增温对土壤N2O和CH4排放的影响与微生物机制研究进展

全球变暖已引起人们的广泛关注,大气温室效应气体浓度增加是导致全球变暖的主要因素之一,土壤是温室效应气体的主要来源。反过来,全球变暖对土壤温室气体的排放具有反馈作用。温度升高不仅会影响植物、动物、微生物的生长及其相互作用,还会影响土壤的物质(尤其是氮、碳)循环过程,从而影响土壤温室效应气体的排放。本文主要总结了增温对土壤主要温室气体N₂O和CH₄排放的影响及其微生物机制。总体来看,增温能够促进这两种温室气体的排放,其排放主要与温度对氨氧化细菌(AOB)、反硝化功能基因、甲烷产生菌和甲烷氧化菌的丰度和组成的影响有关。土壤温室气体排放也受到植物的物种特性、养分吸收和群落组成,以及土壤营养元素含量、含水量、pH值等理化性质的影响。未来应更深入地从微生物角度探讨全球变暖对土壤温室气体排放的反馈作用机制,加强不同增温模式对土壤温室气体排放的影响研究,并关注增温与其他环境因子相互作用对土壤温室气体排放的影响等,以期为全球变暖对土壤温室气体排放反馈作用的预测提供理论依据。     

全球变暖与陆地生态系统研究中的野外增温装置

由于化石燃料燃烧和森林砍伐等人类活动引起的地球大气层中温室气体(主要是二氧化碳)的富集已导致全球平均温度在20世纪升高了0.6 ℃,并将在本世纪继续上升1.4~5.8 ℃。这种地质历史上前所未有的全球变暖将对陆地植物和生态系统产生深远影响,并通过全球碳循环的改变反馈于全球气候变化。作为全球变化生态学的主要研究方法之一,生态系统增温实验能够为生态模型提供参数估计和模型验证。然而由于在世界各地使用的增温装置不同,使得各个生态系统之间的结果比较和整合难以实施,增加了模型预测的不确定性。该文通过比较几种常见的野外增温装置在模拟全球变暖情形时的优缺点,指出利用不同增温装置进行全球变暖研究中应注意的一些问题;同时探讨了全球变暖控制实验研究中的一些关键性的科学问题。     

甲烷代谢古菌分离培养研究进展

全球变暖是全人类面临的一个巨大挑战,而温室气体排放持续上升是全球变暖的关键因素,并引发一系列生态环境问题。甲烷是第二温室气体,对全球变暖的贡献达20%。然而,在甲烷代谢中发挥重要作用的产甲烷古菌和厌氧甲烷氧化古菌(anaerobic methanotroph,ANME)较难培养,极大地限制了人们对甲烷代谢及其影响碳源-汇关系与机制的研究。本文综述了最新产甲烷古菌和ANME富集、分离和培养方法,包括富集培养、原位培养、共培养、微流控技术、稀释分离和固体分离技术、ANME反应器和培养瓶富集培养,以及宏基因组预测和反向基因组学,并对这些方法的优缺点进行了评估,对未来甲烷代谢古菌的富集、分离和培养提出新的建议。     

Understanding and Managing the Risks to Health and Environment from Global Atmospheric Change: A Synthesis

The global atmosphere is changing. Anthropogenic activities are increasing the concentrations of greenhouse gases and releasing synthetic compounds that deplete stratospheric ozone and increase UV-B radiation. Changes of temperature in the Northern Hemisphere during the past century strongly suggest that we are now in a period of rapid global warming relative to the past millennium. Increased concentrations of greenhouse gases are absorbing outgoing infrared radiation in the lower atmosphere, warming the troposphere and cooling the lower stratosphere. Research is beginning to indicate that losses of stratospheric ozone and increases of greenhouse gases are interdependent. Increased greenhouse gases have been implicated in the observed strengthening of stratospheric wind vortices around both poles, in turn setting the stage for further depletion of ozone and increases in UV-B radiation. Although the uncertainties are still large enough to make it difficult to assess health and ecological risks, decisions must be made. Research on indicators of risks to human health and the environment can help reduce the uncertainties in these risks and shorten the time between recognizing the risks of atmospheric change and taking concrete mitigative and adaptive actions.     

