Decrease In Population Density Research Articles

Effects of systemic insecticides on the population dynamics of the dragonfly Sympetrum frequens in Japan: Statistical analyses using field census data from 2009 to 2016

Since the mid-1990s, populations of the common Japanese dragonfly Sympetrum frequens in rice fields have declined severely. Application of systemic insecticides—especially fipronil—to nursery boxes of rice seedlings is suspected to be the main cause of the decline. However, until now there have been insufficient population data to test the causality. We conducted a dragonfly survey from 2009 to 2016 in four prefectures of Japan and compiled the data to enable the comparison of population growth rates along five main census routes over the years. We also estimated the use ratio of each insecticide applied to nursery boxes in rice fields (i.e., the area exposed to insecticide as a ratio of the total rice field area) by prefecture. We then statistically analyzed the effects of the insecticides on the dragonfly’s population growth rates, taking into account the potential confounding factors based on current knowledge. There was a significant negative association between the annual increase in use ratio of the sum of systemic insecticides (e.g., fipronil, imidacloprid, and chlorantraniliprole) and the annual population growth rate of S. frequens. This association suggests that systemic insecticide use affected the decrease in population density of the dragonfly, although some agronomic factors need to be further examined as potential confounders.

Influence of Bacillus thuringiensis application timing on population dynamics of gypsy moth in Mediterranean cork oak forests.

The gypsy moth, Lymantria dispar, is one of the main pests of oak forests worldwide and causes extensive defoliation during its periodic outbreaks. In the Mediterranean region, control of gypsy moth populations in cork oak forests is based on application of Bacillus thuringiensis serovar kurstaki (Btk) formulations. This research investigated the effects of Btk applications carried out in two different population development phases on gypsy moth population dynamics. With this aim, temporal and spatial fluctuation patterns of L. dispar egg density were monitored in cork oak forests treated with Btk applications from 2004 to 2009 in Sardinia (Italy). Applications undertaken during the progradation and culmination phases protected the oak canopies equally in the year of application, leading to a similar decrease in pest population density in the following year. However, the medium-term effectiveness of Btk differed between the two application timings, because only applications in the culmination phase caused a gradual decrease in L. dispar infestations throughout subsequent years. By contrast, when the application was undertaken during the progradation phase, population density increased again after 2-3 years. Moreover, Btk applications in the culmination phase reduced significantly the number of years in which gypsy moth density was damaging compared with those done in progradation. Our results indicate that Btk applications during the culmination phase were more effective than those in the progradation period, because application in the latter case did not suppress the population, but only postponed the outbreak peak by 2-3 years. © 2019 Society of Chemical Industry.

Steady-state probability characteristics of Verhulst and Hongler models with multiplicative white Poisson noise

Based on recently obtained from Kolmogorov–Feller equation exact analytical results for the steady-state probability density function of nonlinear dynamical systems driven by white Poisson noise with exponentially distributed amplitudes of pulses we analyze some models of ecology and genetics. Specifically, we find the steady-state probability distribution of the population density in the framework of well-known Verhulst equation with fluctuating population mortality in the form of Poisson sequence with unipolar pulses, leading to an abrupt decrease in population density at random times. As shown, the most probable value of the population density tends to zero with increasing the mean rate of pulses, that is, to an extinction of biological population in perspective. Further, we consider the stochastic Hongler equation which can serve as an approximate model of genetic selection. In the case of multiplicative white Poisson noise having bipolar exponentially distributed amplitudes of pulses we observe noise-induced transition to bimodality (through the trimodal phase) in the steady-state probability distribution with an increase in the mean frequency of pulses. We also discovered a new phenomenon, namely, a direct transition from unimodality to trimodality with a change in the noise intensity, which could not be detected in the framework of the Gaussian perturbation.

