Climate change : strategies for mitigation and adaptation

The sustainability of life on Earth is under increasing threat due to humaninduced climate change. This perilous change in the Earth's climate is caused by increases in carbon dioxide and other greenhouse gases in the atmosphere, primarily due to emissions associated with burning fossil fuels. Over the next two to three decades, the effects of climate change, such as heatwaves, wildfires, droughts, storms, and floods, are expected to worsen, posing greater risks to human health and global stability. These trends call for the implementation of mitigation and adaptation strategies. Pollution and environmental degradation exacerbate existing problems and make people and nature more susceptible to the effects of climate change. In this review, we examine the current state of global climate change from different perspectives. We summarize evidence of climate change in Earth’s spheres, discuss emission pathways and drivers of climate change, and analyze the impact of climate change on environmental and human health. We also explore strategies for climate change mitigation and adaptation and highlight key challenges for reversing and adapting to global climate change

Trends in Research on Soil Organic Nitrogen over the Past 20 Years

Nitrogen (N), an indispensable mineral nutrient element for plant growth and development, is a major limiting source of productivity in many terrestrial ecosystems. Soil organic nitrogen (SON) is a crucial form of nitrogen (N) in the N cycle within terrestrial ecosystems, acting as either a “source” or a “sink” for environmental N release. In order to illustrate the research trends, evolution process and hotspots of SON, a bibliometric analysis was used to analyze 906 documents based on the ISI (Institute of Scientific Information) Web of Science (WoS) database. The results indicated that (1) the number of published papers on SON research showed a wavy growth from 2000 to 2022 and the research has entered a mature development period; China has been increasing its number of publications and has long been in the lead; (2) the most productive institutions and authors in this subject area are in the USA and China, with the Chinese Academy of Sciences being the key institution performing such research; (3) in the sample, Soil Biology and Biochemistry, Science of the Total Environment, and Biogeochemistry are the leading international journals that have played a key role in the evolution of the field and have laid a solid foundation for future research; (4) the characteristics and maintenance of SON in farmland and SON migration in small watersheds under forest conversion have become research hotspots. Through the in-depth analysis of SON research, this paper provides a better understanding of the development trends of SON over the past 20 years, which can also provide reference for future research

Higher soil capacity of intercepting heavy rainfall in mixed stands than in pure stands in riparian forests

Changes in global precipitation patterns would make wet regions lore humid and extreme precipitation events occur frequently, followed by widespread flooding. Riparian forests are more capable of withstanding floods than inland forests because they are frequently exposed to short-term flooding events. Although many previous studies have investigated the soil water dynamics of terrestrial forests, little is known about how the soil water of riparian forests responds to different amounts of rainfall and which factors mainly regulate the soil water-holding capacity. Here, we employed stable hydrogen isotope to explore the contribution of different magnitudes of rainfall (7.9, 18.6 and 34.1 mm) to the soil water in two types of riparian forests (pure vs. mixed stand of Populus deltoides) in the middle-lower reaches of the Yangtze River, China. We further used structure equation modelling to determine the relative importance of soil properties and vegetation biomass in affecting the contribution of different magnitudes of rainfall to soil water. Our results revealed that there was no significant difference between these two stand types in the contributions of light and moderate rainfall to soil water, while the contribution of heavy rainfall to soil water (CHRSW) in mixed stand was significantly higher than that in pure stand (74.3% vs. 62.9%), suggesting that mixed stand soil has higher water-holding capacity than pure stand soil. Furthermore, soil properties were the best predictor affecting CHRSW, which explained 68% and 59% of the variation in the CHRSW on the 1st and 8th days after rainfall, respectively. Moreover, the root biomass could indirectly affect the CHRSW. Overall, mixed stand soil had a greater capacity in intercepting and storing rainwater than pure stand soil, implying that the mixed stand plantation, rather than the pure stand, should be recommended in riparian forest restoration projects that aim to improve their capacity for alleviating floods. (C) 2018 Elsevier B.V. All rights reserved

Experimental and Numerical Investigation of the Shear Performance of PSCC Shear Connectors with Poured UHPC

