Perturbation

1] In the present contribution we focus our attention on the long-term behavior of meandering rivers, a very common pattern in nature. This class of dynamical systems is driven by the coexistence of various intrinsically nonlinear mechanisms which determine the possible occurrence of two different morphodynamic regimes: the subresonant and the superresonant regimes. Investigating the full range of morphodynamic conditions, we objectively compare the morphologic characteristics exhibited by synthetically generated and observed planimetric patterns. The analysis is carried out examining, through principal component analysis, a suitable set of morphological variables. We show that even in the presence of the strong filtering action exerted by cutoff processes, a closer, although not yet complete, similarity with natural meandering planforms can be achieved only by adopting a flow field model which accounts for the full range of morphodynamic regimes. We also introduce a new morphodynamic length scale, L m , associated with spatially oscillating disturbances. Once normalized with this length scale, the relevant morphologic features of the simulated long-term patterns (e.g., the probability density function of local curvature and the geometric characteristics of oxbow lakes) tend to collapse on two distinct behaviors, depending on the dominant morphologic regime.

1. Mycorrhizal pathways are comprised of fungal hyphae that facilitate carbon transfer between plants. We determined whether net carbon transfer occurred between conspecific conifer seedlings in the field, and whether soil disturbance or access to mycorrhizal pathways affected transfer. 2. We established two soil disturbances and planted pairs of different sized Pseudotsuga menziesii var. glauca seedlings (naturally regenerated or planted) into one of four mesh treatments (0.5, 35, 250 lm or directly into soil) restricting mycorrhizal pathways. We pulse-labelled both seedlings, one with 13 CO 2 and the other with 14 CO 2 , to quantify net carbon transfer. Ectomycorrhizas were identified using morphological and molecular techniques. 3. Net carbon transfers were detected and were not due to re-fixation of respired carbon. More transferred carbon accumulated in shoots than roots. In disturbed soil, there was greater net carbon transfer to natural seedlings than planted seedlings; the reverse pattern was observed in undisturbed soil. For planted seedlings only, the magnitude of net carbon gain was positively related to seedling size and height growth rate. Greater net accumulation of carbon occurred in Rhizopogon vinicolor, a long-distance ectomycorrhizal fungi exploration type (morphological character), than the two other most abundant ectomycorrhizal fungi with contact-and short-distance exploration types. Long-distance exploration types have the potential to form long-distance hyphal connections between plant roots, whereas contact-and short-distance are restricted to short-distance (c. 0-0.25 lm) connections. 4. Synthesis. These results confirm that net carbon transfer occurs through mycorrhizal pathways; however, the amount transferred was very small. Mycorrhizal pathways were facilitating net transfer of carbon to large, vigorous natural seedlings in disturbed soils, whereas smaller planted seedlings received more net carbon gain in undisturbed soils. The size variation within these planted seedlings was great enough to elicit a positive relationship between net carbon gain and seedling size and growth rate. These findings are relevant to regeneration of forests characterized by mixed severity disturbance regimes, which leave a suite of environmental conditions that may result in a greater magnitude of transfer.

Aim We wanted to test whether urbanization has similar effects on biodiversity in different locations, comparing the responses of ground beetle (Coleoptera, Carabidae) assemblages with an urbanization gradient. We also wanted to see if urbanization had a homogenizing effect on ground beetle assemblages.

Traditional sensitivity and elasticity analyses of matrix population models have been used to inform management decisions, but they ignore the economic costs of manipulating vital rates. For example, the growth rate of a population is often most sensitive to changes in adult survival rate, but this does not mean that increasing that rate is the best option for managing the population because it may be much more expensive than other options. To explore how managers should optimize their manipulation of vital rates, we incorporated the cost of changing those rates into matrix population models. We derived analytic expressions for locations in parameter space where managers should shift between management of fecundity and survival, for the balance between fecundity and survival management at those boundaries, and for the allocation of management resources to sustain that optimal balance. For simple matrices, the optimal budget allocation can often be expressed as simple functions of vital rates and the relative costs of changing them. We applied our method to management of the Helmeted Honeyeater (Lichenostomus melanops cassidix; an endangered Australian bird) and the koala (Phascolarctos cinereus) as examples. Our method showed that cost-efficient management of the Helmeted Honeyeater should focus on increasing fecundity via nest protection, whereas optimal koala management should focus on manipulating both fecundity and survival simultaneously. These findings are contrary to the cost-negligent recommendations of elasticity analysis, which would suggest focusing on managing survival in both cases. A further investigation of Helmeted Honeyeater management options, based on an individual-based model incorporating density dependence, spatial structure, and environmental stochasticity, confirmed that fecundity management was the most cost-effective strategy. Our results demonstrate that decisions that ignore economic factors will reduce management efficiency.

Successful defense depends on the ability of the plant to recognize an attacking 'enemy' as early as possible. Early defense responses require enemy-initiated signaling cascades. Their activation ensures an induced response that is quantitative, timely and coordinated with other activities of the host cells. Damage-induced ion imbalances and modulations of channel activities are the first events occurring in the plasma membrane and result in rapid perturbations of the plasma membrane potential (V m ) involving variations of cytosolic Ca 2+ concentrations. Interacting downstream networks of kinases and phytohormones mediate the signal and result in concerted gene activation. Here we review and discuss early events occurring before herbivore attack-related gene expression that are responsible for cascades of events and signal transductions, eventually leading to indirect and direct plant responses.

