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To identify the interaction pattern features and driving forces of intersectoral CO2 emissions, this paper studies the interaction pattern types, interaction linkage strengths and key interaction patterns of 28-sector CO2 emissions flow networks in China from 1997 to 2015 via network motif analysis. Network motif analysis is a useful tool for measuring interactions between agents and their function in networks. This paper extends network motif analysis by investigating the weighted edges of motifs to observe the function of motifs. The results show that in 1997–2002 and 2008–2015, the strongest carbon intensity sectors, including electricity production, metal smelting and gas production, were the greatest contributors to the increase in intersectoral CO2 emissions. From 2003 to 2007, the strongest energy intensity sectors, including electricity production and fuel processing, were the greatest contributors. In contrast, the strongest export intensity sectors, including other electronic equipment, leather manufacturing, instrumentation, and textile, were the largest contributors to the decrease in intersectoral CO2 emissions. Second, the strongest interaction linkages were between construction and nonmetallic products and metal smelting, machinery and construction and metal smelting, construction and nonmetallic products, construction and metal smelting. Third, the key interaction patterns for the increase in intersectoral CO2 emissions were patterns such as infrastructure-export, manufacturing intensive, energy consumption, and energy tracing, while the export-intensive pattern and high export pattern were the key interaction patterns for the decrease in intersectoral CO2 emissions. This paper is beneficial to the establishment of a coordinated emissions reduction mechanism across sectors.

Sectors tend to generate pressure on the environment due to its large amounts of emissions. The aim of this study is to identify critical betweenness sectors and transactions that play an important intermediate role in the supply chain, which can provide additional insights for CO2 emissions. Based on the input-output and energy consumption data in China, the notion of network centrality and structural path analysis method are employed in this paper to identify critical betweenness sectors and transactions, and then the evolutionary trends of betweenness sectors and transactions are analyzed from 2005 to 2015. The results show that some critical betweenness sectors, such as Metal products sector and Electrical equipment sector, have huge potential for carbon emission reduction, which fail to receive sufficient attention from the perspective of production or consumption. Some critical transactions, such as the transaction from Nonmetal products sector to Construction sector, have a large amount of CO2 emissions. The transaction from Metallurgy sector to Electrical equipment sector became increasingly important in China from 2005 to 2015. Additionally, the evolutionary trends of different transactions are significantly different. The findings reveal that special attention should be paid to these critical betweenness sectors and transactions and policy development should be dynamic to respond to changes in CO2 emissions that are generated by different betweenness sectors and transactions.

As the largest carbon emitter, China is facing huge pressure and has a heavy task to control emissions. Previous studies have mainly focused on the production- and consumption-based sectors with large emissions, but few draw the whole picture of emission flows in Chinese supply chains in which direct carbon emissions (DCE) become embodied carbon emissions (ECE).This study aims to combine input-output model and structural path analysis to trace carbon emission flows from primary producer sectors to final consumer sectors based on the data of China in 2012. The results show that the total carbon emissions were 9208.33 Mt, and capital formation was the main final demand with the share of 44.22%. Production and Supply of Electricity released the largest DCE, and Construction was responsible for the largest ECE. Nearly 90% of emissions occurred in upstream sectors of the supply chains, Manufacturing and Electricity/Gas/Water are the important transfer sectors. The distribution of DCE and ECE of different sectors have different patterns. Electricity/Gas/Water released most of its DCE for its two-step downstream sectors (22.64%). Construction got more ECE indirectly from its one-step upstream sectors (29%) and two-step upstream sectors (26%). Controlling inputs from upstream or outputs to downstream can help to develop more effective measures to reduce emissions, especially for achieving the reduction target of one certain sector. Furthermore, some supply chain paths with more emissions, such as “Metal Smelting→ Construction→ Capital formation”, should be paid more attention. Reducing intermediate purchases or using cleaner alternatives can stimulate sectors along the supply chains to control emissions together and construct green supply chains.

