Decline In Population Density Research Articles

Evolutionary Characteristics of Urban Public Space Accessibility for Vulnerable Groups from a Perspective of Temporal–Spatial Change: Evidence from Nanjing Old City, China

Social equity/inequity and equal/unequal rights to the city extend beyond the distribution of urban parks and green spaces, necessitating research on equitable accessibility to encompass a broader range of public spaces. However, previous research has predominantly focused on green spaces, neglecting other types of public spaces. To address this gap, the present study takes the public space pattern of Nanjing Old City as the research object, employing the minimum distance method, the gravity potential method, and bivariate local Moran’s I to evaluate the matching relationship between the demand of socially vulnerable groups and the supply of public spaces, as well as its temporal–spatial evolution from 2010 to 2020. The results reveal spatial heterogeneity in the accessibility of public spaces for vulnerable groups at the block level, with 28.1% of the total number of blocks and 22.1% of the total area of blocks experiencing a supply–demand imbalance in 2010. From 2010 to 2020, under the rapid urban development, construction of public spaces, and the general decline in population density and proportion of vulnerable populations, the supply–demand imbalance has exacerbated the distribution of public spaces at both individual and aggregate levels. This imbalance is reflected in the deteriorated accessibility of public spaces for vulnerable groups. This study reveals the mismatches between development, population movement, and public space construction in the old city of Nanjing over the past decade, providing decision-making suggestions and foundations for the future optimization of public spaces, thereby offering an effective tool for assessing and improving the accessibility and equitable distribution of public spaces based on the needs of vulnerable groups.

Evolutionary Characteristics of Urban Public Space Accessibility for Vulnerable Groups from a Perspective of Temporal–Spatial Change: Evidence from Nanjing Old City, China

Social equity/inequity and equal/unequal rights to the city extend beyond the distribution of urban parks and green spaces, necessitating research on equitable accessibility to encompass a broader range of public spaces. However, previous research has predominantly focused on green spaces, neglecting other types of public spaces. To address this gap, the present study takes the public space pattern of Nanjing Old City as the research object, employing the minimum distance method, the gravity potential method, and bivariate local Moran’s I to evaluate the matching relationship between the demand of socially vulnerable groups and the supply of public spaces, as well as its temporal–spatial evolution from 2010 to 2020. The results reveal spatial heterogeneity in the accessibility of public spaces for vulnerable groups at the block level, with 28.1% of the total number of blocks and 22.1% of the total area of blocks experiencing a supply–demand imbalance in 2010. From 2010 to 2020, under the rapid urban development, construction of public spaces, and the general decline in population density and proportion of vulnerable populations, the supply–demand imbalance has exacerbated the distribution of public spaces at both individual and aggregate levels. This imbalance is reflected in the deteriorated accessibility of public spaces for vulnerable groups. This study reveals the mismatches between development, population movement, and public space construction in the old city of Nanjing over the past decade, providing decision-making suggestions and foundations for the future optimization of public spaces, thereby offering an effective tool for assessing and improving the accessibility and equitable distribution of public spaces based on the needs of vulnerable groups.

Sixty years of species diversity and population density decline of freshwater mussels in a global biodiversity hotspot

Sixty years of species diversity and population density decline of freshwater mussels in a global biodiversity hotspot

Low‐ and high‐intensity fire in the riparian savanna: Demographic impacts in an avian model species and implications for ecological fire management