Spatial dynamics of a hazel dormouse (Muscardinus avellanarius) population at different densities

The dynamics of socio-spatial organisation are little investigated in dormice (Gliridae), a specific group among small mammals. During 2007–2017, 668 adult individuals were captured in a hazel dormouse (Muscardinus avellanarius) population in Lithuania, with the home ranges calculated for 134 males and 62 females. Over the study period, the abundance of the population gradually declined, and it was categorised into three groups: (1) high (1.2–1.4 adults/ha), (2) medium (0.9–1.0 adults/ha) and (3) low (0.4–0.7 adults/ha). When population abundance changed from high to low, the average sizes of home ranges increased from 1.4 ± 0.6 to 2.1 ± 1.2 ha in males and from 0.8 ± 0.5 to 1.1 ± 0.4 ha in females, while the total overlap of home ranges decreased from 57 ± 28 to 35 ± 23% in males and from 77 ± 27 to 44 ± 32% in females. Home ranges of marked individuals changed in consecutive years. In males, the average displacement of the centres of the home ranges was 58 ± 21 m, 75 ± 52 m and 73 ± 39 m at high, medium and low densities, respectively. The dynamics of the spatial relations in the investigated hazel dormouse population are consistent with the general tendency of home ranges to increase when population density decreases. However, the spatial organisation of population is more stable and potentially less related to the dynamics of food resources in comparison with other forest-dwelling small mammals.

Evaluation of Scymnus nubilus (Coleoptera: Coccinellidae) as a biological control agent against Aphis spiraecola and Cinara juniperi (Hemiptera: Aphididae)

Aphids are a major insect pest of forestry systems. In this study, we evaluate the potential of the ladybeetle Scymnus nubilus Mulsant (Coleoptera: Coccinellidae) as a biological control agent against Aphis spiraecola Patch and Cinara juniperi (De Geer) (Hemiptera: Aphididae) infesting Azorean endemic plants reared in forestry nurseries. Aphis spiraecola, infesting Viburnum treleasei Gand. (Dipsacales: Adroxaceae), was the most abundant aphid; however, a higher proportion of Juniperus brevifolia (Seub.) Antoine (Pinales: Cupressaceae) was infested by C. juniperi. Scymnus nubilus fourth instar larvae were able to complete development on both aphid species. Voracity was significantly higher when S. nubilus was fed on A. spiraecola but biomass consumption was significantly lower. The relative growth rate and conversion efficiency of the fourth instar larvae were similar. Field experiments indicated that S. nubilus can contribute to the decrease in pest population densities. However, the fourth instar larvae proved to be more efficient when released onto A. spiraecola; this outcome can be attributed to the distribution patterns of the aphids on the host plant and to the aphid or host plant morphology. Predator density and sleeve cage effect are apparently critical factors in reaching an efficient control. The obtained results provide the essential preliminary information required to establish future programs of biological control against aphids infesting Azorean endemic plants. Developmental and feeding performances, as well as the immediate impact of the predator when released onto A. spiraecola colonies, indicate that S. nubilus could be a useful candidate for reducing aphid populations. © 2019 Society of Chemical Industry.

Cyanobacterial bloom mitigation by sanguinarine and its effects on aquatic microbial community structure

Sanguinarine has strong inhibitory effects against the cyanobacterium Microcystis aeruginosa. However, previous studies were mainly limited to laboratory tests. The efficacy of sanguinarine for mitigation of cyanobacterial blooms under field conditions, and its effects on aquatic microbial community structure remain unknown. To elucidate these issues, we carried out in situ cyanobacterial bloom mitigation tests. Our results showed that sanguinarine decreased population densities of the harmful cyanobacteria Microcystis and Anabaena. The inhibitory effects of sanguinarine on these cyanobacteria lasted 17 days, after which the harmful cyanobacteria recovered and again became the dominant species. Concentrations of microcystins in the sanguinarine treatments were lower than those of the untreated control except during the early stage of the field test. The results of community DNA pyrosequencing showed that sanguinarine decreased the relative abundance of the prokaryotic microorganisms Cyanobacteria, Actinobacteria, Planctomycetes and eukaryotic microorganisms of Cryptophyta, but increased the abundance of the prokaryotic phylum Proteobacteria and eukaryotic microorganisms within Ciliophora and Choanozoa. The shifting of prokaryotic microbial community in water column was directly related to the toxicity of sanguinarine, whereas eukaryotic microbial community structure was influenced by factors other than direct toxicity. Harmful cyanobacteria mitigation efficacy and microbial ecological effects of sanguinarine presented in this study will inform the broad application of sanguinarine in cyanobacteria mitigation.