Straw return is widely applied in China to achieve sustainable grain production. However, inappropriate farm practices can increase greenhouse gas (GHG) emissions and reduce soil organic carbon (SOC) sequestration, thereby increasing the carbon footprint (CFP) and affecting soil fertility and climate change. A 10-year experiment was conducted to evaluate and quantify the effects of straw management on SOC, crop yield, and CFP under a winter wheat–summer maize rotation in the Guanzhong Plain. The experiment involved seven straw-return modes, namely high wheat stubble retention and chopped maize straw return (WH-MC), high wheat stubble retention and chopped maize straw return with sub-soiling every two years (WH-MM), high wheat stubble retention and no maize straw return (WH-MN), both chopped wheat and maize straw return (WC-MC), chopped wheat and maize straw return with sub-soiling every two years (WC-MM), chopped wheat straw return and no maize straw return (WC-MN), and a control with no return of either wheat or maize straw (WN-MN). The results indicate that SOC change, crop yield, and CFP were significantly influenced by the straw-return mode in the annual wheat–maize season. SOC sequestration rate was positively correlated with cumulative plant-derived C input, which ranged from 29.4 Mg C ha −1 in WN-MN to 100.7 Mg C ha −1 in WH-MC. Of all the studied treatments, WH-MC produced the highest grain yield and lowest CFP, which were 26% higher and 20.5% lower than those of the control, respectively. However, crop yield and CFP in the individual wheat or maize seasons were only slightly affected by straw-return mode; only WC-MN in the wheat season and WH-MC, WH-MM, and WC-MN in the maize season produced a significantly higher grain yield and lower CFP compared to the no straw return treatment. Annual GHG emissions were highest in the WC-MM treatment and lowest in WH-MN. Therefore, WH-MC found to be the most suitable straw-return for lowering CFP and enhancing crop yield and SOC sequestration. However, to achieve the coordinated development of agriculture and the livestock industry it is necessary to remove some straw for animal feed and fuel, so WH-MN produced optimum yield and maintained SOC stock with low GHG emissions.

In the rapid process of globalization, merchandise trade has increased year by year, and the circulation and consumption of the energy embodied in the merchandise trade have increased. To study the relevant nature of the global embodied energy trade network (GEETN) from an overall perspective and the control and dependence relationships between various countries and regions from a partial perspective, this paper establishes a GEETN model, through an ecological network analysis (ENA) method and the motif of complex networks for research. From an overall perspective, a GEETN is a system that achieves stability quickly. Some developed countries, such as the United States and the European Union, and some emerging economies, such as China and Russia, play important roles in GEETN. From a partial perspective, in the GEETN model, US is mainly controlled by Asian countries and CA (Canada), EU is mainly controlled by other European countries, both due to their industrial layout in some extent. The scientific value of this article not only includes the improvement of model, but also provides a new perspective and a reference for the formulation of energy and climate change policies.

BRICS nations, as a representative of emerging economies, have rapid economic growth and frequent trade activities, which result in a large amount of embodied energy flow (the embodied energy of BRICS accounts for about 42.3% of the global embodied energy) in the BRICS and all over the world. This article uses multilayer network model to study the embodied energy of the BRICS. By using the weighted degree and betweenness centrality indicators, key sectors and key paths are identified. The results show that the embodied energy circulation in BRICS is still dominated by industry and natural resources sectors, such as Petroleum, Chemical and Non-Metallic Mineral Products sector. The analysis of the key paths allows us to understand Russia and South Africa are exporters of embodied energy, China is an intermediate transmission country, and India and Brazil are importers. The roles of the five countries are different, and they need to perform their own duties, cooperate with collaborative governance, to achieve energy-saving, environmentally-friendly, and efficient development of the BRICS.

