基于遥感和无人机数据的草地NDVI影响因子多尺度分析

为探索不同尺度草地植被的影响因子,本研究基于Landsat遥感影像和无人机多光谱影像等,在村落和地块2个尺度分析西藏草地归一化植被指数(Normalized Difference Vegetation Index,NDVI)的影响因子。结果表明:村落尺度的海拔、坡度、坡向、地表起伏度皆对NDVI有显著的非线性影响,解释比例为37.20%;方差分析表明,地形等因子相近的同类土地利用内部NDVI差异仍较大;运用无人机影像细分同种土地利用类型内部异质性,发现遥感影像中无法辨别的点状、线状地物(石堆、水渠、田间路等)对草地NDVI有一定影响;缓冲区分析表明,非硬化水渠和道路对NDVI的负面影响在1~3 m,硬化水渠和路面对草地的负面影响超过4 m。无人机获取高分辨率多光谱影像的便捷性可以推进更小尺度下人类活动强度以及景观破碎化对植被和生态系统功能影响研究的深入。

改良LAMP检测鸡肉中单增李斯特氏菌的研究

本研究建立一种改良环介导等温扩增(loop-mediated isothermal amplification,LAMP)技术检测鸡肉中单增李斯特氏菌(Listeria monocytogenes,L. monocytogenes)的方法。针对单增李斯特氏菌的溶血素基因(hlyA)设计LAMP引物,对单增李斯特氏菌进行特异性检测,通过荧光曲线和肉眼观察荧光颜色来判定检测结果。试验结果表明:改良LAMP方法检测单增李斯特氏菌具有良好的特异性,7株单增李斯特氏菌呈阳性结果,24株非单增李斯特氏菌呈阴性结果。与聚合酶链反应(polymerase chain reaction,PCR)方法相比,改良LAMP方法具有灵敏度高(5.4×100 fg/μL)、检出限低(3.9×100 CFU/g)的特点,均是PCR结果的100倍。对66份鸡肉样品进行检测,得到改良LAMP方法的敏感性为100%,特异性为98.41%,符合率为98.48%。综上所述,改良LAMP方法能够快速、准确的检测单增李斯特氏菌,具有很好的应用前景。

食品中沙门氏菌FTA膜结合跨越式滚环等温扩增检测方法的建立

为实现食品中沙门氏菌的简便和快速现场检测,本研究采用FTA膜(Flinders technology associates,FTA)结合跨越式滚环等温扩增(Saltatory rolling circle amplification,SRCA)方法(FTA-SRCA)建立一种新型的沙门氏菌检测方法。利用FTA膜快速提取模板DNA,根据沙门氏菌的inv A基因设计及筛选引物,建立FTA-SRCA反应体系。扩增反应在能够实现集约化检测的凹孔板中进行,反应结束后添加荧光染料观察结果。确定了该方法的特异性、灵敏度和人工污染样品的检出限,并对60个实际样品进行检测,评估其敏感性、特异性和符合率。结果表明:检测的17株沙门氏菌均为阳性结果,29株非沙门氏菌均为阴性结果,特异性良好。FTA-SRCA方法的灵敏度为6.81×100 CFU/m L,比PCR方法高100倍,比SRCA方法高10倍。对于人工污染的牛奶样品检测,FTA-SRCA方法的检出限为3.22×100CFU/m L,比PCR方法低1000倍,比SRCA方法低10倍。检测实际样品的敏感性、特异性和符合率分别为100.00%,94.64%,95.00%。本研究建立的FTA-SRCA方法具有操作简便快速、成本低廉、特异性强、灵敏度高、检出限低等优点,可用于食品中沙门氏菌的大批量集约化快速现场检测。

