科尔沁草地不同大气稳定度下湍流特征谱分析

利用科尔沁半干旱风沙草原区涡度相关观测数据,计算并分析了不同大气稳定度条件下湍流的功率谱和协谱.结果表明:经向风速与纬向风速的功率谱在大气不稳定层结、近中性层结、稳定层结条件下谱形均相似,并遵循-2/3定律;近中性层结条件下垂直风速的功率谱没有惯性子区,此时仪器对脉动信号的捕捉不够完全,稳定层结条件下垂直风速功率谱表明观测层产生了泄流和平流;CO_2和H_2O浓度的功率谱分析表明,红外气体分析仪对高频信号的响应能力能够满足实际观测的需要,其功率谱的谱峰随大气稳定度的增强而向高频转移;垂直风速与3种标量的协谱谱形相似,不同大气稳定度下协谱惯性子区长度随大气稳定度的增强而变短,且均符合-4/3定律,说明三维超声风速仪与红外气体分析仪的空间间隔不会对通量观测结果造成显著影响.     

引种植物定植区近地层光合有效辐射特征

为了探讨西双版纳热带植物园引种植物主要定植区近地层的光合有效辐射特征及其变化规律,利用2008—2009年不同季节的小气候观测资料,分析了西双版纳热带植物园引种植物主要定植区近地层的光合有效辐射的季节和日变化特征。结果表明:西双版纳热带植物园区域的光合有效辐射具有明显的日变化和季节差异,雨季最强,旷地的光合有效辐射日总量可达406.6mol·m-2·d-1,雾凉季最弱,旷地光合有效辐射日总量为236.0mol·m-2·d-1;由于受高大树木遮蔽的影响,在沟谷林、龙脑香林和树木园的光合有效辐射数值较低;受太阳高度角变化和林冠林隙的影响,在雨季近地层光合有效辐射会出现突跃现象。各引种植物定植区近地层的光合有效辐射的数值也不同,存在地域差异和季节差异。在具有高大树木、遮蔽较大的定植区,近地层光合有效辐射的数值较小;而遮蔽较小的定植区,情况则反之,近地层光合有效辐射的季节差异与旷地相似,雨季较大,雾凉季较小。在具有高大树木、遮蔽较大的定植区,近地层光合有效辐射与旷地的比值较小,不足旷地的10%,其中在具有多层多种森林群落结构的沟谷林,其最小比值(雾凉季)仅为1.6%;而遮蔽较小的定植区比值较大(>55%)在干热季其数...     

森林蒸散模型参数的确定

以长白山阔叶红松林为研究对象,利用长白山阔叶红松林气象观测塔安装的常规气象梯度观测系统、开路涡动相关系统的观测数据,依据空气动力学基本理论与能量平衡方程建立了森林蒸散机理模型,确定了模型参数,即风速廓线稳定度订正函数φ_m、温度廓线稳定度订正函数φ_h和零平面位移高度d.其中,研究地的零平面位移高度d为17.8m,是平均冠层高度(26m)的0.68.同时,给出了φ_m和φ_h随梯度理查逊数R_i变化的数学表达式.     

科尔沁沙地流动沙丘不同时空尺度水热变化及CO2交换特征

陆面碳循环在气候变化和生态系统碳收支平衡中起到关键作用。水热变化与CO₂交换分析对于深刻揭示荒漠生态系统的区域碳循环规律及机制具有重要意义。本研究选取科尔沁沙地典型流动沙丘为对象,利用涡度相关技术和波文比气象观测系统所测的数据分析近地层水热变化及CO₂交换特征,探讨了日和季节尺度,以及0～10 m垂直空间尺度下流动沙丘近地层温湿度与CO₂交换过程的相互关系。结果表明: 研究区近地表气温垂直变幅在0.4～2 ℃,4—9月,气温随着高度的升高呈减的趋势,其余月份则相反,空气相对湿度季节变幅超过40%;在2018年生长季,沙丘净生态系统碳交换量(NEE)的日均值为-0.02 mg·m^-2·s^-1,全年水平的NEE日均值为0.003 mg·m^-2·s^-1,全年整体上表现为碳源;垂直空间尺度上,垂直温、湿度差与NEE拟合均较好,水热影响拐点分别为10%和0.5 ℃,而全年尺度上温度拟合结果相对较好,水热影响拐点分别为17 ℃和65%。在生长季,研究区近地层垂直温差为负,会抑制流动沙丘对大气CO₂的吸收,而大气高湿环境则会促进流动沙丘对大气CO₂的吸收。不同时间和不同垂直高度上,水热变化与CO₂交换关系较密切,对沙丘碳汇和碳源的产生具有一定的影响,且碳收支对温度的敏感性强于相对湿度。     