Southern Norway holds the last remaining population of wild reindeer (Rangifer tarandus tarandus) in Europe. Roads, railroads, and power lines have fragmented the original population into 26 separate herds. The reindeer populations are regulated directly according to availability of winter forage. These winter ranges, generally at lower elevations, are however, often subjected to development. Effects of infrastructure and associated human activity on the distribution of wild reindeer during winter were investigated in the Nordfjella mountain region of western Norway. Systematic aerial surveys of the distribution of ca. 2500 reindeer were conducted during late winter 1986-1998. Areas within 2.5 km from power lines were used less than available in 6 of the 8 sampling years, and areas beyond this zone more than expected. Density of reindeer was 79% lower within 2.5 km from power lines compared with background areas, and increased with increasing distance from infrastructure for comparable habitat. Available forage in terms of lichen cover declined 15-30-fold with distance, and was lowest in the undisturbed areas with the highest density of grazing animals. Areas within 5 km from resorts or from roads and power lines in combination were avoided in all years. Continued construction of roads, power lines and cabin resorts endanger these available winter ranges, and hence the long term survival of the population. #

. Forest bird diversity in Mediterranean areas affected by wildfires: a multi-scale approach. -Ecography 25: 161-172. Fire is a key mechanism creating and maintaining habitat heterogeneity in Mediterranean landscapes by turning continuous woody landscapes into mosaics of forests and shrublands. Due to the long historical role of fires in the Mediterranean, we hypothesised a moderate negative effect of this type of perturbation on forest bird distribution at a landscape level. We conducted point bird censuses in Aleppo pine forest patches surrounded by burnt shrublands and studied the relationships between three ecological groups of bird species (forest canopy species, forest understorey species, and ubiquitous species) and the features of local habitat, whole patch and surrounding landscape. We used a multi-scale approach to assess the effects of landscape variables at increasing spatial scales on point bird richness. Regarding local habitat components, canopy species were positively associated with tall pines while understorey species with the cover of shrubs and plants from holm-oak forests. Forest birds were positively related to patch size and irregular forest shapes, that is, with high perimeter/size ratios. Thus, these species did not seem to perceive edges as low quality but rather favourable microhabitats. We did not detect any negative effect of isolation or cover of woodlands in the landscape on the presence of forest species after local habitat factors had been accounted for. Finally, only local habitat factors entered the model for ubiquitous species. We suggest that mosaic-like landscapes shaped by fires in the Mediterranean basin are not strongly associated with negative effects fragmentation on forest birds other than those related with habitat loss. S. Herrando ([email protected]) (present address: Grup Català d'Anellament, Girona 168 E-5,

We study the convergence of a general perturbation of the Newton method for solving a nonlinear system of equations. As an application, we show that the augmented Lagrangian successive quadratic programming is locally and q-quadratically convergent in the variable x to the solution of an equality constrained optimization problem, under a mild condition on the penalty parameter and the choice of the Lagrange multipliers.

The main frequency is an important parameter of an electrical power system. The frequency can change over a small range due to generation-load mismatches. Some power system protection and control applications, e.g., frequency relay for load shedding, load-frequency controller, require accurate and fast estimation of the frequency. Most digital algorithms for measuring frequency have acceptable accuracy if voltage waveforms are not distorted. However, due to nonlinear devices, e.g., semiconductor rectifiers, electric arc furnaces, the voltage waveforms can include higher harmonics. The paper presents a new method of measurement of power system frequency, based on digital filtering and Prony's estimation method. Simulation results confirm, that the proposed method is more accurate than others, e.g., than the method based on the measurement of angular velocity of the rotating voltage phasor.

The well-known Regge-Wheeler equation describes the axial perturbations of Schwarzschild metric in the linear approximation. From a mathematical point of view it presents a particular case of the confluent Heun equation and can be solved exactly, due to recent mathematical developments. We present the basic properties of its general solution. A novel analytical approach and numerical techniques for study the boundary problems which correspond to quasi-normal modes of black holes and other simple models of compact objects are developed.

Habitat Reintroduction Tourism A B S T R A C T Brown bears (Ursus arctos) are threatened by habitat loss, habitat fragmentation by infrastructure and human settlements, and have been hunted to local extinction in large areas of their former range. We analyzed the habitat use during the non denning period of 106 radio-collared bears in an expanding bear population in Sweden in relation to resorts and towns, terrain ruggedness, sex and age of bears. Bear use increased substantially with increasing distance to towns and resorts for comparable habitat and terrain types, also for independent scat surveys using DNA-analyses. More than 74% of all female bear locations were in the 29% of the terrain classified as ''rugged'' and located >10 km from any town or resort, whereas similar habitat closer to towns or resorts was avoided. Bears closer to larger settlements and resorts (<10 km) were on average 27-51% younger than in areas beyond (mean 4.4 ± 0.4 versus 8.9 ± 0.8 years for males and 4.4 ± 0.4 versus 6.0 ± 0.2 years for females). Sub-adult bears (<4 years) comprised up to 52% of all bear use within 10 km from resorts and settlements, likely representing exploratory dispersing individuals. These areas, however, contained only 8% of the old males (>7 years), the remaining 92% located beyond 10 km from major resorts and settlements. Recreational resorts are developing rapidly, typically near national parks, and may thus limit expansion or fragment existing bear habitats. Together with active conservation, safeguarding undeveloped corridors of forest and rugged terrain may be important for successful recolonization of the brown bear into its original range.