Integrated modeling predicts shifts in waterbird population dynamics under climate change

Climate change has been identified as one of the most important drivers of wildlife population dynamics. The in‐depth knowledge of the complex relationships between climate and population sizes through density dependent demographic processes is important for understanding and predicting population shifts under climate change, which requires integrated population models (IPMs) that unify the analyses of demography and abundance data. In this study we developed an IPM based on Gaussian approximation to dynamic N‐mixture models for large scale population data. We then analyzed four decades (1972–2013) of mallard Anas platyrhynchos breeding population survey, band‐recovery and climate data covering a large spatial extent from North American prairies through boreal habitat to Alaska. We aimed to test the hypothesis that climate change will cause shifts in population dynamics if climatic effects on demographic parameters that have substantial contribution to population growth vary spatially. More specifically, we examined the spatial variation of climatic effects on density dependent population demography, identified the key demographic parameters that are influential to population growth, and forecasted population responses to climate change. Our results revealed that recruitment, which explained more variance of population growth than survival, was sensitive to the temporal variation of precipitation in the southern portion of the study area but not in the north. Survival, by contrast, was insensitive to climatic variation. We then forecasted a decrease in mallard breeding population density in the south and an increase in the northwestern portion of the study area, indicating potential shifts in population dynamics under future climate change. Our results implied that different strategies need to be considered across regions to conserve waterfowl populations in the face of climate change. Our modelling approach can be adapted for other species and thus has wide application to understanding and predicting population dynamics in the presence of global change.

The mitigating role of regulation on the concentric patterns of broadband diffusion. The case of Finland

This article analyzes the role of Finnish regulation in achieving the broadband penetration goals defined by the National Regulatory Authority. It is well known that in the absence of regulatory mitigation the population density has a positive effect on broadband diffusion. Hence, we measure the effect of the population density on the determinants of broadband diffusion throughout the postal codes of Finland via Geographically Weighted Regression. We suggest that the main determinants of broadband diffusion and the population density follow a spatial pattern that is either concentric with a weak/medium/strong strength or non-concentric convex/concave. Based on 10 patterns, we argue that the Finnish spectrum policy encouraged Mobile Network Operators to satisfy ambitious Universal Service Obligations without the need for a Universal Service Fund. Spectrum auctions facilitated infrastructure-based competition via equitable spectrum allocation and coverage obligation delivery via low-fee licenses. However, state subsidies for fiber deployment did not attract investment from nationwide operators due to mobile preference. These subsidies encouraged demand-driven investment, leading to the emergence of fiber consumer cooperatives. To explain this emergence, we show that when population density decreases, the level of mobile service quality decreases and community commitment increases. Hence, we recommend regulators implementing market-driven strategies for 5G to stimulate local investment. For example, by allocating the 3.5 GHz and higher bands partly through local light licensing.

The opportunity cost of walking away in the spatial iterated prisoner’s dilemma

Previous work with the spatial iterated prisoner’s dilemma has shown that the ability to respond to a partner’s defection by simply “walking away” allows so-called walk away cooperators to outcompete defectors as well as cooperators that do not respond to defection. These findings are important because they suggest a relatively simple route by which cooperation can evolve. But it remains to be seen just how robust the walk away strategy is to ecologically important variables such as population density, strategic error, and offspring dispersal. The results of our simulation experiments show that the evolutionary success of walk away cooperators decreases with decreasing population density and/or with increasing error. This relationship is best explained by the ways in which population density and error jointly affect the opportunity cost of walking away. This opportunity cost also explains why naive cooperators regularly outcompete walk away cooperators in pair-wise competition, something not observed in previous studies. Our results further show that local offspring dispersal can inhibit the evolution of cooperation by negating the protection low population density affords the most vulnerable cooperators. Our research identifies socio-ecological conditions in which forgiveness trumps flight in the spatial iterated prisoner’s dilemma.

