Phylogeography of Schizothorax o'connori (Cyprinidae: Schizothoracinae) in the Yarlung Tsangpo River, Tibet

Schizothorax o'connori is endemic to the Yarlung Tsangpo River on the Tibetan Plateau. We assessed the relative impacts of historical and contemporary factors in organizing genetic variation in S. o'connori populations using mitochondrial cytochrome b sequences. We analyzed 191 samples from 11 populations and identified 78 haplotypes. The phylogenetic analyses and analysis of molecular variance all supported the same conclusions of two well-differentiated east-west phylogroups, separated by the Tsangpo Great Gorge. The split between the two clades accounted for 58% of the genetic variance observed among the examined samples. Waterfalls as effective barriers played an important role in shaping the phylogeographical structure of this species. Analyses of migration rates revealed that upstream dispersal was limited crossing waterfalls. Our study revealed substantial spatial and temporal variation in the influence of landscape features on contemporary patterns of genetic structure in S. o'connori. Interglacial range expansions clearly left their mark on contemporary populations above the Tsangpo Great Gorge.

Benthic algae of the Xiangxi River, China

From June 2000 to June 2002, four sites on the mainstem of the Xiangxi River and one site on each of its major tributaries were sampled 16 times each for benthic algae. All total, 223 taxa (most to species and variety levels) were found (193 Bacillariophyta, 20 Chlorophyta, nine Cyanophyta and one Xanthophyta). The diatoms Cocconeis placentula, Achnanthes linearis, and Diatoma vulgare dominated the system, with relative abundance of 33.3%, 18.8%, and 6.4%, respectively. The abundances of all the other taxa were under 5%, and 210 taxa collectively contributed less than 1% of the total abundance. Taxa diversity peaked in winter and reached a minimum in summer. Species richness varied considerably but was not significantly different over time. Maximum algal density occurred in later winter/spring (1.4 x 10(9) ind./m(2)) but was not significantly different from the minimum density, which occurred in August. Chlorophyll a showed similar seasonal fluctuation but also was not significantly different over time. Canonical correspondence analysis demonstrated that water hardness, depth, conductivity, and alkalinity had important influences on variation of epilithic algae in the Xiangxi River system.

移动对象数据库模型、查询语言及实时交通流分析

提出一种移动对象数据库模型——Dynamic Transportation Network Based Moving Objects Database(简称DTNMOD),并给出了DTNMOD中基于移动对象时空轨迹的网络实时动态交通流分析方法.在DTNMOD中,交通网络被表示成动态的时空网络,可以描述交通状态、拓扑结构以及交通参数随时间的变化过程;网络受限的移动对象则用网络移动点表示.DTNMOD模型包含了完整的数据类型和查询操作的定义,因此可以在任何可扩充数据库(如PostgreSQL或SECONDO)中实现,从而得到完整的数据库模型和查询语言.为了对相关模型的性能进行比较与分析,基于PostgreSQL实现了一个原型系统并进行了一系列的实验.实验结果表明,DTNMOD提供了良好的区域查询及连接查询性能.

子午岭60年辽东栎林种子质量与森林更新

辽东栎是我国暖温带落叶阔叶林地带的优势乔木树种之一。通过26年的定位监测,对子午岭辽东栎林种子质量消减、种子萌发与环境条件、实生苗时空分布动态以及对其森林更新的影响等方面进行了初步探讨。结果表明:辽东栎林在子午岭半阳坡、半阴坡和阴坡3种类型中,平均完好种子占种子总数的26.65%;霉变种子占18.72%;动物取食虫蛀种子在阴坡远高于半阴坡和半阳坡,占到种子总数的26.32%;已发芽的种子占其总数的28.31%,且半阴坡>半阳坡>阴坡。每年均有大量种子生产,但在生境与动物的共同作用下,种子数量和质量受到很大影响,多达73.35%的种子失去生命力,直接影响实生苗的形成;地表覆盖物虽能促进种子的快速发芽,但对成苗却是一个物理障碍,影响是负作用的,主要影响因子是地表覆盖物的厚度和含水量;在辽东栎林下虽有一定的实生幼苗分布,但数量极少,平均密度仅为140~120株/hm2,且不同立地条件差异显著,严重影响森林的天然更新。