The Lower Nhecolândia subregion of the Brazilian Pantanal is part of a large continuous tropical wetland that exhibits a high biodiversity of flora and fauna species, and many threatened habitats. The spatial distribution of these habitats influence the abundance and interactions of animal species, and the change or destruction of habitat can cause the disturbance of key biological processes. This study uses multi-temporal L-band ALOS/PALSAR, C-band RADARSAT-2, and ENVISAT/ASAR data to map ecosystems and create a lake distribution map of the Lower Nhecolândia subregion in the Brazilian Pantanal. First, backscattering analysis was conducted on individual training objects to gain a better understanding of the backscattering characteristics of each class. Then, a Level 1 object-based image analysis (OBIA) classification based on hierarchical principles first classified the region into "Lakes" and "Not Lakes". This was followed by a Level 2 classification defining six vegetation habitats (Forest Woodland, Open Wood Savanna, Open Grass Savanna, Agriculture, Swampy Grassland and Vazantes) which was achieved at an overall accuracy of 83%. A Level 3 classification defined the "Lakes" class into a) Fresh (baías) and Brackish (salinas) lakes (accuracy results of 98%); and a further classification level dividing the fresh lakes, b) Fresh Lakes with floating and emergent vegetation (baías), and Fresh Lakes with the presence of Typha (salobras), and including the Brackish lakes (salinas) (overall accuracy results of 81%). The results of this study provide the first fine spatial resolution classification showing the spatial distribution of terrestrial and aquatic habitats for the entire subregion of Lower Nhecolândia using dual season, dual polarization C and L-band SAR imagery. The produced maps will provide valuable habitat information to help define conservation strategies and aid further research in the area.

This paper considers the use of meiofauna (benthic metazoa 45 to 500 m in size) as biological indicators for monitoring marine environmental health. To date, this abundant and ubiquitous group of invertebrates has been largely neglected in applied sampling programmes; instead, emphasis has been placed upon more conspicuous biological components such as seagrass, macrofauna and epiphytes. In an attempt to redress this balance, this paper sets out three objectives: (1) to explain the reasons for selecting biological response indicators from across the whole spectrum of phylogenetic organisation, (2) to summarise those aspects of meiofaunal life-history and demography that render this group suitable for monitoring anthropogenic pollution and disturbance, (3) to suggest how to optimise the inclusion of meiofauna in monitoring programmes so that they provide maximum information for management purposes. To achieve these objectives the environmental impact assessment framework of Ward and Jacoby (1992) is adopted as a matrix into which the relevant components of meiofaunal ecology are fitted. Using this matrix, meiofauna are shown to have advantages that include their sessile habit, high species diversity, short generation time, direct benthic development and ubiquitous distribution. Disadvantages include their small size, high level of spatial and temporal variability, the potential cost of sample processing and the limited taxonomic literature accessible to non-specialist workers. The paper concludes with a discussion of sampling strategies and methods of analysis that may be used to efficiently incorporate meiofauna as biological response indices into environmental monitoring. Emphasis is placed on cost-effective techniques such as taxonomic minimalism.

The stability of the incompressible attachment-line boundary layer is studied by solving a partial-differential eigenvalue problem. The basic flow near the leading edge is taken to be the swept Hiemenz flow which represents an exact solution of the Navier-Stokes (N-S) equations. Previous theoretical investigations considered a special class of two-dimensional disturbances in which the chordwise variation of disturbance velocities mimics the basic flow and renders a system of ordinarydifferential equations of the Orr-Sommerfeld type. The solution of this sixth-order system by showed that the two-dimensional disturbance is stable provided that the Reynolds number R < 583.1. In the present study, the restrictive assumptions on the disturbance field are relaxed to allow for more general solutions. Results of the present analysis indicate that unstable perturbations other than the special symmetric two-dimensional mode referred to above do exist in the attachment-line boundary layer provided R > 646. Both symmetric and antisymmetric two-and three-dimensional eigenmodes can be amplified. These unstable modes with the same spanwise wavenumber travel with almost identical phase speeds, but the eigenfunctions show very distinct features. Nevertheless, the symmetric twodimensional mode always has the highest growth rate and dictates the instability. As far as the special two-dimensional mode is concerned, the present results are in complete agreement with previous investigations. One of the major advantages of the present approach is that it can be extended to study the stability of compressible attachment-line flows where no satisfactory simplified approaches are known to exist.

This paper presents a simple representation of traffic on a highway with a single entrance and exit. The representation can be used to predict traffic's evolution over time and space, including transient phenomena such as the building, propagation, and dissipation of queues. The easy-to-solve difference equations used to predict traffic's evolution are shown to be the discrete analog of the differential equations arising from a special case of the hydrodynamic model of traffic flow. The proposed method automatically generates appropriate changes in density at locations where the hydrodynamic theory would call for a shockwave; i.e., a jump in density such as those typically seen at the end of every queue. The complex side calculations required by classical methods to keep track of shockwaves are thus eliminated. The paper also shows how the equations can mimic the real-life development of stop-and-go traffic within moving queues.

Aim Worldwide, functional homogenization is now considered to be one of the most prominent forms of biotic impoverishment induced by current global changes. Yet this process has hardly been quantified on a large scale through simple indices, and the connection between landscape disturbance and functional homogenization has hardly been established. Here we test whether changes in land use and landscape fragmentation are associated with functional homogenization of bird communities at a national scale.