Crop residue is a commonly used organic soil amendment in summer maize (June–October)–winter wheat (October–June of next year) rotation systems. However, the effects of different straw return modes on soil aggregation and soil organic carbon (SOC) stocks in different water-stable aggregates have not been extensively investigated in these cropping systems. The objective of this study was to quantify the long-term (7 yr) impact of C input on the SOC content of four soil aggregate size classes (large macroaggregates; small macroaggregates; microaggregates, silt plus clay fraction) and in explicit SOC fractions (free light fraction, free LF; intra-aggregate particulate organic matter, iPOM; mineral-associated matter, mSOM) within the top 40 cm of soil in a wheat–maize double cropping system in Northwest China. Four treatments were examined: (i) no return (control); (ii) return of wheat straw only (WR); (iii) return of maize straw only (MR); and (iV) return of both maize and wheat straw (MR-WR). Over the experimental period, the change in SOC under the four treatments ranged from −0.96 to 5.83 Mg ha −1 and a significant linear relationship between SOC change and cumulative C input (R 2 = 0.9882, P fine iPOM > coarse iPOM > free LF. Straw return significantly increased the C stock in iPOM and mSOM relative to the control. Coarse iPOM was the most sensitive indicator of C change and mSOM was the main form of SOC under long-term straw return. A significant linear relationship existed between cumulative C input and the mass proportion of macroaggregates as well as the C content of SOC fractions (or aggregate fractions). Soil depth had a significant influence on almost all measurements, with greater values observed in the 0–20 cm layer than in the 20–40 cm layer. Overall, return of both maize and wheat straw was the best strategy for improving soil structure, soil organic carbon, and crop yield. However, straw return from one crop was sufficient to maintain initial SOC levels, and conserved straw could be used for cellulosic feedstocks.

Organic amendments are widely used to both manage soil organic C (SOC) and improve soil fertility in agro-ecosystems. However, crop production and the mechanisms of SOC sequestration following organic amendment may be affected by long-term differential N fertilizations, hence driving the dynamics in SOC fractions in cultivated fields. Our 3-yr (2016–2019) field experiment evaluated the responses of SOC sequestration and SOC fractions to organic amendments in soils with long-term contrasting N applications in a winter wheat monoculture system. We compared wheat straw return (St) and farmyard manure application (Fm) in soils with either long-term (2002–2019) N absence (-N) or normal N application (+N). Both St and Fm increased SOC stocks in the 0–20-cm layer, but Fm increased it more than St did. However, St exhibited a greater SOC sequestration rate in +N soils than that in –N soils, whereas Fm exhibited both a lower SOC sequestration rate and efficiency in +N soils than in –N soils. SOC increased across all fractions in all soils after both St and Fm. However, compared with –N soils, +N soils exhibited a lower SOC increase, specifically in the very labile fraction after St, but in the non-labile fraction after Fm. St, Fm, and +N all increased the soil C management index (CMI), but only +N increased wheat yield and its sustainable yield index (SYI). Those relationships indicated that both straw and manure amendments were responsible for both SOC sequestration and increasing the CMI, and N input was fundamentally responsible for an increased SYI and associated plant-C input. Consequently, straw return was expected to be more effective at sequestering SOC when applied to soil having had adequate long-term N application, whereas farmyard manure application was likely more effective when applied in N-deficient soil. Our field study findings provide empirical evidence that soil N availability affects SOC sequestration capacities following organic amendments, and that impacts strategies aimed at further increasing soil fertility improvements via organic amendment, especially considering that different agro-ecosystems are subject to different fertilization regimes.

Nickel, cobalt, and lithium are the most critical raw materials for lithium-ion batteries (LIBs). The increasing demand for these materials has triggered worries about the trade dependency on raw materials. Traditional trade dependency measures make it difficult to identify high-risk countries (regions) from a systematic perspective. This paper proposes a global dependency index to recalculate systemic risks in the trade dependency network. Unlike the traditional trade network analysis, we construct the resource-dependent network by taking the dependency relationship as the edge and the global dependency index as the weight. We use the new network to explore the characteristics of the overall pattern of global trade and the concentration of dependency. Then, considering the heterogeneity of trading agents, country (regional) dependency is analyzed at the local and global levels. The dependency relationship coordinates are constructed to identify high-risk countries (regions). The results show that the trade is highly concentrated. Developed and emerging economies tend to import in quantity. The absolute dependency and global dependency of agents are heterogeneous. The distribution characteristics of agent relationships in the trade dependency coordinates are apparent. According to the results, policymakers and market participants can tailor trade strategies to reduce risks. This accounting method provides ideas for future studies on trade dependency on other resources.

