Assessment of nitrogen leaching from arable land in large river basins: Part I. Simulation experiments using a process-based model

A two-step procedure for analysing nitrogen leaching from arable land in large river basins is suggested: (1) application of a process-based dynamic model for a set of representative conditions in a large river basin to simulate water and nitrogen fluxes and (2) development of a fuzzy-rule based metamodel using the simulated nitrogen fluxes in Step 1 as a training set. After that the metamodel can be used for rapid assessment of water quality inside the considered ranges of parameters, describing natural conditions and management practices. This paper describes Step 1 of the procedure. Step 2 is described in an accompanying paper (Haberlandt et al., Ecological Modelling 150 (3) (2002) 277–294). The advantage of this approach is that it combines the ‘process-based foundation’ with the resulting simplicity of the metamodel. Simulation experiments for analysing nitrogen (N) leaching from arable land were performed using the Soil and Water Integrated Model (SWIM) for a set of representative conditions in the Saale basin (23 687 km²) in Central Europe. The Saale River is one of the main tributaries of the Elbe. In advance, hydrological validation of the model was done for the whole Saale basin and validation of nitrogen dynamics was fulfilled in two mesoscale sub-basins of the Elbe. For the simulation experiments the drainage basin area was sub-divided into five climate zones and nine representative soil classes were chosen. The basic rotation and fertilisation schemes were established using regional information obtained from literature. In addition, the effects of changing the basic rotation to more/less intensive ones and changing fertilisation rates by 50% increase/decrease were studied. The ranges of simulated nitrogen fluxes for the basic rotation and fertilisation schemes are comparable to available regional estimates and differences between sub-regions and soils are plausible. The relative importance of natural and anthropogenic factors affecting nitrogen leaching for the Saale River basin was as follows: (1) soil, (2) climate, (3) fertilisation rate and (4) crop rotation. The simulation experiments provide a basis for a fuzzy-rule based metamodel approach, which aims at rapid water quality assessment of large regions.     

Habitat mapping using machine learning-extended kernel-based reclassification of an Ikonos satellite image

The spatial resolution of satellite imagery suitable for earth resources studies has improved from 80 m (Landsat-MSS, launched in 1972) to 0.6 m (QuickBird, launched in 2001). The conventional pixel-based methods developed for medium resolution satellite images are not suitable for classification of very high spatial resolution images, because the spectral responses of particular habitat classes are much more variable. On the other hand, in the original Barnsley–Barr kernel-based reclassification algorithm not only the spectral information of a pixel but also the textural information in the vicinity of the pixel is used when the pixel labeling decision is made. The first step of the kernel reclassification algorithm is to perform an initial classification of the original image. In the second step, the adjacency-event matrices are computed for each pixel according to co-occurrence frequencies of the initial classes in the kernel window. The degree of matching between an adjacency-event matrix corresponding to specific pixel and the set of class-specific template matrices produced during training is the criterion for pixel re-labeling. We extend the original kernel-based reclassification algorithm with a decision tree-based reclassification, simultaneously taking into account the class-specific similarity images, which are a side-product of the original algorithm. The advantage of decision tree-extended approach over the original approach seems to be the ability of the former to consider more input information, thus increasing the Kappa classification accuracy for an Ikonos image of our study area from 0.56 to 0.60, using a nomenclature containing 10 habitat classes.     

Surviving the change to warning colouration: density-dependent polyphenism suggests a route for the evolution of aposematism

Summary. How warning colouration first appeared remains a disputed question in evolutionary biology. A density-dependent transition from crypsis to aposematism that occurs during phase change in the desert locust (Schistocerca gregaria) provides insight into the conditions under which acquiring warning colouration is adaptive. When crowded for only a few hours, solitarious locusts cease avoiding each other and actively aggregate. This occurs well before they acquire warning colouration. We show that accompanying this early behavioural gregarisation is a remarkable shift in feeding behaviour, in which solitarious insects switch from being deterred by a toxic plant alkaloid to feeding avidly upon foods containing it. A computer simulation shows how crypsis ceases to be effective as an anti-predator strategy when solitarious locusts are crowded, how chemical defence becomes essential as conspicuousness increases with local density, and how warning colouration becomes advantageous under these conditions. These findings provide empirical evidence for an adaptive route for the change from a cryptic edible phenotype to a brightly coloured toxic one.     

