黑河上中游流域植被时空演变规律及其对水热条件的响应特征分析

基于黑河上中游流域1999—2010年SPOT NDVI旬数据及气温、降水旬数据,采用趋势分析和时滞互相关法,对研究区内植被的时空变化规律及其对水热条件的响应特征进行了分析.结果表明:1)1999—2010年,黑河流域上游植被覆盖状况优于中游,中游除张掖市及酒泉市存在人工植被外,其他区域基本不存在人工植被;2)在1999—2010年间黑河上游流域大部分地区的植被均表现出明显退化趋势,中游流域的植被整体表现为轻度退化;3)黑河上中游流域的植被受气温的影响大于降水,而对降水的响应更为迅速.不同类型的植被对气温、降水的响应速度不一.     

老哈河流域地表植被覆盖对干旱的响应

在原有的帕尔默旱度模式中嵌套双源蒸散发能力计算模型和混合产流模型,采用老哈河流域内及周边的15个气象站资料修正模型参数,构建可用于变化环境下植被-干旱响应关系分析并适用于我国北方地区的机理性旱度模式,计算研究区域各栅格逐月的帕尔默干旱指标,通过分析和建立归一化植被指数与帕尔默干旱指标的关系来定量评价老哈河流域不同植被类型归一化植被指数对气象干旱的响应.研究结果表明:(a)在植被生长期的开始和结束阶段,干旱对植被的影响较小;在植被生长期的中间月份,干旱对植被影响较大,其中6月份是研究流域植被的水分敏感期.(b)不同的植被类型受干旱影响的程度不同,干旱对灌丛和草地的影响大于对林地的影响.(c)带虚拟变量的回归模型能够合理地描述季节性的影响,模型的模拟精度较高,因此在考虑季节影响的情况下归一化植被指数可以用于干旱监测.     

2002—2011年河北省植被LAI时空变化特征

利用2002—2011年EOS/MODIS数据的植被指数产品MOD15A2和植被类型产品MCD12Q1及气象观测资料,对比分析了7种典型植被的叶面积指数(LAI)的变化趋势,探讨了河北省植被生长季(5—10月)LAI的时空变化特征及其与气温和降水等影响因子的关系。结果表明:河北省植被生长季年均LAI变化在1.0~1.3之间,2008年最高(1.286),2002年最低(1.066);多年平均LAI的空间分布表现为位于东北部的承德地区最高(可达5.0以上),位于西北部的张家口地区最低(小于0.5);7种典型植被生长季年均LAI差异很大,LAI从高到低依次为阔叶林(2.765)、混交林(2.535)、灌丛(1.867)、稀树草原(1.476)、针叶林(1.331)、农田(1.116)和草原(0.967)。显著影响LAI变化的因子有降水、气温、地形、植被类型及其物候期等,且各因子对植被LAI的影响程度不同。     

基于PROSPECT+SAIL模型反演叶面积指数的较强适用性植被指数的筛选

基于PROSPECT+SAIL植被辐射传输模型,通过控制不同的植被生化变量、地表参数和土壤光谱参数建立光谱数据集,定量地分析了归一化植被指数(NDVI)、比值植被指数(SR)、土壤调节植被指数(SAVI)等10种常用的植被指数(VIs)对叶面积指数(LAI)的响应.利用敏感性函数定量地筛选出具有较强适用性的转换型土壤调节植被指数(TSAVI).在此基础上,分别建立了TSAVI及常用植被指数NDVI反演LAI的模型.以张掖市南部地区的TM影像为数据源,进行了LAI的反演,并利用黑河生态水文遥感试验获得的中游LAI数据集对模型进行精度评价.结果表明:TSAVI–LAI模型最佳拟合关系为指数形式,其反演结果与LAI实测值的偏差最小(0.200),R2最大(0.686),RMSE最小(0.397).TSAVI可以作为较强适用性植被指数来进行LAI的反演.     

几种典型地表类型反照率时序变化特征及其参数化研究

地表反照率对地表能量平衡、气候模式和全球变化研究具有重要的作用.受季节和下垫面影响,地表反照率呈现一定的时序变化特征,刻画这种变化特征可以为地表反照率估算提供背景信息,有利于提高反照率反演精度.目前已有许多研究致力于分析地表反照率时序变化特征和影响因素,但分析仅限于某一特定区域的一种或几种地表类型,同时对反照率与叶面积指数(leaf area index,LAI)、归一化植被指数(normalized difference vegetation index,NDVI)等影响因子的相关性还缺少参数化研究.本文使用美国通量观测网络AmeriFlux观测数据资料,利用该网络站点分布范围广、地表类型丰富的特点,选取其中代表性较强的站点观测数据,分析了落叶阔叶林、常绿针叶林、草地、农田4种典型植被类型地表反照率的时序变化特征.发现各植被地表类型反照率呈现"U"形年内变化特征,在植被生长季,落叶阔叶林、农田、草地3种地表类型反照率均先减小再增大后减小,而常绿针叶林地表反照率变化不明显.利用统计方法分别建立了地表反照率与LAI和NDVI的参数化模型,结果显示:2种估算地表反照率的参数化模型均能较好反映植被生长过程中地表反照率的变化特征,与地面实测数据相比,计算得到的地表反照率具有较高的精度;2种参数化模型估算得到的反照率一致性好,相关系数为0.721 9.该参数化方案可为地表反照率的进一步估算提供背景参考模型.     