Effect of warming and drought on grassland microbial communities

The soil microbiome is responsible for mediating key ecological processes; however, little is known about its sensitivity to climate change. Observed increases in global temperatures and alteration to rainfall patterns, due to anthropogenic release of greenhouse gases, will likely have a strong influence on soil microbial communities and ultimately the ecosystem services they provide. Therefore, it is vital to understand how soil microbial communities will respond to future climate change scenarios. To this end, we surveyed the abundance, diversity and structure of microbial communities over a 2-year period from a long-term in situ warming experiment that experienced a moderate natural drought. We found the warming treatment and soil water budgets strongly influence bacterial population size and diversity. In normal precipitation years, the warming treatment significantly increased microbial population size 40–150% but decreased diversity and significantly changed the composition of the community when compared with the unwarmed controls. However during drought conditions, the warming treatment significantly reduced soil moisture thereby creating unfavorable growth conditions that led to a 50–80% reduction in the microbial population size when compared with the control. Warmed plots also saw an increase in species richness, diversity and evenness; however, community composition was unaffected suggesting that few phylotypes may be active under these stressful conditions. Our results indicate that under warmed conditions, ecosystem water budget regulates the abundance and diversity of microbial populations and that rainfall timing is critical at the onset of drought for sustaining microbial populations.     

土壤溶解性有机碳在陆地生态系统碳循环中的作用

土壤溶解性有机碳(DOC)是有机碳库的活跃组分,在陆地生态系统碳循环中发挥重要作用.本文从碳循环重要性着手,综述了土壤DOC在土壤碳固持与温室气体排放中的作用;结合我国的现实情况(如土壤酸化、气候变暖等),探讨了土壤DOC的相关影响因素如土壤性质、环境因素、人为活动对土壤DOC的影响及作用机制,对进一步理解土壤DOC在陆地生态系统碳循环与温室气体减排中的作用具有重要意义.     

Global Warming: Predicting OPEC Carbon Dioxide Emissions from Petroleum Consumption Using Neural Network and Hybrid Cuckoo Search Algorithm

Background

Global warming is attracting attention from policy makers due to its impacts such as floods, extreme weather, increases in temperature by 0.7°C, heat waves, storms, etc. These disasters result in loss of human life and billions of dollars in property. Global warming is believed to be caused by the emissions of greenhouse gases due to human activities including the emissions of carbon dioxide (CO₂) from petroleum consumption. Limitations of the previous methods of predicting CO₂ emissions and lack of work on the prediction of the Organization of the Petroleum Exporting Countries (OPEC) CO₂ emissions from petroleum consumption have motivated this research.

Methods/Findings

The OPEC CO₂ emissions data were collected from the Energy Information Administration. Artificial Neural Network (ANN) adaptability and performance motivated its choice for this study. To improve effectiveness of the ANN, the cuckoo search algorithm was hybridised with accelerated particle swarm optimisation for training the ANN to build a model for the prediction of OPEC CO₂ emissions. The proposed model predicts OPEC CO₂ emissions for 3, 6, 9, 12 and 16 years with an improved accuracy and speed over the state-of-the-art methods.

Conclusion

An accurate prediction of OPEC CO₂ emissions can serve as a reference point for propagating the reorganisation of economic development in OPEC member countries with the view of reducing CO₂ emissions to Kyoto benchmarks—hence, reducing global warming. The policy implications are discussed in the paper.     