Abstract Climate change is driving changes in fire frequency and intensity, making it more urgent for conservation managers to understand how species and ecosystems respond. In tropical monsoonal savannas—Earth's most fire‐prone landscapes—ecological fire management aims to prevent intense wildfires late in the dry season through prescribed low‐intensity burns early in the dry season. Riparian habitats embedded within tropical savannas represent critical refuges for biodiversity, yet are particularly fire‐sensitive. Better understanding of the impact of fire—including prescribed burns—on riparian habitats is therefore key but requires long‐term detailed post‐fire monitoring of species' demographic rates, as effects may persist and/or be delayed. We analyse impacts of (prescribed) low‐intensity and (prescribed but escaped) high‐intensity fire in northern Australian riparian and adjacent savanna habitat. We quantify multi‐year impacts on density, survival, reproduction and dispersal of an endangered riparian bird, the western purple‐crowned fairy‐wren (Malurus coronatus coronatus), in a well‐studied individually marked population. Following low‐intensity fire, bird density was reduced by >20% in burnt compared to adjacent unburnt riparian habitat for ≥2.5 years. This was a result of reduced breeding success and recruitment for 2 years immediately following fire, rather than mortality or dispersal of adults. In contrast, high‐intensity fire (in a dry year) resulted in a sharp decline in population density by 50% 2–8 months after fire, with no signs of recovery after 2.5 years. The decline in density was due to post‐fire adult mortality, rather than dispersal. Breeding success of the (few) remaining individuals was low but not detectably lower than in unburnt areas, likely because breeding success was poor overall due to prevailing dry conditions. Synthesis and applications. Even if there is no or very low mortality during fire, and no movement of birds away from burnt areas, both low‐ and high‐intensity fire in the riparian zone reduce population density. However, the mechanism by which this occurs, and recovery time, differs with fire intensity. To minimise impacts of fire on riparian zones in tropical savannas, we suggest employing low‐intensity prescribed burns under optimal conditions shortly after the breeding season.

The levelling-off and recent rapid decline in population density of the highly prolific invasive lionfish on the Saba Bank, Eastern Caribbean

Since its introduction in the Western Atlantic more than 30 years ago, the lionfish (Pterois volitans/miles complex) has spread throughout the Gulf of Mexico, the Caribbean and the Western Tropical Atlantic, with massive and unprecedented ecological impacts. This invasion is among the most studied marine fish invasions but very little is still really known about the population dynamics of the species and the factors ultimately governing its abundance. The species was first documented on the Saba Bank in 2010 and rapidly increased in abundance till the end of 2014. In this note we document its rise and subsequent decline in density and thereby describe the species’ third apparent local population boom-bust event for the Greater Caribbean. We also document gradual increases in the mean size of lionfish of the Eastern Caribbean Saba Bank that coincided with the increase and subsequent decline in abundance. Contrary to the previously documented epizootic disease outbreak associated with the population crash observed in the Gulf of Mexico we were unable to find any signs of the occurrence of epizootic disease. We suggest that the population decline on the Saba Bank might have been due to non-local causes. Boom-bust dynamics are often witnessed in biological invasions and have critical implications for both understanding and managing invasive species. While the underlying cause for the boom-bust event we document remains unknown, our work suggests that in the region, ecological feedback mechanisms are gradually developing that can help level-off deleterious population excesses of this invasive species.

Identifying the Driving Forces of Alpine Wetland Dynamic Changes in the Yellow River Source National Park from 2000 to 2020

The Yellow River Source National Park (YRSNP), one of largest alpine wetlands in China which serves as the origin of the Yellow River, is situated in the heart of the Qinghai–Tibetan Plateau. The alpine wetland ecosystem, which is its primary ecological system, is crucial for maintaining ecological balance, preserving biodiversity, and facilitating the sustainable development of the Yellow River Basin. In this study, based on the Google Earth Engine (GEE) platform combined with Landsat 5 7 8 remote sensing images, we used a random forest classification model to identify and classify the alpine wetland from 2000 to 2020 and analyze its pattern of dynamic changes. The main driving forces that drive the change of the alpine wetland area in the YRSNP from 2000 to 2020 are identified using a random forest regression analysis in combination with data on precipitation, temperature, potential evapotranspiration, soil moisture, and population density. The results show that: (1) From 2000 to 2020, the average overall accuracy of remote sensing classification and extraction of the YRSNP alpine wetlands is 0.8492 and the Kappa coefficient is 0.8051. (2) From 2000 to 2020, the shrinking trend of the YRSNP alpine wetland area is restrained. However, the lake wetland, marsh wetland, and marsh meadow all increase by 0.58%, 0.06%, and 3.34%, respectively, whereas the river wetland shows a declining trend. (3) The results of the identification of driving forces indicate that soil moisture is the main factor influencing the dynamic changes of the alpine wetland, although the decline in population density has a favorable impact on the alpine wetland. The results can provide scientific basis for maintaining the stability, diversity, and sustainability of the alpine wetland ecosystem in the Yellow River Source National Park.

