垃圾填埋场ET封顶系统水分平衡数值分析

针对垃圾填埋场压实黏土最终封顶易受气候影响而开裂(干裂缝或冻融裂缝),其工程特性显著降低的缺陷,介绍了新型ET(蒸发传输)封顶系统的工作机理.在同时考虑降水和蒸发补给的作用下,建立了水汽在ET封顶系统迁移的一维数学模型.以大连市1976年的降水和蒸发补给气候条件为边界条件,模拟了ET封顶系统中的水汽在1a内变化规律.从分析模拟结果得出,距地面越近含水率受降水、蒸发补给气候条件的影响越显著,且随着深度的增加出现明显的峰值滞后现象.阻隔土壤层中的水分未达到饱和状态,说明总厚为150cm的ET封顶系统完全可以抵御大连市近48a以来最大强降水的冲击.对降水强度、降水持续时间以及阻隔层的厚度等参数进行了分析.数值分析与试验数据对比结果表明,计算值和试验数据基本吻合,验证了模型的可靠性.研究工作为建造垃圾填埋场ET封顶系统提供了理论依据.     

Evolution of leaf-form in land plants linked to atmospheric CO2 decline in the Late Palaeozoic era

The widespread appearance of megaphyll leaves, with their branched veins and planate form, did not occur until the close of the Devonian period at about 360 Myr ago. This happened about 40 Myr after simple leafless vascular plants first colonized the land in the Late Silurian/Early Devonian, but the reason for the slow emergence of this common feature of present-day plants is presently unresolved. Here we show, in a series of quantitative analyses using fossil leaf characters and biophysical principles, that the delay was causally linked with a 90% drop in atmospheric pCO2 during the Late Palaeozoic era. In contrast to simulations for a typical Early Devonian land plant, possessing few stomata on leafless stems, those for a planate leaf with the same stomatal characteristics indicate that it would have suffered lethal overheating, because of greater interception of solar energy and low transpiration. When planate leaves first appeared in the Late Devonian and subsequently diversified in the Carboniferous period, they possessed substantially higher stomatal densities. This observation is consistent with the effects of the pCO2 on stomatal development and suggests that the evolution of planate leaves could only have occurred after an increase in stomatal density, allowing higher transpiration rates that were sufficient to maintain cool and viable leaf temperatures.     

普洱市近59a参考作物蒸散量时空变化特征

利用普洱市地面气象观测站1959～2017年逐日气象资料,采用FAO 56-Penman-Monteith(FAO-PM)法、距平分析、回归分析和地理信息技术研究了普洱市参考作物蒸散量(reference crop evapotranspiration, ET_0)的年代际、年际和年内不同时间尺度下时空变化特征。结果表明:普洱市平均ET_0年代均值2011～2017年最大,为1 196.2 mm,1959～1960年最小,为1 101.0 mm;ET_0年代均值高值区在普洱西部南侧,低值区在普洱西部西盟北侧、北部景东以北及东南部江城东部边缘。普洱市各气象站ET_0年际变化均呈波动性上升趋势,其中西盟站平均ET_0年值年际波动最大,江城站ET_0年值年际波动最小。多年平均ET_0年值空间分布景东、江城、澜沧以西北地区较小,孟连和澜沧的南部较大。各气象站ET_0季节均值春季最大,夏季次之,秋、冬季逐渐减小,各气象站多年ET_0月均值的变化趋势基本一致,曲线均为双峰型,最高峰值出现在4、5月,第二峰值出现在8、9月。     

基于标准化降水蒸散指数的宁夏中部干旱带干旱趋势分析

基于标准化降水蒸散指数(SPEI),选取1960～2012年宁夏中部干旱带的海原、同心、麻黄山、兴仁、盐池五个气象站的降水和平均气温资料作为代表,计算各站SPEI序列,研究宁夏中部干旱带在不同时间尺度、不同季节尺度下的干湿演变趋势、干旱发生强度和频次变化以及干旱发生范围变化。结果表明:①SPEI中起决定性作用的因素是降水;②SPEI值的变化对不同时间尺度的敏感性不同,时间尺度越小,干湿变化趋势越明显,甚至是正负波动振荡;③宁夏中部干旱带干湿变化明显,不同季节均呈湿润化趋势,且以轻度干旱和中度干旱为主,干旱发生范围和干旱发生强度总体呈缩小趋势。     

Acceleration of global warming due to carbon-cycle feedbacks in a coupled climate model

The continued increase in the atmospheric concentration of carbon dioxide due to anthropogenic emissions is predicted to lead to significant changes in climate. About half of the current emissions are being absorbed by the ocean and by land ecosystems, but this absorption is sensitive to climate as well as to atmospheric carbon dioxide concentrations, creating a feedback loop. General circulation models have generally excluded the feedback between climate and the biosphere, using static vegetation distributions and CO2 concentrations from simple carbon-cycle models that do not include climate change. Here we present results from a fully coupled, three-dimensional carbon-climate model, indicating that carbon-cycle feedbacks could significantly accelerate climate change over the twenty-first century. We find that under a 'business as usual' scenario, the terrestrial biosphere acts as an overall carbon sink until about 2050, but turns into a source thereafter. By 2100, the ocean uptake rate of 5 Gt C yr(-1) is balanced by the terrestrial carbon source, and atmospheric CO2 concentrations are 250 p.p.m.v. higher in our fully coupled simulation than in uncoupled carbon models, resulting in a global-mean warming of 5.5 K, as compared to 4 K without the carbon-cycle feedback.     

