景观分类与评价的生态原则

在分析景观定义的基础上 ,概述了景观分类的生态学原则 ,提出了自然、经营和人工等不同景观类型的特性和研究重点 ,并对景观的独特性、多样性、功效性、宜人性及美学价值的评价进行了探讨 .文章还介绍了景观保护的概念和实践     

Ecological rehabilitation of the lowland basin of the river Rhine (NW Europe)

In this paper, the status of ecological rehabilitation of the Dutch lowland basin of the river Rhine has been reviewed. The historical perspective, mainly with regard to river regulation measures in the past, is given. The lower river Rhine comprises a man-dominated, strongly regulated catchment, polluted water and sediments, and annihilated and deteriorated ecosystems. During the past 25 years, the water quality and, to a lesser extent, the sediment quality, has improved considerably, hence leading to improvement of biotic diversity. The rehabilitation of lost and disturbed ecosystems started some 15 years ago. The non-refutable boundary conditions for restoration projects are protection against flooding and transport by cargo ships. Holistic ecological theories to promote river catchment management are available, but the rehabilitation projects dominantly rely on local and regional planning policies. The use and application of ecological criteria are increasingly playing a role in rehabilitation schemes. Ecological rehabilitation mainly focuses on nature conservation and restoration strategies, i.e. exploiting the hydrodynamic and morphodynamic potentials of the flowing river, and introducing a semi-natural grazing regime by large herbivores. Particularly the creation of new secondary channels contributes to the restoration of riverine habitat diversity and heterogeneity, and hence to the species diversity. The assessment of a number of rehabilitation projects has led to the conclusion that no general statement can be given concerning `success' or `failure' of specific restoration measures. The overall balance of 14 assessed projects out of approximately 30 running projects is positive. The highly dynamic river Waal offers the best possibilities for the restoration of natural sandy levees and back swamps. It will be very difficult to rehabilitate the hardwood floodplain forests under the present management conditions. Further recovery of the river biota depends on continued decrease of pollution, an increase of morphological dynamics, and the development of the original natural habitats.     

Analysis and classification of vegetation based on family composition

Summary The distributions of 54 plant families in 105 samples were studied to determine their indicator value in the vegetation of the Pacific Northwest. Families may be characteristic of particular environments or geographic conditions or they may distinguish between sets of samples. Principal components analysis, numerical classification, and stepwise discriminant analysis were used in this study.Principal components analysis identifies a family if it is common or dominant and has a distribution concentrated at one extreme of an axis of variation. Families with consistent patterns of distribution are useful in distinguishing between groups of samples previously created by numerical classification methods.Twenty-three families that contain environmental, successional, or geographical information were identified according to one or more methods.Nomenclature for species names in Washington follows Hitchcock & Cronquist (1973). Species names from the Alsek River, Yukon Territory, follows authorities cited by Douglas (1974).This study was funded in part by the U.S. National Science Foundation and by the Graduate School, University of Washington. We thank A.R. Kruckeberg, M.J. Cushman, R.A. Lerner, V. Seymour and A.F. Watson for thoughtful comments and stimulating discussion and R.W. Fonda, R.T. Kuromoto, G.W. Douglas and J.A. Belsky for the use of their data.     

Oligochaetes of the River Rhine. Preliminary records

Oligochaetes from bottom surveys of the Rhine River from Lake Constance to the Dutch border were identified to species in order to specify the response of communities to river pollution and impoundment. In these preliminary surveys, 37 species of Naididae and Tubificidae were determined, far more than the few easily identifiable species normally identified from such surveys. These studies will allow comparison to the oligochaete populations of other large European river systems.     

A Bayesian method for classification of images from electron micrographs

Particle classification is an important component of multivariate statistical analysis methods that has been used extensively to extract information from electron micrographs of single particles. Here we describe a new Bayesian Gibbs sampling algorithm for the classification of such images. This algorithm, which is applied after dimension reduction by correspondence analysis or by principal components analysis, dynamically learns the parameters of the multivariate Gaussian distributions that characterize each class. These distributions describe tilted ellipsoidal clusters that adaptively adjust shape to capture differences in the variances of factors and the correlations of factors within classes. A novel Bayesian procedure to objectively select factors for inclusion in the classification models is a component of this procedure. A comparison of this algorithm with hierarchical ascendant classification of simulated data sets shows improved classification over a broad range of signal-to-noise ratios.     

