Spatial error propagation when computing linear combinations of spectral bands: The case of vegetation indices

The collection of accurate and timely information on land use, crops, forest and vegetation are increasingly based on remote sensing spectral measurements produced by satellites. The most recent spacecrafts like the Earth Observing 1 (EO-1) produce a rich source of information being endowed with hyperspectral sensors that can provide up to 200 or more channels. In many instances such a multivariate signal has to be reduced to just one single value per pixel representing a particular characteristic of land. Linear combinations of bands are the general form of many indices. Since each individual image used to construct indices contains errors, when combined they produce a propagation of errors, a process that can distort a final output map. In this paper we measure the extent of error propagation when building linear vegetation indices. We consider three types of indices: the difference vegetation index (DVI), selected Kauth-Thomas indices (SBI, GVI and WET), and principal components, using benchmarking examples taken from the remote sensing literature. The main implication emerging from these examples is that the SBI and the first principal component are the indices more prone to error propagation. The formalization presented here allows a user to derive measures of error propagation in cases where technical characteristics of a sensor and physical characteristics of a landscape are known. These results can help a user to choose between alternative vegetation indices, and to associate a measure of reliability with such indices.     

Evaluating stream restoration projects

River and stream restoration projects are increasingly numerous but rarely subjected to systematic postproject evaluation. Without conducting such evaluation and widely disseminating the results, lessons will not be learned from successes and failures, and the field of river restoration cannot advance. Postproject evaluation must be incorporated into the initial design of each project, with the choice of evaluation technique based directly upon the specific project goals against which performance will be evaluated. We emphasize measurement of geomorphic characteristics, as these constitute the physical framework supporting riparian and aquatic ecosystems. Techniques for evaluating other components are briefly discussed, especially as they relate to geomorphic variables. Where possible, geomorphic, hydrologic, and ecological variables should be measured along the same transects. In general, postproject monitoring should continue for at least a decade, with surveys conducted after each flood above a predetermined threshold. Project design should be preceded by a historical study documenting former channel conditions to provide insights into the processes suggest earlier, potentially stable channel configurations as possible design models.     

Ski slope vegetation in central Honshu,Japan

To determine the status of the vegetation of ski slopes in northeastern-central Honshu, Japan, 94 plots (2×2 m) were set up on five ski areas (101–520 m elevation) which were established between 1945 and 1985 by forest clear-cutting, land modification, and seeding. Six vegetation types were recognized: five grasslands dominated byDigitaria adscendens, Miscanthus sinensis, Zoysia japonica, Festuca rubra, andPteridium aquilinum var.latiusculum, respectively, and bare areas of very low to no vegetation cover. Of the dominant species,F. rubra is the only introduced species; it does not, however, appear to persist. After the introduced grassland declinesM. sinensis or annual grasslands develop. Native plants, especially woody species, can establish inM. sinensis grassland but do not establish in the other grasslands. It is concluded that the introduction of exotic species is inappropriate to maintain ski slope vegetation, and the development ofM. sinensis grassland is desirable to promote natural revegetation.     

AQUATIC HABITAT CONDITION INDEX,STREAM TYPE,AND LWESTOCK BANK DAMAGE IN NORTHERN NEVADA1

ABSTRACT: The quality of stream habitat varies for a variety of natural and anthropogenic reasons not identified by a condition index. However, many people use condition indices to indicate management needs or even direction. To better sort natural from livestock influences, stream types and levels of ungulate bank damage were regulated to estimates of aquatic habitat condition index and stream width parameters in a large existing stream inventory data base. Pool/riffle ratio, pool structure, stream bottom materials, soil stability, and vegetation type varied significantly with stream type. Pool/riffle ratio, soil and vegetation stability varied significantly with ungulate bank damage level. Soil and vegetation stability were highly cross-correlated. Riparian area width did not vary significantly with either stream type or ungulate bank damage. Variation among stream types indicates that riparian management and monitoring should be stream type and reach specific.     

Transforming the Response in Experiments Based on Percentage Cover of Vegetation

Many ecological studies use popular variables such as percentage cover of the vegetation to assess the effects of different treatments or environmental management or conditions. Starting with sparse vegetation, the growth in percentage cover is likely to be sigmoidal, and, unless repetitive cover is measured, it will have an upper asymptote of 100%. If the initial cover values under different treatments or management regimes are not equal, then the different growth rates due to the unequal starting values will be confounded with the different treatments.A family of suitable growth curve models can be fitted to the data arising under different treatments, so that one or more of the interpretable fitted parameters of the model can be considered as "responses" to the different treatments. These responses can be analysed to compare the effects of different treatments or environmental conditions, using either parametric or non-parametric methods. The suggested approach is illustrated by application to a particular data set from the literature. The implications for the design of field studies and for the analysis of other vegetational variables are discussed.     

城市景观水体的污染控制和修复技术

分析了城市景观水体的特点及其水质污染状况,表明景观水体处理的必要性和迫切性。综述近年来景观水体的污染控制和修复技术及其机理。提出城市景观水体污染控制的关键应将污水处理的常规生物处理技术与生态处理技术有效结合,以合乎城市生态建设的要求。     

Effects of the <Emphasis Type="Italic">Astacus astacus</Emphasis> L. Population on Biomass of Macrophytes in a Fresh Water Body

In experiments performed in aquariums, the daily consumption of Chara vulgaris alga by crayfish (Astacus astacus L.) has been determined. These quantitative data have been used to make a prognosis of the effect of the A. astacus population on the biomass of macrophytes in Lake Berezovo (Pskov oblast). The density of the crayfish population and the biomass of higher aquatic vegetation in the lake have been determined in field studies. Extrapolation of the results of laboratory experiments to a natural water body has shown that crayfish are capable of controlling no less than 40% of submersed macrophytes in the area used by their population.__________Translated from Ekologiya, No. 4, 2005, pp. 300–305.Original Russian Text Copyright © 2005 by Kholodkevich, Shumilova, Fedotov, Zhuravlev.     

利用 TM1∶10万卫星图象研究四川富顺——南溪地区土地利用现状及开发途径

土地资源是国家基本资源之一。土地利用状况反映在一个地区土地开垦的指数、土地利用方向、土壤类型、水土流失、植被及覆盖面积、水体类型及覆盖面积等方面,而各种土壤、植被和水体,对日光或不同波长电磁波,有不同的反射、透射和发射特征,在卫片上表现为不同的信息。利用 TM 图象,可区分地表各种土壤、植被和水体的分布,掌握一个地区土地利用现状,制定正确的开发途径。     

云南省姚安县水土保持生态修复措施的效益研究

姚安县是“长江上中游水土保持生态修复工程”项目县，在该县的洋派河小流域修筑同样面积的4个径流小区，采取不同的生态修复措施，分别为对照地（即撂荒地）、人工补植地（人工种植澳洲金合欢）、封禁措施地、坡耕地（人工耕种的坡耕地）4种，修复中控制人类活动对自然的过度干扰和侵害，充分利用生态自我恢复能力，大面积实施生态自我修复，提高植被覆盖度减少水土流失。从植被重要值，土壤理化性质，土壤的保土保水量以及经济效益等方面进行对比分析计算，研究结果如下：生态修复后人工补植地和封禁地:①植被恢复迅速，植被覆盖度达到60%以上；②土壤的结构得到改善，封禁地全N含量最高，补植地当人工恢复达到一定年限后含N量也会增加；③土壤的保持水土量增加；④生态修复后，经济效益得到明显提高。