陆地生态系统野外增温控制实验的技术与方法

由于人类活动导致的碳排放急剧增加, 工业革命以来全球地表温度显著增加约1 ℃, 未来全球气候还将持续变暖, 到21世纪末最高可升温4 ℃。这种前所未有的气候变化不仅影响陆地植被的适应策略, 也深刻影响生态系统的结构和功能。其中陆地生态系统碳收支对全球变暖的反馈, 是决定未来气候变化强度的关键因素, 因此全球已经开展了大量的生态系统尺度的野外增温控制实验, 研究生态系统碳收支对气温升高的响应, 从而提高地球系统模型的预测精度。然而由于增温技术和方法的不同, 不同研究的结果之间难以进行比较。该文系统总结了常见的野外增温技术和方法, 包括主动增温和被动增温, 阐述了其优缺点、适用对象以及相关研究成果。同时简要介绍了野外增温控制实验的前沿研究方向——新一代野外增温技术(包括全土壤剖面增温和全生态系统增温)和基于新一代增温技术开展的野外增温联网实验。     

Potential feedback mediated by soil microbiome response to warming in a glacier forefield

Mountain glaciers are retreating at an unprecedented rate due to global warming. Glacier retreat is widely believed to be driven by the physiochemical characteristics of glacier surfaces; however, the current knowledge of such biological drivers remains limited. An estimated 130 Tg of organic carbon (OC) is stored in mountain glaciers globally. As a result of global warming, the accelerated microbial decomposition of OC may further accelerate the melting process of mountain glaciers by heat production with the release of greenhouse gases, such as carbon dioxide (CO₂) and methane. Here, using short‐term aerobic incubation data from the forefield of Urumqi Glacier No. 1, we assessed the potential climate feedback mediated by soil microbiomes at temperatures of 5°C (control), 6.2°C (RCP 2.6), 11°C (RCP 8.5), and 15°C (extreme temperature). We observed enhanced CO₂‐C release and heat production under warming conditions, which led to an increase in near‐surface (2 m) atmospheric temperatures, ranging from 0.9°C to 3.4°C. Warming significantly changed the structures of the RNA‐derived (active) and DNA‐derived (total) soil microbiomes, and active microbes were more sensitive to increased temperatures than total microbes. Considering the positive effects of temperature and deglaciation age on the CO₂‐C release rate, the alterations in the active microbial community structure had a negative impact on the increased CO₂‐C release rate. Our results revealed that glacial melting could potentially be significantly accelerated by heat production from increased microbial decomposition of OC. This risk might be true for other high‐altitude glaciers under emerging warming, thus improving the predictions of the effects of potential feedback on global warming.     

Methane Hydrate: Killer cause of Earth's greatest mass extinction

The cause for the end Permian mass extinction, the greatest challenge life on Earth faced in its geologic history, is still hotly debated by scientists. The most significant marker of this event is the negative δ¹³C shift and rebound recorded in marine carbonates with a duration ranging from 2000 to 19 000 years depending on localities and sedimentation rates. Leading causes for the event are Siberian trap volcanism and the emission of greenhouse gases with consequent global warming. Measurements of gases vaulted in calcite of end Permian brachiopods and whole rock document significant differences in normal atmospheric equilibrium concentration in gases between modern and end Permian seawaters. The gas composition of the end Permian brachiopod-inclusions reflects dramatically higher seawater carbon dioxide and methane contents leading up to the biotic event. Initial global warming of 8–11 °C sourced by isotopically light carbon dioxide from volcanic emissions triggered the release of isotopically lighter methane from permafrost and shelf sediment methane hydrates. Consequently, the huge quantities of methane emitted into the atmosphere and the oceans accelerated global warming and marked the negative δ¹³C spike observed in marine carbonates, documenting the onset of the mass extinction period. The rapidity of the methane hydrate emission lasting from several years to thousands of years was tempered by the equally rapid oxidation of the atmospheric and oceanic methane that gradually reduced its warming potential but not before global warming had reached levels lethal to most life on land and in the oceans. Based on measurements of gases trapped in biogenic and abiogenic calcite, the release of methane (of ∼3–14% of total C stored) from permafrost and shelf sediment methane hydrate is deemed the ultimate source and cause for the dramatic life-changing global warming (GMAT > 34 °C) and oceanic negative-carbon isotope excursion observed at the end Permian. Global warming triggered by the massive release of carbon dioxide may be catastrophic, but the release of methane from hydrate may be apocalyptic. The end Permian holds an important lesson for humanity regarding the issue it faces today with greenhouse gas emissions, global warming, and climate change.     