次生林林窗光环境时空特征及其对下层植被的影响

林窗是森林中经常发生的重要中小尺度干扰，在森林天然更新中起着重要作用。灌木和草本植物通过与乔木幼苗竞争林窗资源（尤其是光）而影响林窗树种更新，因此，研究林窗光环境时空特征及其与下层植被关系对揭示林窗树种更新机制具有重要意义。然而，林窗光环境的时空异质性及有效测量方法的缺乏导致这方面研究很少。本研究提出了林窗立体结构的相片测量法；基于林窗立体结构、坡度和坡向改进了目前广泛用于估测林窗光环境的林窗光指数(gap light index, GLI)模型，并提出了林窗内任意位置最大光照时长(potential sunshine duration, PSD)的计算方法；采用改进的GLI和PSD分析了东北次生林3个不同大小林窗（110，270，510 m2）及其对应的9个模拟林窗中2007年光环境的时空特征；通过在12个人工林窗中连续3年的植被调查，研究了林窗形成后前3年下层木本和草本植物对4个光强梯度的响应，主要结论如下： 1. 林窗立体结构和光环境的测量方法：1) 等角椭圆扇形法计算的林窗面积比目前使用较多的等角多边形法具有更高的精度；2) 半球面影像法可以测量林窗面积和形状，且精度较高；3) 双半球面影像法不仅可以测量林窗面积、形状，还可以测量任意方位林窗边缘木高度；4) 改进的GLI可以快速、精确计算林窗任意位置的直射光和散射光；5) PSD可用于分析林窗光照强度时空特征。 2. 东北次生林林窗光环境时空特征：1) 水平空间结构（地面层）：光环境空间异质性高，最大值位于林窗北部，坡向对光分布格局影响大而对光强影响小，光强随林窗面积的增大和边缘木高度的降低而增加；2) 垂直空间结构（林窗南北轴）：不同高度层光强最大值均位于林窗南北轴中心偏北，南北轴距地面越高光强最大值则越靠近轴中心；光强随距地面高度下降而衰减，最大衰退速率点位于轴中心偏南，靠近该点光强衰退线呈指数形，远离该点则趋于直线形；3) 光成分特征（地面层南北轴）：南坡林窗整个南北轴上直射光大于散射光，北坡模拟林窗南半轴散射光大于直射光，而北半轴相反；南坡林窗中直射光的均值及其变化范围都比其对应的北坡模拟林窗大，然而，坡向对散射光影响不大；南坡林窗和北坡模拟林窗北半轴的全光和直射光均比南半轴大，但散射光没有这种显著的规律；4) 时间特征：不同月份PSD在相同大小林窗中分布格局十分相似，6月份林窗中被光照射面积和PSD均值最大，而10月份最小；各月PSD在南北轴上从南到北逐渐增加，在东西轴上自西向东缓慢增加。 3. 林窗早期下层植被对光强梯度的响应：1) 木本植物物种丰富度随光照强度的增加而增高，且在林窗形成后的第2和3年均存在显著相关性；2) DCA排序第一轴表明，木本植物物种组成仅第1年在4个光强梯度间存在显著差异，而在各年间存在显著差异；草本植物物种组成在4个光强梯度上存在显著差异，但在各年间不存在显著差异；3) 木本植物生物体积(biovolume)随光强梯度升高而增加，而植株密度不存在显著变化；生物体积逐年增加，平均年增长率为20.3%，植株密度逐年下降，平均年减少率为30.0%；4) 草本层盖度和高度在4个光强梯度间均不存在显著差异，但在林窗形成后的第2、3年均显著比第1年大。

