Remote sensing of grassland–shrubland vegetation water content in the shortwave domain

This study compares the ability of spectral approaches operating in the shortwave optical domain to predict absolute and relative vegetation water content (AWC and RWC, respectively) across northern prairie grassland–shrubland. We collected vegetation water content and spectral radiometer data over plots of comparable ground resolution (0.5 m) at seven field sites in the Canadian mixed grass prairie in June 2004. We then aggregated observations to scale these data “up” to an observational scale consistent with that of Landsat-TM satellite imagery (30 m). This allowed us to assess abilities of three spectral approaches to predict AWC and RWC at both observational scales. These approaches were: individual vegetation indices, a combination of spectral bands and a combination of spectral derivatives. Our results showed that (a) the band-combination approach provides the most accurate and precise estimates of AWC and RWC at both 0.5 and 30 m sampling resolutions; (b) the combination of bands providing the greatest predictive abilities are those that emphasize the contrast in reflectance between the NIR and SWIR spectral regions; (c) the band-combination approach predicts AWC with much greater accuracy and precision than RWC and (d) the predictive ability of the band-combination approach decreases only slightly when plot-level data are aggregated to a 30 m sampling resolution. These results are generally consistent with the results of other studies and with theory. While our results suggest that simple spectral methods (e.g. linear band-combinations or indices) are good predictors of AWC over grazed and ungrazed grassland–shrubland landscapes at plot- and Landsat spatial resolutions, they are less encouraging for the estimation of RWC. Despite their good predictive abilities, the temporal and geographical portabilities of the spectral approaches for estimating AWC must be further assessed before they can be considered reliable and robust predictive tools. Thus, the further testing of these techniques over larger geographical extents is required.     

青藏高原中北部地貌变形的遥感表征及其生态地质学意义

遥感地质特征显示青藏高原北部,在澜沧江—温泉与东昆仑南缘—阿尼玛卿两条岩石圈断裂之间区域存在着4个正交叠加在早期北西—南东向构造地貌上的北东—南西向第四纪坳陷。其中西羌塘北部坳陷和长江源坳陷的地堑式裂陷地貌特征明显,而黄河源坳陷和若尔盖坳陷发育程度较低,但它们均是在青藏高原大陆构造变形的统一动力学背景下,地貌发生东西向伸展变形的产物。进一步研究表明,它们的形成不仅与青藏高原中南部所发育的近南北向裂谷具有同样的动力学意义,而且已成为影响该地区生态系统的主要因素。     

中国地磁台网的K指数测量结果分析

Ｋ指数以０,１,……,９的数字分为１０级,以３小时为一时段,简单、直观、清晰地表示出地磁场受太阳微粒辐射而形成的扰动变化的程度。Ｋ指数测量是地磁台日常工作的重要内容之一。正确地区别Ｋ变化与非Ｋ变化是测量Ｋ指数的基本要求和关键所在。我国地磁台站从１９８９年开始用规则日变化ＳＲ代替“铁曲线”来识别Ｋ变化与非Ｋ变化,使测量方法与国际上的通行做法相一致。本文通过对我国地磁台站的Ｋ频次分布统计指出,在采用新     

SZGC—93型数字工程地震仪

ＳＺＧＣ－９３型数字工程地震仪是专为工程地震勘探而研制的。经过两年多的实际生产使用表明：该仪器精度高、性能稳定、操作方便。是一种实用性较好的野外专用设备。本文介绍了它的组成：论述了其各个单元电路的工作原理及主要技术指标;最后说明了该设备两年多来的实际应用成果。     

Integrative Monitoring Analysis Aiming at the Detection of Spatial and Temporal Trends of Metal Accumulation in Mosses