Abstruct-Acoustic noise emission from PWM-VSI inverter driven induction motors is a well-known problem. The generated noise depends mainly on two factors: the harmonic content of the supply voltage waveform and the mechanical resonance frequencies of the induction motor. It is necessary to know the mechanical resonances to optimize the switching scheme of the inverter to reduce the noise emission. Measuring the resonance frequencies is normally a laborious process. This paper introduces a new method for estimating the mechanical resonances from acoustic noise measurements. Employing random modulation of the output voltage of the inverter, the voltage spectrum can be spread over a wide frequency range. Using the spectrum analysis of the measured acoustic noise, the resonances can easily be estimated as the dominant frequencies of the acoustic noise spectrum. The method was tested on a 2.2-kW induction motor at no load and full load. Some of the mechanical resonances of the motor at no load were calculated by the Holzer method. The calculations showed good agreement with the sound measurements.

Spherical symmetry in f (R) gravity is discussed in details considering also the relations with the weak field limit. Exact solutions are obtained for constant Ricci curvature scalar and for Ricci scalar depending on the radial coordinate. In particular, we discuss how to obtain results which can be consistently compared with General Relativity giving the well known post-Newtonian and post-Minkowskian limits. Furthermore, we implement a perturbation approach to obtain solutions up to the first order starting from spherically symmetric backgrounds. Exact solutions are given for several classes of f (R) theories in both R = constant and R = R(r).

Site productivity and disturbances are among the main factors determining plant community composition. With increasing site productivity, plant diversity is often reduced and the importance of traits associated with light competition increases. Small-scale disturbances created by mole activity are assumed to affect this dynamics by two factors: increasing site heterogeneity and providing survival opportunity for weaker light competitors. These effects are expected to become stronger with increasing site productivity. To test this hypothesis we compared species composition on molehills and in undisturbed plots within grasslands and along a productivity gradient. The differences in species composition were evaluated both by species diversity and by traits representing trade-offs between species' response to competition and disturbance. Species diversity generally decreased with site productivity, while disturbances had no significant contribution to the variation among samples. When analyzing shifts in species traits, we found a central role of site productivity, but also a significant, though secondary, effect of molehill disturbances. In particular, communities showed increased potential height and specific leaf area and decreased seed weight and Ellenberg's light indicator values with increasing site productivity, supporting the assumption of increasing light limitation along the gradient. Species observed on molehills were generally less shade tolerant, especially in the more productive grasslands. We conclude that, although overall plant community composition is mainly shaped by large environmental gradients such as site productivity, small-scale disturbances may contribute to local environmental heterogeneity and trait variation by enabling species less adapted to light competition to survive.

There have been few reports of invasions in continental rain forests, especially for exotic animals. This study provides original data concerning the potential of exotic drosophilid species to colonize the Amazonian tropical rain forest. To investigate if the structure of drosophilid assemblages differed in response to anthropogenic disturbance, we performed a taxonomic survey at six sites within the Yasuni National Park in Ecuadorian Amazonia along a disturbance gradient from pristine to clearcut artificial forest. A total of 7425 individuals from 34 species were collected of which seven species were exotic. There was significant variation in the assemblage composition along this disturbance gradient; 31 percent of which was explained by the presence of exotic species, particularly at the most disturbed sites, through nonmetric multidimensional scaling and SIMPER analyses. These results confirm the susceptibility of continental rain forests to invasion by exotic species. There is an urgent need to develop and implement monitoring systems, for example, based on drosophilid assemblage surveys, to detect exotic invasions in continental tropical forests.

Closed fishing seasons are sometimes imposed during the breeding period of harvested species in the belief that this will achieve greater annual reproductive output, but no studies have modelled the validity of this. We specifically tested this by simulating reproductive output and yield when closed seasons are imposed at different times of the year, using the limpet Cymbula granatina as a base case for a per-recruit model because (a) the reproduction of individuals that are not harvested is not disturbed by the act of harvesting and (b) the individuals do not aggregate to reproduce, an act that would make them more prone to capture. Model outputs showed that implementation of a closed fishing season during the breeding period does not increase the reproductive output of the population and has only marginal effects on yield if total annual fishing effort remains unchanged. This outcome is, however, dependent on the particular characteristics of the species, particularly whether the species is prone to disturbance or aggregates to breed. When the model was tuned to simulate species that are disturbed by fishing or do become vulnerable to fishing because they aggregate to breed, the reproductive output and yield were substantially increased by the imposition of a closed season during the breeding period. Thus, closure of fishing during the breeding period is effective only for species that conform to either of these conditions, or as a means of reducing annual fishing mortality. The frequent application of closed seasons to species that are not disturbed by harvesting and do not aggregate to breed is therefore generally invalid, despite wide belief that it will improve reproductive success.

Meles meles numbers have been reported from long-term studies on local populations and national surveys in Britain. One theory proposed to explain this population change, is that increased protective legislation has led to reduced levels of persecution, allowing the population to expand. In the present study, we show that the badger population in Northern Ireland has not increased in parallel with the British population, and investigate whether sustained high persecution levels are responsible. As legal protection of badgers in Northern Ireland was not increased at the same time as in Britain, a simultaneous decrease in persecution would not be expected. We test two hypotheses: (i) where there is no change in the level of sett disturbance, the number of social groups will remain unchanged and, (ii) if sett disturbance affects group size, those groups suffering from most disturbance will be smallest. We demonstrate that badger sett disturbance affects both social group size and the number of social groups, thus influencing overall badger density. We also show that high levels of sett disturbance are constraining the growth of the Northern Ireland badger population and discuss what lies behind the apparent failure of the protective legislation in this country.