长白山阔叶红松林种子雨组成与时空格局

种子雨是森林植物种群更新的主要方式之一，是森林生态系统自我繁衍和恢复的主要手段。为了解长白山阔叶红松林种子雨的组成及其时空变化，参照BCI 50ha 样地技术规范，在长白山阔叶红松林25ha长期监测样地内设置了150个种子收集器，从2006年5月15日到2007年11月8日，每15天收集掉落于收集器中的果实、种子及其相关附属物等。所收到的样品分别鉴定其种类并分为成熟种实、未成熟种实、花絮、果实或种子碎片及其附属物4类，记录各类别的数量，然后分别烘干称重。 研究期间，共收集到11科12属22种木本植物的种子及其它生殖器官残体，包括成熟种实16种，未成熟种实17种，花序12种，翅2种，果实或种子碎片及其附属物10种。累计收集到种实136664粒，其中成熟种实32358粒，占所有种实总数的23.80%。种实数最多的树种是紫椴(Tilia amurensis)，其次为水曲柳(Fraxinus mandshuica)，两个树种种实数占总数的89.54%。种实总重量为3320.93g，其中成熟种实总重量为1242.85g，占37.4%。成熟种实中水曲柳和紫椴的重量最大，其次是色木槭(Acer mono)，假色槭(A. pseudo-sieboldianum)、糠椴(T. mandshuric)和红松(Pinus koraiensis)。 种子雨数量年际变化明显，2006年种子雨密度为1370.25粒/m2，2007年为249.47粒/m2，差异极显著(P<0.001)。但不同年份种子雨的季节动态趋势一致，均有两个明显的大高峰期和一个小高峰期。不同物种种子雨扩散的时间格局大致可以分为“单峰”和“双峰”两种类型，在时间上体现了不同物种的更新策略。 150个收集器均收到了成熟种实，各收集器中的种实数呈偏态分布，种实数在150-250之间的收集器数量最多，共68个，种实数小于50的收集器有5个，种实数大于250的收集器共37个。样地内成熟种实数量及其空间分布差异明显，收集器中种实数在1000个以上的有3个，最多达1511个，聚集分布于样地的西北角；收集器中种实数最少的只有22个种实。种实重量的空间分布与种实数分布一样存在较明显的空间差异，只是差异性相对偏弱一些，且与种实数量的空间分布不一致。

黄土高原旱作小麦化感表达在根际土中的时空异质性研究

采用盆栽试验基于统计学方法,对4种不同品种小麦在4个连续生长期根系表层土壤(0~20cm)化感潜势时空异质性进行了研究。结果表明:不同品种小麦之间根系土壤化感潜势差异极显著(P=0.01),随生育期变化,化感潜力的变异与品种有关,一般15cm为普通小麦耕层土壤化感潜力的转折位点。变异函数分析显示,4种小麦根系土壤化感潜势变化是独立、随机、异质性的。"碧玛1号"、"丰产3号"、"宁冬1号"、"小偃22号"变异函数理论模型分别为线形模型、球型模型、指数模型和高斯模型。其中"小偃22号"的化感背景值和化感潜力空间结构比随生育期增大,导致0~20cm表层土壤化感表达具有高度的空间异质性。4种普通小麦的化感表达均存在时空异质性,其中"宁冬1号"的表层土壤化感表达具有很好的分形特征,其空间分布格局的变异存在尺度依赖。"宁冬1号"化感潜势在表层土壤的空间分布趋于离散表达,化感潜力的有效纵向半径和有效延深半径分别为5cm和14cm。这种时空变异格局可能与根系发育特征、根系翻转运动及土壤环境有关,化感实施过程可能为熵增过程。根系表层土壤化感潜势时空异质性的研究可为监测化感作用实施,定位有效化感物质和合理利用土壤化感潜势提供理论...

黄土丘陵区退耕地植被景观时空变异特征

对黄土丘陵区退耕地植被特征的时空变异性进行了研究。结果表明,不同植被类型区植被特征之间差异不是很显著,仅延安与安塞在物种丰富度之间和安塞与吴旗在物种多样性之间存在较显著的差异(0.01

黄土丘陵区小流域土壤特性时空动态变化研究

以安塞大南沟为例首次在流域范围内对几项土壤表面特性进行连续定位测定,初步研究了其时空动态变化规律。结果表明,大南沟流域内土壤随机糙度、抗剪力和团粒稳定性具有一定的空间变化规律,不同土地利用方式间有显著差异。不同地貌类型农耕地土壤随机糙度、抗剪力无明显差异,而团粒稳定性则差异显著。年内各测定周期间土壤随机糙度、抗剪力和团粒稳定性随时间变异不显著。