Monitoring the toxicity of organic compounds dissolved in Rhine water

Organic concentrates of the River Rhine water were tested for toxicity with a 15 minute test (Microtox^TM) on luminescent bacteria (Photobacterium phosphoreum, Bacteria). A total number of 18 stations in the Dutch lower Rhine area were sampled five times with an interval of one month (April 1988–August 1988), whereas two stations located the most apart (Lobith and Maassluis) were sampled with two-week intervals in the period between January and October. The river samples were concentrated by neutral absorption on XAD resins, followed by elution with acetone. Toxicity is expressed on a relative scale. The relative toxicity is in the range of approximately 3 to 18, which means that the organic toxicants present in Rhine water had to be concentrated between 55-and 330-fold. During transport in The Netherlands, the dissolved organic toxicity contained in the water of the River Rhine decreases gradually, either as a consequence of degradation, or by adsorption to newly formed particulates. In the industrialized areas of the lower Rhine in The Netherlands a slight, but temporary increase of toxicity is observed.Since water quality improved strongly with respect to inorganic (heavy metal) pollution, the organic toxicity reflects the actual pollutional status more closely than in former days.The speed and simplicity of the combination of XAD concentration and Microtox toxicity determination enables large-scale monitoring studies on organic toxicants in moderately polluted surface water.     

On the potential of basing an ecological typology of aquatic sediments on the nematode fauna: An example from the River Rhine

In Dutch river sediments nematodes can occur in high numbers; azoic seediments are as yet unknown. In aseries of samples takenj from the river Rhine and its estuaries, nematode density varied from 5.000 to 1.7 million per square metre, and about 50 genera were identified. Anoxic conditions appear to have less influence on the nematode abundance than the presence of ammonia. Based on nematode genera, an ecological typology of aquatic soils would appear to be feasible. The use of nematodes in environmental studies is discussed.     

Ordination and classification in the upland Rugege forest (Rwanda,Central Africa)

Summary Quantitative data on habitat and vegetation from 42 releves of the Rugege forest have been submitted to different ordination and classification methods.The habitat factors which have an important effect upon vegetation are: hydromorphy, abundance of tree layer and depth of soil.The different ordination (principal components analysis and reciprocal averaging) and numerical classification methods applied to the same set of data lead to consistent results. The numerical classification seems better than the Braun-Blanquet's method.Four groupings have been defined.The future developments of ecological studies in the Rugege forest are discussed in relation to the forest conservation.All data presented in this work were collected during my stay in the National Institute of Scientific Research of Rwanda, 1971 – 1972. Part of the computations (numerical analysis and principal components analysis) was carried out at the Nijmegen University's IBM 370/155; I am happy to thank Dr. E. van der Maarel and Dr. J.G.M. Janssen for their welcome and assistance. The reciprocal averaging ordinations and the principal components analysis on the basis of correlation between relevés were performed on the Louvain-La-Neuve University's IBM 370/158; I am very grateful to Professeur Berthet for this important assistance.This paper corresponds to part of a thesis presented at the Liège University on 7th November 1973.     

Microbial dechlorination of hexachlorobenzene in a sedimentation area of the Rhine River

In sedimentation areas of polluted rivers, microbial dechlorination of chlorinated aromatics may be of great environmental significance. This reaction may take place in the deeper, anaerobic sediment layers and involves replacement of a chlorine in the pollutant molecule by hydrogen. In this study, the microbial dechlorination of hexachlorobenzene in a sedimentation area of the Rhine River is evaluated by using Rhine water pollution data, concentrations in historical sediment samples and in recent sediment cores, and the results of anaerobic laboratory incubations with Lake Ketelmeer sediment. The various data support the conclusion that microbial dechlorination of hexachlorobenzene has occurred in the anaerobic sediment. Up to 80% of the hexachlorobenzene deposited in the early 1970s has been dechlorinated. The maximum half-life of hexachlorobenzene in the sediment is found to be 7 years.Two limitations of microbially mediated dechlorination in the natural environment have become clear. In the first place, a residual concentration of about 40 g/kg remains unaltered in the sediment or transformation rates of this fraction are at least extremely low. Secondly, the lower chlorinated benzenes that are produced from hexachlorobenzene appear to accumulate in the anaerobic sediment.     

Fixation of dissolved silicate and sedimentation of biogenic silicate in the lower river Rhine during diatom blooms

Concentrations of dissolved silicate and particulate biogenic silicate were measured in three branches of the lower river Rhine in The Netherlands in order to analyse the role of this element in the eutrophication of the river basin. Particulate silicate followed the seasonal development of the phytoplankton, which was dominated by diatoms. The concentration of dissolved silicate fell during blooms (< 0.1 mg.l^–1 ), but the amounts of biogenic silicate measured ( 1 mg.l^–1) were insufficient to explain the seasonal decrease in the dissolved fraction; this indicates retention of silicate upstream. Some particulate biogenic silicate in river water settled in man-made sedimentation areas in the Rhine delta. The observations suggest that changes in silicate fixation in the Rhine may have contributed to the incidence of non-diatom phytoplankton blooms in receiving waters.     