太湖生态系统能量闭合特征及其影响因素

地表能量不闭合不仅限制了涡度相关观测数据在陆面模型发展和验证等应用性研究中的价值,还给生态系统CO2源汇特征辨析带来不确定性。基于太湖避风港站2012年涡度相关通量、辐射、气象和水温梯度观测数据,分析了太湖能量闭合的多尺度(小时、日和月)时间变化特征,阐述了大气稳定度、摩擦风速和湖风对太湖能量闭合状况的影响。结果表明:太湖小时尺度的能量闭合度为0.59,且昼夜差异较小;日尺度的能量闭合度为0.73,在内陆水体观测结果中处于中等水平;月平均能量闭合度呈现冬季高、夏季低的季节变化特征;年平均时太湖仍有27%的能量不闭合。因摩擦风速减小,太湖能量闭合度在大气极不稳定条件下要比弱不稳定条件下结果低0.3;对于太湖这类大型浅水湖泊,其能量闭合度全天都受动力湍流交换强度制约,能量闭合度随摩擦风速增大而显著提高;虽然湖风发生使太湖小时尺度的能量闭合度降低了0.1,但其影响在日尺度上并不明显。     

热带季节雨林林冠上方和林内近地层CO2浓度的时空动态及其成因分析

 为探讨西双版纳独特地方气候背景下,热带季节雨林CO₂浓度的时空变化特征和不同时间尺度上环境因素对森林CO₂浓度时间分布的作用,以及 为研究热带季节雨林的碳通量、净生态系统交换量(Net ecosystem exchange, NEE)等提供支持,我们利用热带季节雨林林冠上方和林内近地层 CO₂浓度连续监测资料,结合同步气象资料进行了统计分析。研究结果表明：在植被生理活动、土壤呼吸以及林内湍流的共同作用下,西双版纳 热带季节雨林CO₂浓度表现出明显的日变化、季节变化和林冠上下差异。在日尺度上,林冠上方的CO₂浓度时间变化曲线为“单峰型”,林内近 地层CO₂浓度时间变化曲线为“双峰型”,造成林内近地层傍晚第二个峰值的主要因子是地形因子作用下形成的局地环流。在季节尺度上,林冠 上方CO₂浓度主要受林冠代谢作用的影响,呈现雨季低、干季高的特点,而林内近地层的CO₂浓度则主要受地表呼吸过程所控制,季节变化趋势 与林冠上方相反。林冠上方CO₂浓度低于林内近地层CO₂浓度,且差异较大;在日尺度上,各月（除12月外）CO₂浓度的最大差值皆大于80 mg·m ^－3,且出现在傍晚;在季节尺度上,最大值为-62.9 mg·m^－3,出现在10月,最小值为-8.4 mg·m^－3,出现在12月。     

森林蒸散模型参数的确定

以长白山阔叶红松林为研究对象,利用长白山阔叶红松林气象观测塔安装的常规气象梯度观测系统、开路涡动相关系统的观测数据,依据空气动力学基本理论与能量平衡方程建立了森林蒸散机理模型,确定了模型参数,即风速廓线稳定度订正函数ψm、温度廓线稳定度订正函数ψh和零平面位移高度d。其中,研究地的零平面位移高度d为17．8m,是平均冠层高度(26m)的0．68。同时,给出了ψm和ψh随梯度理查逊数Ri变化的数学表达式。     