黑河流域地下水埋深与气候变化对植被覆盖的影响研究

植被是联结土壤、大气、水分的自然纽带,在一定程度上,植被变化能在全球变化研究中充当"指示器"的作用.黑河流域位于我国西北干旱地区,气候变化敏感,以黑河流域为研究区,采用1998—2008年Spot-Vegetation的NDVI数据,以同时期的气象数据和区域地下水埋深数据为基础,通过ENVI、Arcgis等软件对数据进行统计分析,利用多元统计模型分析植被指数NDVI与年均温、年地下水埋深之间的定量关系,得出如下结论:1)黑河流域植被覆盖呈上升趋势,其中春季增加趋势最大;在空间分布上,黑河流域上中游的张掖、金塔等地区植被覆盖增加趋势明显,植被覆盖下降的区域主要在下游地区.2)黑河流域的年均地下水水位整体上呈下降趋势,地下水位埋深由年均3.09m上升到4.67m,其中地下水埋深较深的位置主要集中在上游,处于张掖市张掖农场周围,下游地区埋深普遍较浅.3)植被覆盖指数NDVI与温度成正相关,与地下水位埋深呈现负相关,综合分析NDVI变化趋势与气候变化和地下水之间的关系,建立三者之间的定量关系.本研究为定量评价由植被覆盖为主要表征的区域生态环境状况提出了科学的依据.     

黑河流域植被FAPAR时间序列模拟分析与预测

以2001?2010年黑河全流域MODIS FAPAR产品为研究对象, 结合同期MODIS土地覆盖分类产品, 提取FAPAR随时间变化的趋势项、周期项及残差, 对趋势和周期成分建立自回归模型, 并结合卡尔曼滤波方法过滤反演误差噪声, 获取高质量的FAPAR时间序列数据。在此基础上, 进一步分析黑河全流域不同植被类型FAPAR时间序列的变化差异, 并选取具有不同植被季相变化特征的研究区, 利用该方法预测某一时刻该区域各像元的FAPAR。结果表明: 黑河流域不同类型植被的FAPAR都具有明显的季节变化特征; 受气候等条件的影响, 流域不同区域的同种植被存在差异。提出的时间序列分析与预测方法适用于不同植被类型, FAPAR预测结果与MODIS当日产品较为相似, 预测误差约为3%。     

皇甫川流域不同土地利用对群落结构和植物多样性的影响

分别用多样性指数、丰富度指数、均匀度指数和群落的结构特征对皇甫川流域五分地沟试验示范区内不同土地利用类型的植被状况进行分析.结果表明:(1)10种土地利用类型多样性指数顺序为:白榆林天然草地中间锦鸡儿灌丛小叶杨林撂荒地油松林沙棘灌丛沙柳灌丛人工草地侧柏林.(2)均匀度指数和丰富度指数分别是侧柏林和中间锦鸡儿灌丛高于其它土地利用类型.天然草地和中间锦鸡儿的群落结构比其它土地利用类型的群落结构复杂.综合植物多样性指数和植物群落的结构特点,天然草地、中间锦鸡儿灌丛和白榆林有利于物种多样性保护,在植被恢复过程中应加大对天然草地的保护并扩大中间锦鸡儿和白榆林的种植面积.     

基于RS和GIS的黑河流域景观生态综合评价

利用2006年Landsat TM影像、土壤数据、DEM数据及气象资料,基于RS和GIS技术,针对土地沙漠化、土壤盐渍化和水土流失等主要生态问题,选取植被类型、干旱指数、地形、降水侵蚀力值等8个指标,建立了景观生态综合评价模型,评价了黑河流域景观生态质量.结果表明:(1)黑河流域景观生态综合指数平均值为5.870,以3级和4级为主体,占总面积的68.65%,景观生态质量一般;(2)景观生态质量水平分布表现出明显的区域差异,呈现出流域上游最好、中游次之、下游最差的特点,从行政范围来看,民乐县、山丹县、甘州区、祁连县和肃州区较好,额济纳旗、金塔县、嘉峪关市等则较差.     

