Vertical Dispersion Research Articles

The Impact of Vertical and Horizontal Wage Dispersion on Employee Collusion and Effort in Tournaments

We investigate the effect of vertical wage dispersion, defined as the difference in wages between superiors and subordinates, on subordinates’ behaviors in a competitive setting. We propose that higher vertical wage dispersion shifts subordinates’ pay referent from peers to superiors, thereby reducing their motivation to compete and increasing collusion against the superiors. Our experimental study tests this likelihood in a repeated tournament where the employee that exerts the highest effort wins the prize. Consistent with our predictions, we find that higher vertical wage dispersion increases subordinates’ desire to reduce the vertical pay gap and increases their trust in other subordinates. As a result, collusion increases and total effort drops. Crucially, we find that when vertical pay dispersion is high, the introduction of horizontal wage dispersion between subordinates shifts their pay referent back to their peers, creating the opposite effects on employee effort and collusion. We contribute to the growing research on pay dispersion by studying how wage differences alter employees’ pay referent for social comparison, which affects how they interact with their peers. We also extend tournament research by studying how a contextual variable outside the tournament, i.e., ex ante wage dispersion, could affect employees’ willingness to compete or to collude. An implication of our finding is that high vertical wage dispersion may make tournament incentives less effective for organizations.

Dynamics of DiskMass Survey galaxies in refracted gravity

We aim to verify whether refracted gravity (RG) is capable of describing the dynamics of disk galaxies without resorting to the presence of dark matter. RG is a classical theory of gravity in which the standard Poisson equation is modified with the introduction of the gravitational permittivity, which is a universal monotonic function of the local mass density. We used the rotation curves and the radial profiles of the stellar velocity dispersion perpendicular to the galactic disks of 30 disk galaxies from the DiskMass Survey (DMS) to determine the gravitational permittivity. RG describes the rotation curves and the vertical velocity dispersions by requiring galaxy mass-to-light ratios that are in agreement with stellar population synthesis models, and disk thicknesses that are in agreement with observations, once observational biases are taken into account. Our results rely on setting the three free parameters of the gravitational permittivity for each individual galaxy. However, we show that the differences of these parameters from galaxy to galaxy can, in principle, be ascribed to statistical fluctuations. We adopted an approximate procedure to estimate a single set of parameters that may properly describe the kinematics of the entire sample and suggest that the gravitational permittivity is indeed a universal function. Finally, we showed that the RG models of the individual rotation curves can only partly describe the radial acceleration relation (RAR) between the observed centripetal acceleration derived from the rotation curve and the Newtonian gravitational acceleration originating from the baryonic mass distribution. Evidently, the RG models underestimate the observed accelerations by 0.1 to 0.3 dex at low Newtonian accelerations. An additional problem that ought to be considered is the strong correlation, at much more than 5σ, between the residuals of the RAR models and three radially-dependent properties of the galaxies, whereas the DMS data show a considerably less significant correlation, at more than 4σ, for only two of these quantities. These correlations might be the source of the non-null intrinsic scatter of the RG models: this non-null scatter is at odds with the observed intrinsic scatter of other galaxy samples different from DMS, which is consistent with zero. Further investigations are required to assess whether these discrepancies in the RAR originate from the DMS sample, which might not be ideal for deriving the RAR, or whether they are genuine failures of RG.

Vertical dispersal of nucleopolyhedrovirus occlusion bodies in soil by the earthworm Amynthas gracilus: a field-based estimation

ABSTRACTThe soil is the most important environmental reservoir for nucleopolyhedrovirus occlusion bodies (OBs). We employed a diet + soil bioassay technique to demonstrate that the earthworm Amynthas gracilus was capable of vertical transport of Spodoptera frugiperda multiple nucleopolyhedrovirus (SfMNPV) occlusion bodies (OBs) under field conditions. Incubation of OBs with earthworms in sand did not adversely affect the prevalence of virus-induced mortality, but variation in insect mortality was markedly increased, possibly due to changes in the particle size distribution following earthworm processing of OB-contaminated sand. We conclude that earthworms are likely to interact frequently with soil OB populations.