浓度的时空动态及其成因分析

为探讨西双版纳独特地方气候背景下,热带季节雨林CO₂浓度的时空变化特征和不同时间尺度上环境因素对森林CO₂浓度时间分布的作用,以及 为研究热带季节雨林的碳通量、净生态系统交换量(Net ecosystem exchange, NEE)等提供支持,我们利用热带季节雨林林冠上方和林内近地层 CO₂浓度连续监测资料,结合同步气象资料进行了统计分析。研究结果表明：在植被生理活动、土壤呼吸以及林内湍流的共同作用下,西双版纳 热带季节雨林CO₂浓度表现出明显的日变化、季节变化和林冠上下差异。在日尺度上,林冠上方的CO₂浓度时间变化曲线为“单峰型”,林内近 地层CO₂浓度时间变化曲线为“双峰型”,造成林内近地层傍晚第二个峰值的主要因子是地形因子作用下形成的局地环流。在季节尺度上,林冠 上方CO₂浓度主要受林冠代谢作用的影响,呈现雨季低、干季高的特点,而林内近地层的CO₂浓度则主要受地表呼吸过程所控制,季节变化趋势 与林冠上方相反。林冠上方CO₂浓度低于林内近地层CO₂浓度,且差异较大;在日尺度上,各月（除12月外）CO₂浓度的最大差值皆大于80 mg·m ^－3,且出现在傍晚;在季节尺度上,最大值为-62.9 mg·m^－3,出现在10月,最小值为-8.4 mg·m^－3,出现在12月。     

不同水分管理下稻田土壤CH4和N2O排放与微生物菌群的关系

采用MPN计数法对黑土(海伦)和草甸棕壤(沈阳)稻田生长季4种微生物菌群数量进行了测定,同时采用封闭式箱法对CH4和N2O通量进行观测,以深入了解稻田生物源温室气体排放的微生物学过程,两地试验田均采用长期淹灌与间歇灌溉两种不同水分管理,对实验结果多元回归分析,结果表明,海伦与沈阳两地稻田两种水分管理条件下CH4通量季节变化与产甲烷菌数季节变化存在极显著正相关关系沈阳稻田生长季CH4通量季节变化与甲烷氧化菌数季节变化具有显著正相关性,间歇灌溉条件下黑土稻田N2O通量与反硝化菌数呈显著性正相关关系,两种水分管理条件下沈阳稻田N2O通量与硝化菌数具有显著正相关关系,间歇灌溉条件下沈阳稻田N2O通量与反硝化菌数呈显著性正相关关系。     

利用双波长方法对非均匀地形人工林蒸散的测量

千米级地表蒸散通常利用遥感影像并结合经验或半经验模型进行估算,且估算结果还需结合地表实测数据进行验证,但实际中很难获得与遥感像元尺度匹配的实测数据.本研究在黄河小浪底森林生态系统定位研究站人工林的生长期(2016年7月1日-10月19日),基于近红外与微波联合观测技术进行千米级地表蒸散的观测分析.结果表明:近红外与微波联合技术在不同天气条件下均能表现出良好的日变化特征,且整体能量闭合率可达0.87.该技术对空气湿度的变化敏感,土壤湿度的变化对该项技术的结果影响较小.不同波文比条件和大气稳定度均会使该技术的观测产生不同程度的误差,与涡动相关方法相比,误差在合理范围.采用双波长方法研究得出,该区域的最大日蒸散量为3.5 mm,总蒸散量为162.4 mm.     

Rates of recombination in the ribosomal DNA of apomictically propagated Daphnia obtusa lines

Ribosomal (r)DNA undergoes concerted evolution, the mechanisms of which are unequal crossing over and gene conversion. Despite the fundamental importance of these mechanisms to the evolution of rDNA, their rates have been estimated only in a few model species. We estimated recombination rate in rDNA by quantifying the relative frequency of intraindividual length variants in an expansion segment of the 18S rRNA gene of the cladoceran crustacean, Daphnia obtusa, in four apomictically propagated lines. We also used quantitative PCR to estimate rDNA copy number. The apomictic lines were sampled every 5 generations for 90 generations, and we considered each significant change in the frequency distribution of length variants between time intervals to be the result of a recombination event. Using this method, we calculated the recombination rate for this region to be 0.02-0.06 events/generation on the basis of three different estimates of rDNA copy number. In addition, we observed substantial changes in rDNA copy number within and between lines. Estimates of haploid copy number varied from 53 to 233, with a mean of 150. We also measured the relative frequency of length variants in 30 lines at generations 5, 50, and 90. Although length variant frequencies changed significantly within and between lines, the overall average frequency of each length variant did not change significantly between the three generations sampled, suggesting that there is little or no bias in the direction of change due to recombination.     