Assembled steel-composite bridges generally use stud connectors to achieve the connection between the deck slab and the steel main girders. However, the commonly-used cluster studs weaken the integrity of the precast deck slabs and are not conducive to reducing the size of the precast deck slabs. Based on the excellent mechanical performance of UHPC, a precast steel-concrete composite bridge system consisting of precast bridge deck slabs, bonding cavities, and steel girders was proposed in this study. The system was named PSCC (Precast Steel-Concrete Connectors). To verify the applicability of PSCC connectors in engineering, push-out tests and finite element analysis were carried out in this paper to investigate the shear performance and influence parameters of PSCC connectors. The results showed that compared with the full bonding at the steel-UHPC interface, the shear bearing capacity of the specimens with 30% debonded area rate (the ratio of defect area to total interface area) and the shear bearing capacity of the specimens with 60% debonded area rate decreased by 0.35% and 9.74%, the elastic stiffness decreased by 14.86% and 21.72%, and the elastic-plastic stiffness decreased by 1.6% and 12.8%, respectively. When the steel-UHPC percentage of debonded area is less than 30%, the shear resistance of PSCC connectors is affected very little. However, when the steel-UHPC percentage of debonded area is 60%, the shear resistance of PSCC connectors is greatly affected. Therefore, adequate filling of the UHPC connection layer should be ensured in the project. In addition, the PSCC connectors have excellent ductility, their characteristic slip value Su is much higher than the EC4 specification of 6 mm, and they have better shear performance than conventionally installed stud connectors. According to the results of the parametric analysis, it was found that the failure mode of the PSCC connectors was shear reinforcement fracture when the area ratio of shear reinforcement to stud was less than 1.55, under the premise of the same material strength. On the contrary, the failure mode of PSCC connections was stud fracture. When the transverse spacing of both studs and shear reinforcement is 4d, the PSCC connectors can maintain a high ultimate load capacity while reducing the amount of UHPC in the bonding cavity. Therefore, 4d was chosen as the best spacing for both studs and shear reinforcement

Effects of Forest Gap on Soil Microbial Communities in an Evergreen Broad-Leaved Secondary Forest

Forest gaps play a crucial role in community succession and assembly in forest ecosystems; therefore, they have recently been recognized and implemented as effective forest management practice all over the world. Forest gaps are commonly created as small disturbances in secondary forests to improve forest regeneration, nutrient cycling, ecosystem functioning, and biodiversity. The objective of this study was to investigate the responses of the physico-chemical and biological properties and microbial communities in soil to different sizes of forest gaps—including small gaps (60–80 m2), medium gaps (130–160 m2), and large gaps (270–300 m2)—and to examine the driving factors that influence soil microbial community structure and composition. The results show that Gram-positive bacteria, Gram-negative bacteria, fungi, arbuscular mycorrhizal fungi (AMF), and actinomycetes were mainly aggregated in the gaps, and the structural diversity of soil microbial communities was related to the gap size (p p 2) always significantly improved the availability of soil nutrients, and good management practices in secondary forests can provide effective microenvironments for soil microbes

Effects of Forest Gap on Soil Microbial Communities in an Evergreen Broad-Leaved Secondary Forest

Forest gaps play a crucial role in community succession and assembly in forest ecosystems; therefore, they have recently been recognized and implemented as effective forest management practice all over the world. Forest gaps are commonly created as small disturbances in secondary forests to improve forest regeneration, nutrient cycling, ecosystem functioning, and biodiversity. The objective of this study was to investigate the responses of the physico-chemical and biological properties and microbial communities in soil to different sizes of forest gaps—including small gaps (60–80 m2), medium gaps (130–160 m2), and large gaps (270–300 m2)—and to examine the driving factors that influence soil microbial community structure and composition. The results show that Gram-positive bacteria, Gram-negative bacteria, fungi, arbuscular mycorrhizal fungi (AMF), and actinomycetes were mainly aggregated in the gaps, and the structural diversity of soil microbial communities was related to the gap size (p < 0.05). The soil microbial community diversity increased and then decreased with an increase in gap size. Moreover, the effects of the available phosphorus, soil pH, soil water content, available potassium, nitrate nitrogen and ammonium nitrogen on changes in microbial biomass were significant (p < 0.05). The gap area and gap position and their combined interactions also had significant effects on soil nutrients, which impacts the soil microbial community. Medium gaps (130–160 m2) always significantly improved the availability of soil nutrients, and good management practices in secondary forests can provide effective microenvironments for soil microbes

Seed vigor of contrasting rice cultivars in response to elevated carbon dioxide

Although a number of studies have shown that rising atmospheric carbon dioxide concentration, [CO2], can differentially affect the growth and yield potential of rice (Oryza sativa L.) cultivars, there has been no attempt to determine if the response is associated with changes in seed vigor, an essential aspect of crop establishment. Because previous investigations have shown that [CO2] can change the grain structure and quality of rice seed, we hypothesized that [CO2] would decrease vigor via decreased germination rates. To test this hypothesis, we used an in situ, free-air CO2 enrichment (FACE) system to assess seed quality in six rice cultivars that differed in their growth and reproductive response to rising [CO2]. Elevated [CO2] had no effect on seed hull thickness or seed specific gravity, but did significantly reduce total nitrogen and protein concentration for all cultivars. Despite the changes in grain physical and chemical traits associated with germination, no clear indication of quantitative effects of elevated [CO2] on rice germination was found