Meteorological characteristics within boundary layer and its influence on PM2.5 pollution in six cities of North China based on WRF-Chem

North China is recognized as one of the region with most severe air pollution in China, and the PM2.5 in six major cities (Beijing, Tianjin, Shijiazhuang, Taiyuan, Jinan and Zhengzhou) of this region was measured to be 108.7–186.0 μg m−3 in January 2017 and 39.2–56.3 μg m−3 in July 2017. This study conducts the meteorological and chemical simulations based on WRF-Chem, and explores the impacts of meteorology and emissions on PM2.5 (particulate matter with aerodynamic diameters ≤ 2.5 μm) pollutions. Simulations show a noticeable seasonal variation in planetary boundary layer height (PBLH) and relative humidity (RH), but a similar trend in wind speed (WS). Compared to PM2.5 good condition (≤75 μg m−3), daily PBLH decreased by 7.6–39.6% in January and 9.2–44.1% in July during PM2.5 polluted condition (75~150 μg m−3), and by 22.3–51.2% in January during severely polluted condition (≥150 μg m−3). PBLH is thought of as the key factor for PM2.5. Then, the synergy between PBLH and other meteorological factors are studied. For a 100 m failing in PBLH, the decrease in surface WS reaches 0.2–0.8 m s−1 0.1–0.3 m s−1 in January and July. It means a synergic effect of unfavorable horizontal and vertical dispersions, more adversely in January than in July. While, RH presents an increasing trend with PBLH falling, about +2.1~+3.2% in January and +2.7~+4.6% in July per 100 m falling in PBLH. Considering the improvement of high RH in heterogeneous chemistry to form the secondary PM2.5, we believe that the disadvantaged dispersion condition is always accompanied by enhanced secondary PM2.5 formation chemistry. Then, we summarize the average simulated PM2.5 under various combinations of PBLH, WS and RH, and find that under the same meteorological combination, PM2.5 in January was about 1.7–3.6 times that of July, which could be explained by the more emissions of PM2.5 and its precursors in January. Finally, we determine the unfavorable meteorology condition based on current regional emissions and China's standard (hourly PM2.5<75 μg m−3), low PBLH (<600 m) or middle-high RH (>40%) for January, high RH (>60%) & low-middle WS (<4 m·s-1), or middle RH (40~60%) & low PBLH (<400 m) for July. These unfavorable meteorological conditions accounted for 75.8% in January and 47.8% in July. Therefore, it is still necessary to continuously reduce anthropogenic emissions in this region for attainment of China's PM2.5 standards.

Long-term trends of global maximum atmospheric mixed layer heights derived from radiosonde measurements

The height of the atmospheric mixed layer is a critical parameter controlling the vertical dispersion of pollutants. Here we calculate daily maximum mixed layer height (MMLH) using operational radiosonde and surface meteorological measurements made at 219 carefully selected WMO weather stations and analyze their long-term trends from 1973 to 2018. We found that 74 stations showed significant increases in MMLH, whereas 48 sites showed negative trends. Positive trends are mainly found in Central US, Europe, Africa, East and Southeast Asia and East Australia. Stations over the coastal US, India and West Australia generally exhibit negative trends. The trends can be attributed to changes in vertical temperature gradient between 950 and 700 hPa and diurnal temperature range (DTR). in general decreased and caused positive MMLH trends over the majority of the regions. DTR decreases globally, causing negative MMLH trends (corresponding to decreased DTR), and plays a more important role over India and Central Asia.

