Decrease In Population Density Research Articles

Cooperation in public goods game does not require assortment and depends on population density.

The threshold public goods game is one of the best-known models of nonlinear public goods dilemmas. Cooperators and defectors typically coexist in this game when the population is assumed to follow the so-called structured deme model. In this paper we develop a dynamical model of a general N-player game in which there is no deme structure: individuals interact with randomly chosen neighbours and selection occurs between randomly chosen pairs of indi- viduals. We show that in the deterministic limit the dynamics in this model leads to the same replicator dynamics as in the structured deme model, i.e. coexistence of cooperators and defectors is typical in threshold public goods game even when the population is completely well-mixed. We extend the model to study the effect of density dependence and density fluctuation on the dynamics. We show analytically and numerically that decreasing population density increases the equilibrium frequency of cooperators till the fixation of this strategy, but below a critical density coop- erators abruptly disappear from the population. Our numerical investigations show that weak density fluctuations enhance cooperation, while strong fluctuations suppress it.

Effects of poor recruitment on riverine Smallmouth Bass population dynamics

AbstractObjectiveAltered flow regimes pose significant risks to the stability of populations of riverine Smallmouth Bass Micropterus dolomieu. Periods of poor recruitment, due to early life stage mortality resulting from high‐flow events, can cause size‐structure and density alterations of populations. The aim of this study was to opportunistically test for changes in dynamic rates of a riverine Smallmouth Bass population using a long‐term data set that spanned a period of poor recruitment.MethodsOur study evaluated size‐specific CPUE (fish/h), mortality, growth, and condition and tested for recruitment determinants of Smallmouth Bass through three consecutive years of poor age‐0 recruitment in the South Branch Potomac River, West Virginia. We used fall nighttime boat electrofishing surveys during 2009–2022 to monitor this population before and after the poor‐recruitment time frame (2016–2018).ResultAge‐0 CPUE was greater during the time frame prior to the poor‐recruitment time frame. However, there was no difference in the CPUE of quality‐length Smallmouth Bass between the two time frames and CPUE of preferred‐length fish was greater during the poor‐recruitment time frame. Growth and relative weight increased during the poor‐recruitment time frame. There was no significant difference detected in mortality between the recruitment time frames. Streamflow during the spawning period was a significant factor influencing fall recruitment of age‐0 Smallmouth Bass. A Ricker density‐dependent model with an added streamflow term performed as well as a basic, log‐linear streamflow model and a density‐independent model that also incorporated a streamflow term.ConclusionOur results provide evidence of density‐dependent structuring in this population. Decreases in population density increased population dynamic rates that maintained or improved size structure. High adult biomasses did not increase age‐0 recruitment. Many riverine Smallmouth Bass populations may display favorable density‐dependent responses to declines in juvenile recruitment. Thus, management agencies should better understand the resiliency of these populations prior to establishing expensive programs or regulations, which may be ineffective, to combat alterations in juvenile recruitment.

A review of heavy metal risks around e-waste sites and comparable municipal dumpsites in major African cities: Recommendations and future perspectives

In Africa, the effects of informal e-waste recycling on the environment are escalating. It is regularly transported from developed to developing nations, where it is disassembled informally in search of precious metals, thus increasing human exposure to harmful compounds. Africa has a serious problem with e-waste, as there are significant facilities in Ghana and Nigeria where imported e-waste is unsafely dismantled. however, because they are in high demand and less expensive than new ones, old electronic and electrical items are imported in large quantities, just like in many developing nations. After that, these objects are frequently scavenged to recover important metals through heating, burning, incubation in acids, and other techniques. Serious health hazards are associated with these activities for workers and individuals close to recycling plants. At e-waste sites in Africa, there have been documented instances of elevated concentrations of hazardous elements, persistent organic pollutants, and heavy metals in dust, soils, and vegetation, including plants consumed as food. Individuals who handle and dispose of e-waste are exposed to highly hazardous chemical substances. This paper examines heavy metal risks around e-waste sites and comparable municipal dumpsites in major African cities. Elevated concentrations of these heavy metals metal in downstream aquatic and marine habitats have resulted in additional environmental impacts. These effects have been associated with unfavourable outcomes in marine ecosystems, such as reduced fish stocks characterized by smaller sizes, increased susceptibility to illness, and decreased population densities. The evidence from the examined studies shows how much e-waste affects human health and the environment in Africa. Sub-Saharan African nations require a regulatory framework that includes specialized laws, facilities, and procedures for the safe recycling and disposal of e-waste.