Trends in Research on Forest Ecosystem Services in the Most Recent 20 Years: A Bibliometric Analysis

Forest resources and the flow of ecosystem services they provide play a key role in supporting national and regional economies, improving people’s lives, protecting biodiversity, and mitigating the impacts of climate change. Based on the ISI (Institute of Scientific Information) Web of Science (WoS) database, we used a bibliometric approach to analyze the research status, evolution process, and hotspots of forest ecosystem services (FES) from a compilation of 8797 documents published between 1997 and 2019. The results indicated that: (1) research on forest ecosystem services has developed rapidly over the past 23 years. Institutions in the United States and other developed countries have significantly contributed to undertake research on the topic of ecosystem services. (2) The 11 hotpot key focus areas of completed research were payments for ecosystem services, biodiversity conservation, forest governance, ecosystem approaches, climate change, nitrogen, ecosystem management, pollination, cities, ecological restoration, and policy. (3) The trade-off relationships among ecosystem services, ecosystem resilience and stability have become the research frontier in this field. (4) Future research on FES will likely focus on the formation and evolution mechanism of ecosystem services; the interaction, feedback and intrinsic connections of ecosystem services at different scales; analysis of the trade-offs and synergies; unified evaluation standards, evaluation systems, model construction and scenario analyses; in-depth studies of the internal correlation mechanism between forest ecosystem services and human wellbeing; and realization of cross-disciplinary and multi-method integration in sustainable forest management and decision-making

Responses of ephemeral plant germination and growth to water and heat conditions in the southern part of Gurbantunggut Desert

Ephemeral plants in the southern part of Gurbantunggut Desert were systematically monitored from 2002 to 2004 and the meteorological data and soil moisture during the same period were analyzed. The results show that the ephemeral plants germination and growth are sensitive to the changes of water and heat condition. The time for daily temperature over 0 degrees C in early spring in 2003 was delayed nearly 10 d compared with that in 2002, while the soil water changed little in the same period. Observation showed that there were 28 ephemeral species germinated in 2002, their life period was about 70 d in spring, and the maximum cover of ephemeral synusia reached 46.4%. However, only 17 ephemeral species germinated in 2003, their life period was about 50 d in spring, and their maximum cover was only 20.8%. The height of ephemeral plants was significantly higher in 2002 than that in 2003. It can be seen that ephemeral plant germination and growth in spring are strongly dependent on temperature. The changes of water conditions can affect ephemerals germination and growth as well. Because no heavy precipitation occurred during summer in 2002, only a few ephemerophytes were observed in autumn after ephemerals completed their life circle in early spring. However, about 60 mm precipitation was recorded from July to August both in 2003 and in 2004. Some ephemerals such as Erodium oxyrrhynchum and Carex physodes, etc. covered the dune surface rapidly with a cover > 10%. Therefore, the ephemerals not only germinate in autumn after the early spring, some species may germinate in summer if adequate rainfall occurs. The study on responses of ephemerals growth to water and heat conditions not only has a certain ecological significance but also contributes a better understanding to the effect of climate changes on the desert surface stability

Carbon dioxide (CO2) levels this century will alter the protein, micronutrients, and vitamin content of rice grains with potential health consequences for the poorest rice-dependent countries

Declines of protein and minerals essential for humans, including iron and zinc, have been reported for crops in response to rising atmospheric carbon dioxide concentration, [CO2]. For the current century, estimates of the potential human health impact of these declines range from 138 million to 1.4 billion, depending on the nutrient. However, changes in plant-based vitamin content in response to [CO2] have not been elucidated. Inclusion of vitamin information would substantially improve estimates of health risks. Among crop species, rice is the primary food source for more than 2 billion people. We used multiyear, multilocation in situ FACE (free-air CO2 enrichment) experiments for 18 genetically diverse rice lines, including Japonica, Indica, and hybrids currently grown throughout Asia. We report for the first time the integrated nutritional impact of those changes (protein, micronutrients, and vitamins) for the 10 countries that consume the most rice as part of their daily caloric supply. Whereas our results confirm the declines in protein, iron, and zinc, we also find consistent declines in vitamins B1, B2, B5, and B9 and, conversely, an increase in vitamin E. A strong correlation between the impacts of elevated [CO2] on vitamin content based on the molecular fraction of nitrogen within the vitamin was observed. Finally, potential health risks associated with anticipated CO2-induced deficits of protein, minerals, and vitamins in rice were correlated to the lowest overall gross domestic product per capita for the highest rice-consuming countries, suggesting potential consequences for a global population of approximately 600 million