超材料在可重构电磁学中的应用与发展

介绍了超材料在微波(0.3~300 GHz)、太赫兹(0.3~100 THz)和近红外频段(100~790 THz)中的可重构电磁学的调控方法和研究现状,并依照功能分类,对在可重构电磁学方面的应用分别做了综合性归纳描述,最后对其在可重构电磁学方向的未来可能的发展趋势做了进一步的展望。     

科尔沁沙地典型植被群落土壤水分异质性

半干旱沙区土壤水分对植物的成活与生长具有重要的影响.通过对不同植物种类区土壤水分的调查分析表明, 不同植物种类对土壤水分的影响存在显著差别.沙区地下水位深, 土壤水分主要依靠降雨补充, 固沙植物的生长明显地影响了土壤水分供给量, 乔木林地的土壤水分状况最差,灌木树种对深层土壤水分消耗少. 荒地的土壤水分状况最好.在半干旱沙地建立人工植被过程中, 应依照土壤水分状况配置植物种类.     

Semi-analytical analysis of the response of the air temperature over the land surface to the global vegetation distribution

Response of the air temperature over the land surface to the global vegetation distribution is investigated, using a three-dimensional governing equation to simulate the steady, large-scale, limited amplitude perturbation of the free, inviscid and adiabatic atmosphere. The adoption of the static equation leads to a temperature governing equation in the terrain following coordinate. With the prescribed temperature as the upper boundary condition and the radiation balance as the lower boundary condition, the semi-analytical solution of the global circulation temperature can be calculated. In this article, only the air temperature （at 2 m height） over the land surface is analyzed, and the result suggests that this model can simulate the air temperature pattern over the land surface reasonably. A better simulation occurs when a simple feedback of the albedo on the temperature is included. Two sensitivity experiments are analyzed through this model. One suggests that the air temperature over the land surface descends obviously when the land surface is covered with ice all over, while another suggests that the air temperature rises a little when the land surface is covered with forest except the ice-covered area. This model appears to be a good tool to study the response of the air temperature to the vegetation distribution. Limitations of the model are also discussed.     

Decadal co-variability of the summer surface air temperature and soil moisture in China under global warming

The self-calibrating Palmer Drought Severity Index (PDSI) is calculated using newly updated ground observations of monthly surface air temperature (SAT) and precipitation in China. The co-variabilities of PDSI and SAT are examined for summer for the period 1961-2004. The results show that there exist decadal climate co-variabilities and strong nonlinear interactions between SAT and soil moisture in many regions of China. Some of the co-variabilities can be linked to global warming. In summer,sig-nificant decadal co-variabilities from cool-wet to warm-dry conditions are found in the east region of Northwest China,North China,and Northeast China. An important finding is that in the west region of Northwest China and Southeast China,pronounced decadal co-variabilities take place from warm-dry to cool-wet conditions. Because significant warming was observed over most areas of the global land surface during the past 20-30 years,the shift to cool-wet conditions is a unique phenomenon which may deserve much scientific attention. The nonlinear interactions between SAT and soil moisture may partly account for the observed decadal co-variabilities. It is shown that anomalies of SAT will greatly affect the climatic co-variabilities,and changes of SAT may bring notable influence on the PDSI in China. These results provide observational evidence for increasing risks of decadal drought and wet-ness as anthropogenic global warming progresses.     

毛乌素沙地中国沙棘克隆生长对土壤水分含量的响应

通过生物量测定和跟踪挖掘法,研究了毛乌素沙地中国沙棘克隆种群生长特征和形态特征对土壤水分条件的可塑性反应 。结果表明:低水分条件下,植株个体和种群都较小,子株数量、萌蘖根条数和分枝级数较少,而隔离区较长,种群趋向于游击型 ; 高水分条件下,植株个体和种群都较大,子株数量、萌蘖根条数和分枝级数较多,而隔离区较短,种群趋向于集团型。在生物 量分配方面,低水分条件下,枝条、叶片、根系和地上生物量分配比例较大; 高水分条件下,树干、萌蘖根和地下生物量分配比 例较大。土壤水分条件差异引起中国沙棘个体大小和种群大小的分化,进而导致了种群适合度的差异。     

The response of clonai growth of Hippophae rhamniodes L.subsp sinensis to the availability of soil moisture in Mu Us sand land

通过生物量测定和跟踪挖掘法,研究了毛乌素沙地中国沙棘克隆种群生长特征和形态特征对土壤水分条件的可塑性反应.结果表明:低水分条件下,植株个体和种群都较小,子株数量、萌蘖根条数和分枝级数较少,而隔离区较长,种群趋向于游击型;高水分条件下,植株个体和种群都较大,子株数量、萌蘖根条数和分枝级数较多,而隔离区较短,种群趋向于集团型.在生物量分配方面,低水分条件下,枝条、叶片、根系和地上生物量分配比例较大;高水分条件下,树干、萌蘖根和地下生物量分配比例较大.土壤水分条件差异引起中国沙棘个体大小和种群大小的分化,进而导致了种群适合度的差异.     