An Investigation of the Precipitation Net Effect on the Particulate Matter Concentration in a Narrow Valley: Role of Lower-Troposphere Stability

AbstractPrecipitation modulates the pollutant concentration in the atmosphere directly and indirectly through different mechanisms. Wet deposition, including in-cloud scavenging and below-cloud scavenging, is one of the main drivers of particulate matter removal from the atmosphere. Our focus is to assess the net effect of precipitation on the pollutant concentration using observations, a nonparametric conditional analysis, and the signed overlapping coefficient complement index. The study considers not only the direct near-surface aerosol below-cloud scavenging, but also the indirect effect associated with the induced lower-troposphere stability limiting the vertical dispersion, leading to a pollutant concentration increase. We consider the precipitation effects on fine and coarse particulate matter concentration. Probability density functions of the pollutant concentration during precipitation events and under dry conditions are analyzed for every hour of the day. The net effect of precipitation on the fine and coarse particulate matter concentration is strongly dependent on the atmospheric stability. During the nighttime and before midmorning, the atmosphere is stable; a precipitation event during this time induces below-cloud scavenging, reducing the concentration of particulate matter in the atmosphere. During the afternoon, unstable atmospheric conditions are predominant, and aerosols disperse vertically; a precipitation event during this period stabilizes the atmosphere, generating early stabilization that, together with the continued anthropogenic emissions during the day, leads to near-surface pollutant accumulation, offsetting the washout effect of the precipitation.

Research on muzzle dynamic analysis of an overhead weapon station with the viscoelastic elastomer damper

Live firing tests are difficult to realize, thus it is not clear whether the viscoelastic elastomer damper can effectively reduce the recoil force and recoil displacement, which determines the firing accuracy of the overhead weapon station. This paper constructed a rigid-flexible coupling dynamics model of overhead weapon station with the viscoelastic elastomer damper. The dynamic simulation parameters of the damper were determined according to the static pressure test results. A characterization method of the firing dispersion of the overhead weapon station was then proposed. Additionally, the influences of the viscoelastic elastomer damper and the spring damper on the muzzle dynamic characteristics and firing dispersion of the overhead weapon station were studied. The results show that: the recoil displacement and the recoil-return time with the viscoelastic elastomer damper were respectively reduced by 69.83% and 33.50% compared to the spring damper; By contrast the spring damper, the horizontal and vertical dispersion standard deviations of the overhead weapon station with the viscoelastic elastomer damper at different firing conditions were respectively decreased an average of 39.48% and 43.68%, while the firing dispersion was increased by an average of 41.89%. These results prove that the viscoelastic elastomer damper can significantly reduce and shorten the recoil displacement and the recoil time of the machine gun overhead weapon station, effectively reduce the muzzle jump and improve the firing accuracy of the overhead weapon station.

The dependence of the consumption of dissolved oxygen on lake morphology in ice covered lakes

Abstract The consumption of oxygen in ice-covered lakes is analyzed and related to biological oxygen demand and sediment oxygen demand. An approach for computing dissolved oxygen concentration is suggested assuming horizontally mixed waters and negligable vertical dispersion. It is found that the depletion of dissolved oxygen is mainly due to the transfer of oxygen at the water/sediment interface. The morphology of a lake is very important for how fast the dissolved oxygen concentration is reduced during winter.

Atmospheric benzene measurements in the main metropolitan and industrial areas of Spain from 2014 to 2017

We report atmospheric benzene measurements in the main metropolitan and industrial areas across Spain from 2014 to 2017 period. We have used hourly benzene levels measured at air-quality stations influenced by urban and industrial environments. Annual mean levels ranged between 0.3 and 2.4 μg m−3 with an hourly maximum values of 112 μg m−3 in Tarragona. Industrial stations can reach concentrations of one order of magnitude greater than urban sites. Higher annual averages are also reported in the industrial stations (maximum ~3.5 μg m−3 in Aviles). When the monthly pattern is taken into account, the industrial sites also presented higher values than urban sites; urban stations show higher monthly values always in winter, ranging between <0.5 μg m−3 and ~3 μg m−3. Three different features were observed in industrial stations according to their monthly pattern. A different diurnal pattern was also found in urban stations compared with the industrial sites. Applying a criterion, four exceedance events were selected as representatives of the behaviour of industrial and traffic stations. These events were analysed in detail along with the weather conditions, using ERA5 reanalysis data from ECMWF (European Centre for Medium Range Weather Forecasts). The benzene events occurred under weather conditions governed by high pressure systems. In these cases, the accumulation of benzene in the lower atmosphere was favoured by both the lower wind speed and height of the ABL, which would lead to minor horizontal and vertical dispersion.