The reduction of nesting habitat has likely contributed to the decline of Humboldt penguins in Peru. We investigated the eects of using dierent nesting sites and nest types on the breeding success of Humboldt penguins at Punta San Juan, the largest colony in Peru, between 1993 and 1996. The majority of penguins bred on cli tops (72%) where breeding success was high (1.03±1.18 edglings/nest). In contrast, penguins nesting on beaches had lower breeding success (0.44±1.1¯edglings/nest), with reproductive failure mostly due to nest¯ooding during ocean swell years. The breeding success of penguins using surface nests (1.02±1.07 edglings/nest) was similar to that of those using burrows (0.89±0.97¯edglings/nest) and crevices (0.85±1.15¯edglings/nest) on cli slopes and beaches, respectively. Nevertheless, on cli tops where the main guano deposits are located, burrows were the most successful nests (1.41¯edglings/nest). Halting guano extraction around the main breeding areas may increase the availability of burrowing substrates and, thus breeding success of this endangered species. #

We review the effects of human impact on biodiversity of European forests in the light of recent views on disturbances and succession in ecosystems, and discuss recent ideas on how biodiversity affects ecosystem functions such as productivity and ecosystem stability. With this as a background we discuss how to better manage European forests for both production and biodiversity. We argue that the next generation of forestry practices need to understand and mimic natural disturbance dynamics much better than the present ones. Of particular importance is the fact that most species in European forests have evolved in forests that were to a large extent in¯uenced by large grazers, ®rst by megaherbivores and later, in historic times, by domestic animals. We highlight several areas where new knowledge and management tools are urgently needed: (i) How do species survive and adapt to the natural disturbance regimes in different regions and forest types? (ii) How can new and imaginative forest management practices be devised that take natural disturbance regimes into account? (iii) How does forest biodiversity affect ecosystem function and stability in a changing world, in particular in the light of predicted climate changes? (iv) How are ecological processes at different levels and scales related to diversity, and how do different management practices affect biodiversity? (v) How can ef®cient agroforestry methods be developed to preserve biodiversity? (vi) What is the role of humans and human behaviour for sustainable management of ecosystems? #

The influences on forest stream invertebrate communities of riparian forest type (native/exotic Pinus radiata) and logging, with or without native forest riparian buffers, were investigated at 28 stream sites on Coromandel Peninsula, New Zealand. Stream reaches were surveyed under summer, baseflow conditions in six riparian/forest vegetation types: native forest, mature pine plantations with pines planted to the stream edge, mature pine plantations with native forest in the riparian area, clearcut pine plantations, and logged pine plantations with patch buffers of native forest vegetation (upstream areas clearcut) or continuous buffers along the perennially flowing stream length. Multivariate analyses showed that clearcut reaches differed in invertebrate community structure from pine and native forested reaches, and from logged reaches with continuous riparian buffers. Communities at patch buffer sites were intermediate between these groups. Amongst the common taxa, mayflies were the most sensitive to clearcut logging, with three species less abundant at clear-cut and/or patch buffer sites; only the algalpiercing caddis Oxyethira albiceps (Hydroptilidae) responded positively to logging. Clearcut reaches had lowest diversity, taxon richness, relative abundance and numbers of the sensitive mayfly, stonefly and caddisfly taxa, and index of biotic integrity. In contrast, sites that had been logged leaving continuous buffers did not differ in these biometrics from those in intact native or mature plantation forest, indicating that buffers greatly reduced disturbance associated with logging. Logged sites with patch buffers had biometric values intermediate between clearcut and forested/continuous buffered reaches, indicating less protection from logging impact. Correlation and multiple regression analyses showed that logging impacts are strongly related to increases in periphyton biomass and water temperature, associated with changes in stream lighting, and increased channel instability/fine sediment. The findings indicate that late-rotation exotic pine plantations can support very similar stream invertebrate communities to native forests, and highlight the benefit of retaining forested buffers along stream riparian areas to avoid harvesting impacts on stream habitat and invertebrate communities. #

The effects of human activity on bird behaviour and distribution have been studied extensively in recent years, but variation in their response to disturbance is still poorly understood. Here, we analyse variation in the behaviour of wintering whooper swans Cygnus c. cygnus, to determine whether their susceptibility to human activity changes with time, location and the type of disturbance involved. Overall, the swans' feeding activity varied within and between years, and in relation to feeding site, but there was less variation in the amount of time spent alert. Disturbance frequency resulting from human activity was lower with increasing flock size and with increased distance to the nearest road or track. Distances that humans could approach before alerting the birds similarly varied with field characteristics (e.g. size and proximity to roads or tracks), and also with the type of disturbance involved. The distance at which >5% of the flock became alert because of human activity decreased with the number of previous disturbance incidents in the day, indicating that swans become less sensitive to disturbance events if daily disturbance frequency is high, but there was no evidence that habituation to disturbance persisted over longer periods. The time taken for the birds to resume undisturbed behaviour varied with the duration of the disturbance event, which in turn depended on the type of disturbance involved, with pedestrians alerting the birds for longer periods than vehicles and aircraft. Recovery rates following disturbance were also associated with field size, flock size and the proportion of the flock alerted. Feeding activity was influenced by a range of variables, including year, season, field location, crop type and the number of days that the flock had used the field (32.9% of variance in the data explained by these variables), with disturbance factors explaining an additional 4.9% of variance in the proportion feeding per hour. Conversely, alert activity was influenced mainly by disturbance events. The range of factors influencing the swans' feeding behaviour, and variability in their response to human activity, has implications for management programmes and for attempts to predict the effects of human activity on the birds at a local and larger scale.