Hospitalization and readmission after single-level fall: a population-based sample

BackgroundSingle-level falls (SLFs) in the older US population is a leading cause of hospital admission and rates are increasing. Unscheduled hospital readmission is regarded as a quality-of-care indication and a preventable burden on healthcare systems. We aimed to characterize the predictors of 30-day readmission following admission for SLF injuries among patients 65 years and older.MethodsWe conducted a retrospective cohort study using the Nationwide Readmission Database from 2018 to 2019. Included patients were 65 and older, admitted emergently following a SLF with a primary injury diagnosis. Hierarchical logit regression was used to model factors associated with readmission within 30 days of discharge.ResultsOf 1,338,905 trauma patients, 65 years or older, 61.3% had a single-level fall as the mechanism of injury. Among fallers, the average age was 81.1 years and 68.5% were female. SLF patients underwent more major therapeutic procedures (56.3% vs. 48.2%), spent over 2 million days in the hospital and incurred total charges of over $28 billion annually. Over 11% of SLF patients were readmitted within 30 days of discharge. Increasing income had a modest effect, where the highest zip code quartile was 9% less likely to be readmitted. Decreasing population density had a protective effect of readmission of 16%, comparing Non-Urban to Large Metropolitan. Transfer to short-term hospital, brain and vascular injuries were independent predictors of 30-day readmission in multivariable analysis (OR 2.50, 1.31, and 1.42, respectively). Palliative care consultation was protective (OR 0.41). The subsequent hospitalizations among those 30-day readmissions were primarily emergent (92.9%), consumed 260,876 hospital days and a total of $2.75 billion annually.ConclusionsSLFs exact costs to patients, health systems, and society. Transfer to short-term hospitals at discharge, along with brain and vascular injuries were strong predictors of 30-day readmission and warrant mitigation strategy development with consideration of expanded palliative care consultation.

Exploring the nexus of climate variability, population dynamics, and maize production in Togo: Implications for global warming and food security

Maize, which serves as the primary staple crop in Togo, plays a crucial role in supporting rural communities and ensuring food security. Comprehending the complex relationship between Togo's maize production, population dynamics, and climate variability is crucial for mitigating the impacts of global warming and guaranteeing long-term food security. The present study examines the climate patterns and their impact on maize cultivation in Togo for the period spanning from 1990 to 2020. During this temporal interval, significant variations were seen in important climate indices. The levels of rainfall and the frequency of wet days exhibited notable fluctuations, whereas the temperature and concentrations of air pollutants, specifically carbon dioxide (CO2) and nitrous oxide (N2O), had a persistent rising trajectory. The recorded temperature exhibited an increase from 27 ​°C in 1990 to 29 ​°C in 2020. The levels of CO2 emissions had a substantial increase from 1000 ​kt in 1990 to an estimated 2500 ​kt in 2020. Similarly, the emissions of N2O witnessed a notable rise of more than 800 ​kt over the same time frame. Using time series analysis, we examined the temporal characteristics and employed ARIMA predictive models to project maize production over the upcoming decade, considering the gradual decrease in rural population density. The studies highlight the significant implications of global warming on a worldwide scale, exerting a profound impact on the Earth. The agriculture sector, specifically maize production, had notable variations in yield and overall output. Notwithstanding the inherent fluctuations in output, maize continues to maintain its position as the most widely consumed and preferred crop in Togo, even in the face of the country's rapidly expanding population. As a result, Togo has increased its imports of maize to satisfy the growing demand. The present study sheds light on the intricate relationship between production parameters, including yield and quantity, and a range of environmental variables such as the frequency of precipitation, temperature, and levels of N2O, in addition to rural and urban population density. The statement underscores the pressing necessity to confront the issue of global warming and its subsequent impacts on agricultural methodologies. Furthermore, the results underscore the significance of considering population dynamics and climate variables in the prediction of forthcoming agricultural outcomes.