Spatial Prediction of N2O Emissions in Pasture: A Bayesian Model Averaging Analysis

Nitrous oxide (N₂O) is one of the greenhouse gases that can contribute to global warming. Spatial variability of N₂O can lead to large uncertainties in prediction. However, previous studies have often ignored the spatial dependency to quantify the N₂O – environmental factors relationships. Few researches have examined the impacts of various spatial correlation structures (e.g. independence, distance-based and neighbourhood based) on spatial prediction of N₂O emissions. This study aimed to assess the impact of three spatial correlation structures on spatial predictions and calibrate the spatial prediction using Bayesian model averaging (BMA) based on replicated, irregular point-referenced data. The data were measured in 17 chambers randomly placed across a 271 m² field between October 2007 and September 2008 in the southeast of Australia. We used a Bayesian geostatistical model and a Bayesian spatial conditional autoregressive (CAR) model to investigate and accommodate spatial dependency, and to estimate the effects of environmental variables on N₂O emissions across the study site. We compared these with a Bayesian regression model with independent errors. The three approaches resulted in different derived maps of spatial prediction of N₂O emissions. We found that incorporating spatial dependency in the model not only substantially improved predictions of N₂O emission from soil, but also better quantified uncertainties of soil parameters in the study. The hybrid model structure obtained by BMA improved the accuracy of spatial prediction of N₂O emissions across this study region.     

Product Carbon Footprints and Their Uncertainties in Comparative Decision Contexts

In response to growing awareness of climate change, requests to establish product carbon footprints have been increasing. Product carbon footprints are life cycle assessments restricted to just one impact category, global warming. Product carbon footprint studies generate life cycle inventory results, listing the environmental emissions of greenhouse gases from a product’s lifecycle, and characterize these by their global warming potentials, producing product carbon footprints that are commonly communicated as point values. In the present research we show that the uncertainties surrounding these point values necessitate more sophisticated ways of communicating product carbon footprints, using different sizes of catfish (Pangasius spp.) farms in Vietnam as a case study. As most product carbon footprint studies only have a comparative meaning, we used dependent sampling to produce relative results in order to increase the power for identifying environmentally superior products. We therefore argue that product carbon footprints, supported by quantitative uncertainty estimates, should be used to test hypotheses, rather than to provide point value estimates or plain confidence intervals of products’ environmental performance.     

Past, Present and Future Levels of Greenhouse Gases in the Atmosphere and Model Projections of Related Climatic Changes

Ice core analyses of polar ice reveal a high correlation betweenclimatic change and variations in the atmospheric concentrationsof greenhouse gases (carbon dioxide and methane) over the last160 000 years. Although the resolution of the data is not sufficientto determine the phase relationship between the respective variations,it is generally believed that climate change occurred firstas a result of the quasi-periodic variations of the Earth'sorbital parameters. However, data and model results are consistentwith the hypothesis that climate and atmospheric concentrationsof greenhouse gases interact via a positive feedback loop. The more recent increase in greenhouse gases since pre-industrialtimes can be related to human activities. Climate models predicta significant global warming of several degrees within the nextcentury if the industrial emissions increase unabated. On theother hand, accelerated policies on emission control will significantlyreduce the warming after a response time of a few decades.     

螟长距茧蜂、玉米螟与春玉米间相互关系的初步研究

研究表明,螟长距茧蜂发生高峰期比玉米螟成虫高峰期大约推迟6-9天,与春玉米抽雄期相一致。玉米抽雄开花时绝大部分玉米螟幼虫处在易被螟长距茧蜂寄生的Ⅲ、Ⅳ龄。玉米开花后雄穗的形态结构和营养成分发生改变,致使幼虫下垂转移寻找更适宜的食物。螟长距茧蜂被取食玉米雄穗的玉米螟幼虫所吸引。其寄生与玉米螟幼虫的发育和玉米生育期密切相关。     

Integrating phylogeography and physiology reveals divergence of thermal traits between central and peripheral lineages of tropical rainforest lizards