Introduction 1.1. Historic Garry oak ecosystems and First Nations burning Garry oak (Quercus garryana Dougl.) meadows (called prairies in the adjacent northwest United States) are considered one of Canada's most endangered ecosystems (Pojar, 1980; Fuchs, 2001; Stewart, 2001), occurring uniquely in the province of British Columbia on southeast Vancouver Island, adjacent Gulf Islands, and in the Fraser Valley (Erickson, 1993). Urban encroachment, changes in disturbance regime and exotic species threaten the ecosystem. On moist sites, shade-intolerant Garry oaks are replaced by Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) unless maintained by disturbance, such as fire (Roemer, 1972; Stewart, 2001). The majority of historic and present-day Garry oak meadows are located within the traditional territories of the Coast Salish First Peoples, who, prior to European settlement, utilized a wide-range

The potential impact of human disturbance on wintering waterbirds using intertidal mudflats was considered by relating their numbers to the presence of nearby footpaths, roads, railroads, and towns. Data were obtained for six English estuaries from the Wetland Bird Survey Low Tide Count scheme. Counts were undertaken monthly from November to February, and data were available for an average of 2.8 years per estuary for the period 1992-1993 to 1999 -2000. Count sections and the positions of man-made landscape features were mapped using a GIS. Generalized linear models tested whether bird numbers varied according to the estuary, month, area, whether or not the section bordered water, and the pro-portion of each section within a specified distance of each landscape feature. In addition, the proximity of sections to the nearest footpath access point was considered. Numbers of six of nine species, northern shelduck (Tadorna tadorna), red knot (Calidris canutus), dunlin (Calidris alpina), black-tailed godwit (Limosa limosa), Eurasian curlew (Numenius arquata) and common redshank (Tringa totanus), were significantly lower where a footpath was close to a count section, while those of brant (Branta bernicla) were greater. Northern shelduck, black-bellied plover (Pluvialis squatarola), dunlin, and black-tailed godwit numbers were reduced close to railroads and those of common ringed plover (Charadrius hiaticula), black-bellied plover, and Eurasian curlew close to roads. Common ringed plover numbers were greater close to towns. The relative distances to which species were affected by footpaths corresponded to published information concerning their flight distances in response to human disturbance. The study provided evidence that sustained disturbance associated with footpaths, roads, and railroads reduced local habitat quality for waterbirds and the carrying capacity of estuaries.

Water-column mixing is known to have a decisive impact on plankton communities. The underlying mechanisms depend on the size and depth of the water body, nutrient status and the plankton community structure, and they are well understood for shallow polymictic and deep stratified lakes. Two consecutive mixing events of similar intensity under different levels of herbivory were performed in enclosures in a shallow, but periodically stratified, eutrophic lake, in order to investigate the effects of water-column mixing on bacteria abundance, phytoplankton abundance and diversity, and rotifer abundance and fecundity. When herbivory by filter-feeding zooplankton was low, water-column mixing that provoked a substantial nutrient input into the euphotic zone led to a strong net increase of bacteria and phytoplankton biomass. Phytoplankton diversity was lower in the mixed enclosures than in the undisturbed ones because of the greater contribution of a few fast-growing species. After the second mixing event, at a high biomass of filter-feeding crustaceans, the increase of phytoplankton biomass was lower than after the first mixing, and diversity remained unchanged because enhanced growth of small fast-growing phytoplankton was prevented by zooplankton grazing. Bacterial abundance did not increase after the second mixing, when cladoceran biomass was high. Changes in rotifer fecundity indicated a transmission of the phytoplankton response to the next trophic level. Our results suggest that water-column mixing in shallow eutrophic lakes with periodic stratification has a strong effect on the plankton community via enhanced nutrient availability rather than resuspension or reduced light availability. This fuels the basis of the classic and microbial food chain via enhanced phytoplankton and bacterial growth, but the effects on biomass may be damped by high levels of herbivory.

Yellow-poplar (Liriodendron tulipifera L.) is a large, rapidly growing, shade-intolerant tree species common after disturbances on moist sites in the Appalachian Mountains. The species is typically scattered throughout old-growth mesophytic forests, where periodic gap formation creates conditions favorable for yellow-poplar establishment and growth. On abandoned agricultural fields, however, it is common for nearly monospecific forests of yellow-poplar to develop.

Observed 15 species of primate to assess the effects of zoo visitors on their social behavior. When visitors were present primates were less affiliative, more active, but more aggressive. These changes were particularly marked in arboreal monkeys, especially in smaller species, and were reduced by 50% by lowering the height of spectators. Detailed observations of a group of mandrills indicated that with increasing numbers of visitors the monkeys showed a linear increase in attention to visitors, in activity, and in stereotyped behavior. Findings indicate that visitors are a source of stressful excitement rather than of enrichment.

The distribution of phytoplankton abundance, biomass and species composition coupled with environmental factors and metazooplankton was studied relatively intensively and over a period of four consecutive years in five ponds featuring a gradient of increasing salinity from near to that of sea water to a nine-fold concentration from 2000 to 2003. The results indicate that the physical characteristics of the water (temperature and salinity) were quite similar over the years. Nutrients, which were concentrated in pond A1, decreased with increases in salt concentration. The composition of the phytoplankton community showed strong seasonality. Diatoms dominated in the first ponds A1, A16 and C2-1, followed by dinoflagellates. Chlorophyceae dominated the phytoplankton community in the hypersaline ponds M2 and TS. Cyanobacteriae were relatively abundant in ponds M2 and TS. The highest phytoplankton density and biomass were found in the ponds with the highest salinity due to the proliferation of Dunaliella salina (Chlorophyta: Volvocales). The inter-annual study of phytoplankton succession in the Sfax solar salterns showed slight differences among the years of study due to the stability of the environmental conditions. Phytoplankton communities were permanently primitive, stage 1 e structured as they failed to build complexity because of salt stress which operates for longer and above any other variables. This reduced frequency of disturbance to the existing course of regulation, allowed the community to "mature" from its "primitive" state, rather than experience frequent structural setbacks.