Morphology of Trichoderma reesei QM 9414 in submerged cultures

The microscopic morphology of Trichoderma reesei QM 9414, growing in submerged culture, was studied by image analysis. The morphology was characterized by the total hyphal length, the total number of tips, the number of actively growing tips, and the length of the main hypha. To describe the growth of a single mycelium a simple model is set-up. The main features of the model are: (1) saturation type kinetics for the tip extension of the individual branches within the mycelium; and (2) random branching with a frequency function, which is proportional to the total hyphal length. The model is used to simulate a population of mycelia, where spore germination is described with a log-normal distribution. From the simulation of the population, the average properties of the mycelia, e.g., the average total hyphal length, are calculated, and by fitting the model to experimental data the model parameters are estimated. Finally, the distribution function with respect to the mycelia properties, that is, number of tips and total hyphal length, is calculated, and it corresponds well with the experimental determination of the distribution function. (c) 1995 John Wiley & Sons Inc.     

Body temperature predicts maximum microsatellite length in mammals

A long-standing mystery in genome evolution is why short tandem repeats vary so much in length and frequency. Here, we test the hypothesis that body temperature acts to influence the rate and nature of slippage-based mutations. Using the data from both 28 species where genome sequencing is advanced and 76 species from which marker loci have been published, we show that in mammals, maximum repeat number is inversely correlated with body temperature, with warmer-blooded species having shorter 'long' microsatellites. Our results support a model of microsatellite evolution in which maximum length is limited by a temperature-dependent stability threshold.     

Estimating sampling efficiency of diurnal Lepidoptera in farmland

Setting up effective survey strategies for biodiversity monitoring in agro-ecosystems is a major task in order to detect adverse effects on biodiversity before negative changes will manifest. Here, we studied the relative costs required for the monitoring of butterflies and selected diurnal moths (Papilionoidea et Hesperioidea; Zygaenoidea: Zygaenidae) in farmland. Analysing data from a well-established Lepidoptera monitoring system in Switzerland, we assessed the influence of inspection periods, inspection frequency and transect length on counts of diurnal Lepidoptera. Furthermore, we estimated the number of transects in relation to sampling effort necessary to detect changes of a given effect size for recorded species number (and abundance). Reducing the counting frequency from seven to four inspections per season still yielded 80–90 % of the species, as long as peak abundances in summer months were included. The variation in observed species number was mostly independent of inspection frequency, but strongly increased when transect length was reduced to less than 1 km. Sedentary Lepidoptera species are especially valuable indicators as their occurrences are directly linked to local effects on biodiversity, and the proportion of recorded sedentary species was not substantially affected by reduced inspection frequency. Transects of 1–1.5 km length were generally the most cost-efficient to detect an effect on total species number of diurnal Lepidoptera in arable landscapes, given that travelling distances between transects were short. Studying effects on rare species or selected species groups would involve higher sampling intensity and costs. Surveying schemes with reduced inspection frequency and transect lengths can detect changes in species richness and total abundance of diurnal Lepidoptera cost-effectively. Facing expected changes in agricultural policy and management, the results and recommendations presented here will help to implement and improve cost-efficient Lepidoptera schemes to monitor changes in arable landscapes.     

The relationship between fecundity and fertility in the mouthbrooding cichlid fish Tilapia leucosticta

The development of fry in the mouth of the female mouthbrooder Tilapia leucosticta Trewavas is described. The egg production by fish of various lengths is plotted and a curvilinear regression for standard and total length fitted. The number of eggs produced is approximately equal tothe square of the total length in centimetres of the parent fish. The brood numbers of 460 femalesare plotted against length, and linear regressions for mean brood number and mean fry number fitted. The relationship between the expressions for numbers of fry brooded and egg production gives anestimate of brooding efficiency that decreases with increasing parent length. Individual female fish show signs of reripening and the timing of this process is estimated from gonad state and from the length of fry brooded in the mouth. The relationship between fecundity (egg production) and fertility (fry brooded) is considered and the effect of maturation size, growth rate and spawning frequency assessed.     