Enrofloxacin hydrochloride toxicological effects on crucian carp reflected by serological changes and neurotoxicity

Due to its water solubility and wide applicability, enrofloxacin hydrochloride (EH) may enter aquatic ecosystems and cause negative effects on aquatic organisms. This study aimed to explore toxicological effects via serological changes and neurotoxicity, which were induced by EH exposure in crucian carp (Carassius auratus var. Pengze). The drug residues in brain tissue and protein content in serum were determined to analyze serological changes. Alterations in brain tissue structure and function, cerebral microvessels permeability, and the expressions of gene and protein regarding blood-brain barrier (BBB) were studied to reflect the neurotoxicity. Employing a validated high-performance liquid chromatography (HPLC) method, EH residues could be detected at various time-points throughout the experiment. Enzyme-linked immunosorbent assay (ELISA) showed that EH increased the levels of S100B, NSE and GFAP proteins in serum. Additionally, there was a significant positive correlation between serum S100B, NSE protein contents and EH residues (P < 0.05). Hematoxylin and eosin (H&E) staining revealed brain damage from EH exposure by the formation of vacuoles in brain glial cells, pyknosis of the nucleus, and a decrease in cell population density. Transmission electron microscope (TEM) revealed morphological changes in microvessels and condensation of astrocyte nucleus. Evans blue (EB) permeability test visualized an obvious increase in cerebral microvessels leakage. The real-time quantitative PCR (qPCR) results indicated that EH up-regulated the mRNA expression levels of S100B, NSE and GFAP, down-regulated the mRNA expression levels of P-gp, ZO-1, Occludin and Claudin-5. The Western blot (WB) results demonstrated increased NSE and GFAP protein expressions, decreased P-gp and Occludin protein expressions following EH exposure in brain, in consistent with the gene expressions, respectively. In conclusion, these findings indicated that EH brought about marked rise in serum biomarker levels and disrupted the central nervous system (CNS) of crucian carp. These data would help elucidate the mechanism underlying EH-induced neurotoxicological effects.

Understanding the indirect impacts of urbanization on vegetation growth using the Continuum of Urbanity framework

Numerous studies investigated the direct impacts of urbanization on the loss and fragmentation of vegetated lands associated with urban expansion. Fewer studies, however, have examined the indirect impacts of urbanization on vegetation related to changes in livelihoods, lifestyles, and connectivity in non-urbanized areas, especially in the context of large-scale urban-rural migration. Here, we employ the Continuum of Urbanity framework to examine how changes in livelihoods, lifestyles, and connectivity in non-urbanized areas associated with urbanization affect vegetation, and thereby to understanding the indirect impacts of urbanization. We found there was a significant trend in human-induced EVI (HEVI) increase in non-urban areas, and such trend was coupled with decreased population density (PD) in forest land and grassland, but increased population density in cropland. The negative correlation between PD and HEVI became increasingly stronger from 2000 to 2011, but weakened since 2011. Livelihood income, lifestyles represented by consumption, and information connectivity to the outside world indirectly impacted HEVI by driving PD changes in non-urban areas. This indirect effect has shifted from positive to negative over the 20 years. These findings suggest that the indirect impacts of urbanization on vegetation growth are complicated and multifaceted, and understanding such impacts would be critically important to help turn urbanization into an opportunity for regional sustainable development.

Evaluating the cascade dam construction effects on endemic fish habitat and population status in spawning sites of Lancang River (in Tibet), China

Cascade dam constructions will alter the habitat of spawning sites and affect fish population in the Lancang River basin. This paper examines the impacts of cascade dam construction on four spawning sites, focusing on two co-distributed and endemic fish species: Schizothorax prenanti and Schizothorax davidi. An ecohydraulic modeling framework that combined hydro-morphodynamic, habitat, and population models was used to investigate changes in habitat quality and fish population under two scenarios: no-dam and with-dam. Fish habitat quality was evaluated using the habitat suitability index, and population fluctuations were assessed by the abundance and density of fish populations at all life stages. The simulation results indicated that cascade dam construction would fragment the spawning site habitat in the tailwater zone of the main stream and result in a decrease in fish population abundance and density. Conversely, spawning site habitats in backwater zone of tributaries would improve, and fish population abundance and density would increase. Additionally, the simulation results showed that the magnitude of fish population variations varied by species and life stages. These results highlight the different responses of spawning site location, fish species, and life stages to dam construction, which can help identify areas of the habitat with higher potential for finer-scale endemic fish conservation and recovery efforts. This study provides a comprehensive framework tool for fish ecological evaluation in dammed rivers, which has the potential to assist decision-makers involved in river ecosystem ecological conservation.

