Evaluation and re-understanding of the global natural gas hydrate resources

Natural gas hydrate(NGH)has been widely considered as an alternative to conventional oil and gas resources in the future energy resource supply since Trofimuk’s first resource assessment in 1973.At least 29 global estimates have been published from various studies so far,among which 24 estimates are greater than the total conventional gas resources.If drawn in chronological order,the 29 historical resource estimates show a clear downward trend,reflecting the changes in our perception with respect to its resource potential with increasing our knowledge on the NGH with time.A time series of the 29 estimates was used to establish a statistical model for predict the future trend.The model produces an expected resource value of 41.46×1012 m3 at the year of 2050.The statistical trend projected future gas hydrate resource is only about 10%of total natural gas resource in conventional reservoir,consistent with estimates of global technically recoverable resources(TRR)in gas hydrate from Monte Carlo technique based on volumetric and material balance approaches.Considering the technical challenges and high cost in commercial production and the lack of competitive advantages compared with rapid growing unconventional and renewable resources,only those on the very top of the gas hydrate resource pyramid will be added to future energy supply.It is unlikely that the NGH will be the major energy source in the future.

Late-entry commercial thinning effects on Pinus banksiana:growth, yield, and stand dynamics in Québec, Canada

We studied late-entry commercial thinning effects on growth, yield, and regeneration in a 48-year-old jack pine(Pinus banksiana Lamb.) stand. Applied thinning intensities were 27, 32, and 47% of merchantable basal area(BA) excluding skidding trails. After 15 years, mean diameter at breast height of surviving trees in the 47% BA removal increased by 4.9 cm(25%) compared to the unthinned control. The 47% BA removal also increased gross merchantable volume(GMV) tree-1by 46% compared to the control. The 27% BA removal had twice as much GMV ha-1compared to the 47% BA removal after15 years. Moreover, cumulative GMV ha-1was much higher in the 27% BA removal than in the unthinned control. The highest thinning intensity produced larger trees on average, while the lowest thinning intensity maximized volume production per hectare. Maintenance of acceptable growing stock throughout the 15-year period in the 27% BA removal could provide other ecosystem functions such as biodiversity enhancement or wildlife habitat by delaying senescence. Regeneration data showed that a shift in species composition occurred in the understory. After 15 years, the understory was dominated by black spruce(Picea mariana(Mill.) B.S.P.), white birch(Betula papyrifera Marsh.), and trembling aspen(Populus tremuloides Michx.). If regenerating jack pine is an objective after final overstory removal, additional efforts will be needed to re-establish this species.

How can the forest sector mitigate climate change in a changing climate? Case studies of boreal and northern temperate forests in eastern Canada

Background:Forest based climate mitigation emerged as a key component of the Paris Agreement,and thus re-quires robust science to reduce uncertainties related to such strategies.The aim of this study was to assess and compare the cumulative effects on carbon dynamics of forest management and climate change on boreal and northern temperate forest sector in eastern Canada for the 2020–2100 period.Methods:We used the spatially explicit forest landscape model LANDIS-II and its extension Forest Carbon Suc-cession,in conjunction with the Carbon Budget Model for Harvested Wood Products framework.We simulated the dynamics of forest composition and carbon flows from forest ecosystems to wood products and their substitution effect on markets under increasing climate forcing,according to a tonne-year approach.Simulations were con-ducted for a series of forest management scenarios based on realistic practices principally by clearcut in the boreal territory and continuous-cover forestry in the northern temperate one.These scenarios included:i)a business-as-usual scenario(BaU),representing the current management strategy,ii)increased harvesting by 6.3%to 13.9%,iii)increased conservation(i.e.reduced harvesting by 11.1%to 49.8%),iiii)and a scenario representing the natural evolution of the forest landscape(i.e.without any management activity).Results:Our study revealed that increasing harvesting levels had contrasting effects on the mitigation potential in northern temperate(enhance net sequestration)and boreal forest sector(enhance net emissions)in comparison to the BaU from 2040 onwards,regardless of the future climate.Carbon storage in wood products and the substi-tution effect were not sufficient to offset carbon emissions from ecosystems.Moreover,climate change had a strong impact on the capacity of both landscapes to act as carbon sinks.Northern temperate landscapes became a net source of carbon over time due to their greater vulnerability to climate change than boreal landscapes.Conclusions:Our study highlights the need to consider the initial landscape characteristics in simulations to maximize the mitigation potential of alternative forest management strategies.The optimal management solution can be very different according to the characteristics of forest ecosystems.This opens the possibility of optimizing management for specific forest stands,with the objective of maximizing the mitigation potential of a given landscape.