Ecological and demographic impacts of a recent volcanic eruption on two endemic patagonian rodents.

Catastrophic events can significantly impact the demographic processes that shape natural populations of organisms. However, linking the outcomes of such events to specific demographic parameters is often challenging due to a lack of detailed pre-event data. The eruption of the Puyehue-Cordon Caulle volcanic complex on 4 June 2011 had profound consequences for the biota of southwestern Argentina. Our long-term behavioral, ecological, and demographic studies of two species of tuco-tucos (Ctenomys sociabilis and C. haigi) that occur in the region most heavily impacted by ash fall from the eruption provided an unusual opportunity to assess the effects of this event on natural populations of mammals. The post-eruption density of the study population for each species was markedly reduced compared to pre-eruption values, with the relative magnitude of this reduction being greater for the group-living C. sociabilis. The more extensive data set for this species indicated that ash fall from the eruption altered the food resources available to these animals; differences in pre- and post-eruption stable isotope signatures for fur samples from C. sociabilis were consistent with observed changes in vegetation. Per capita female reproductive success was also reduced in this species during the first breeding season following the eruption. Based on our detailed demographic records for C. sociabilis, neither survival of yearling females from 2010 to 2011 nor the percentage of unmarked females in the study population in 2011 differed from pre-eruption values. Instead, the post-eruption decrease in population density for C. sociabilis appeared to reflect reduced within-population recruitment of juvenile females to the 2011 breeding population. Although the eruption did not result in the local extinction of either study population, the demographic consequences detected are likely to have impacted the effective sizes of these populations, creating important opportunities to link specific demographic parameters to previously reported decreases in genetic variability detected after this significant natural event.

서울, 자카르타, 마닐라, 방콕 대도시권의 도시확산 비교 분석

This study starts from the issue that the urbanization in developing countries has accelerated urban sprawl through Western-style low-density residential development represented by single-family detached housing. It therefore aims to empirically verify that Korean-style high-density residential development characterized by multi-family housing (‘apartment’), by contrast, has contributed to compact urban development, restricting urban sprawl. International comparison among Seoul, Jakarta, Manila, and Bangkok metropolitan regions shows that the Seoul metropolitan region has the highest proportion of the population living in the central region, compared with the peripheral region. By estimating population density functions, it further demonstrates that the Seoul metropolitan region has the largest gradient, which means the steepest decrease in population density as the distance from the metropolitan center increases. These results confirm that the Seoul metropolitan region is characterized by the most compact urban development owing to the high-density housing development, while the metropolitan regions in the Southeast Asia, particularly Manila and Bangkok metropolitan regions, suffer from the sprawled urban development pattern coupled with the low-density housing development.

Factors affecting Dupont´s lark distribution and range regression in Spain.