Study on Urban Expansion and Population Density Changes Based on the Inverse S-Shaped Function

For decades, the continuous advance of urbanization has led to the continuous expansion of urban land and rapid increase in the total area of cities. The phenomenon of urban land expansion faster than population growth has become widespread. High population density can lead to problems such as traffic congestion and exacerbated air pollution and can hinder sustainable development, affecting the quality of life of urban residents. China is currently in a phase of rapid urbanization, with high urban population density and rapid decline in urban population density. The decrease in urban population density is conducive to promoting sustainable urban development. This study selected 34 cities in China as sample cities and analyzed the spatial expansion and population density changes using land use and population density data from 2000, 2005, 2010, 2015, and 2020 in order to provide reference for controlling population density and promoting sustainable urban development. The conclusions of the study are as follows: In the 34 sample cities, the average urban radius was only 11.61 km in 2000, but reached 17.98 km in 2020, with an annual growth rate of 2.5%. There were significant spatial differences in urban expansion. Beijing and Shanghai, as the most developed cities in China, had urban radii exceeding 40 km, while the less developed cities of Liaoyang and Suzhou had urban radii of only 9 km. Although the population density decreased in most cities, the population density values in first-tier cities in China, such as Tianjin, Beijing, and Shanghai, continued to rise. Cities with loose spatial expansion patterns had faster decreases in population density than compact-type cities. The rate of urban spatial expansion was negatively correlated with changes in population density, with cities that had faster urban spatial expansion also having faster declines in artificial ground density.

Population Dynamics of Intertidal Resident Species during a Reduction in Asian Shore Crab Population

Hemigrapsus sanguineus (Asian shore crab), which is native to coastal estuarine habitats along the east coast of Asia, have overtaken a wide range of the coast in the northeastern region of the United States. Intertidal population densities of Hemigrapsus sanguineus, Cancer irroratus (Atlantic rock crab), Littorina littorea (Common periwinkle), and Modiolus demissus (Atlantic Ribbed Mussel), among others, were measured at three sample sites from 8/2/22 to 11/14/22 using quadrat sampling techniques. A period of removal was enacted solely upon Sample site #1 from 9/28/22 to 11/2/22 to cause a reduction in the Asian shore crab population. During the period of removal, no statistically significant changes in Asian shore crab demographics (Carapace size/sex ratios) would be observed (p = 0.181 for carapace size changes). There would however be an 8% decrease in Asian shore crab population density within Sample site #1, comparative to a 1% increase at Sample site 2. Rock crab population density at Sample site #1 would increase by a relatively drastic 31%, whereas the Rock crab population would experience only a 7% increase at Sample site #2. The Shannon-Weiner diversity index was used to derive the effective number of species (ENS). There would be a drastic difference in change of ENS following the removal period at Sample site #1 (increase of 0.248 ENS), and the change of ENS at Sample site #2 (decrease of 0.024 ENS), suggesting the reduction in Asian Shore Crab population played a role in increased population diversity of intertidal resident species.

Global patterns in urban green space are strongly linked to human development and population density

Urban green space is important for alleviating high temperatures, pollution, and flooding in cities. Furthermore, it is becoming increasingly clear that urban green space is important for the mental and physical health of humans residing in cities and that urban green space may harbor unique biodiversity. Understanding the extent and drivers of urban green space is thus important. While urban green space has been mapped and studied at local to national scales, the global patterns and drivers of urban green space remain unknown, potentially hampering effective planning and allocation of resources toward reaching sustainable development goals. Here, we quantified the effect of environmental and socio-economic drivers (temperature, precipitation, human development, and population density) on urban green space globally by focusing on national capital cities. We used satellite imagery to map urban green space using two measures: the Normalized Difference Vegetation Index (NDVI), and the fractional cover of “green” land cover classes. NDVI is useful as it includes all vegetated surfaces, also small ones like gardens. However, land cover classes allow the exclusion of certain classes such as sports fields or cropland. We used boosted regression trees to show that climatic variables accounted for 75 % of the relative influence in urban green space, with a positive effect of precipitation and a negative effect of temperature. Importantly, socioeconomic variables accounted for 25 % of the influence on global urban green space, with a positive effect of human development index (HDI) and a negative effect of population density. HDI in relation to urban green space has not previously been tested globally, and our study shows that significantly affects urban greenspace. The results demonstrate that cities where development status is low and population densities are high, typically in the Global South, have less urban green space than the climate would predict. The results therefore suggest that human wellbeing does not only benefit directly from increasing human development and decreasing population densities in urban areas, but that these effects may be compounded by also improving nature’s contribution to people.