Reduction of global natural gas hydrate(NGH)resource estimation and implications for the NGH development in the South China Sea

There have been at least 29 groups of estimates on the global natural gas hydrate(NGH)resource since1973,varying greatly with up to 10,000 times and showing a decreasing trend with time.For the South China Sea(SCS),35 groups of estimations were conducted on NGH resource potential since 2000,while these estimates kept almost the same with time,varying between 60 and 90 billion tons of oil equivalent(toe).What are the key factors controlling the variation trend?What are the implications of these variations for the NGH development in the world and the SCS?By analyzing the investigation characteristics of NGH resources in the world,this study divided the evaluation process into six stages and confirmed four essential factors for controlling the variations of estimates.Results indicated that the reduction trend reflects an improved understanding of the NGH formation mechanism and advancement in the resource evaluation methods,and promoted more objective evaluation results.Furthermore,the analysis process and improved evaluation method was applied to evaluate the NGH resources in the SCS,showing the similar decreasing trend of NGH resources with time.By utilizing the decreasing trend model,the predicted recoverable resources in the world and the SCS are(205-500)×10^(12)m^(3)and(0.8-6.5)×10^(12)m^(3),respectively,accounting for 20%of the total conventional oil and gas resources.Recoverable NGH resource in the SCS is only about 4%-6%of the previous estimates of 60-90 billion toe.If extracted completely,it only can support the sustainable development of China for 7 years at the current annual consumption level of oil and gas.NGH cannot be the main energy resource in future due to its low resource potential and lack of advantages in recovery.

Magnesium research in Canada:Highlights of the last two decades

The highlights of major Canadian research projects of last two decades that aimed at advancing applications of magnesium and its alloys,being at the heart of lightweighting and ecological sustainability, are outlined. The research at universities, government laboratories, and other dedicated institutions, funded primarily through federal programs, was accompanied by strong activities of the industrial sector involved in designing and building the machinery for magnesium processing and production of components from magnesium alloys. The overall research directions matched the global trends of overcoming the key challenges that prevent magnesium alloys to play the major role in large-scale applications. Among industrially oriented projects the processing technologies in liquid, semisolid and solid states such as casting, twin roll casting, injection molding, rolling, extrusion, forging, and joining techniques were frequently pursued. Although the fundamental research aimed at understanding of a variety of magnesium behaviors and structural peculiarities up to nano and atomic levels, its essence spread around the inherently poor formability and high reactivity at room and elevated temperatures, including the ignition/flammability concerns.In recent years, a shift in research interests was observed and novel directions emerged such as magnesium air batteries, biodegradable alloys, additive manufacturing, and magnesium-rich high entropy alloys. The volume of data gathered in this report may constitute a base for specifically oriented assessments, analyses, and drawing conclusions.

Evaluating and quantifying the effect of various spruce budworm intervention strategies on forest carbon dynamics in Atlantic Canada