Goal and Scope. The UNECE heavy metals in Mosses Surveys provide data on the accumulation of metals in naturally growing mosses throughout Europe. Using Germany as an example, this article concentrates on the elaboration and application of methods of data analysis that are necessary for a comprehensive interpretation of spatial and temporal trends in metal accumulation.Methods and Results. The sampling of mosses, and the chemical analysis of Cr, Cu, Fe, Ni, Pb, Ti, V and Zn in 1990, 1995 and 2000 are summarized briefly. The variogram analyses detect distinct autocorrelation structures in the sample data which may consequently be estimated for all sites in Germany without monitoring metal accumulation by means of ordinary kriging. A procedure for the geostatistical detection of spatial outliers was developed and applied and, after the elimination of the spatial outliers, several measurements were seen to indicate an adequate quality of the geostatistical estimations. The cluster analyses of the z-transformed estimation data result in a nominal multi-element index that indicates regional metal accumulation types over time. Percentile statistics serve for computation of an ordinal, scaled, multi-element accumulation index which is spatially differentiated over time in terms of multivariate, statistically defined ecoregions. The integrative statistical analysis reveals, from 1990 to 2000, that the metal accumulation declines up to 80% in some of the ecoregions. Hot spots of metal accumulation are mapped and interpreted by means of metadata analysis.Conclusions. Dot maps depict the spatial structure of the metal accumulation without spatial bias. This information, detailed with respect to metal species and space, should be generalized for better supporting the interpretation. The combination of geostatistical analysis and estimation, percentile and multivariate statistics is suitable for the calculation of indices that serve for a comprehensive mapping of metal accumulation in the ecoregions over time, for quantifying the bias of the surface estimation, and for mapping spatial outliers and hot spots of metal accumulation.     

Geomorphic analysis of large alluvial rivers

Geomorphic analysis of a large river presents particular challenges and requires a systematic and organised approach because of the spatial scale and system complexity involved. This paper presents a framework and blueprint for geomorphic studies of large rivers developed in the course of basic, strategic and project-related investigations of a number of large rivers. The framework demonstrates the need to begin geomorphic studies early in the pre-feasibility stage of a river project and carry them through to implementation and post-project appraisal. The blueprint breaks down the multi-layered and multi-scaled complexity of a comprehensive geomorphic study into a number of well-defined and semi-independent topics, each of which can be performed separately to produce a clearly defined, deliverable product. Geomorphology increasingly plays a central role in multi-disciplinary river research and the importance of effective quality assurance makes it essential that audit trails and quality checks are hard-wired into study design. The structured approach presented here provides output products and production trails that can be rigorously audited, ensuring that the results of a geomorphic study can stand up to the closest scrutiny.     

Drought monitoring

Drought detection, monitoring and indices are closely related to its definition. The specific definition chosen for a particular drought analysis will affect the procedures one uses in drought detection and monitoring. The traditional Palmer Drought Severity Index (PDSI) has been proven to be ineffective in regions of predominantly irrigated agriculture.The recently developed ALERT (Automated Local Evaluation in Real Time) system is proposed for use in monitoring the spatial and temporal variations of drought in real time. The ALERT system uses standardized instruments, radio frequencies, software and hardware. It was originally developed as a flash flood waming system by local flood control districts and the National Weather Service. However, now it has expanded to over 100 other uses in the areas of natural and man-made disaster detection and warning. The successful ALERT system indicates the need for the continued development of a national drought monitoring index that is applicable to a wide range of climate, hydrologic and water resource environments.     

Error in polygon overlay processing of geomorphic data

Predictive models for calculating sediment yield and discharge require accurate areal data. Such models may be unrealistic when using digitized data given the potential error involved in compiling and digitizing thematic polygon maps. The estimation of boundary variability for digitized polygon maps of a 0·34 km² area of badlands in Dinosaur Provincial Park, Alberta shows the effects of positional errors introduced during mapping and digitizing processes. Polygon overlay of maps of surface features and slopes produced high frequencies of very small polygons and some unlikely combinations of slopes and surface features, and decreased reliability in areal measurements in the composite map. At an epsilon band width of 0·7 m, a reasonable estimate of boundary variability, 31·7 per cent of the resultant overlaid map can be considered unreliable.     

分形理论及其在地貌学中的应用──分形地貌学研究综述及展望

本文简介了分形的有关基本概念,回顾了分形理论在海岸、流水、喀斯特地貌等多种地貌类型和流域地貌发育的形态研究中,以及在地貌过程研究中的应用的新近成果,并提出了今后分形地貌学研究的五个主要方面.