In this work, we analyse factors explaining the distribution and range regression of Dupont’s lark in Spain, the only European country in which this threatened alaudid is present. Dupont’s lark is an extremely elusive and scarce species, distributed across a reduced and strongly fragmented range, showing a metapopulational structure with unknown dispersive and connective mechanisms. We used maximum entropy modelling (Maxent) on nearly 15,000 Dupont’s lark observations (1985–2015) to assess the probability of presence at a 1 km resolution across its European range. Moreover, we tested the probability of extinction by comparing pre- and post-2000 observations by means of a GLM over a subset of cells with presence-absence data. We obtained strong model fitting (AUC = 0.919), in which species occurrence was explained by low values of plant productivity (NDVI), climate (high temperature range and medium annual precipitation), land use (increasing with sclerophyllous scrubland), flat topography and human disturbance (associated with low human population density). The species also tolerates dry farming, but not other farm types or forest cover. The probability map identified two main regions known as the species' core areas: the steppes of the Iberian System and the Ebro Valley. The North Plateau is characterised by a dispersed structure of small and very fragmented patches of suitable habitat, while a succession of discontinuous probability patches form an Eastern Corridor connecting the central core areas to the southernmost populations. Finally, the model identified small and isolated patches of high probability of presence along the eastern coastline. The species tends to occur in the best available areas but, at the same time, the model revealed a large area of suitable but unoccupied habitat. Our results correct the previous estimation of occupation area from 1,480 to 1,010.78 km2, a reduction of 26.22%. The current distribution of Dupont’s lark is almost completely covered by Important Bird Areas (IBAs), highlighting their importance for bird conservation, but only 44.89% is included in Natura 2000 Special Protection Areas (SPAs). A comparison of pre- and post-2000 periods revealed a range contraction of 44%. Probability of extinction increased with higher temperature range and lower annual precipitation, and with decreases in population density, which suggests that this species is extremely vulnerable to both climate change and rural abandonment, due to its dependence on traditional grazing. These results suggest the need for a re-evaluation of the conservation status of Dupont’s lark in Spain. They urge the preservation of not only current extant populations, but also the unoccupied suitable areas that could be critical for metapopulation structure, and the development of policies addressing the preservation of traditional grazing.

Contrasting effects of dams with and without reservoirs on the population density of an amphidromous goby in southwestern Japan

Dam construction affects the distribution and abundance of freshwater fishes, particularly for diadromous species. Amphidromous fishes spawn in rivers, and hatched larvae descend to the sea (or standing water body such as lakes) immediately after hatching, grow there typically for a few months, and then ascend rivers as small juveniles. Landlocked populations of amphidromous fishes above dams and their migration between dam reservoirs and inlet streams (landlocked migration) have often been reported. In these cases, population density in the inlet streams may be increased by dam reservoirs, owing to reduced migration distance, which results in higher return rates. On the other hand, dams without reservoirs do not promote landlocked migration and merely act as a barrier to their upstream migration, resulting in decreased population density. In this study, we examined such contrasting effects of dams with and without reservoirs on the population density of an amphidromous goby, Rhinogobius fluviatilis, in two river systems (the Shigenobu and Yoshino Rivers) of Shikoku Island, Japan. In the Shigenobu River, where more than 300 sediment-control dams and weirs (barriers without reservoirs) have been installed, our analysis showed that the goby density decreased sharply with increasing the number of barriers higher than or equal to 2 m. On the other hand, in the Yoshino River, where we investigated both landlocked populations above water storage dams (with reservoirs) and non-landlocked populations in tributaries without water storage dams, the analysis showed that the goby density increased with decreasing the distance from standing water body (i.e. the sea or dam reservoirs). Furthermore, monthly surveys at sites above and below a water storage dam showed that the recruitment of ascending juveniles above the dam was more abundant and seasonally earlier than that below the dam, probably owing to reduced migration distance and increased return rates. Our results have implications for understanding how dams alter natural distribution patterns of amphidromous fishes.

Cannibalism of Pupae by Caterpillars of the Ranchman's Tiger Moth, Arctia Virginalis, (Lepidoptera: Erebidae)

While once dismissed as an artifact of unnatural laboratory conditions, cannibalism is now widely accepted as a common behavior exhibited by multiple insect taxa, including primarily herbivorous species. In some cases cannibalism provides a means of acquiring nutrients and defensive compounds, reducing competition, and decreasing population density. For plants, inducing insect cannibalism is a defense mechanism to decrease damage by pests. Despite the growing awareness of cannibalism, its causes, and its ecological importance, few model systems exist, largely because observations of cannibalism are not reported. Here, we investigated the cannibalism of pupae by caterpillars of the ranchman's tiger moth, Arctia virginalis, [Lepidoptera: Erebidae] based on an observation of a late instar caterpillar attacking the pupa of a conspecific in our laboratory. We conducted separate laboratory and field experiments to confirm this observation and determine the propensity for cannibalism under more natural conditions. We confirmed our observation of cannibalism in the laboratory experiment but failed to detect evidence of this behavior in the field. Consequently, the frequency of cannibalism, the conditions under which it occurs, and its impact on the population dynamics of A. virginalis are still unknown.