Tropical ectotherms are regarded as being especially threatened by global warming, but the extent to which populations vary in key thermal physiological traits is little known. In general, central and peripheral populations are most likely to differ where divergent selection pressures are un-opposed by gene flow. This leads to the prediction that persistent and long-isolated lineages in peripheral regions, as revealed by phylogeography, may differ physiologically from larger centrally located lineages. We test this prediction through comparative assays of critical thermal limits (minimum and maximum critical thermal limits, CT(min), CT(max)) and optimal performance parameters (B80 and T(opt)) across central and peripheral lineages of three species of ground-dwelling skinks endemic to the rainforests of northeast Australia. Peripheral lineages show significantly increased optimal performance temperatures (T(opt)) relative to central populations as well as elevated CT(min), with the latter trait also inversely related to elevation. CT(max) did not vary between central and peripheral lineages, but was higher in a forest edge species than in the forest interior species. The results suggest that long-isolated populations in peripheral rainforests harbour genotypes that confer resilience to future warming, emphasizing the need to protect these as well as larger central habitats.     

Urban air pollution and climate change: “The Decalogue: Allergy Safe Tree” for allergic and respiratory diseases care

Background

According to the World Health Organization, air pollution is closely associated with climate change and, in particular, with global warming. In addition to melting of ice and snow, rising sea level, and flooding of coastal areas, global warming is leading to a tropicalization of temperate marine ecosystems. Moreover, the effects of air pollution on airway and lung diseases are well documented as reported by the World Allergy Organization.

Methods

Scientific literature was searched for studies investigating the effect of the interaction between air pollution and climate change on allergic and respiratory diseases.

Results

Since 1990s, a multitude of articles and reviews have been published on this topic, with many studies confirming that the warming of our planet is caused by the “greenhouse effect” as a result of increased emission of “greenhouse” gases. Air pollution is also closely linked to global warming: the emission of hydrocarbon combustion products leads to increased concentrations of biological allergens such as pollens, generating a mixture of these particles called particulate matter (PM). The concept is that global warming is linked to the emission of hydrocarbon combustion products, since both carbon dioxide and heat increase pollen emission into the atmosphere, and all these particles make up PM10. However, the understanding of the mechanisms by which PM affects human health is still limited. Therefore, several studies are trying to determine the causes of global warming. There is also evidence that increased concentrations of air pollutants and pollens can activate inflammatory mediators in the airways. Our Task Force has prepared a Decalogue of rules addressing public administrators, which aims to limit the amount of allergenic pollen in the air without sacrificing public green areas.

Conclusions

Several studies underscore the significant risks of global warming on human health due to increasing levels of air pollution. The impact of climate change on respiratory diseases appears well documented. The last decades have seen a rise in the concentrations of pollens and pollutants in the air. This rise parallels the increase in the number of people presenting with allergic symptoms (e.g., allergic rhinitis, conjunctivitis, and asthma), who often require emergency medical care. Our hope is that scientists from different disciplines will work together with institutions, pharmaceutical companies and lay organizations to limit the adverse health effects of air pollution and global warming.

     

Dynamic and complex microclimate responses to warming and grazing manipulations

Synthesis efforts that identify patterns of ecosystem response to a suite of warming manipulations can make important contributions to climate change science. However, cross‐study comparisons are impeded by the paucity of detailed analyses of how passive warming and other manipulations affect microclimate. Here we document the independent and combined effects of a common passive warming manipulation, open‐top chambers (OTCs), and a simulated widespread land use, clipping, on microclimate on the Tibetan Plateau. OTCs consistently elevated growing season averaged mean daily air temperature by 1.0–2.0°C, maximum daily air temperature by 2.1–7.3°C and the diurnal air temperature range by 1.9–6.5°C, with mixed effects on minimum daily air temperature, and mean daily soil temperature and moisture. These OTC effects on microclimate differ from reported effects of a common active warming method, infrared heating, which has more consistent effects on soil than on air temperature. There were significant interannual and intragrowing season differences in OTC effects on microclimate. For example, while OTCs had mixed effects on growing season averaged soil temperatures, OTCs consistently elevated soil temperature by approximately 1.0°C early in the growing season. Nonadditive interactions between OTCs and clipping were also present: OTCs in clipped plots generally elevated air and soil temperatures more than OTCs in nonclipped plots. Moreover, site factors dynamically interacted with microclimate and with the efficacy of the OTC manipulations. These findings highlight the need to understand differential microclimate effects between warming methods, within warming method across ecosystem sites, within warming method crossed with other treatments, and within sites over various timescales. Methods, sites and scales are potential explanatory variables and covariables in climate warming experiments. Consideration of this variability among and between experimental warming studies will lead to greater understanding and better prediction of ecosystem response to anthropogenic climate warming.     