DICHOTOMY IN THE DISTRIBUTION OF MARITIME ACTIVITY BETWEEN MARINE SUB-REGIONS OF EUROPE

Coastal settlements tend to have higher population density and economic clustering compared to inland territories. The tendency of an increasing socio-economic disbalance in favor of coastal spaces – the coastalization, has attracted the attention of the global academic community. Numerous assumptions are made on the cause of the coastalization phenomenon with the maritime activity and tourism being the primary ones. The aim of this study is to evaluate the role of the coast and tourist seaport infrastructure in the distribution of the population and tourist accommodations in cities across different sea basins of Europe. The research design implies verification of the two hypotheses: the area around the tourist seaport will have H1. The highest population density and H2. The highest density of collective accommodation facilities (CAFs) in the coastal zone of the municipality, decreasing with distance. The methodology has a two-stage structure. Firstly, the quantitative evaluation is done to allocate the tourist seaports of 28 European countries using MarineTraffic database and measure the density of population and CAFs by territorial zones using statistics. Secondly, the qualitative assessment is done presenting highlights of case studies by four sea basins (Baltic Sea, Black and Azov Sea, Northeast Atlantic Ocean, Celtic Sea, and Mediterranean Sea) and six sub-basins. 43 seaports of Europe specialize on tourism (over 90% of inbound ships). Most tourist seaports belong to the Mediterranean basin (58.1%), followed by the basin of the Northeast Atlantic Ocean (25.6%), the Azov-Black (11.6%) and Baltic (4.7%) sea basins. Cities with the tourist seaports are represented by a variety population sizes: from under 50 thousand people to over a million. Despite the differences across sea basins, the general pattern suggests a decline of population density and CAFs with the distance from the tourist seaport. Tourist seaports act as the nuclei of coastalization in Europe. The spatial proximity to the seaport has a positive influence on the density of population – the highest in the territorial zone of 2-5 km distance from the seaport, and an even higher effect on the concentration of CAFs – the highest numbers up to 1 km of the tourist seaport. We should note that population structure and tourism activity of some smaller cities are skewed towards larger adjacent cities, with the agglomeration effect outbreaking the role of the seaport.

Airports and population density: where benefits outweigh costs

ABSTRACT This study investigates the impact of airports on population density distribution in the surrounding areas. Using data for 197 European airports, results show that a 10% increase in airport activity leads to a growth in population density of 3.8%. While moving farther from the city centre leads to a decline in population density, we demonstrate that, on average, population density increases up to 7.5 km from the airport, then starts to decrease beyond that threshold. This threshold can be interpreted as the point in space where positive effects start outweighing negative externalities.

Reexamination of the Purported Rapid Population Decline of Plains Spotted Skunks in the Mid-Twentieth Century

Spilogale putorius interrupta (Plains Spotted Skunk) was once common across its range in the United States from the Mississippi River to the Rocky Mountains, but it is now rare and being considered for protection under the federal Endangered Species Act. Disease and introduction of agricultural chemicals have been suggested as potential causes of an ostensible rapid decline of >90% in Plains Spotted Skunk populations in the 1940s. I examined published scientific literature, agency reports, and other historical accounts to determine if such a decline actually took place and if there is any evidence that these factors could have caused such a decline. I found anecdotal information implying that there were declines in some states, but I found no substantiation of a widespread precipitous decline during the 1940s-1950s. Harvest records of Plains Spotted Skunks, Didelphis virginiana (Virginia Opossum), and Mephitis mephitis (Striped Skunk) from the central United States all demonstrate similar rates of decline and this, along with nationwide information suggest that the fall in Plains Spotted Skunk harvests during this period was due to a crash in demand across the entire fur market. There was an extensive rabies epidemic during this period but little data supportive of it causing a population crash. Similarly, usage of chemicals for agricultural pest and weed control was found throughout the species range, but only on such a small percentage of farms it is unlikely to have had significant impact on their population. The Plains Spotted Skunk most likely experienced a long, gradual decline in population density and scientists should undertake research focused on potential causes of decline relevant to this timescale such as changes in agricultural practices or predator guilds so as to develop testable hypotheses that will lead to effective conservation actions that will benefit the species.