With international trade, energy embodied in goods flows between sectors at a global scale and forms a complex network. Using the world input-output tables from 1995 to 2009, this study aims to apply complex network theory to study the evolutionary features of global embodied energy flow between sectors. The results show that 80% of flows are between different countries, while 80% of embodied energy is consumed in the national production process. Over time, embodied energy consumption increases, and sectors tend to import more energy from sectors in other countries. The network is sensitive; change in some sector or flow can quickly spread and impact the whole system. Only 0.02% of key flows possess large amounts of embodied energy and account for 80% of embodied energy. Sectors with large-scale impact, strong impact, strong intermediary ability, and strong central ability play key roles in the network. Furthermore, the network presents an obvious clustering feature. More than 60% of sectors cluster into the top 3 largest communities, and sectors in EU countries cluster into the biggest community and attract more sectors to join. Therefore, the key flows, key sectors and key communities should receive more attention when making energy-related policies.

Organic amendment can increase soil zinc (Zn) availability and its uptake in cereals. Conversely, Zn transformation in soil may modify soil organic carbon (SOC) dynamics. To date, the effects of the simultaneous addition of organic material and Zn fertilizer on soil SOC storage and crop Zn enrichment have received little attention. Here, with a view to clarifying this problem, a 2-year wheat-based field study was conducted on the Loess Plateau in China with the following treatments: control, SR alone (SR7.5, 7.5 Mg·ha−1), ZF alone (ZF15, 15 kg Zn·ha−1), and SR plus ZF (ZF15SR7.5). The results indicate that loss of SOC after 2 years was 0.6 Mg·ha−1 in the control soil, and an input of 2.2 Mg C·ha−1·y−1 was needed to maintain the pre-experimental SOC stock. However, the increase in SOC storage after 2 years was 1.0 Mg·ha−1 in soil with SR7.5 and 2.6 Mg·ha−1 in soil with ZF15SR7.5, which accounted for 9.3% and 24% of residue-C input, respectively. On the other hand, the concentration of available Zn in soil with ZF15 was 3-fold higher than that in the control soil, but lower than that in soil with ZF15SR7.5 in both years. The Zn uptake by wheat and the grain Zn concentration also increased as the soil Zn availability increased, especially in the second year. Most importantly, in soil with ZF15SR7.5, the wheat grain Zn concentration reached 38 mg·kg−1 after 2 years, and the estimated dietary-absorbed Zn was 3.65 mg·d−1, which met the recommended Zn intake of 3 mg·d−1 for adults. Therefore, combining SR and ZF shows a promising synergistic effect for the enhancement of both SOC storage and wheat grain Zn bioavailability on China’s Loess Plateau and other drylands.

Straw return is a widely recognized strategy for increasing soil organic carbon (SOC) sequestration and improving soil quality and crop productivity. A 4-year-long field experiment established in 2008 was conducted to investigate the effects of the combined return of maize and wheat straw on the SOC stock at a soil depth of 0–20 cm in an intensive summer maize (Zea mays L.)–winter wheat (Triticum aestivum L.) cropping system in the Guanzhong Plain. The study involved four treatments with four replicates: low return of maize and wheat straw (ML–WL), low return of maize straw and high return of wheat straw (ML–WH), high return of maize straw and low return of wheat straw (MH–WL), and high return of maize and wheat straw (MH–WH). Compared with the SOC stock in the pre-experimental soil, the SOC stock in the 0–20 cm soil layer decreased by 2.6% under the ML–WL treatment, and in contrast, increased by 1.9% in ML–WH and 14.4% in MH–WH. Similarly, the stabilization rate gradually increased from 2.4% in ML–WH to 10.0% in MH–WH, though an obvious decrease of 6.8% was found in the ML–WL treatment. A significant linear relationship (P