Spruce budworm (SBW) outbreaks are one of the most devastating natural disturbances in spruce-balsam fir forests of eastern North America. Both early intervention strategy (EIS) and foliage protection strategy (FP) are being tested to limit forest losses, but the quantitative impact on forest carbon (C) dynamics is still unclear. In this study, we designed 19 separate scenarios of no intervention or varying success of EIS, FP, and their combination on SBW caused defoliation and mortality. We then used the TRIPLEX-Insect model to quantify their effects on forest C dynamics in the forests of the four provinces of Atlantic Canada. A scenario applying FP to 10%of the area with the greatest potential C losses of living biomass, protecting foliage in 10%of the forests is more realistic than higher proportion of FP given the high cost and large areas involved, resulted in reducing average cumulative net ecosystem productivity (NEP) from 2020 to 2039 by 56%–127%compared to a no outbreak scenario.Our results showed that FP would have to be applied everywhere to reduce tree mortality and increase NEP more than 8 years of successful EIS applied. However, if EIS can be successfully implemented for 12 years, it will maintain more forest C than FP applied everywhere during a moderate outbreak. We also found that the combination of EIS followed by FP in 10%of the areas disturbed by the SBW could maintain average cumulative NEP at similar levels to no defoliation in every province of Atlantic Canada. Black/red spruce forests younger than 60years old underwent the smallest changes in C dynamics whether using EIS, FP, or both. This highlights the importance of forest species, forest age, and their interactions on the effectiveness of a treatment during SBW outbreak. Overall, 31%–76%of the study area in Atlantic Canada could convert from a C sink to a source by 2039,if no protective measures are used under the worst-case scenarios, thus contributing to future climate warming.

Have some landscapes in the eastern Canadian boreal forest moved beyond their natural range of variability?

Background: In the contxt of ecosystem management, the present study aims to compare the natural and the present-day forested landscapes of a large territory in Quebec(Canada). Using contemporary and long-term fire cycles, each natural forst landscape is defined according to the variability of its structure and composition, and compared to the present-day landscape. This analysis was conducted to address the question of whether human activities have moved these ecosystems outside the range of natural landscape variability.Methods: The study encompassed a forested area of 175 000 km2 divided into 14 landscapes. Using a framework that integrates fire cycles, age structure and forest dynamics, we characterized the forest composition and age structures that resulted from three historical fire cycles(110,140, and 180 years) representative of the boreal forest of eastern Canada. The modeled natural landscapes were compared with present-day landscapes in regard to the proportion of old-growth forests(landscape level) and the proportion of late-successional forest stands(landscape level and potential vegetation type).Results: Four landscapes(39%) remain within their natural range of variability. In contrast, nine landscapes(54%)show a large gap between natural and present-day landscapes. These nine are located in the southern portion of the study area, and are mainly associated with Abies-Betula vegetation where human activities have contributed to a strong increase in the proportion of Populus tremuloides stands(early-successional stages) and a decrease of oldgrowth forest stands(more than 100 years old). A single landscape(7%), substantially changed from its potential natural state, is a candidate for adaptive-based management.Conclusion: Comparison of corresponding natural(reference conditions) and present-day landscapes showed that ten landscapes reflecting an important shift in forest composition and age structure could be considered beyond the range of their natural variability. The description of a landscape's natural variability at the scale of several millennia can be considered a moving benchmark that can be re-evaluated in the context of climate change.Focusing on regional landscape characteristics and long-term natural variability of vegetation and forest age structure represents a step forward in methodology for defining reference conditions and following shifts in landscape over time.

Production characteristics and sweet-spots mapping of the Upper Devonian-Lower Mississippian Bakken Formation tight oil in southeastern Saskatchewan, Canada

A workflow that helps identify potential production sweet spots in the Middle Bakken tight oil play is proposed based on analysis of large amounts of production data. The proposed approach is a multivariate statistical model that extracts relevant information from a training dataset of production wells to facilitate geological similarity comparison between economic and sub-economic production wells. The model is applied to the Middle Bakken tight oil play in southeastern Saskatchewan. Data screening for diagnostic geological indicators for sweet spots reveals that several geological factors indicative for conventional oil reservoirs seem to work for the Middle Bakken tight oil play as well. These factors include: a) the NE Torqunay-Rocanville Trend serving as a preferred regional migration path for connecting mature source rock in southern Williston Basin and the Middle Bakken tight reservoir in southeastern Saskatchewan; b) the oils in the Bakken tight reservoirs along the U.S. and Canada border are more likely from local matured Bakken source rocks; c) subtle structural components enhancing the convergence of dispersed hydrocarbons over a large area; d) top seal and lateral barrier improving preservation, thus favouring oil productivity; e) orientation of maximum horizontal stress coincident with the direction of the variogram spatial continuity in ultimate recoverable reserves, so the direction of horizontal well has a significant impact on the oil productivity.