Complex Linkage between Watershed Attributes and Surface Water Quality: Gaining Insight via Path Analysis

Understanding the influence of various variables on surface water quality is extremely important for protecting ecosystem health. The principal aim of this study is to assess the direct (DE), indirect (IE) and total effects (TE) of socio-economic, terrestrial and hydrological factors on surface water quality via path analysis through the lens of 15 sub-basins located on Indus basin, Pakistan. Four path models were selected based on Comparative Fit Index (CFI) = 0.999 value. First path model showed that rangelands having low population density decline river runoff which decreases instream Electrical Conductivity (EC) because of lower anthropogenic activities. Second path model depicted that croplands having higher population density enhance river runoff due to irrigation tail water discharge which decline instream EC because of dilution. Third path model showed that croplands with higher population density enhance river runoff which increases instream NO3 concentration because of unscientific application of irrigation water. Fourth path model unveiled that croplands enhance Gross Domestic Product (GDP) which enhance river runoff and instream NO3 concentration. To protect ecosystem health, Best Management Practices (BMPs), precision farming and modern irrigation techniques should be adopted to reduce irrigation tail water discharges containing pollutants entry in Indus River. Doi: 10.28991/cej-2021-03091683 Full Text: PDF

Expansion in the shrinking cities: Does place-based policy help to curb urban shrinkage in China?

Currently, China is experiencing rapid urbanization, while most cities with a persistent population loss are experiencing urban expansion. This seemingly contradictory pattern of “expansion in shrinkage” arises from the place-based policies. According to the efficiency-priority principle, place-based policies should be applied to densely populated cities. For regional balance, however, these policies are being increasingly implemented in shrinking cities. As a result, the following often-overlooked but highly important question arises: are place-based policies beneficial for shrinking cities? Alternatively, can the pattern of “expansion in shrinkage” succeed in the long run? Concerning these issues, we first identified 37 population-shrinking cities and 144 density-shrinking cities from 2006 to 2016 in China. By using the upgrade of development zones as the source of the exogenous variation in the implementation of place-based policies, we identified the causal effects of place-based policies on urban shrinkage. The results show that a development zone policy helps to curb the population loss of shrinking cities, and this effect is enhanced over time. In contrast, the declining population density did not show a significant change due to the expansion of urban construction land caused by the development zone policy. This indicates that in the short term, the development zone policy in shrinking cities curbs population loss at the expense of resource allocation efficiency. In the third year of the policy, however, the decline in urban population density begins to slow down. This is a signal that the development zone policy in shrinking cities may recover the initial efficiency loss, while curbing population loss in the future. In the long run, the success of the “expansion in shrinkage” pattern depends on the urban agglomeration economy. In addition, the curbing-effect on population loss is different depending on the characteristics of cities and development zones.

Loss of vocal culture and fitness costs in a critically endangered songbird.

Cultures in humans and other species are maintained through interactions among conspecifics. Declines in population density could be exacerbated by culture loss, thereby linking culture to conservation. We combined historical recordings, citizen science and breeding data to assess the impact of severe population decline on song culture, song complexity and individual fitness in critically endangered regent honeyeaters (Anthochaera phrygia). Song production in the remaining wild males varied dramatically, with 27% singing songs that differed from the regional cultural norm. Twelve per cent of males, occurring in areas of particularly low population density, completely failed to sing any species-specific songs and instead sang other species' songs. Atypical song production was associated with reduced individual fitness, as males singing atypical songs were less likely to pair or nest than males that sang the regional cultural norm. Songs of captive-bred birds differed from those of all wild birds. The complexity of regent honeyeater songs has also declined over recent decades. We therefore provide rare evidence that a severe decline in population density is associated with the loss of vocal culture in a wild animal, with concomitant fitness costs for remaining individuals. The loss of culture may be a precursor to extinction in declining populations that learn selected behaviours from conspecifics, and therefore provides a useful conservation indicator.