Study on spatial pattern of land-use change in China during 1995-2000

It is more and more acknowledged that land-use/cover dynamic change has become a key subject urgently to be dealt with in the study of global environmental change. Supported by the Landsat TM digital images, spatial patterns and temporal variation of land-use change during 1995 -2000 are studied in the paper. According to the land-use dynamic degree model, supported by the 1km GRID data of land-use change and the comprehensive characters of physical, economic and social features, a dynamic regionalization of land-use change is designed to disclose the spatial pattern of land-use change processes. Generally speaking, in the traditional agricultural zones, e.g., Huang-Huai-Hai Plains, Yangtze River Delta and Sichuan Basin, the built-up and residential areas occupy a great proportion of arable land, and in the interlock area of farming and pasturing of northern China and the oases agricultural zones, the reclamation I of arable land is conspicuously driven by changes of production conditions, economic benefits and climatic conditions. The implementation of "returning arable land into woodland or grassland" policies has won initial success in some areas, but it is too early to say that the trend of deforestation has been effectively reversed across China. In this paper, the division of dynamic regionalization of land-use change is designed, for the sake of revealing the temporal and spatial features of land-use change and laying the foundation for the study of regional scale land-use changes. Moreover, an integrated study, including studies of spatial pattern and temporal process of land-use change, is carried out in this paper, which is an interesting try on the comparative studies of spatial pattern on change process and the change process of spatial pattern of land-use change.

Method for calculating ecological water storage and ecological water requirement of marsh

As one of the most typical wetlands, marsh plays an important role in hydrological and economic aspects, especially in keeping biological diversity. In this study, the definition and connotation of the ecological water storage of marsh is discussed for the first time, and its distinction and relationship with ecological water requirement are also analyzed. Furthermore, the gist and method of calculating ecological water storage and ecological water requirement have been provided, and Momoge wetland has been given as an example of calculation of the two variables. Ecological water use of marsh can be ascertained according to ecological water storage and ecological water requirement. For reasonably spatial and temporal variation of water storage and rational water resources planning, the suitable quantity of water supply to marsh can be calculated according to the hydrological conditions, ecological demand and actual water resources.

A Video Quality Assessment Metric Based on Human Visual System

It is important for practical application to design an effective and efficient metric for video quality. The most reliable way is by subjective evaluation. Thus, to design an objective metric by simulating human visual system (HVS) is quite reasonable and available. In this paper, the video quality assessment metric based on visual perception is proposed. Three-dimensional wavelet is utilized to decompose video and then extract features to mimic the multichannel structure of HVS. Spatio-temporal contrast sensitivity function (S-T CSF) is employed to weight coefficient obtained by three-dimensional wavelet to simulate nonlinearity feature of the human eyes. Perceptual threshold is exploited to obtain visual sensitive coefficients after S-T CSF filtered. Visual sensitive coefficients are normalized representation and then visual sensitive errors are calculated between reference and distorted video. Finally, temporal perceptual mechanism is applied to count values of video quality for reducing computational cost. Experimental results prove the proposed method outperforms the most existing methods and is comparable to LHS and PVQM.

Variability of surface circulation in the South China Sea from satellite altimeter data

11-year satellite altimeter sea surface height (SSH) anomaly data from January 1993 to December 2003 are used to present the dominant spatial patterns and temporal variations of the South China Sea (SCS) surface circulation through Empirical Orthogonal Function (EOF) analysis. The first three EOF modes show the obvious seasonal variations of SSH in the SCS. EOF mode one is generally characterized by a basin-wide circulation. Mode two describes the double-cell basin scale circulation structure. The two cells were located off west of the Luzon Island and southeast of Vietnam, respectively. EOF mode three presents the mesoscale eddy structure in the western SCS, which develops into a strong cyclonic eddy rapidly from July to September. EOF mode one and mode three are also embedded with interannual signals, indicating that the SCS surface circulation variation is influenced by El Nino events prominently. The strong El Nino of 1997/98 obviously changed the SCS circulation structure. This study also shows that there existed a series of mesoscale eddies in the western SCS, and their temporal variation indicates intra-seasonal and interannual signals.