Exotic species have become increasingly significant management problems in parks and reserves and frequently complicate restoration projects. At the same time there may be circumstances in which their removal may have unforeseen negative consequences or their use in restoration is desirable. We review the types of effects exotic species may have that are important during restoration and suggest research that could increase our ability to set realistic management goals. Their control and use may be controversial; therefore we advocate consideration of exotic species in the greater context of community structure and succession and emphasize areas where ecological research could bring insight to management dilemmas surrounding exotic species and restoration. For example, an understanding of the potential transience of exotics in a site and the role particular exotics might play in changing processes that influence the course of succession is essential to setting removal priorities and realistic management goals. Likewise, a greater understanding of the ecological role of introduced species might help to reduce controversy surrounding their purposeful use in restoration. Here we link gen-eralizations emerging from the invasion ecology literature with practical restoration concerns, including circumstances when it is practical to use exotic species in restoration.

Receptivity of a high-speed boundary layer on a flat plate to acoustic disturbances is investigated using a combined numerical and asymptotic approach. The leading-edge receptivity problem is discussed with emphasis on physical mechanisms associated with scattering and diffraction of acoustic waves. Analytical solutions provide insight into the interplay of these mechanisms as a function of the angle of incidence of external acoustic waves. The theoretical predictions are in good agreement with the wind-tunnel experimental data of Maslov et al. obtained at free-stream Mach number 6. The leading-edge receptivity model is incorporated into the multiplemodes method to account for the inter-modal exchange downstream from the leading edge. This combined modelling resembles basic features of the direct numerical simulation of Ma & Zhong. A comparative analysis of the leading-edge receptivity and the inter-modal exchange associated with non-parallel effects is presented. The theory allows fast evaluation of the receptivity coefficients and clarifies the physics of the receptivity process. The theoretical results may guide further direct numerical simulations and experimental studies of boundary layer receptivity at supersonic and hypersonic speeds.

Deux séquences d'essais ont été conduites au Centre d'épuration Rive-Sud (Longueuil, Que.) dans le but d'évaluer les performances du procédé de coagulation-floculation avec recirculation des boues produites. Lors des essais, l'évolution de la qualité des eaux traitées dans deux filières parallèles alimentées simultanément par une même eau brute, dont l'une intègre la recirculation, a été suivie. Les résultats montrent que la recirculation entraîne une dégradation significative de la qualité de l'eau. Ces résultats, qui ne corroborent pas ceux de travaux précédents (F. Monette et al. Revue canadienne de génie civil, 27 : 702-718, 719-734, 2000), s'expliquent par des infrastructures inadéquates pour intégrer la recirculation. La forte concentration de coagulant employée limite également les gains de rendements associés à la recirculation. Le procédé réagit rapidement aux variations de charge de l'eau brute et de concentrations de réactifs. La présence de fines particules, générées par les turbulences induites par la pompe de recirculation, rend le conditionnement des boues légèrement plus difficile. Finalement, la mesure de la turbidité des eaux du floculateur constituerait un excellent outil indicateur du taux de recirculation.

Abstract-Improved reliability and fault tolerant operation of inverter-fed variable frequency ac drives are very impor-tant for critical industrial applications. The paper describes variable frequency, variable voltage operation of a three-phase induction motor drive in ...

This paper reviews recent research into the ecological impacts of recreation and tourism on coastal marine fauna in Australia. Despite the high and growing importance of water-based recreation to the Australian economy, and the known fragility of many Australian ecosystems, there has been relatively limited research into the effects of marine tourism and recreation, infrastructure and activities, on aquatic resources. In this paper we have reviewed the ecological impacts on fauna that are caused by outdoor recreation (including tourism) in Australian coastal marine ecosystems. We predict that the single most potentially severe impact of recreation may be the introduction and/or dispersal of nonindigenous species of marine organisms by recreational vessels. Such introductions, together with other impacts due to human activities have the potential to increasingly degrade recreation destinations. In response, governments have introduced a wide range of legislative tools (e.g., impact assessment, protected area reservation) to manage the recreational industry. It would appear, however, that these instruments are not always appropriately applied.

Deux séquences d'essais ont été conduites au Centre d'épuration Rive-Sud (Longueuil, Que.) dans le but d'évaluer les performances du procédé de coagulation-floculation avec recirculation des boues produites. Lors des essais, l'évolution de la qualité des eaux traitées dans deux filières parallèles alimentées simultanément par une même eau brute, dont l'une intègre la recirculation, a été suivie. Les résultats montrent que la recirculation entraîne une dégradation significative de la qualité de l'eau. Ces résultats, qui ne corroborent pas ceux de travaux précédents (F. Monette et al. Revue canadienne de génie civil, 27 : 702-718, 719-734, 2000), s'expliquent par des infrastructures inadéquates pour intégrer la recirculation. La forte concentration de coagulant employée limite également les gains de rendements associés à la recirculation. Le procédé réagit rapidement aux variations de charge de l'eau brute et de concentrations de réactifs. La présence de fines particules, générées par les turbulences induites par la pompe de recirculation, rend le conditionnement des boues légèrement plus difficile. Finalement, la mesure de la turbidité des eaux du floculateur constituerait un excellent outil indicateur du taux de recirculation.