黑河流域上中游植被蒸散发时空演变趋势及其影响因子分析

结合遥感产品及气象站点数据,分析了黑河上中游2001—2012年蒸散发(ET)时空演变规律及分布格局,对比分析地表温度(LST)、空气温度、降雨、水汽压、相对湿度、风速6个环境因子对ET的影响.结果显示,2001—2012年时间段黑河上中游年ET有略微下降趋势(R2=0.01),12a的年平均ET为470.3mm,年ET最小值出现在2001年,2002年发生了"突增",2003—2007年呈现上下波动趋势,2008年发生了"突降",2008—2012年呈现了显著上升的趋势(R2=0.97),同时上、中游区域年平均ET呈不同的变化趋势.对整个研究区域生长季内ET呈显著影响的因子为降雨、空气温度和水汽压.同时,由于气象条件及地表供水条件的时空变化,针对不同区域及不同植被类型,影响ET变化的主要环境因子也发生变化,除空气温度和水汽压之外,农田ET对能量供给的太阳总辐射变化较为敏感,草地ET对水分供给的降雨变化较为敏感,林地ET则对表征大气湍流情况的风速变化较为敏感,而灌木ET对地表温度的变化较敏感.     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

海南岛地体及其毗邻陆缘晚中生代—新生代古地磁研究和构造演化

本文叙述了对海南岛及其毗邻大陆边缘白垩纪到第四纪地层岩石进行古地磁研究的全部工作过程。通过分析岩石中剩余磁矢量的磁偏角及磁倾角的变化,提出海南岛白垩纪以来经历的构造演化模式如下:早期伴随顺时针旋转而向南迁移,后期伴随逆时针转动并向北运移。联系该地区及邻区的地质、地球物理资料,对海南岛上述的构造地体运动提出以下认识:北部湾内早期有一拉张作用,主要是该作用使湾内地壳显著伸长减薄,形成北部湾盆地。从而导致了海南岛的早期构造运动,而海南岛后期的构造运动则主要是受南海海底扩张的影响。海南地体运动规律的阐明对于了解北部湾油气盆地的形成演化有重要的理论和实际意义。     

Exciton Seebeck in Molecular Systems

Various applications relevant to the exciton dynamics,such as the organic solar cell,the large-area organic light-emitting diodes and the thermoelectricity,are operating under temperature gradient.The potential abnormal behavior of the exicton dynamics driven by the temperature difference may affect the efficiency and performance of the corresponding devices.In the above situations,the exciton dynamics under temperature difference is mixed with     

Achieving Unusual States of Matter Under High Pressure

The elongation method,originally proposed by Imamura was further developed for many years in our group.As a method towards O(N)with high efficiency and high accuracy for any dimensional systems.This treatment designed for one-dimensional(ID)polymers is now available for three-dimensional(3D)systems,but geometry optimization is now possible only for 1D-systems.As an approach toward post-Hartree-Fock,it was also extended to     

《Chinese Science Bulletin》SUBJECT INDEX TO VOLUME 59(2014)

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An on-line scaling method for improving scalability of a database cluster

The explosive growth of the Internet and database applications has driven database to be more scalable and available, and able to support on-line scaling without interrupting service. To support more client's queries without downtime and degrading the response time, more nodes have to be scaled up while the database is running. This paper presents the overview of scalable and available database that satisfies the above characteristics. And we propose a novel on-line scaling method. Our method improves the existing on-line scaling method for fast response time and higher throughputs. Our proposed method reduces unnecessary network use, i.e. , we decrease the number of data copy by reusing the backup data. Also, our on-line scaling operation can be processed parallel by selecting adequate nodes as new node. Our performance study shows that our method results in significant reduction in data copy time.     

An improved R-tree based on childnode''s probability

R-Tree is a good structure for spatial searching. But in this indexing structure,either the sequence of nodes in the same level or sequence of traveling these nodes when queries are made is random. Since the possibility that the object appears in different MBR which have the same parents node is different, if we make the subnode who has the most possibility be traveled first, the time cost will be decreased in most of the cases. In some case, the possibility of a point belong to a rectangle will shows direct proportion with the size of the rectangle. But this conclusion is based on an assumption that the objects are symmetrically distributing in the area and this assumption is not always coming into existence. Now we found a more direct parameter to scale the possibility and made a little change on the structure of R-tree, to increase the possibility of founding the satisfying answer in the front sub trees. We names this structure probability based arranged R-tree (PBAR-tree).     

Integrating GIS Web services based on mediating architecture

The geographic information service is enabled by the advancements in general Web service technology and the focused efforts of the OGC in defining XML-based Web GIS service. Based on these models, this paper addresses the issue of services chaining,the process of combining or pipelining results from several interoperable GIS Web Services to create a customized solution. This paper presents a mediated chaining architecture in which a specific service takes responsibility for performing the process that describes a service chain. We designed the Spatial Information Process Language (SIPL) for dynamic modeling and describing the service chain, also a prototype of the Spatial Information Process Execution Engine (SIPEE) is implemented for executing processes written in SIPL. Discussion of measures to improve the functionality and performance of such system will be included.