Mapping and Influencing the Mechanism of CO2 Emissions from Building Operations Integrated Multi-Source Remote Sensing Data

Urbanization has led to rapid growth in energy consumption and CO2 emissions in the building sector. Building operation emissions (BCEs) are a major part of emissions in the building life cycle. Existing studies have attempted to estimate fine-scale BCEs using remote sensing data. However, there is still a lack of research on estimating long-term BCEs by integrating multi-source remote sensing data and applications in different regions. We selected the Beijing–Tianjin–Hebei (BTH) urban agglomeration and the National Capital Region of Japan (NCRJ) as research areas for this study. We also built multiple linear regression (MLR) models between prefecture-level BCEs and multi-source remote sensing data. The prefecture-level BCEs were downscaled to grid scale at a 1 km2 resolution. The estimation results verify the method’s difference and accuracy at different development stages. The multi-scale BCEs showed a continuous growth trend in the BTH urban agglomeration and a significant downward trend in the NCRJ. The decrease in energy intensity and population density were the main factors contributing to the negative growth of BCEs, whereas GDP per capita and urban expansion significantly promoted it. Through our methods and analyses, we contribute to the study of estimating greenhouse gas emissions with remote sensing and exploring the environmental impact of urban growth.

Eutrophication and contamination dynamics of Schweriner See, NE-Germany, during the past 670 years – A multi-proxy approach on lacustrine surface sediments and sediment cores

A multi-proxy study on sedimentary records from Schweriner See (See = lake), NE-Germany, covering the past 670 years (from 1350 CE to today) combined with sediment surface samples to better understand lake internal dynamics enables to reconstruct local and supra-regional eutrophication and contamination trends. Our approach shows that a thorough understanding of depositional processes is crucial for core site selection since at Schweriner See wave- and wind-induced processes in shallow water areas (e.g. reworking) or carbonate precipitation resulting from groundwater inflow may have altered the desired (in this case anthropogenic) signal. In Schweriner See both eutrophication and contamination have been directly influenced by sewage and population dynamics of the city of Schwerin and its surroundings. A higher population density resulted in increased sewage volume, which was discharged directly into Schweriner See since 1893 CE. Maximum eutrophication was reached in the 1970s but a solid improvement in water quality only occurred after the German reunification (1990) as a combined result of a decrease in population density and the connection of all households to a new sewage treatment plant, which stopped the discharge of sewage waters into Schweriner See. These counter measurements were traced within the sediment records. Eutrophication and contamination trends were detected within the lake basin as shown by remarkable similarities in signals between several sediment cores. To get an understanding of regional contamination tendencies east of the former inner German border in the recent past we compared our results with sediment records from the southern Baltic Sea area, which show similar contamination trends.

HOUSING PREFERENCE STRUCTURES IN EAST ASIA: AN EMPIRICAL STUDY AND NON-PARADIGMATIC SHIFTS BETWEEN NEARBY METROPOLES

A systematic research flow was applied to the Southern Metropolis in Taiwan not only to recount residents’ considerations in this cultural area but also to compare them with those of other metropolitans on the island in relation to general housing concerns. The constructs and factors in housing decision-making were justified using the literature, confirmed with experts in the field, and organised as a decision hierarchy that formed the foundation of a survey. The investigation combined the analytic hierarchy process and Student’s t-test, both of which are credible methods, to facilitate a grounded process for mind mining. The importance of constructs/factors were thus assessed on a numerical basis, and a set of unforeseen insights were explored for the different parties of interest (e.g., buyers, construction companies, agents, asset managers, etc.). Opinion gaps between different sample groups were identified. This set of empirical knowledge filled the gap in the literature. It is noteworthy that among the constructs in the region studied, (housing) ‘conditions’ dominated ‘price’, while ‘location and transport’ was the least important. A ‘non-paradigmatic shift’ in people’s total housing preference structure, which changed gradually with decreasing population density and increasing plain geography from the north to the south between nearby metropoles, was observed, despite the niche but commensurable cultural norm in East Asia being the overall scenario of the island. Some existing claims about the housing preferences in this area were also either supported or rebutted by the quantitative evidence(s).