藏北羌塘牧民家庭人口特征和收入构成之间的关系

为探讨牧民家庭人口特征和收入构成之间的关系,通过半结构式访谈调查了藏北羌塘高寒草甸、高寒草原和荒漠草原区682户牧民,比较了其家庭规模、劳动力、抚养比、草场面积、放牧强度、家庭收入及其多样性的差异,结合多元线性回归评价了家庭人口特征对收入构成的影响。结果显示:羌塘地区牧民家庭规模大(5.3人·户^(-1))、抚养比高(0.62)、劳动力充足(3人·户^(-1))但受教育年限短(2.3年),高度依赖政策性收入;高寒草甸区牧民家庭规模、劳动力数量及受教育年限、抚养比和放牧强度等指标显著高于高寒草原和荒漠草原区(P<0.05),后两者之间无显著差异;荒漠草原区牧民家庭草场面积和政策性收入较高(P<0.05);家庭规模、文盲率和抚养比是影响高寒草原和荒漠草原牧民收入构成的主要因子,人口特征对高寒草甸牧民收入影响不显著。综上所述,建议分区精准施策以提高牧民生计。

实时荧光跨越式滚环等温扩增技术检测食品中的志贺氏菌

该研究建立一种实时荧光跨越式滚环等温扩增(real-time fluorescence saltatory rolling circle amplification,RFSRCA)技术快速检测志贺氏菌(Shigella)。该方法以志贺氏菌的ipaH基因设计引物,使用32株不同菌株对RF-SRCA方法的特异性进行分析,根据实时荧光曲线法对RF-SRCA方法的灵敏度和检出限进行判定,并使用该方法对60份食品样品进行检测。结果表明:13株志贺氏菌菌株呈阳性结果,19株非志贺氏菌菌株呈阴性结果,说明该方法特异性良好;RF-SRCA的灵敏度为5.97×10^(0)fg/μL,比普通SRCA方法高10倍;其在人工污染牛奶样品中的检出限为8.6×10^(0)CFU/mL,比普通SRCA方法检出限低10倍;60份食品样品中阳性样品数为2份,其检出率与SRCA方法一致,为3.33%。综上,RF-SRCA方法在检测志贺氏菌方面操作简单,特异性强,灵敏度高,能够实现快速检测。

Response of Ecosystem Respiration to Experimental Warming and Clipping at Daily Time Scale in an Alpine Meadow of Tibet

The alpine meadow,as one of the typical vegetation types on the Tibetan Plateau,is one of the most sensitive terrestrial ecosystems to climate warming.However,how climate warming affects the carbon cycling of the alpine meadow on the Tibetan Plateau is not very clear.A field experiment under controlled experimental warming and clipping conditions was conducted in an alpine meadow on the Northern Tibetan Plateau since July 2008.Open top chambers(OTCs) were used to simulate climate warming.The main objective of this study was to examine the responses of ecosystem respiration(R eco) and its temperature sensitivity to experimental warming and clipping at daily time scale.Therefore,we measured R eco once or twice a month from July to September in 2010,from June to September in 2011 and from August to September in 2012.Air temperature dominated daily variation of Reco whether or not experimental warming and clipping were present.Air temperature was exponentially correlated with R eco and it could significantly explain 58～96% variation of R eco at daily time scale.Experimental warming and clipping decreased daily mean R eco by 5.8～37.7% and-11.9～23.0%,respectively,although not all these changes were significant.Experimental warming tended to decrease the temperature sensitivity of R eco,whereas clipping tended to increase the temperature sensitivity of R eco at daily time scale.Our findings suggest that R eco was mainly controlled by air temperature and may acclimate to climate warming due to its lower temperature sensitivity under experimental warming at daily time scale.

Clipping Alters the Response of Biomass Production to Experimental Warming: A Case Study in an Alpine Meadow on the Tibetan Plateau, China

预言人的活动怎么将影响高山的草地的反应到未来温暖有许多无常。在这研究，有温暖控制并且抓紧的一个领域实验在北西藏在三举起(4313 m， 4513 m 和 4693 m ) 在一块高山的草地被进行测试抓紧将改变在生物资源生产上温暖效果的假设。自从 2008 年 7 月，开的最高的房间(OTC ) 被用来增加温度， OTC 由约 0.9 楴湯挠癯牥 ? 桴 ? 题传 G 整 ? 敮 ? 牰摯 ' 讟 N 楶祴眠獡瘠牥 ? 增加了空气温度潬 ? 湩㈠ ?? 潣灭牡摥琠??? 愠摮ㄠ吗？？

