questions and thus inform ecosystem and evolutionary research more broadly. [Copyright &y& Elsevier]

We describe with molecular model studies based on the intrinsic parameters of van't Hoff's regular tetrahedron nucleophilic and electrophilic addition-substitution reactions via a selected reaction coordinate for the displacement of carbon. Geometries of stable, intermediate transition complexes or transition states are compared with the corresponding ab initio values. Specific attention is given on the hypervalent and nonhypervalent character of carbon supported by ab initio calculations, our model consideration and experimental evidence. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011 [ABSTRACT FROM AUTHOR]

We investigated post-photosynthetic fractionation and carbon transfer mechanisms of different plant functional types growing under the same climatic conditions in North-eastern China. The variations in δC of trunk and branches were compared with leaf δC at different canopy heights of Pinus koraiensis (evergreen coniferous species), Larix gmelinii (deciduous coniferous species) and Quercus mongolica (deciduous broad-leaved species). Results showed that δC of leaves increased (became more enriched) with increasing canopy height for both coniferous species ( P. koraiensis, L. gmelinii) but not for Q. mongolica (a deciduous broad-leaved species). δC of both trunk and branches also increased with sampling height for the evergreen conifer P. koraiensis but did not significantly vary for either of the deciduous species ( L. gmelinii or Q. mongolica), except a significant increase in branch δC for L. gmelinii. Similarly, δC of trunk and branches were strongly correlated with leaf δC only in the evergreen conifer, P. koraiensis. C was consistently more enriched in trunk, branches, and roots compared to leaves in all three species. Our findings suggest that, even under the same climatic conditions, different plant functional types may exhibit different carbon transfer mechanisms. This is contrary to the previous hypothesis that different carbon transfer mechanisms operate in forests of different climatic zones, especially in tropical and temperate forests. Particularly, the differences occur predominantly between evergreen and deciduous trees rather than between coniferous and broad-leaved trees. The significant difference in δC between leaves and wood tissues confirms a previous post-photosynthetic isotope fractionation in temperate forests. [ABSTRACT FROM AUTHOR]

Abstract: We characterized the seasonal cycle of productivity in Reloncaví Fjord (41°30′S), Chilean Patagonia. Seasonal surveys that included measurements of gross primary production, community respiration, bacterioplankton secondary production, and sedimentation rates along the fjord were combined with continuous records of water-column temperature variability and wind forcing, as well as satellite-derived data on regional patterns of wind stress, sea surface temperatures, and surface chlorophyll concentrations. The hydrography and perhaps fjord productivity respond to the timing and intensity of wind forcing over a larger region. Seasonal changes in the direction and intensity of winds, along with a late-winter improvement in light conditions, may determine the timing of phytoplankton blooms and potentially modulate productivity cycles in the region. Depth-integrated gross primary production estimates were higher (0.4–3.8gCm−2 d−1) in the productive season (October, February, and May), and lower (0.1–0.2gCm−2 d−1) in the non-productive season (August). These seasonal changes were also reflected in community respiration and bacterioplankton production rates, which ranged, respectively, from 0.3 to 4.8gCm−2 d−1 and 0.05 to 0.4gCm−2 d−1 during the productive and non-productive seasons and from 0.05 to 0.6gCm−2 d−1 and 0.05 to 0.2gCm−2 d−1 during the same two periods. We found a strong, significant correlation between gross primary production and community respiration (Spearman, r=0.95; p<0.001; n=12), which suggests a high degree of coupling between the synthesis of organic matter and its usage by the planktonic community. Similarly, strong correlations were found between bacterioplankton secondary production and both gross primary production (Spearman, r=0.7, p<0.05, n=9) and community respiration (Spearman, r=0.8, p<0.05, n=9), indicating that bacterioplankton may be processing an important fraction (8–59%) of the organic matter produced by phytoplankton in Reloncaví Fjord. In winter, bacterial carbon utilization as a percentage of gross primary production was >100%, suggesting the use of allochthonous carbon sources by bacterioplankton when the levels of gross primary production are low. Low primary production rates were associated with a greater contribution of small cells to autotrophic biomass, highlighting the importance of small-sized plankton and bacteria for carbon cycling and fluxes during the less productive winter months. Fecal pellet sedimentation was minimal during this period, also suggesting that most of the locally produced organic carbon is recycled within the microbial loop. During the productive season, on the other hand, the area exhibited a great potential to export organic matter, be it to higher trophic levels or vertically towards the bottom. [Copyright &y& Elsevier]