Spatial and environmental effects on hydrophytic macrophyte occurrence in the Upper Rhine floodplain (Germany)

The occurrence of exclusively submerged macrophytes (hydrophytes) was analyzed on a data set of 608 mapped stream segments with a total length of 106 km from the Upper Rhine floodplain. There were three objectives. The first was to test the evidence of plot-sized bias which occurs when structural homogenous river sections are mapped. In the dataset, with a broad range of areas sampled, this bias was small but the mapping procedure nevertheless had some disadvantages for ecological interpretation of hydrophyte data. The second objective was to test for spatial autocorrelation of species composition among consecutive stream sections. Results showed that spatial autocorrelation is an intrinsic and not easily interpretable feature, which might weaken the interpretative strength of pure species–environment relationships in streams. The third objective was to analyse species–environment relationships, by redundancy analysis. The analyses gave satisfying distribution patterns of the 25 most frequent hydrophytes, using a small group of environmental parameters—current, shading, turbidity and maximum depth. They could be assigned into three groups—rheophilic, potamale and related to groundwater influence. The high amount of unexplained variability in species data is due to the large data set where the high plasticity of most hydrophytes becomes apparent and thus resulting in a broad niche overlap. The study gives a representative overview over one of the richest regions in Germany for hydrophytes. Handling editor: S. M. Thomaz     

The application of multivariate land classification to vegetation survey in the Wicklow Mountains,Ireland

Multivariate land classification and land cover mapping by aerial photographic interpretation were used to model spatial variation of land cover in the Wicklow Mountains, Ireland and to structure a stratified random sampling programme of upland blanket bog vegetation. The total area of blanket bog with gully-erosion features was estimated as 33% of the area studied. Vegetation with hand peat-cutting patterns was estimated at 5%, and there was 35% undissected (intact) vegetation. There were differences between land classes in the estimated area of land cover with gully-erosion features or hand peat-cutting patterns.Sample vegetation quadrats, stratified by land class and aerial photographic land cover type, were grouped by their plant species composition. The groups represented ombrotrophic mire, soligenous mire and shrub heath vegetation. There was significant association between vegetation group and land class, related to variation in regional landscape type, but no significant association between vegetation group and the aerial photographic land cover types, undissected (intact) and dissected (gullied and cut-over) peats. It is proposed that the similarity of vegetation between undissected and dissected blanket bog is related to vegetation regeneration. The need to consider differences in vegetation distribution, composition and dynamics in ecological management strategies is emphasised. The study demonstrated the value of stratified random field sampling for cost-efficient regional ecological assessment in upland blanket bog landscapes typified by the Wicklow mountains, Ireland.     

Comparison of nitrification rates in three branches of the lower river Rhine

The nitrogen cycle in the lower river Rhine was analysed, using data on concentrations of ammonium, nitrite and nitrate, measured in the period from 1972 to 1986. The massive discharge of ammonium in densely populated areas in the Federal Republic of Germany led to microbial nitrification, detectable as decreases in ammonium and nitrite concentrations in the lower river Rhine over reaches 85–133 km long. The distribution of the nitrogen-rich Rhine waters over three different branches in the Netherlands permits some of the factors governing microbial nitrification in the river bed to be discriminated. In the fast-flowing main channel, intensively used by ships, nitrification is more important than in the smaller branches, despite the short residence time of the water in the main channel. Differences in the flow rate of water, in grain size distribution of sediments, and in intensity of shipping (aeration, turbulence) seemed to be responsible for the different rates of nitrification.     

Bacterial community in the rhizosphere and rhizoplane of wild type and transgenic eucalyptus

The rhizosphere is a niche exploited by a wide variety of bacteria. The expression of heterologous genes by plants might become a factor affecting the structure of bacterial communities in the rhizosphere. In a greenhouse experiment, the bacterial community associated to transgenic eucalyptus, carrying the Lhcb1-2 genes from pea (responsible for a higher photosynthetic capacity), was evaluated. The culturable bacterial community associated to transgenic and wild type plants were not different in density, and the Amplified Ribosomal DNA Restriction Analysis (ARDRA) typing of 124 strains revealed dominant ribotypes representing the bacterial orders Burkholderiales, Rhizobiales, and Actinomycetales, the families Xanthomonadaceae, and Bacillaceae, and the genus Mycobacterium. Principal Component Analysis based on the fingerprints obtained by culture-independent Denaturing Gradient Gel Electrophoresis analysis revealed that Alphaproteobacteria, Betaproteobacteria and Actinobacteria communities responded differently to plant genotypes. Similar effects for the cultivation of transgenic eucalyptus to those observed when two genotype-distinct wild type plants are compared.     