Biomass Allocation Patterns of Alpine Grassland Species and Functional Groups along a Precipitation Gradient on the Northern Tibetan Plateau

Variations in the fractions of biomass allocated to functional components are widely considered as plant responses to resource availability for grassland plants. Observations indicated shoots isometrically relates to roots at the community level but allometrically at the species level in Tibetan alpine grasslands. These differences may result from the specific complementarity of functional groups between functional components, such as leaf, root,stem and reproductive organ. To test the component complementary responses to regional moisture variation, we conducted a multi-site transect survey to measure plant individual size and component biomass fractions of common species belonging to the functional groups: forbs, grasses, legumes and sedges on the Northern Tibetan Plateau in peak growing season in 2010. Along the mean annual precipitation(MAP) gradient, we sampled 70 species, in which 20are in alpine meadows, 20 in alpine steppes, 15 in alpine desert-steppes and 15 in alpine deserts,respectively. Our results showed that the size of alpine plants is small with individual biomass mostly lower than 1.0 g. Plants keep relative conservative component fractions across alpine grasslands at the individual level. However, the complementary responses between functional components to moisture variations specifically differ among functional groups. These results indicate that functional group diversity may be an effective tool for scaling biomass allocation patterns from individual up to community level. Therefore, it is necessary andvaluable to perform intensive and systematic studies on identification and differentiation the influences of compositional changes in functional groups on ecosystem primary services and processes.

Alpine grassland fPAR change over the Northern Tibetan Plateau from 2002 to 2011

在这研究，包括数字照相机和参考面板( DCRP )的二个不同方法并且在为测量的 situ fPAR 观察传统在里面很短的高山的草植被的 situ 点 fPAR 被比较，，并且由在在北西藏的高原，它对气候敏感上的高山的草地上的 situ 点数据变化并且对人为的活动脆弱。结果证明 MODIS 高山的草地 fPAR 产品，由使用 DCRP 检验了，并且在有的 situ fPAR 观察传统在空间、时间的规模的一种重要关系。十的 MODIS fPAR 趋势分析显示出那，平均成长季节 fPAR 增加了 1.2 ? ㈠ ? 猰? 桴 ? 湩牣慥敳 ? 牣灯眠瑡牥搠浥湡 ? 湡 ? 湩整獮晩敩 ? 呅爠獥汵楴杮映潲 ? 汧扯污眠牡業杮眠汩 ? 敲畤散眠瑡牥爠獥畯 ' 元棯 e 牵汰獵? 牐 ' 虨宫摤嫕?呅 ?L 畯 ? ┴木┴愠摮椠据敲獡 ? 楳湧晩捩湡汴 ? 桴 ? 物楲慧楴湯眠瑡牥搠浥湡 ? 湩挠潲 ?

Climatic and geographic factors affect ecosystem multifunctionality through biodiversity in the Tibetan alpine grasslands

Ecosystem multifunctionality(EMF), the simultaneous provision of multiple ecosystem functions, is often affected by biodiversity and environmental factors. We know little about how the interactions between biodiversity and environmental factors affect EMF. In this case study, a structural equation model was used to clarify climatic and geographic pathways that affect EMF by varying biodiversity in the Tibetan alpine grasslands. In addition to services related to carbon, nitrogen, and water cycling, forage supply, which is related to plantproductivity and palatability, was included in the EMF index. The results showed that 72% of the variation in EMF could be explained by biodiversity and other environmental factors. The ratio of palatable richness to all species richness explained 8.3% of the EMF variation. We found that air temperature, elevation, and latitude all affected EMF, but in different ways. Air temperature and elevation impacted the aboveground parts of the ecosystem, which included plant height, aboveground biomass, richness of palatable species, and ratio of palatable richness to all species richness. Latitude affected EMF by varying both aboveground and belowground parts of the ecosystem, which included palatable speciesrichness and belowground biomass. Our results indicated that there are still uncertainties in the biodiversity–EMF relationships related to the variable components of EMF, and climatic and geographic factors. Clarification of pathways that affect EMF using structural equation modeling techniques could elucidate the mechanisms by which environmental changes affect EMF.