Primordial Ocean Chemistry and its Compatibility with the RNA World

We examine the stability of three key components needed to establish an RNA World under a range of potential conditions present on the early earth. The stability of ribose, cytosine, and the phosphodiester bond are estimated at different pH values and temperatures by extrapolating available experimental data. The conditions we have chosen range from highly acidic or alkaline hydrothermal vents, to the milder conditions in a primordial ocean at a range of atmospheric CO₂ partial pressures.     

Stomatal frequency adjustment of four conifer species to historical changes in atmospheric CO2

The species-specific inverse relation between atmospheric CO(2) concentration and stomatal frequency for many woody angiosperm species is being used increasingly with fossil leaves to reconstruct past atmospheric CO(2) levels. To extend our limited knowledge of the responsiveness of conifer needles to CO(2) fluctuations, the stomatal frequency response of four native North American conifer species (Tsuga heterophylla, Picea glauca, Picea mariana, and Larix laricina) to a range of historical CO(2) mixing ratios (290 to 370 ppmV) was analyzed. Because of the specific mode of leaf development and the subsequent stomatal patterning in conifer needles, the stomatal index of these species was not affected by CO(2). In contrast, a new measure of stomatal frequency, based on the number of stomata per millimeter of needle length, decreased significantly with increasing CO(2). For Tsuga heterophylla, the stomatal frequency response to CO(2) changes in the last century is validated through assessment of the influence of other biological and environmental variables. Because of their sensitive response to CO(2), combined with a high preservation capacity, fossil needles of Tsuga heterophylla, Picea glauca, P. mariana, and Larix laricina have great potential for detecting and quantifying past atmospheric CO(2) fluctuations.     

Immunofluorescent analysis of meiotic recombination in the domestic cat

The paper presents the analysis of the frequency, density, and distribution of recombination sites in the male meiosis of the domestic cat (Felis silvestris catus). The study was carried out using immunofluorescent staining of synaptonemal complex (SC) proteins, centromeric proteins and mismatch repair protein MLH1, a reliable marker of crossingover sites. We mapped 2633 sites of crossing over in 1098 individual autosomes. Based on these data, we estimated the total length of the genetic map of the domestic cat to be 2176 centimorgans. Positive correlation between the length of SC and the number of recombination sites common for mammalians was also found in the domestic cat. It was shown that this species was characterized by the highest density of recombination and the lowest interference in mammals.     

Predicting evolution of floral traits associated with mating system in a natural plant population

Evolution of floral traits requires that they are heritable, that they affect fitness, and that they are not constrained by genetic correlations. These prerequisites have only rarely been examined in natural populations. For Mimulus guttatus, we found by using the Riska-method that corolla width, anther length, ovary length and number of red dots on the corolla were heritable in a natural population. Seed production (maternal fitness) was directly positively affected by corolla width and anther size, and indirectly so by ovary length and number of red dots on the corolla. The siring success (paternal fitness), as estimated from allozyme data, was directly negatively affected by anther-stigma separation, and indirectly so by the corolla length-width ratio. Genetic correlations, estimated with the Lynch-method, were positive between floral size measures. We predict that larger flowers with larger reproductive organs, which generally favour outcrossing, will evolve in this natural population of M. guttatus.     

Growth and mortality of the brushtooth lizardfish (Saurida undosquamis) in Iskenderun Bay (eastern Mediterranean Sea) using length frequency analysis

The growth and mortality of brushtooth lizardfish Saurida undosquamis (Richardson, 1848) in Iskenderun Bay (eastern Mediterranean Sea) were investigated based on length frequency data using the fisat software. Total length of the sampled 4711 fish ranged from 6.0 to 39.0 cm. The von Bertalanffy growth function estimates were L_∞ = 42.00 cm, k = 0.51 year^‐1, t₀ = −0.29 years. Total mortality rate (Z) was computed as 1.76 year^‐1 and the exploitation ratio was 0.51, indicating that the brushtooth lizardfish stock is on the verge being overfished.