Settlement changes after peak population: Land system projections for China until 2050

China has experienced unprecedented urbanization in the past few decades, fueled by population growth, economic development, and rural to urban migration. In the future, economic growth as well as rural to urban migration is expected to continue, but demographic scenarios indicate that the population of China will peak and subsequently decline. As a result, it is unsure how urban areas will develop after peak population. In this study we further develop the CLUMondo land system model to simulate land system changes in China until 2050. Our application represents a range of settlement systems, from dense urban areas to village landscapes, differing in their built-up area as well as their population density to enable the simulation of different settlement change trajectories. Our results show that a UN high population scenario in combination with a continued decline in population density leads to an increase of built-up land of about 48%. Conversely, the UN low population scenario in combination with a constant population density could be accommodated within the current amount of built-up land in China. Due to prevailing cropland protection policies, increase in built-up land will mostly lead to a loss of natural areas, hence our scenarios highlight the opportunity space for limiting land take and saving natural areas. This study also demonstrates the need for more nuanced representation of settlement systems for the assessment of land change trajectories.

Bioecology of the guava weevil Conotrachelus psidii Marshall (Coleoptera: Curculionidae)

The guava weevil, Conotrachelus psidii Marshall (Coleoptera: Curculionidae), is a key pest in guava and information concerning the bioecology of this insect is scarce. This work aimed to verify the bioecology of certain aspects of this insect's lifecycle by observations of the period during which the larvae abandon the fruits in order to enter the soil to pupate, the effect of different soil types on penetration times and the subsequent emergence of adults from the soil. Adult population levels were monitored over a two year period and the possible relationship between population density and climatic factors investigated. The abandonment of guava fruits by the larvae was evaluated during two time periods (day-time and night-time). The time taken for 4th instar larvae to penetrate 3 different soil types was observed. The time these insects remained underground and subsequent adult emergence periodicity was evaluated following the release of 4th instar larvae into trays filled with soil. These trays were maintained in the field and observations carried out three times a day (morning, noon, and afternoon). Path analysis was used to investigate the relationship between the climate variables and adult population density. Soil penetration by 4th instar larvae was fastest in clay soils and slowest in sand. There was no difference (p = 0.075) between the number of larvae that abandoned the fruits during the day (51%) and during the night (49%). A majority of the adults emerged from the soil during daytime (86.84%), which was significantly different (p < 0.001) to the number of adults emerging during the night (13.16%). When comparing adult emergence during different periods of the day, the majority emerged in the afternoon (93.94%), with only 6% emerging in the morning (p < 0.001). The average time period between penetration of the soil by 4th instar larvae and adult emergence was approximately nine months (272 days). Adult population density fluctuations were similar during both years studied here, with the lowest population seen from May to August, a peak in November, and then a decline in population density until March. Path analysis showed that rainfall positively influenced C. psidii population density. The results of this work will be important for the development of sustainable IPM programs aiming to control this serious pest of guava orchards.

Alarming decline of bovids in Kasanka National Park, Zambia: A case study of the puku antelope (Kobus vardonii)

AbstractKnowledge about antelope populations and their status is a key for conservation. In November 2019, we used distance sampling to perform a re‐survey of the bovid species in Kasanka National Park, Zambia, with a focus on the puku (Kobus vardonii). Data collection and subsequent analyses were of the same design as in a previous survey in 2009–2010. This allowed for the direct comparison between survey periods, especially for the data collected in November 2010 and 2019. The estimated puku population size decreased from 5,038 (range 3,268–7,238) animals in 2009–2010 to 819 (range 250–2,708) animals in 2019, representing an 84% decline. Smaller group sizes were observed. Changes in population structure (decline in male abundance, fewer male groups) and spatial distribution (decline in population density, especially along the park boundaries) of puku showed signs of increased poaching activities in Kasanka National Park. Also, puku became more vigilant and demonstrated significantly longer flight distances in 2019 in comparison with 2010. A strong decline in puku in combination with clear signs of poaching, as well as the reduced species richness and sightings of other bovids, should become an agenda for long‐term conservation of Kasanka National Park.