Species-area relationship within and across functional groups at alpine grasslands on the northern Tibetan Plateau,China

The species-area relationship(SAR) is one of the most fundamental concepts in community ecology and is helpful for biodiversity conservation.However,few studies have systematically addressed this topic for different alpine grassland types on the Tibetan Plateau,China.We explored whether the plant composition of different functional groups affects the manner in which species richness increases with increasing area at scales ≤ 1.0 m^2.We also compared species richness(S) within and across forbs,legumes,sedges and grasses,with sampling subplot area(A) increasing from 0.0625 m^2 to 1.0 m^2 between alpine meadow and steppe communities.We applied a logarithmic function(S = b_0 + b_1 ln A) to determine the slope and intercept of SAR curves within and across functional groups.The results showed that the logarithmic relationship holds true between species richness and sampling area at these small scales.Both the intercept and slope of the logarithmic forbs-area curves are significantly higher than those for the three other functional groups(P < 0.05).Forb accounts for about 91.9 % of the variation in the intercept and 75.0% of the variation in the slope of the SAR curve when allfunctional groups' data were pooled together.Our results indicated that the different SAR patterns should be linked with species dispersal capabilities,environmental filtering,and life form composition within alpine grassland communities.Further studies on the relationship between species diversity and ecosystem functions should specify the differential responses of different functional groups to variations in climate and anthropogenic disturbances.

The Dynamics of Rubidium Atoms in THz Laser Fields

By using B-spline basis set combined with model potential,energy levels and wave functions of rubidium atoms are obtained.Using a time-dependent multi-level approach,we study the dependence of the population of rubidium atoms excited from a low lying state to a target state on the parameters of a single or two broadband terahertz laser pulses.The population redistribution between the states n=23 and n=24 due to the interaction with terahertz pulses is analyzed in detail.Population oscillation in the initial and final states as a function of the time delay between two half cycle pulses is shown,and the oscillation period is the same as the Kepler period of the selected states.The calculation results agree well with the experiment and can be explained by the semiclassical picture.

Coherent Control of Molecular Orientation by a Terahertz Few-Cycle Laser Pulse

The coherent control of molecular orientation by a terahertz few-cycle laser pulse is theoretically studied.It is demonstrated that the field-free molecular orientation results from the interference contributions between the odd and even rotational wave packet,and therefore the constructive and destructive interferences lead to the observation of the positive and negative orientations,corresponding to the positive and negative degrees.Furthermore,the enhancement or suppression of the molecular orientation can be coherently manipulated by precisely controlling the carrier-envelope phase of the terahertz few-cycle pulse.

Coherent Control of Molecular Alignment and Orientation by a Femtosecond Two-Color Laser Pulse

The coherent control of molecular alignment and orientation by a femtosecond two-color laser pulse is studied theoretically.The effect of the carrier-envelope phase of the femtosecond two-color laser pulse on molecular alignment and orientation is discussed,and it is shown that the enhancement or suppression of the molecular orientation can be coherently manipulated by precisely controlling the carrier-envelope phase of the femtosecond two-color laser pulse.In addition,the time-dependent angular distributions of the molecular axis are presented.

Population Evolution of Rydberg Rubidium Atoms by Half-Cycle Pulses

Using the B-spline basis set method combined with model potential,the Stark energy level of rubidium atoms in the vicinity of n=30 is presented.By using a using time-dependent multilevel approach,we calculate the population redistribution of high Rydberg rubidium atoms under the interaction of external time-dependent half-cycle pulses.Our numerical results show that the population of rubidium atoms can be driven to lower or higher n levels with a train of half cycle pulses,the final population distribution of all the l states for the same n is observed after these interactions.

Coherent Control of Lithium Atom by Adiabatic Rapid Passage with Chirped Microwave Pulses

Using the time-dependent multilevel approach and the B-spline technique,populations of Rydberg lithium atoms in chirped microwave pulses are demonstrated.Firstly the populations of two energy levels are controlled by the microwave pulse parameters.Secondly the atoms experience the consequence 70s-71p-72s-73p-74s in a microwave field using optimized microwave field parameters.It is shown that the coherent control of the population transfer in the microwave field from the initial to the target states can be accomplished by optimizing the microwave field parameters.