Система расселения Калининградской области: дазиметрический анализ

The article examines the settlement system of the Kaliningrad region using the dasymet­ric method, first proposed in the early 20th century by the Russian geographer V. P. Se­menov-Tyan-Shansky as a more precise alternative to population density cartograms. Several dasymetric analysis approaches (buffer zone delineation and grid methods) of the settlement system and mapping of the territory in the Kaliningrad Oblast are demonstrated using GIS tools. Areas of the highest population concentration within the region, coinciding with the agglomeration's influence territory, have been identified. A decrease in population density to the east of Kaliningrad is also shown. For the municipal entities of the Kaliningrad region, the area and density of inhabited territories have been calculated. Dasymetric analysis has re­vealed areas of compact placement of rural settlements, aligning with the designated govern­ment rural agglomerations. The conclusion is drawn regarding the existence of stronger con­nections between settlements within different municipal entities and the potential for the ex­pansion of rural agglomerations beyond administrative boundaries. The connectivity of rural and urban settlements within the boundaries of the Kaliningrad agglomeration suggests the formation of second-order agglomerations. The dasymetric method can be utilized in further research to analyze the settlement system for studying the development of rural territories.

Land Use and Urban Sprawl in the Case of the City of Rabat in Morocco: An Integrated Approach Using Remote Sensing, Geospatial Modeling, and Machine Learning

This document is produced as part of a project of mapping, monitoring and prediction of urban sprawl in the city of Rabat, using algorithms of machine Learning, remote sensing and geographic information system. It therefore aims to determine and monitor the urban sprawl of the city of Rabat, using new Geo-spatial technologies, this socio-economic mechanism is theoretically based on the increase in the horizontal area of the city, and a decrease in population density. On the contrary, the city of Rabat is characterized by a negative growth rate between the years 2004-2014 at about -0.79% different from 1.2% at the national level, and defined by a higher population density of 255 inhabitants per km2, these statistics were directed to a hypothesis that indicates a horizontal confinement of the city of Rabat and reverse immigration to per-urban territories. In addition, this project is mainly aimed at the implementation of a computerized simulation model for the characterization and prediction of the urban expansion of the city of Rabat for 40 years (1990, 2000, 2010, 2020, 2030). To conclude, the city of Rabat has experienced a very slow urban sprawl, thanks to the green belt put in 1971, and the modernization strategy that has been adapted in recent years to eliminate informal housing, in addition to the development of roads and the new TGV railway line, and also to the lack of land use, of which many large villas of several hectares were built. Although this mechanism is moving very slowly, the city of Rabat has had negative consequences on the territory and the environment. So, local authorities need a creative, innovative and intelligent urban planning programme to both eliminate the effects of this mechanism, and build the pillars of the functional city (smart city).

Brown trout density effects on the macroinvertebrate and biofilm communities of headwater streams: a cage experiment

Salmo trutta is a key species of headwater streams that is able to influence the structure of these ecosystems through predation. Populations of this species are being threatened by climate change and hydrological alteration. In order to understand how their disappearance would affect the ecosystem structure of headwater streams, we used cage experiments to analyse different biofilm and macroinvertebrate structural parameters and the biodiversity of their communities under different trout densities. Due to a heavy rain event, our experiment was destroyed on the 10th day, but the role of trout as stream ecosystemic structure drivers was observed, as multiple parameters were modulated by their presence or absence. In the high-density treatments, a significant reduction in the biomass of macroinvertebrate families that fed on biofilms was observed due to direct predation on them, which caused the biofilms to be more autotrophic. A decrease in brown trout population densities could cause cascading trophic effects on the ecosystem structure of headwater streams

Mechanism for the restoration of degraded typical steppe by nitrogen and phosphorus co-addition.