The Joint Effects of Supervisor Pay Transparency and Vertical Pay Dispersion on Reporting Honesty

ABSTRACTWe experimentally investigate how supervisor pay transparency interacts with vertical pay dispersion to affect subordinates' reporting honesty in a budgeting setting. We find that the effect of supervisor pay transparency relative to pay secrecy becomes more negative as vertical pay dispersion becomes higher. Our findings suggest that while supervisor pay transparency complements an egalitarian pay structure by increasing reporting honesty, it does not fare along with high vertical pay dispersion as the combination of the two appears to decrease reporting honesty, even when such high dispersion can be justified. Further investigation suggests that our result is not driven by the feeling of unfairness toward high supervisor pay, but by a benchmarking effect (i.e., subordinates use supervisor pay as a pay standard and try to find ways to earn a similar amount).

Characterization and behavior of Hydrogen Sulfide plumes released from active sulfide-tar springs, Hit-Iraq

The characteristics and behavior of the H2S pollution plume in the emission zone of spring water and wastewater are determined by a total of 120 readings of H2S in the air and 24 samples of dissolved gas analysis during the observation period. Monitoring data is adjusted to determine the behavior of air pollution plumes and their relationship to emission sources by using statistical techniques and spatial analysis. The value of H2S emissions to the atmosphere was 6.62 kg/year by an emission factor of 0.0055 mg/s. The study revealed an important correlation between the continuous emission of H2S and its sources from springs and wastewater that is explained by exponential relation Fit (Y = a ebX), [H2S concentration. In air (mg/1000 cc)] = 0.00015 exp {0.0107 (H2S conc. In water mg/l)}. The spatial distribution maps of H2S showed that 38% of Hit's space is exposed to H2S concentration under the influence of the unpleasant odor, eye irritation, and corrosion in infrastructure parts (air conditioning apparatus). The characteristics of the H2S pollution plume, which were reflected in the behavior of H2S distribution of the exposed area, varied due to the variation of dispersion processes resulting from wind speed change. The concentration of H2S was 11.6 times when the wind speed decreased by 15.7 times. The wind speed affected the results of the mechanical dispersion coefficient in a positive relationship. Vertical and horizontal mechanical dispersion values in unstable weather conditions increased by 192 times and 243 times than in extremely stable weather conditions.

Enhancing the local air quality benefits of roadside green infrastructure using low-cost, impermeable, solid structures (LISS)

Communities located in near-road environments face adverse health effects due to elevated exposures to traffic-related air pollution (TRAP). While the use of a combination of solid structures (i.e. sound walls) and vegetation barriers can be an effective TRAP mitigation tool, installing these barriers can also present challenges to local communities. Sound walls are costly, and building these structures often requires the involvement of federal, state, and local permitting agencies. In this paper, we proposed that the use of low-cost, impermeable, solid structures (LISS), e.g., an impermeable thin wooden, plastic or metal fence, combined with vegetation can provide an effective option for local communities to improve near-road air quality due to lower costs and easier implementation. We conducted Large Eddy Simulations (LES) for different design scenarios of LISS and vegetation barriers under various conditions. Our results indicate that (i) combining LISS and vegetation is more effective than either alone, (ii) combining a less dense vegetation and LISS can be as effective as a dense vegetation barrier, (iii) In certain scenarios, depending on wind speed and particle size, vegetation barriers alone might lead to elevated pollutant concentrations; however, combining LISS with vegetation can mitigate those negative impacts, (iv) placing LISS closer to the freeway and in front of the vegetation barrier enhances vertical dispersion of pollutants, and (v) increasing LISS height promotes pollutant concentration reduction. These design recommendations can be used by urban planners, developers, and local community leaders to evaluate and implement green infrastructure to mitigate TRAP.