Design parameters for coastal dikes

This paper presents results of the assessment of the design parameters leading to the definition of the crest level of a coastal dike along the German North Sea. Procedures to estimate the design water level have been proposed, distinguishing between comparative and single value procedures. The transformation of the wave characteristics from deep water towards the shallow foreshore was achieved through the application of a spectral wave model. To improve the wave parameter estimations, the existing model was nested to a grid with a higher resolution closer to the coast. The estimation of the wave run-up followed the Dutch procedure with some adjustments to the local wave characteristics and dike geometry. The computed maximum crest level of 8.4 m is below the crest height of the existing dike, which is 8.8 m. However a proposal for a more economical design should be carefully evaluated, paying attention to the uncertainties encountered in this research. The general recommendation is to enhance the reliability of the hindcasted wave parameters through calibration and validation of the wave model and to include in the design process an investigation of the effect of the medium term morphological developments.     

The Modelling of Turbulence from Traffic in Urban Dispersion Models — Part II: Evaluation Against Laboratory and Full-Scale Concentration Measurements in Street Canyons

The paper addresses the problem of the parameterisation of traffic induced turbulent motion in urban dispersion models. Results from a variety of full-scale and wind-tunnel studies are analysed and interpreted within a modelling framework based on scaling considerations. The combined effects of traffic and wind induced dispersive motions are quantified for different traffic situations (variable traffic densities, vehicle velocities and vehicle types) and incorporated into the developed parameterisations. A new dispersive velocity scale is formulated and recommendations regarding its application in urban dispersion models are given. The necessity of accounting for traffic induced air motions in predictions of street-canyon pollution levels is demonstrated. Further research is needed to verify the empirical constants in the proposed parameterisations and to generalize the developed approach for a broader range of urban building configurations, meteorological conditions, and traffic situations.     

水资源供需平衡动态模拟分析方法

本文根据多水源供水系统的特点，从优化利用水资源，改善与保护水环境质量出发，建立限水资源供需平衡的动态分析模型，该模型较为客观地反映了需水量与可供水量之间的时空矛盾，可为供水系统的运行管理提供较为精确的决策依据。模型已在台山市区环境规划中得到了应用，效果良好。     

Stability and Mixing of a Vertical Axisymmetric Buoyant Jet in Shallow Water

The stability, mixing and effect of downstream control on axisymmetric turbulent buoyant jets discharging vertically into shallow stagnant water is studied using 3D Reynolds-averaged Navier–Stokes equations (RANS) combined with a buoyancy-extended k –ε model. The steady axisymmetric turbulent flow, temperature (or tracer concentration) and turbulence fields are computed using the finite volume method on a high resolution grid. The numerical predictions demonstrate two generic flow patterns for different turbulent heated jet discharges and environmental parameters (i) a stable buoyant discharge with the mixed fluid leaving the vertical jet region in a surface warm water layer; and (ii) an unstable buoyant discharge with flow recirculation and re-entrainment of heated water. A stratified counterflow region always appears in the far-field for both stable and unstable buoyant discharges. Provided that the domain radius L exceeds about 6H, the near field interaction and hence discharge stability is governed chiefly by the jet momentum length scale to depth ratio l_M/H, regardless of downstream control. The near field jet stability criterion is determined to be l_M/H = 3.5. A radial internal hydraulic jump always exists beyond the surface impingement region, with a 3- to 6-fold increase in dilution across the jump compared with vertical buoyant jet mixing. The predicted stability category, velocity and temperature/concentration fields are well-supported by experiments of all previous investigators.     