The reduction of soil nutrient content is one of the major reasons caused grassland degradation in China. Nutrient addition is thus considered as an effective measure for the restoration of degraded grasslands. However, over-fertilization can lead to decrease in plant diversity. To clarify the appropriate amount of nutrient addition and the underlying mechanism that promotes grassland restoration, we set up a nitrogen and phosphorus co-addition experiment in a degraded typical steppe of Inner Mongolia, and examined the responses at community, functional group and species levels to nutrient addition. The results showed that nutrient addition enhanced biomass while did not reduce species richness at the community level. The biomass showed a saturation response with the increases of nutrient addition, which approached saturation under the 12.0 g N·m-2, 3.8 g P·m-2 treatment. Species richness increased significantly under the lower nutrient treatments (N <9.6 g·m-2, P < 3.0 g·m-2) compared with the control, while the two high nutrient treatments did not alter species richness. At the functional group level, biomass and abundance of perennial rhizome grasses increased significantly with the increases of nutrient addition levels. Biomass and density of annuals increased significantly under high nutrient addition levels. However, the abundance and biomass of perennial bunchgrasses and perennial forbs were rarely affected. At the species level, six target species responded differently to nutrient addition. Biomass of Leymus chinensis was significantly increased due to the increase of population density and individual biomass. Biomass of Stipa grandis, Agropyron cristatum and Cleistogenes squarrosa change little. Biomass of Potentilla acaulis and Carex korshinskyi were reduced due to the decreases in individual biomass and population density, respectively. As a measure of restoring degraded grassland, nutrient addition could significantly increase biomass and species diversity, decrease biomass of the degradation indicator species, and increase biomass of perennial rhizomes grasses.

Impact of 40 Years Use of Different Herbicide Strategies and Crop Rotations on Weed Communities in Two Sites of the Czech Republic

Understanding the impact of farming practices on the composition of weed communities has important implications for the sustainability of weed management strategies. This study analyses data from a 40-year experiment established at two sites in the Czech Republic in 1972. The impact of herbicide strategies on the weed communities was evaluated in multi-crop rotation (MCR) with 50% cereals, and simple crop rotations (SCR) with 75% cereals. The following two herbicide strategies were compared: (1) simple treatment with synthetic auxins only in the simple crop rotation, and (2) targeted herbicide combinations with particular use of sulfonylureas, triazines, ureas and synthetic auxins. Untreated plots were included for reference purposes. Results showed that crop was the major factor determining weed community composition and explained 18% of the total variation in the case of untreated controls. However, herbicide treatment reduced the crop effect to 11%. The highest average increase of Shannon’s diversity index was by 25.4% after 44 years at the untreated plots in SCR, and it decreased by 15.1% at the treated plots in MCR. Weed species evenness € increased at all plots by an average of 23%. Simpson’s dominance index decreased at untreated plots in both crop rotations and plots treated with auxins, with the highest 44.8% decrease at the untreated plots in SCR. On the contrary, Simpson’s index increased by 33,3% on the treated plots in MCR. Herbicide selection depended on the occurrence and density of target weed species, and led to greater decrease in weed diversity and population densities in the diversified crop rotations.

Effects of Antibiotics on the Uterine Microbial Community of Mice

The gut microbiota is involved in the maintenance of physiological homeostasis and is now recognized as a regulator of many diseases. Although germ-free mouse models are the standard for microbiome studies, mice with antibiotic-induced sterile intestines are often chosen as a fast and inexpensive alternative. Pathophysiological changes in the gut microbiome have been demonstrated, but there are no reports so far on how such alterations affect the bacterial composition of the uterus. Here we examined changes in uterine microbiota as a result of gut microbiome disruption in an antibiotics-based sterile-uterus mouse model. Sterility was induced in 6-week-old female mice by administration of a combination of antibiotics, and amplicons of a bacteria marker gene (16S rRNA) were sequenced to decipher bacterial community structures in the uterus. At the phylum-level, Proteobacteria, Firmicutes, and Actinobacteria were found to be dominant, while Ralstonia, Escherichia, and Prauserella were the major genera. Quantitative comparisons of the microbial contents of an antibiotic-fed and a control group revealed that the treatment resulted in the reduction of bacterial population density. Although there was no significant difference in bacterial community structures between the two animal groups, β-diversity analysis showed a converged profile of uterus microbiotain the germ-free model. These findings suggest that the induction of sterility does not result in changes in the levels of specific taxa but in a reduction of individual variations in the mouse uterus microbiota, accompanied by a decrease in overall bacterial population density.