Urban Form, Growth, and Accessibility in Space and Time: Anatomy of Land Use at the Parcel-Level in a Small to Medium-Sized American City

Using the City of Corvallis, Oregon, a small to medium sized American city, as a test-bed, this paper examines the City’s urban growth in relation to urban accessibility. This relationship is explored in an anatomic spatial-temporal fashion, taking account of: the number and size of developed land use parcels over time; urban accessibility from residential to non-residential land use areas; and the statistical relationships between urban form and urban accessibility. This investigation of land use is structured around use-classification and examined within a range of dimensional and demographic measurements over 5-year time periods from 1853 to 2014; concurrently, urban accessibility is measured by the least-cost path distance as calculated through the OD cost matrix analysis in GIS. The results indicate that the city grew spatially at different rates and its urban accessibility experienced both ups and downs over time. The city’s population growth corresponded closely with urban growth and its decreasing population density negatively impacted on the city’s urban accessibility to commerce, industry, and office for most time periods. Significantly, while the urban density increased steadily after 1950s concurrent with an increase in urban sprawl, in contrast to previous studies on the metropolitan condition, the urban density had no evident impact on urban accessibility in Corvallis. Instead, increasing the land-use mix was a more effective and feasible approach to reduce urban travel path distance and enhance accessibility than increasing population density or urban development density. Accordingly, this research provides evidence-based policy recommendations for planning sustainable urban mobility and urban form in small to medium-sized cities.

The rhizosphere of the halophytic grass Sporobolus robustus Kunth hosts rhizobium genospecies that are efficient on Prosopis juliflora (Sw.) DC and Vachellia seyal (Del.) P.J.H. Hurter seedlings

The aim of this study was to survey the abundance and genetic diversity of legume-nodulating rhizobia (LNR) in the rhizosphere of a salt-tolerant grass, Sporobolus robustus Kunth, in the dry and rainy seasons along a salinity gradient, and to test their effectiveness on Prosopis juliflora (SW.) DC and Vachellia seyal (Del.) P.J.H. Hurter seedlings. The results showed a significant decrease in LNR population density and diversity in response to salinity, particularly during the dry season. A phylogenetic analysis of the 16S-23S rRNA ITS region clustered the 232 rhizobium isolates into three genera and 12 distinct representative genotypes: Mesorhizobium (8 genotypes), Ensifer (2 genotypes) and Rhizobium (2 genotypes). Of these genotypes, 2 were only found in the dry season, 4 exclusively in the rainy season and 6 were found in both seasons. Isolates of the Mesorhizobium and Ensifer genera were more abundant than those of Rhizobium, with 55%, 44% and 1% of the total strains, respectively. The abundance of the Mesorhizobium isolates appeared to increase in the dry season, suggesting that they were more adapted to environmental aridity than Ensifer genospecies. Conversely, Ensifer genospecies were more tolerant of high salinity levels than the other genospecies. However, Ensifer genospeciesproved to be the most efficient strains on P. juliflora and V. seyal seedlings. We concluded that S. robustus hosts efficient rhizobium strains in its rhizosphere, suggesting its ability to act as a nurse plant to facilitate seedling recruitment of P. juliflora and V. seyal in saline soils.

Exploring Determinants of Urban Form in China through an Empirical Study among 115 Cities

This study aims to analyze and explain the factors that influence the urban form of Chinese cities through an empirical analysis of a cross-sectional dataset of 115 cities in 2000 and 2010. Four spatial metrics, including population density, a contiguity index, a fractal dimension index, and a shape index, are used to quantify urban form. The paper compares urban form across four economic zones and across cities of different sizes. Ordinary least square and first-difference regression models are used to analyze the determinants of urban form. The results show that urban sprawl in China is characterized by decreased population density and greater irregularity and complexity of urban built-up areas. Metrics, such as Gross Domestic Product, population, transportation costs, and economical structure are associated with urban form in different ways, and urban expansion based on large-scale industrialization and real estate development is unsustainable in the new era.