Individual-based model of population dynamics in a sea urchin of the Kerguelen Plateau (Southern Ocean), Abatus cordatus, under changing environmental conditions

The Kerguelen Islands are part of the French Southern Territories, located at the limit of the Indian and Southern oceans. They are highly impacted by climate change, and coastal marine areas are particularly at risk. Assessing the responses of species and populations to environmental change is challenging in such areas for which ecological modelling can constitute a helpful approach. In the present work, a DEB-IBM model (Dynamic Energy Budget – Individual-Based Model) was generated to simulate and predict population dynamics in an endemic and common benthic species of shallow marine habitats of the Kerguelen Islands, the sea urchin Abatus cordatus. The model relies on a dynamic energy budget model (DEB) developed at the individual level. Upscaled to an individual-based population model (IBM), it then enables to model population dynamics through time as a result of individual physiological responses to environmental variations. The model was successfully built for a reference site to simulate the response of populations to variations in food resources and temperature. Then, it was implemented to model population dynamics at other sites and for the different IPCC climate change scenarios RCP 2.6 and 8.5. Under present-day conditions, models predict a more determinant effect of food resources on population densities, and on juvenile densities in particular, relative to temperature. In contrast, simulations predict a sharp decline in population densities under conditions of IPCC scenarios RCP 2.6 and RCP 8.5 with a determinant effect of water warming leading to the extinction of most vulnerable populations after a 30-year simulation time due to high mortality levels associated with peaks of high temperatures. Such a dynamic model is here applied for the first time to a Southern Ocean benthic and brooding species and offers interesting prospects for Antarctic and sub-Antarctic biodiversity research. It could constitute a useful tool to support conservation studies in these remote regions where access and bio-monitoring represent challenging issues.

GPS tracking data of Western marsh harriers breeding in Belgium and the Netherlands.

In this data paper three datasets are described containing GPS tracking and acceleration data of Western marsh harriers (Circus aeruginosus) breeding in Belgium and the Netherlands. The Western marsh harrier is included as a threatened bird species in Annex I of the European Bird Directive due to the steep decline in population densities. In order to collect data of habitat use and migration behaviour, Western marsh harriers were equipped with light-weight solar powered GPS trackers developed by the Institute for Biodiversity and Ecosystem Dynamics (IBED) at the University of Amsterdam (University of Amsterdam Bird Tracking System, UvA-BiTS). These trackers automatically collect and store data on the bird’s activity and 3D position in time and transmit these data to ground stations.The datasets were collected by the Research Institute for Nature and Forest (INBO) and the Dutch Montagu’s Harrier Foundation. Tracked Western marsh harriers were breeding in the northeast of the Dutch province of Groningen and on the opposite side of the river Ems in Germany (H_GRONINGEN), in the region of Waterland-Oudeman near the Belgian-Dutch border (MH_WATERLAND), and at the left bank of the Scheldt estuary, close to the Belgian-Dutch border and north of the city of Antwerp (MH_ANTWERPEN). Most individuals remained within 10 km from their nesting sites during the breeding season and wintered in West Africa. H_GRONINGEN contains 987,493 GPS fixes and 3,853,859 acceleration records of four individuals since 2012. MH_WATERLAND contains 377,910 GPS fixes of seven individuals. Sampling in this region began in 2013. Three more Western marsh harriers were tagged in the Scheldt estuary near Antwerp more recently in 2018 (one individual) and 2019 (two individuals) for the MH_ANTWERPEN study, which contains 47,917 GPS fixes and 227,746 acceleration records.The three Western marsh harrier datasets were published as separate studies in Movebank (https://www.movebank.org) and archived as data packages in Zenodo (https://www.zenodo.org) to ensure long-term preservation and versioning of the data.