Relativistic Quadrupole Polarizability for the Ground State of Hydrogen-Like Ions

The static quadrupole polarizabilities for hydrogen-like ions from Z =1 to Z =100 in the 1S1/2 ground state are calculated to high precision by solving the Dirac equation using the B-spline Galerkin method.The results are consistent with the expression of Kaneko [J.Phys.B 10 (1977) 3347] at low Z.The quadrupole oscillator strength sum Σn f(2)gn is computed to be zero to a very high degree of precision.

Calculation of Multiphoton Transition in Li Atoms via Chirped Microwave Pulse

The position and width of avoided crossings of Li atom energy levels in a static electric field is presented by using the B-spline basis set method combined with the model potential.Using the time-dependent multilevel approach,the population of Li atoms is transferred to the target state completely by one-photon,two-photon or a single multiphoton adiabatic rapid passage,which requires only a small frequency sweep.The calculation results agree well with the experiment and novel explanations are given to understand the experimental results.

藏北两个临近不同高寒草地碳通量对气候条件的响应

生态系统碳循环应对气候变化的敏感性研究是“碳中和”背景下的重要议题。青藏高原高寒草地面积广阔,碳储量丰富,脆弱性高,近年来随着观测技术尤其是涡度相关技术和模拟技术的发展,已有不少研究致力于揭示青藏高原高寒草地生态系统碳水通量对气候变化的响应过程。但是,相同气候背景下不同高寒草地类型对环境变化的响应规律及敏感性尚不清楚。本研究基于藏北高原两个临近的高寒草地生态系统,高寒草甸和高寒湿地涡度相关观测的碳水通量数据,对比分析了不同水分条件下藏北高寒草甸和高寒湿地碳循环的气候敏感性。结果表明,高寒草甸的碳交换量要显著小于高寒湿地,高寒草甸是碳中性的,年净CO_(2)交换量为(18.09±40.66) g C·m^(-2) ,而高寒湿地是稳定的碳汇,年净CO_(2)固定量为(155.09±32.85)g C·m^(-2) 。水分条件对高寒草甸和高寒湿地植被光响应曲线最大的光合速率(α)的影响较弱,与饱和光强下的总初级生产力(Amax)呈显著正相关关系。水分对生态系统呼吸与温度的指数响应关系的调节作用主要体现在基础呼吸值(a)上,高寒湿地a的均值是高寒草甸的3.76倍,而对两个高寒草地生态系统呼吸敏感性(Q10)的调节均不显著。高寒草甸和高寒湿地Q10的均值(1.84)以及随温度升高而减小的趋势基本一致。藏北高寒草地生态系统的碳源汇特征对环境因子的响应取决于多因素共同限制,因此,基于区域性的联网协同观测有助于更加清晰地理解高寒生态系统碳交换响应气候变化的机理。

降水变化对藏北高寒草原化草甸降水利用效率及地上生产力的影响

降水总量、分配方式及其发生时间共同决定了青藏高原植被生长的水分条件,而降水利用效率(PUE,地上生产力与降水量的比值)是评估降水与植被生产力关系的有效指标.本研究以藏北当雄高寒草原化草甸为研究对象,利用多年生物量采样数据与同期遥感EVI植被指数建立线性模型,反演了2000—2016年地上净初级生产力(ANPP),结合同时期气象数据,以生长季降水量(GSP)表征降水总体状况,改进的降水集度指标(PCI)表征生长季降水分配,降水重心(PC)表征降水集中时间,并结合生长季均温(GST),利用结构方程分析了气候因子对当雄草地降水利用效率和地上生产力的影响.结果表明:当雄草地ANPP主要受生长季降水影响,GSP与ANPP呈显著正相关,而GST与PUE、ANPP无显著相关关系;PCI与PUE呈显著正相关,表明降水集中分布有利于PUE增加;PCI与ANPP相关的间接系数大于直接系数,表明PCI通过PUE影响ANPP;降水集中时间(PC)变化则对PUE和ANPP没有显著影响.在青藏高原显著的气候变暖背景下,降水量和降水集度的变化都将会对藏北高寒草地的地上生产力产生重要影响.