The Relative Importance of Natural Disturbances and Local Site Factors on Woody Vegetation Regeneration Diversity across a Large, Contiguous Forest Region

Stand-level diversity after natural disturbance can potentially differ across a large, contiguous forest region despite being dominated by the same canopy species throughout as differences in disturbance types and local site conditions can regulate species distribution. Our main objective was to examine the relative importance of natural disturbances (spruce budworm (Choristoneura fumiferana) outbreak, windthrow, and their interaction) and local site factors (climate, physiography, and stand structure and composition variables) on woody vegetation diversity among three, physiographically distinct locations across a large, contiguous forest region. Seventy-six Abies balsamea-Betula spp. stands affected by natural disturbance were compared and analysed using canonical ordination methods, diversity indices, and ANOVA. Different combinations of factors were important for vegetation re-establishment at each location. Differences in alpha (α), beta (β), gamma (γ), Shannon’s H’, and evenness (J) diversity indices were observed among locations across the study region. Our findings indicate that while certain processes are important for maintaining canopy dominance by Abies balsamea and Betula spp. throughout the region, different combinations of factors were important for creating variation in woody species diversity among locations that resulted in greater woody species diversity at the regional scale.

Exploring Factors Influencing Species Natural Regeneration Response Following Harvesting in the Acadian Forests of New Brunswick

In the Acadian Forest Region of northeastern North America, forest managers are under increasing public pressure to restore the forest to a more historic, natural condition by reducing in clearcutting and promoting partial-cut treatments that more closely emulate historic, local natural disturbance regimes. However, although numerous studies on the effects of partial-cutting on forest regeneration response have been conducted in surrounding temperate and boreal forest ecosystems, there are few studies that directly explore responses to various forms of harvesting within the Acadian Forest ecosystem, with its unique mixture of northern hardwoods and boreal forest species. Here, we conducted one of the first retrospective studies on forest regeneration following a variety of harvesting methods in the Acadian Forest using univariate and multivariate regression trees to assess regeneration response in 50 naturally-regenerating, harvested forest sites in New Brunswick, Canada. Our study shows that regeneration was highly influenced by harvest type, overstory composition, and environmental conditions as reflected by ecoregion classification. Canopy opening size (as controlled by harvest method) significantly influenced the dominance of regenerating species. The presence of conspecific overstory trees increased the likelihood of their regeneration following disturbance, supporting the direct-regeneration hypothesis, especially for species with limited seed dispersal (e.g., sugar maple (Acer saccharum Marsh.) and American beech (Fagus grandifolia Ehrh.). Despite reported problems elsewhere in eastern North America, neither American beech nor balsam fir (Abies balsamea (L.) Mill.) constituted significant competition for the desired species on a broad scale, but the presence of beech was a significant deterrent for yellow birch (Betula alleghaniensis Britt.).

Decoupling between Plant Productivity and Growing Season Length under a Warming Climate in Canada’s Arctic

Given the short duration of growing season in the Arctic, a strong correlation between plant productivity and growing season length (GSL) is conventionally assumed. Will this assumption hold true under a warming climate? In this study, we addressed the question by investigating the relationship between net primary productivity of leaves (NPPleaf) and GSL for various tundra ecosystems. We quantified NPPleaf and GSL using long-term satellite data and field measurements. Our results indicated that the relationship was not significant (i.e., decoupled) for 44% to 64% of tundra classes in the southern Canadian Arctic, but significant for all classes in the northern Canadian Arctic. To better understand the causes of the decoupling, we further decomposed the relationship into two components: the correspondence of interannual variations and the agreement of long- term trends. We found that the longer the mean GSL for a tundra class, the poorer the correspondence between their interannual variations. Soil moisture limitation further decoupled the relationship by deteriorating the agreement of long-term trends. Consequently, the decoupling between NPPleaf and GSL would be more likely to occur under a warming climate if the tundra class had a mean GSL > 116 (or 123) days with a dry (or moist) soil moisture regime.