Correlations among vegetation strata and environmental variables in subalpine spruce-fir forests,southeastern British Columbia

A set of forest vegetation-environment data consisting of 110 plots from subalpine spruce-fir forests in southeastern British Columbia was analyzed with multivariate methods. The aims were to describe and compare relationships among plots using species composition data from four strata of the forest (trees, shrubs, herbs, bryophytes), and to compare patterns in the separate strata with patterns in the environmental data. Weak but statistically significant correlations were detected among PCA axes from all four strata, with a tendency for correlations to be stronger between axes of adjacent strata. Relationships between stratal patterns and environmental variation were examined by correlating PCA axes with environmental variables separately, and jointly with canonical correlation analysis. Linear composites of the environmental data identified by the first canonical axis were similar for shrub, herb, and bryophyte strata implying similar responses to environmental variation in understorey strata; however, < 16% of the total variance was explained. No clear relationships emerged between tree stratum and environmental variation. Probable determinants of pattern in the tree stratum include historical events such as fire and winter snowpack, as well as possible interactions between species. Collectively, these events bear little resemblance to existing environmental conditions in the forest.Nomenclature used by BCMF follows Crum, Steere & Anderson (1973), Hale & Culberson (1970), and Stottler & Crandall-Stottler (1977) for non-vascular plants, and Taylor & MacBryde (1977) for vascular plants.The British Columbia Ministry of Forests provided the data on which this paper is based, as well as a grant to pay for the computer time used. We are grateful to G. Utzig for initially suggesting that a project of this nature be done, and to S. Phelps for helping with the retrieval of computer data files from tape. This paper has greatly benefited from discussions with P. Comeau and R. K. Scagel, and the comments of two anonymous reviewers.     

Nitrification rates in the lower river Rhine as a monitor for ecological recovery

The rate of in situ nitrification was tested as an indicator of the toxicological quality of the river Rhine. Concentration changes of ammonium ions over 85 to 133 km long reaches of three river branches downstream of the densely populated Ruhr-area (F.R.G.) were calculated from a data base for the period 1972 to 1986. Concentrations of ammonium in the river exceeded values of 1 mg N/l in winter. Because of the very high input of ammonium, bacterial nitrification dominated over other nitrogen processes. Relative rates of nitrification in the three river branches were proportional to the water temperature for the individual years. Nitrification rates in the river increased by a factor of ca. 4 during the period of 1972 to 1986. Toxic substances, whose concentrations decreased in the same period of time, were proposed as inhibitors of in situ nitrification rather than e.g. a low oxygen saturation of the water. The improvement of the conditions in the river, indicated by the in situ rate of nitrification, was also documented by data on macrofauna and fish populations.     

Cellular responses in the skin of rainbow trout (Oncorhynchus mykiss) exposed to Rhine water

Trout, Oncorhynchus mykiss , were exposed to water from the Rhine for 24 days and their skin examined by light and electron microscopy. Relative to control fish mitotic figures were common and seen throughout the epidermis. Pavement cells in fish exposed to Rhine water contained significantly more secretory vesicles than control fish. Necrotic pavement cells were apparent after 24 h, and apoptotic cells from day 4 on. Mucous secretion was intense and the differentiation of mucous cells was stimulated. Some of these cells synthesized mucus of high electron density, probably of a serous composition. Leucocytes invaded the dermis and epidermis, and towards the end of the experiment many apoptotic and necrotic lymphocytes were found. In the dermis fibroblasts were abundant and actively producing collagen. Pigment containing cytoplasmic extensions of melanocytes penetrated into the epidermis. After 14 and 24 days of exposure many pigment cells, melanocytes, iridocytes and xanthocytes became apoptotic. Most of these changes are known from fish exposed to heavy metals, acid water or other stressful treatments, indicating that exposure to Rhine water is a stressful experience for trout.     

On the interpretation of principal components analysis in ecological contexts

Summary Principal components analysis is well suited for many data analysis problems in ecology, particularly for data reduction and hypothesis generation; but the structure of PCA is poorly suited for indirect gradient analysis. Whatever the intended application of PCA, the user must exercise special care in selecting data transformations to prevent the analysis from being overwhelmed by the purely numerical effects in the variance structure of the data.I would like to thank R. H. Whittaker, H. G. Gauch, R. E. Moeller, and S. R. Searle for their guidance and assistance.