Population density and developmental stress in the Neolithic: A diachronic study of dental fluctuating asymmetry at Çatalhöyük (Turkey, 7,100-5,950 BC).

The transition from foraging to farming is usually associated with unprecedented population densities coupled with an increase in fertility and population growth. However, little is known about the biological effects of such demographic changes during the Neolithic. In the present work, we test the relationship between diachronic changes in population size, relative exposure to developmental stressors, and patterns of dental fluctuating asymmetry in the Neolithic population of Çatalhöyük (Turkey, 7,100-5,950 cal BC). We calculate fluctuating asymmetry of mesio-distal and bucco-lingual diameters of upper and lower permanent canines and first and second molars on a large (N = 259) sample representing adults of both sexes and various age classes. Results show only a moderate decrease of fluctuating asymmetry during the late phase of occupation of the site, possibly linked to a decrease in population density, and no differences in asymmetry between sexes. Though preliminary, our data reflect the presence of developmental stressors throughout the occupation of the site, albeit with a slight improvement in living conditions during the latest periods of occupation. At the same time, these data confirm the key role of diet as buffer against the detrimental effects of fluctuating demographic pressures on the biology of prehistoric human populations.

Quantifying urban growth in 10 post-Soviet cities using Landsat data and machine learning

ABSTRACTUrbanization is one of the most irreversible anthropogenic forms of land use. Unplanned and rapid urban growth can result in environmental degradation, sprawl, and unsustainable production and consumption practices. The unique challenges facing the post-Soviet countries throughout the transition period highlight the critical need for a quantitative assessment of urban dynamics. Total of 32 Level-1 precision terrain corrected (L1T) Landsat scenes with 30 m resolution and auxiliary population and economic data were utilized to quantify the urban expansion dynamics in 10 cities across nine post-Soviet republics. Land cover was classified by using Support Vector Machine (SVM) learning algorithm with overall accuracies ranging from 87% to 97% for 29 classification maps over three time steps. The initial time step was the year 1989 ± 2, the middle time step was the year 2000 ± 2, and the final time step was the year 2015 ± 2. The results demonstrated several spatial and temporal urban expansion patterns across the post-Soviet region. The urban land area in several cities increased significantly over the study period. The average annual urban expansion rate was 1.6 ± 0.7 % per year for 10 cities over the study period and the average area of land converted to new urban environment was 227 ± 224 km2 with a corresponding average per cent increase of 54.5 ± 26.7%. Furthermore, the results demonstrated significant decrease in overall population densities across the 10 cities with an average decrease of −26.9 ± 14.8% over the study period. The urban expansion rates considerably outpaced the urban population growth rates in all 10 cities during the last quarter of a century, indicating more expansive urban growth patterns.

Cast away: drift as the main determinant for larval survival in western fire salamanders (Salamandra salamandra) in headwater streams

AbstractUnidirectional drift is amongst the most relevant population regulators in riverine animal populations. Drift occurs randomly, but it can also be a behavioural response to abiotic and biotic stressors, or the result of catastrophic events such as heavy rain. In this study, we investigate the spatiotemporal distribution of larvae of the fire salamander (Salamandra salamandra) in three headwater streams in the Eifel mountains, Western Germany. We marked 568 salamander larvae to conduct capture–recapture estimates of abundance, and followed their individual fate throughout the season. Population density of larval salamanders along the stream showed both strong temporal and spatial variation. Random drift of salamander larvae was particularly rare, and drift did not result in a size structuring of larval populations in the field. Yet, catastrophic events of high summer precipitation were the best predictor for pulse‐wise restructuring of the salamander larvae's density distribution. Strong discharge coincided with a severe decrease in population density, and thus appears to be the most relevant cause of mortality for salamander larvae. Furthermore, we find strong indications that drift has the potential to influence this species’ evolutionary processes, as well as its ecological prevalence.