Effect of Clouds on the Diurnal Evolution of the Atmospheric Boundary-Layer Height Over a Tropical Coastal Station

The growth of the daytime convective atmospheric boundary layer, which plays a pivotal role in the vertical mixing and dispersal of water vapour and pollutants, is modulated by cloud radiative effects. Assessment of this cloud effect is sparse in any geographical region and non-existent over tropical coastal regions. We investigate the effect of clouds on the diurnal evolution of boundary-layer height over tropical coastal location Thumba (8.5°N, 77°E) during onshore and offshore flow using multi-year (2010–2016) microwave radiometer profiler observations. The boundary-layer height during both cloudy and clear-sky periods increases rapidly from 0800 LT (local time = UTC + 5.1 h) to attain a daytime peak around noon (400–1500 m). The seasonal mean noontime boundary layer height during cloudy periods is lower than that during clear-sky periods by > 900 m (> 400 m) when offshore (onshore) flow prevails during winter and pre-monsoon seasons. The forenoon growth rate of the boundary-layer height during clear-sky offshore flow is rapid (> 380 m h−1) compared to that during cloudy offshore (160 m h−1), clear-sky onshore (160–250 m h−1), and cloudy onshore (> 100 m h−1) flow. Effects of shortwave cloud radiative forcing and soil temperature on the noontime boundary-layer height and their interdependencies are presented. These observations reveal the contrasting and significant effect of clouds on the growth of the daytime boundary layer during onshore and offshore flow, and the coupled effects of cloud radiative forcing and soil temperature on boundary-layer height over tropical coastal regions, which provide essential constraints for evaluating model simulations.

The vertical profiles of carbonaceous aerosols and key influencing factors during wintertime over western Sichuan Basin, China

With Tibetan Plateau higher than 4 km to the west, the location of Sichuan Basin is unique all around the world and provides a good platform to study air pollution in the urban agglomerations over the complex terrain. To fill in the blanks on vertical distributions of PM1 (the particles smaller than 1 μm) and carbonaceous aerosols within the basin, by means of high topographic relief, PM1 were off-line sampled during 20 January to 2 February 2018 at eight sites with increasing altitudes from the basin to southeastern margins of the Tibetan Plateau. The regional potential sources for each site were revealed by HYbrid-Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model and concentration-weighted trajectory (CWT) method. The lowest carbonaceous aerosol levels occurred at Lixian, while the highest OC (organic carbon) (EC, elemental carbon) was at Hongyuan (the altitude of 3500 m) (Ande, a rural site) due to more primary emissions. The pollutants inside the basin can be transported the altitudes from 2 km to 3 km by vertical dispersion, but they cannot be dispersed to higher altitudes. The vertical stratification of the pollutants was obvious and easily formed “high-low-high” pattern from Sichuan Basin to southeastern Tibetan Plateau, especially during highly polluted episodes. The regional potential sources significantly varied as the increased altitudes. Regional pollution was significant inside the basin. The sources at the altitudes from 2 km to 3 km originated from southeastern margins of the Plateau and surrounding cities, while those at higher altitudes were transported from southeastern margins of the Plateau. The impact of basic meteorological variables (temperature, wind speed and vapor pressure) on carbonaceous aerosols was opposite between the basin and Plateau sites. This study was essential to understanding formation mechanisms of severe pollution episodes and thus to making control measures for the urban agglomerations inside the mountainous terrain.