The effects of human trampling on two marine intertidal communities were experimentally tested in the upper-shore algal-barnacle assemblage and mid-shore mussel bed communities. On two shores, we trampled experimental plots 250 times every month for a year, and then allowed plots to recover for a further year. Results from the upper shore community showed that foliose algae were susceptible to trampling, and suffered significant declines shortly after trampling started. Canopy cover remained high in untrampled control plots. Barnacles were crushed and removed by trampling. Algal turf was resistant to trampling, and increased in relative abundance in trampled plots. In general the algal-barnacle community recovered in the year following trampling. In the mussel bed community, mussels from a single layer bed were removed by trampling, By contrast, mussels at a second site were in two layers, and only the top layer was removed during the trampling phase. However, mussel patches continued to enlarge during the recovery phase, so that by the end of the second year, experimental plots at both sites had lost mussels and bare space remained. Mussel beds did not recover in the 2 years following cessation of trampling. Control plots lost no mussels during the trampling and recovery phase. Barnacle and algal epibionts on mussels were significantly reduced by tramping. Overall, trampling can shift community composition to an alternate state dominated by low profile algae, and fewer mussels.

A simple and relatively accurate technique for classifying time-series Landsat Thematic Mapper (TM) imagery to detect levels of forest harvest is the topic of this research. The accuracy of multidate classification of the normalized difference vegetation index (NDVI) and the normalized difference moisture index (NDMI) were compared and the effect of the number of years (1 -3, 3 -4, 5 -6 years) between image acquisition on forest change accuracy was evaluated. When Landsat image acquisitions were only 1 -3 years apart, forest clearcuts were detected with producer's accuracy ranging from 79% to 96% using the RGB-NDMI classification method. Partial harvests were detected with lower producer's accuracy (55 -80%) accuracy. The accuracy of both clearcut and partial harvests decreased as time between image acquisition increased. In all classification trials, the RGB-NDMI method produced significantly higher accuracies, compared to the RGB-NDVI. These results are interesting because the less common NDMI (using the reflected middle infrared band) outperformed the more popular NDVI. In northern Maine, industrial forest landowners have shifted from clearcutting to partial harvest systems in recent years. The RGB-NDMI change detection classification applied to Landsat TM imagery collected every 2 -3 years appears to be a promising technique for monitoring forest harvesting and other disturbances that do not remove the entire overstory canopy. D

General aspects of the Fluctuation-Dissipation Relation (FDR), and Response Theory are considered. After analyzing the conceptual and historical relevance of fluctuations in statistical mechanics, we illustrate the relation between the relaxation of spontaneous fluctuations, and the response to an external perturbation. These studies date back to Einstein's work on Brownian Motion, were continued by Nyquist and Onsager and culminated in Kubo's linear response theory. The FDR has been originally developed in the framework of statistical mechanics of Hamiltonian systems, nevertheless a generalized FDR holds under rather general hypotheses, regardless of the Hamiltonian, or equilibrium nature of the system. In the last decade, this subject was revived by the works on Fluctuation Relations (FR) concerning far from equilibrium systems. The connection of these works with large deviation theory is analyzed. Some examples, beyond the standard applications of statistical mechanics, where fluctuations play a major role are discussed: fluids, granular media, nanosystems and biological systems.

Over the last few decades, the damage identification methods of civil and mechanical structures have been drawing much interest from various fields. Wavelet analysis, a relatively new mathematical and signal processing tool, is one of such methods that has been studied recently. It is a time-frequency analysis that provides more detailed information about non-stationary signals which traditional Fourier analysis miss. This rather new method has been applied to various fields including civil, mechanical and aerospace engineering, especially for damage detection and structural health monitoring (SHM). The purpose of this paper is to provide the review of the research that has been conducted on damage detection by wavelet analysis. First, the theory of wavelet analysis is presented including continuous and discrete wavelet transform followed by its application to SHM. Then more specific applications-namely crack detection of a beam and mechanical gear and roller damage-are presented. #

1. In river corridors, water plays a key role in connecting various landscape patches. This 'hydrological connectivity' operates on the four dimensions of fluvial hydrosystems: longitudinal, lateral, vertical, and temporal. The present review focuses on: (1) lateral connectivity that links the main course of a river with floodplain waterbodies; and (2) vertical connectivity, the exchanges between the surface and groundwater via infiltration into the alluvial aquifer and exfiltration of phreatic water from the hillslope aquifer. 2. The biocomplexity of fluvial hydrosystems results from interactions between processes operating at various spatial and temporal scales. Differences in the nature and intensity of hydrological connectivity contribute to the spatial heterogeneity of riverine floodplains, which results in high alpha, beta and gamma diversity. Differences in connectivity also provide complementary habitats that are required for the parts of life cycles and life-cycles of some species. Hydrological connectivity also produces antagonistic effects, even within the same waterbody. 3. Two temporal scales are distinguished in connectivity dynamics. River level fluctuations within years lead to a pulsing connectivity that drives the functioning of floodplain ecosystems, namely the exchange of organic matter and inorganic nutrients and the shift between production and transport phases. On the scale of decades to centuries, the interactions between various processes increase the biocomplexity of floodplains; for example, river dynamics, which create highly connected waterbodies, compensate for succession that tends towards disconnection. Alternatively, river-bed incision leads to the reduction of fluvial dynamics and to the disconnection of waterbodies, although river incision may increase vertical connectivity where waterbodies are supplied by the hillslope aquifer.