2017年九寨沟M_s7.0级地震震源过程反演与烈度估计

2017年8月8日,在我国四川省九寨沟县发生一次M_s7.0级地震.在快速响应的基础上,重新筛选远场地震波形资料并收集覆盖震中区的InSAR资料对主震的震源破裂过程重新进行了反演分析,收集震后约13 h的余震震相数据对余震进行了双差定位,并基于此对发震断层的复杂性进行了讨论,提出了有待进一步研究的问题.最后,利用反演得到的有限动态破裂模型对地震烈度进行了估计.

玉米农田蒸散过程及其对气候变化的响应模拟

应用基于生理生态学过程的EALCO模型,对玉米农田生态系统的蒸散(ET)过程进行了模拟,在模型检验基础上,使用该模型模拟了玉米农田生态系统ET过程对未来气候变化的响应。结果表明,EALCO模型中能量与水过程的动态耦合机制使模型能够较好地模拟农田蒸散过程,基于涡度相关法的观测值与模型模拟值在小时、日尺度上均吻合较好,模型可以解释67%的日蒸散的变化特征。对土壤蒸发与冠层蒸腾的分别模拟显示,生长季土壤蒸发约占ET的36%。温度的升高会引起ET与冠层蒸腾的增加,同时土壤蒸发减少;ET对降水减少的响应较为敏感,主要表现在土壤蒸发的下降。大气CO2浓度升高对冠层蒸腾影响显著,该情景下冠层蒸腾下降幅度最大。研究所假设的2100年气候情景下,该农田生态系统生长季蒸散将减少,然而相对于降水的减少而言,蒸散的减少量较小,即水分支出项相对增加,因此,发生土壤水分匮乏的可能性加大,这可能会加剧该地区的暖干化趋势,给作物产量及生态环境带来威胁。

大兴安岭地区森林火险变化及FWI适用性评估

根据研究区内及附件气象站每日气温、相对湿度、24小时降水和风速计算1987—2006年大兴安岭每日的加拿大林火天气指数系统(FWI)各组分值。利用空间插值方法,获得1987—2006年所有森林火灾发生日的FWI系统各组分值。大兴安岭林区森林火灾主要发生在落叶针叶林(61.3%)、草地(23.9%)和落叶阔叶林(8.0%),主要火源是雷击火(占57.1%)。4—6月份森林火灾发生时的FWI、FFMC和ISI平均值高。根据1987—2006年FWI组分指数的分布和火发生情况,对森林火险指数进行了分级,低、中、高、很高和极高火险的FWI取值范围分别为0～2.5,2.6～10.0,10.1～18.0,18.1～31.0,≥31.1。FWI对大兴安岭地区森林火险有显著的指示意义,FFMC和ISI对预测火灾的发生与蔓延有较好的指示作用。1987—2001年每年明显有春季和秋季2个火险期,但2002—2006年火险期显著延长。春季火险严重度指数(SSR)波动幅度比较大,夏季SSR和春季SSR有相反的波动趋势,2000—2006年秋季火险严重度明显升高。

集料碱活性快速检测法对比研究

为探讨中国快速砂浆棒法（CAMBT）与其它集料碱活性快速检测法的相关性及对国外岩石的适应性，采用混凝土棱柱体法（CPT）、快速砂浆棒法（AMBT）、压蒸法和CAMBT研究了11种国外不同源集料的膨胀行为，同时还研究了集料颗粒尺寸对CAMBT中集料膨胀的影响．结果表明：CAMBT，AMBT及压蒸法的检测结果具有一致性，但均不能完全正确地判定这些集料的碱活性，它们在夸大RG集料碱活性的同时，还漏判了PO集料的碱活性；集料在现有快速法中的膨胀率与其在CPT中的膨胀率无明显相关性，因此快速法不能很好地表征集料在混凝土中的碱活性程度；CAMBT中集料颗粒尺寸对不同集料膨胀程度的影响不同，其中0．15～0．80mm集料颗粒尺寸对集料膨胀而言不是最敏感粒级；采用2．5～5．0mm单粒级集料颗粒，可以比现有标准检测方法更好地预测集料在混凝土中的膨胀行为．