Formation of OSA and dispersion of polycyclic aromatic hydrocarbons in a tropical estuary as a tool in the prevention of environmental impacts: influence of the biogeochemical characteristics of the estuary.

The formation of an oil-suspended particulate material aggregate (OSA) is one of the weathering processes that occur after the spill of oil in marine environments, responsible for the dispersion of hydrocarbons. Oil and particle aggregates are formed from the interaction between small oil droplets and suspended particulate matter (SPM). In general, SPM are fine particles which may be inorganic minerals or organic particles in the water column. OSAs provide vertical dispersion of oil along the water column depending on the acquired density (buoyancy), and may remain near the surface, water column, or bottom of water bodies. The present study examines the formation of these aggregates through the laboratory simulation of an oil spill in the waters of the São Paulo river estuary. The main objective was to investigate the dispersion of polycyclic aromatic hydrocarbons (PAHs), verifying which estuary characteristics most influenced the formation of OSAs and in addition to determine the regions of probable ecotoxicological impact due to the negative buoyancy of the formed aggregate. The results show that there was greater dispersion to the water column, mainly of lighter PAHs, ranging from 85,804.05ngg-1 (P11C) to 566,989.84ngg-1 (P17C). The percentage of dispersed PAH concentration per experimental unit ranged from 9.90% in unit P2 to 75.27% in unit P18. The formation of OSAs was influenced mainly by salinity and chlorophyll a. As the most vulnerable regions, the impacts are one mouth (P2 and P4), one central region (P7, P8, and P10), and one source (P18).

Vertical life: impact of roof height on beetle diversity and abundance on wildflower green roofs

Abstract Despite their increasing popularity in an urban setting, we still know relatively little in how well-extensive green roofs support biodiversity in terms of vertical connectivity from terrestrial habitats. Most green roof biodiversity studies have not considered whether the roof height affects community composition and abundance of species present. This study focused on evaluating beetle diversity and abundance in relation to roof height, with emphasis on wildflower roofs. The key results of the study confirm previous studies found that extensive wildflower green roofs are capable of supporting fairly rich beetle communities, including some rare/scarce species. However, an increase of roof height was found to negatively impact both beetle abundance and richness, despite all recorded species being well adapted to active flight and thus dispersal. In addition forb cover decreased with roof height which consequently influenced beetle community structure. These results are therefore indicative that further research is required on species communities found on extensive green roofs that are less adapted to active flight and consequently vertical dispersal. This study further highlights the need for vertical and horizontal connectivity between green roofs and the surrounding natural habitats as a management tool to increase the general ecological value of urban green spaces.

Investigation of thermo-mechanical response of a geothermal pile through a small-scale physical modelling

Energy piles have been used around the world to harvest geothermal energy to heat and cool residential and commercial buildings. In order to design energy geo-structures, thermo-mechanical response of the geothermal pile must be carefully understood. In this paper, a small scale physical model is designed and a series of heating thermal cycles with various vertical mechanical loads are performed. The instrumented pile is installed inside a dry sand bed. Changes in pile head displacement, shaft strains and pile and sand temperatures are monitored using an LVDT, strain gauges and thermocouples, respectively. Prolonged heating cycles, which would continue until boundary temperature changes, would allow the investigation of excessive heat injection when service loads are active on the pile. The thermal response is discussed including confirmation of a temperature influence zone around the pile, the increase in soil temperature, and minimum vertical heat dispersion in the soil. The mechanical response includes plastic settlements when the vertical load passes 20% of ultimate capacity. Plastic settlements have been observed at the half of the capacity reported for the shorter thermal cycles in similar models. The decrease in the capacity indicates a reduction in elastic response of the soil during longer thermal cycles.