Mammalian herbivores confer resilience of Arctic shrub‐dominated ecosystems to changing climate

Climate change is resulting in a rapid expansion of shrubs in the Arctic. This expansion has been shown to be reinforced by positive feedbacks, and it could thus set the ecosystem on a trajectory toward an alternate, more productive regime. Herbivores, on the other hand, are known to counteract the effects of simultaneous climate warming on shrub biomass. However, little is known about the impact of herbivores on resilience of these ecosystems, that is, the capacity of a system to absorb disturbance and still remain in the same regime, retaining the same function, structure, and feedbacks. Here, we investigated how herbivores affect resilience of shrub‐dominated systems to warming by studying the change of shrub biomass after a cessation of long‐term experimental warming in a forest–tundra ecotone. As predicted, warming increased the biomass of shrubs, and in the absence of herbivores, shrub biomass in tundra continued to increase 4 years after cessation of the artificial warming, indicating that positive effects of warming on plant growth may persist even over a subsequent colder period. Herbivores contributed to the resilience of these systems by returning them back to the original low‐biomass regime in both forest and tundra habitats. These results support the prediction that higher shrub biomass triggers positive feedbacks on soil processes and microclimate, which enable maintaining the rapid shrub growth even in colder climates. Furthermore, the results show that in our system, herbivores facilitate the resilience of shrub‐dominated ecosystems to climate warming.     

Responses of soil N2O emissions to experimental warming regulated by soil moisture in an alpine steppe

土壤氧化亚氮(N₂O)排放是大气N₂O不可忽视的来源。然而, 目前学术界在气候变暖对土壤N₂O排放影响方面的认识仍存在较大争议, 且调控土壤N₂O排放的微生物机制尚不明确。为此, 该研究以青藏高原高寒草原生态系统为研究对象, 使用透明开顶箱(OTCs)模拟气候变暖, 并基于静态箱法测定了2014和2015年生长季(5-10月)的土壤N₂O通量, 同时利用定量PCR技术测定了表层(0-10 cm)土壤中氨氧化古菌(AOA)和氨氧化细菌(AOB)的基因丰度。结果显示: 增温处理导致2014和2015年生长季表层(0-10 cm)土壤温度分别升高了1.7 ℃和1.6 ℃, 土壤体积含水量下降了2.5%和3.3%, 其他的土壤理化性质没有发生显著变化。土壤N₂O通量呈现年际差异, 2014和2015年生长季的平均值分别为3.23和1.47 μg·m ^-2·h ^-1, 然而, 增温处理并没有显著改变土壤N₂O通量。2014年生长季主导硝化作用的AOA和AOB的基因丰度分别为5.0 × 10 ⁷和4.7 × 10 ⁵拷贝·g ^-1, 2015年为15.2 × 10 ⁷和10.0 × 10 ⁵拷贝·g ^-1。尽管基因丰度存在显著的年际差异, 但在两年中与对照相比并未发生显著变化。在生长季尺度上, 增温导致的土壤N₂O变化量与其引起的土壤水分变化量之间显著正相关, 而与土壤温度的变化量之间没有显著相关关系。以上结果表明, 增温导致的土壤干旱会抑制土壤N₂O通量对增温的响应, 意味着未来评估气候变暖情景下土壤N₂O排放量时需考虑增温引发的土壤干旱等间接效应。