河北省人口增长与土地资源及粮食供求关系的研究

分析了河北的人口现状、特．点及预测，论述了人口、土地与粮食供求之间的矛盾关系，指出人口压力是土地退化的根本原因．最后提出了解决人口、土地、粮食之间矛盾的建设性对策．     

三峡工程对长江口南汇边滩近期演变影响初步预测

利用DELFT3D模型建立了长江口二维泥沙数学模型,通过实测水文泥沙资料对模型进行了验证.在此基础上,分别将上游洪、枯季流量概化和外海典型潮波组合,建立了长期冲淤模型.通过10年实测地形资料对模型进行的验证,显示该模型较好地模拟了长江口水沙运动以及长期冲淤演变过程.考虑三峡工程蓄水后上游来水来沙的变化,对近期南汇边滩的演变趋势给出预测,结果显示:三峡工程实施之后的5～20年,南汇边滩发育基本稳定,上游来沙量的减少不会造成大幅度冲刷,边滩整体继续向东南方向演变.     

黄河三角洲地物遥感分类研究进展与趋势

黄河三角洲地物种类众多,利用各种技术对黄河三角洲的地物进行分类与识别,有助于对该地区的资源进行合理的利用,同时对该地区的可持续发展具有重要的意义。对目前主要用于黄河三角洲地物遥感分类的卫星数据以及分类方法进行梳理和分析,总结了前人研究的不足,最后对黄河三角洲复杂地物分类方法的未来发展趋势进行了展望,为中国黄河三角洲地物的遥感分类以及动态监测提供参考和借鉴。     

全球关键矿产资源潜力评价理论方法的发展趋势与进展

目前,关键矿产是国际矿业市场关注的热门资源,具有特殊的属性和政治经济地位,越来越成为影响一个国家发展的战略性矿产.由于每个国家的关键性矿产资源不尽相同,其潜力评价工作进程也不尽相同,每个国家都有其独特的矿产资源潜力评价的理论与方法.简要回顾了关键矿产的国家演变策略,从国际环境、科技进步、国家政策等方面的不同,简要汇总全...     

国际经济格局趋势下的中国普通劳动者权益保护问题研究

多年来,中国被称为"世界工厂"。然而中国的主要出口商品都是一些中低端产品,制造业的技术含量普遍较低,其竞争力建立在廉价的劳动力成本之上,与此对应的是中国普通劳动者权益福利的丧失。中国人口基数巨大,劳动力市场供大于求。因此,提高普通劳动者权益不能只靠单纯的行政措施,而要顺应国际经济发展的大趋势,建立层次合理的产业结构。通过产业结构调整来增加就业岗位,吸纳劳动力,依靠市场的力量提高普通劳动者的福利。     

渭-库绿洲土地利用/覆被变化与蒸散量时空特征分析

以新疆维吾尔自治区渭干河-库车河三角洲绿洲为研究对象,利用支持向量机法(SVM)对1997和2015年Landsat TM/OLI遥感影像获取土地利用/覆被类型信息,基于SEBAL模型对研究区蒸散发(ET)进行估算并分析土地利用/覆被类型对ET的影响.研究结果表明:1997—2015年渭-库绿洲土地利用/覆被类型变化较显著,总体呈"一增四减"的变化趋势;不同土地类型的SEBAL模型参数和ET具有明显差异,而水体中ET与LAI、NDVI、SAVI之间呈反相对应;而研究区2期ET空间分布特征基本一致,整体表现为西高东低、北高南低的分布规律,植被覆盖越高,ET越高,而低植被覆盖区域地表温度越高,则ET越低,表明土地利用类型变化对ET的空间分布具有一定的影响..     

基于CNKI数据库对中国土地利用方式变化影响土壤有机碳趋势研究的文献计量分析

众多学者研究发现人类活动深刻影响着土壤有机碳的含量和组成,揭示了不同地区土地利用方式变化对土壤有机碳的影响机制.为了从整体把握该领域研究动态和发展趋势,该文利用CiteSpace可视化软件对该领域2002—2021年的234篇文献进行计量分析.结果表明：2002—2021年,土地利用变化对土壤有机碳的影响领域经历了三个研究阶段,先是文献量逐年缓慢增加的起步阶段(2002—2007年),再是快速增加的上升阶段(2008—2011年),而后是趋于平缓的稳定发展阶段(2012—至今);核心作者吴金水、吴建国、江长胜等人发文量较大,逐渐形成了三支稳定的研究团队;突变关键词表明研究热点主要集中在湿地土壤、有机碳组分等方面.总结现有的研究成果可以发现林地、耕地两类土地利用类型的土壤有机碳含量研究较为成熟,湿地土壤有机碳及其微观层面的有机碳组成和化学结构将成为今后的研究趋势.