Simulating future salinity dynamics in a coastal marshland under different climate scenarios

AbstractSalinization is a well‐known problem in agricultural areas worldwide. In the last 20–30 yr, rising salinity in the upper, unconfined aquifer has been observed in the Freepsumer Meer, a grassland near the German North Sea coast. For investigating long‐term development of salinity and water balance during 1961–2099, the one‐dimensional Soil–Water–Atmosphere–Plant (SWAP) model was set up and calibrated for a soil column in the area. The model setup involves a deep aquifer as the source of salt through upward seepage. In the vertical salt transport equation, dispersion and advection are included. Six different regional outputs of statistical downscaling methods were used as climate scenarios. These comprise different rates of increasing surface temperature and different trends in seasonal rainfall. The simulation results exhibit opposing salinity trends for topsoil and deeper layers. Although projections of some scenarios entail decreasing salinities near the surface, most of them project a rise in subsoil salinity, with the strongest trends of up to +0.9 mg cm−3 100 yr−1 at −65 cm. The results suggest that topsoil salinity trends in the study area are affected by the magnitude of winter rainfall trends, whereas high subsoil salinities correspond to low winter rainfall and high summer temperature. How these projected trends affect the vegetation and thereby future land use will depend on the future management of groundwater levels in the area.

Vertical Pay Dispersion, Peer Observability, and Misreporting in a Participative Budgeting Setting

ABSTRACTIn this study, we examine the joint effect of vertical pay dispersion and peer observability on subordinates' misreporting choices. We adopt a participative budgeting setting in which two subordinates report to one superior, and we manipulate vertical pay dispersion (low/high) and peer observability (absent/present). Subordinates have private information about actual project costs and can over‐report project costs to the superior without detection and thus create budgetary slack. When a peer's reporting choices are observable, we predict and find that peer reporting choices have an asymmetric influence on the focal subordinates' reporting choices, and this asymmetric influence depends on the level of vertical pay dispersion. Specifically, we find that when vertical pay dispersion is low, subordinates who observe peer reports containing low slack misreport less, whereas observing peer reports that contain high slack has no significant effect. However, when vertical pay dispersion is high, subordinates who observe peer reports containing high slack misreport more, whereas observing peer reports that contain low slack has no significant effect. Driven by these asymmetric effects, subordinates misreport less in the presence of peer observability than in its absence when vertical pay dispersion is low and misreport more in the presence of peer observability than in its absence when vertical pay dispersion is high. Overall, our findings suggest that when a firm has a more egalitarian pay structure (i.e., low vertical pay dispersion), an open information policy is conducive to a more honest reporting environment, whereas under a more hierarchical pay structure (i.e., high vertical pay dispersion), open information policies can compromise the honesty of subordinates' reports.

Oak, Quercus chenii, dispersal in fragmented urban forests: acorn horizontal and vertical dispersal, seedling establishment and growth

Habitat fragmentation results in the loss of seed dispersers and subsequently leads to low regeneration and functional decline of forests. However, very few studies on disperser decline and seedling regeneration have been conducted in urban forest systems. In three isolated forest patches in Wuhan, central China, acorn dispersers, acorn dispersal, acorn deposition patterns in soil seed banks and seedling recruitment of the dominant animal-dispersed tree species (Quercus chenii) were investigated over four consecutive years (2014 to 2017). The hypothesis tested was that the loss of acorn dispersers caused by forest fragmentation leads to low regeneration and functional degradation of the urban forest system. As predicted by the hypothesis, very few acorn dispersers (only a few Chinese white-bellied rats, Niviventer confucianus, and Eurasian jays, Garrulus glandarius, were observed) existed in the forest patches; thus, almost all of the acorns were left on the soil surface under the mother trees, where conditions are not favorable for germination and establishment. Large acorns had higher probabilities of germination and seedling establishment than did small acorns when they were buried in the soil. These results suggest that regeneration of fragmented urban forests is increasingly hampered by sharp reduction in seed disperser abundance. Planting large seeds in the soil may compensate for the low regeneration caused by disperser loss in fragmented urban forests.