The heterogeneity and change in the urban structure of metropolitan areas in the United States, 1990\u20132010

While the population of the United States has been predominantly urban for nearly 100 years, periodic transformations of the concepts and measures that define urban places and population have taken place, complicating over-time comparisons. We compare and combine data series of officially-designated urban areas, 1990–2010, at the census block-level within Metropolitan Statistical Areas (MSAs) with a satellite-derived consistent series on built-up area from the Global Human Settlement Layer to create urban classes that characterize urban structure and provide estimates of land and population. We find considerable heterogeneity in urban form across MSAs, even among those of similar population size, indicating the inherent difficulties in urban definitions. Over time, we observe slightly declining population densities and increasing land and population in areas captured only by census definitions or low built-up densities, constrained by the geography of place. Nevertheless, deriving urban proxies from satellite-derived built-up areas is promising for future efforts to create spatio-temporally consistent measures for urban land to guide urban demographic change analysis.

Can data from native mosquitoes support determining invasive species habitats? Modelling the climatic niche of Aedes japonicus japonicus (Diptera, Culicidae) in Germany

Invasive mosquito species and the pathogens they transmit represent a serious health risk to both humans and animals. Thus, predictions on their potential geographic distribution are urgently needed. In the case of a recently invaded region, only a small number of occurrence data is typically available for analysis, and absence data are not reliable. To overcome this problem, we have tested whether it is possible to determine the climatic ecological niche of an invasive mosquito species by using both the occurrence data of other, native species and machine learning. The approach is based on a support vector machine and in this scenario applied to the Asian bush mosquito (Aedes japonicus japonicus) in Germany. Presence data for this species (recorded in the Germany since 2008) as well as for three native mosquito species were used to model the potential distribution of the invasive species. We trained the model with data collected from 2011 to 2014 and compared our predicted occurrence probabilities for 2015 with observations found in the field throughout 2015 to evaluate our approach. The prediction map showed a high degree of concordance with the field data. We applied the model to medium climate conditions at an early stage of the invasion (2011–2015), and developed an explanation for declining population densities in an area in northern Germany. In addition to the already known distribution areas, our model also indicates a possible spread to Saarland, southwestern Rhineland-Palatinate and in 2015 to southern Bavaria, where the species is now being increasingly detected. However, there is also evidence that the possible distribution area under the mean climate conditions was underestimated.

A Negative Binomial Regression Model of the Observed Population Density of Heterodera glycines after Annual Corn Rotation in Nebraska.

In Nebraska, rotation of soybean (Glycine max) fields to corn (Zea mays) is a major practice to manage the soybean cyst nematode (SCN; Heterodera glycines). However, factors associated with SCN population density decline during corn rotation are not clearly defined. This study addresses that question using a modeling approach. Seventy-nine fields were sampled in 2009, 2010, and 2011 to determine SCN population densities (eggs/100 cm3 of soil) before and after rotation. After rigorous field screening and model testing and validation, the regression model was developed, where Log Pf is the natural log of SCN eggs at the end of the rotation year, Pi is the population density before rotation, and pH is the soil pH. Model goodness-of-fit was assessed through residual analysis, information criteria, and other remedial measures. Model overdispersion was 1.04. Validation in a 50 and a 75% random sample from the original data set showed little change in model regression coefficients, standard errors, and associated significance, confirming model fit and performance. The model indicates that for one-unit increase in soil pH, SCN Pf is expected to increase by 53.7% at constant Pi, and correspondingly, a 10% change in Pi will result in about 8.3% change in Pf at constant soil pH. The model suggested that SCN population levels before corn rotation and soil pH are major determinants of observed SCN population density reduction after annual corn rotation in Nebraska. This model has potential for use in SCN risk analysis and in predicting SCN population decline after corn rotation in the state.