Males in the shade: habitat use and sexual segregation in the Galápagos sea lion (Zalophus californianus wollebaeki)

In many sexually dimorphic species adult sexes tend to segregate socially, spatially, or in habitat use. Several hypotheses have been formulated regarding underlying mechanisms. We investigated terrestrial habitat use and sexual segregation in a tropical otariid, the Galápagos sea lion (Zalophus californianus wollebaeki), where most of the hypotheses can be ruled out a priori. Factors relating to thermoregulation and costs of locomotion were of prime importance for habitat use. Habitats directly adjacent to the sea, with simple structured flat surfaces, shade, and tide pools were most frequented, but sexes and age classes differed in their usage patterns. Sexual segregation, both spatial and by habitat was pronounced in the reproductive period (RP), but remained high during the nonreproductive period (NRP). A GLM model of habitat use showed that in both seasons adult males frequented habitat types that adult females and other age classes used much less. Males were most abundant in suboptimal inland habitats, which offered only shade for cooling. Females with newborns differed in habitat use from females with older offspring and lone females. Spatial and habitat segregation are explained most parsimoniously as by-products of social processes, primarily intrasexual competition and female avoidance of male harassment, linked to the polygynous mating system.Electronic Supplementary Material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

A new approach to graphical and numerical analysis of links between plant chemotaxonomy and secondary metabolism from HPLC data smoothed by a simplex mixture design

Summary. HPLC analysis of secondary metabolites represents an efficient tool for the studying of plant chemical diversity under different aspects: chemotaxonomy, metabolomics, adaptative responses to ecological factors, etc. Statistical analyses of HPLC databases, e.g. correlation analysis between HPLC peaks, can reliably provide information on the similarity/dissimilarity degrees between the chemical compounds. The similarities, corresponding to positive correlations, can be interpreted in terms of analogies between chemical structures, synchronic metabolisms or co-evolution of two compounds under certain environment conditions, etc. . In terms of metabolism, positive correlations can translate precursor-product relationships between compounds; negative correlations can be indicative of competitive processes between two compounds for a common precursor(s), enzyme(s) or substrate(s). Furthermore, the correlation analysis under a metabolic aspect can help to understand the biochemical origins of an observed polymorphism in a plant species. With the aim of showing this, we present a new approach based on a simplex mixture design, Scheffé matrix, which provides a correlation network making it possible to graphically visualise and to numerically model the metabolic trends between HPLC peaks. The principle of the approach consisted in mixing individual HPLC profiles representative of different phenotypes, then from a complete mixture set, a series of average profiles were calculated to provide a new database with a small variability. Several iterations of the mixture design provided a smoothed final database from which the relationships between the secondary metabolites were graphically and numerically analysed. These relationships were scale-dependent, namely either deterministic or systematic: the first consisted of a monotonic global trend covering the whole variation field of each metabolites’ pair; the second consisted of repetitive monotonic variations which gradually attenuated or intensified along a global trend. This new metabolomic approach was illustrated from 404 individual plants of Astragalus caprinus (Leguminoseae), belonging to four chemical phenotypes (chemotypes) on the basis of flavonoids analysed in their leaves. After smoothing, the relationships between flavonoids were numerically fitted using linear or polynomial models; therefore the co-response coefficients were easily interpreted in terms of metabolic affinities or competitions between flavonoids which would be responsible of the observed chemical polymorphism (the four chemotypes). The statistical validation of the approach was carried out by comparing Pearson correlations to Spearman correlations calculated from the smoothed and the crude HPLC database, respectively. Moreover, the signs of the smoothed relationships were finely supported by analogies and differences between the chemical structures of flavonoids, leading to fluent interpretation in relation to the pathway architecture.     

GEOGRAPHIC INFORMATION SYSTEMS AS A TOOL IN WATER USE DATA MANAGEMENT1

ABSTRACT: The temporal and locational attributes of water use data are ideally suited for analysis using a geographic information system (GIS) approach. A GIS combines spatial database management, statistical analysis, and cartographic modelling capabilities within a computer hardware and software configuration. Texas water use data for selected categories in 1980 and 1986 were analyzed using ARC/INFO to demonstrate the utility of GIS for water resource information management. Examples of data analysis and display are presented to illustrate the effectiveness of cartographic representations to communicate water use data.