中亚热带人工针叶林对未来气候变化的响应

利用基于生理生态学过程的EALCO模型,探讨了千烟洲中亚热带人工针叶林生态系统对未来气候变化的响应.结果表明:CO2浓度、温度和降水的变化对该人工林生态系统碳水通量影响的程度不同,其中CO2浓度>温度>降水.CO2浓度是生态系统总光合生产力(GPP)的主要驱动因子,温度与CO2浓度均是控制生态系统呼吸的主要环境因子,温度的升高使植物地上部分呼吸明显增加,而CO2浓度升高则对土壤呼吸影响较大.温度升高使蒸散(ET)增加,而CO2浓度升高则使ET减少.在未来气候变化情景(2100年)下,该人工林生态系统的净初级生产力将增加22%,说明其仍具有较强的固碳潜力.

波茨坦砂岩的微观结构和碱活性快速检测方法的适应性

为研究集料微观结构对碱活性快速检测方法中对岩石适应性的影响,采用混凝土棱柱体法、快速砂浆棒法、压蒸法、中国快速砂浆棒法研究了波茨坦砂岩的膨胀行为,并研究了膨胀后试件的微观结构。结果表明:快速砂浆棒法、压蒸法、中国快速砂浆棒法均不能正确判定波茨坦砂岩的碱活性,主要是由于这些方法使用的集料中含大量粒径太小、不能反映该砂岩特殊结构特征的颗粒;对该类岩石,除活性组分的类型、数量外,岩石的微观结构特征能够显著影响碱–集料反应发生的位置和膨胀行为。在快速法中采用能够保持岩石原有结构特征的集料粒径是正确鉴定类似波茨坦砂岩微观结构岩石及其它非均质、多矿物岩石碱活性的关键。

两类典型碱活性岩石试体在碱溶液中的膨胀行为

为确定以Spratt硅质灰岩(SL岩石)和Pittsburg泥质白云质灰岩(PL岩石)为代表的两类典型碱活性岩石试体在碱性环境中的膨胀来源和发展评定岩石碱活性的方法,研究了不同条件下SL和PL岩石在砂浆和混凝土中的膨胀行为.研究结果表明:SL岩石在砂浆和混凝土中均呈高ASR膨胀性,尽管其中的少量白云石可发生去白云石化反应;决定PL岩石高膨胀性的机制是ACR,与传统的ASR有本质不同,尽管其中含有的少量微晶石英可参与与碱的反应并可能对岩石的膨胀有一定贡献.采用能保持岩石微观结构构造特征的颗粒尺寸是正确评估PL岩石碱活性的关键.利用ASR和ACR对粉煤灰等混合材及含锂化合物的不同响应,特别是LiOH的抑制ASR膨胀和引发ACR膨胀的双重效应,在实验室可以快速区别同时含有白云石和石英的灰岩类集料的活性来源.

Effect of sulfation during carbonation on CO_2 capture in calcium looping cycle

Abstract： Two Canadian limestones with different properties were tested to determine the effect of SO2 during the carbonation of sorbent on the CO2 capture performance in Ca- looping. When the reaction gas is mixed with SO2, the carbonation ratio of the sorbent is always lower than that without SO2 for each cycle under the same conditions, and the sulfation ratio increases almost linearly with the increase in the cycle times. At 650 ℃, there is little difference in the carbonation ratio of the sorbent during the first four cycles for the two carbonation time, 5 and 10 rain at 0. 18% SO2. The indirect sulfation reaction that occurs simultaneously with the carbonation of CaO is responsible for the degradation of the sorbent for CO2 capture, and the carbonation duration is not the main factor that affects the ability of the sorbent. 680℃ is the best carbonation temperature among the three tested temperatures and the highest carbonation ratio can be obtained. Also, the sulfation ratio is the highest. The probable cause is the different effects of temperature on the carbonation rate and sulfation rate. A higher SO2 concentration will decrease the carbonation ratio clearly, but the decrease in the carbonation capability of the sorbent is not proportional to the increase of the SO2 concentration in flue gases.