Effect of Road Traffic on Two Amphibian Species of Differing Vagility

Abstract: Vehicular traffic can be a major source of mortality for some species. Highly vagile organisms may be at a disadvantage in landscapes with roads because they are more likely to encounter roads and incur traffic mortality. To test this prediction, we assessed the population abundance of two anuran species of differing vagility, the leopard frog (    Rana pipiens , more vagile) and the green frog (    Rana clamitans , less vagile), at 30 breeding ponds. Traffic density, an index of the amount of potential traffic mortality, was measured in concentric circles radiating from the ponds out to 5 km. We conducted multiple linear regressions relating population abundance to traffic density, pond variables, and landscape habitat variables and found that leopard frog population density was negatively affected by traffic density within a radius of 1.5 km. There was no evidence that the presence of vehicular traffic affected green frog populations. These results suggest that traffic mortality can cause population declines and that more vagile species may be more vulnerable to road mortality than less vagile species.     

基于生态保护的道路规划策略

分析了路段与景观两个尺度上的道路生态环境影响,结合当今景观生态学、道路生态学的研究成果,系统论述了与道路交通规划建设相关的生态策略：（1）在区域尺度上,依据生态敏感度规划路网密度、保持大型自然空间的生态完整性、提倡非生态敏感地段的交通集中、增加路网的区域水平渗透性;（2）在路段规模上,自然空间的生境避让、保持重要地段的自然连续性、打破交通生态瓶颈、减少道路交通的环境影响、补偿道路建设的生态影响等。这些策略旨在为可持续道路交通提供基于生态合理性的规划原则与方法。     

高速公路绿化带对交通噪声的衰减效果研究

公路绿化带可对交通噪声产生一定衰减作用,这对于减轻路域环境噪声污染具有重要意义。然而,针对高速公路绿化带种植树种、种植密度、林带宽度等多种因素对降噪效果影响的研究尚属空白。该研究采用选取试验点进行原位调查的方法,研究了山东省3条主要高速公路路侧绿化带对交通噪声的衰减效果,并探讨了林带宽度和郁闭度对噪声衰减的影响。研究结果表明,高速公路绿化带对交通噪声有一定的减轻作用,但在不同的绿化模式下,衰减效果存在较大差别。交通噪声的绿化衰减同林带宽度有很大关系,对于较宽林带,靠近声源前半部分的林带对噪声有较好的减轻作用,但后半部分的减噪效果较小。林带的对噪声的绿化衰减与林带宽度以及宽度和郁闭度的乘积均呈极显著的线性关系。     

Amphibian Encounter Rates on Roads with Different Amounts of Traffic and Urbanization

Abstract: Although amphibians have relatively high rates of road mortality in urban areas, the conditions under which traffic threatens the survival of local amphibian populations remain unclear. In the Sandhills region of North Carolina (U.S.A.), we counted living and dead amphibians along two transects (total length 165 km) established on roads in areas with varying degrees of urbanization. We found 2665 individuals of 15 species, and amphibian encounter rates declined sharply as traffic and urban development increased. Regression‐tree models indicated that 35 amphibians/100 km occurred on roads with <535 vehicles/day, whereas the encounter rate decreased to only 2 amphibians/100 km on roads with >2048 vehicles/day. Although mortality rate peaked at higher traffic levels (47% dead on roads with >5200 vehicles/day), the number of dead amphibians was highest at low levels of traffic. This suggests that areas where amphibian mortality is concentrated may actually contain the largest populations remaining on a given road transect.     

Role of Light Availability and Dispersal in Exotic Plant Invasion along Roads and Streams in the H. J. Andrews Experimental Forest, Oregon

Abstract: We examined the roles of dispersal mechanism, a biological barrier; light availability, an environmental barrier; and level of disturbance, a physical barrier, in explaining the spatial patterns of exotic plant species along road and stream segments in a forest landscape in the western Cascade Range of Oregon (U.S.A). The presence or absence of 21 selected exotic plant species and light levels were observed along 0.3- to 1.0-km transects within four habitat types. Each habitat represented a different level of disturbance: high-use roads, low-use roads, abandoned roads, and streams in the H. J. Andrews Experimental Forest. Nearly 300 50 × 2–m sampling units were surveyed along five transects in each habitat type. We used ordination (nonmetric multidimensional scaling) and logistic regression to analyze data. All of the nearly 200 sampling units along roads with high and low levels of vehicle traffic contained at least one exotic plant species, and some contained as many as 14. Streams that were most recently disturbed by floods 20–30 years ago and abandoned spur roads with no traffic for 20–40 years also had numerous exotic species. Roads and streams apparently serve multiple functions that enhance exotic species invasion in this landscape: they act as corridors or agents for dispersal, provide suitable habitat, and contain reservoirs of propagules for future episodes of invasion. Species-specific dispersal mechanisms, habitat characteristics, and disturbance history each explain some, but not all, of the patterns of exotic species invasion observed in this study.     

Ecological Effectiveness of Agri-Environment Schemes in Different Agricultural Landscapes in The Netherlands

Abstract:  Agri-environment schemes are an instrument used by western European countries to counteract the negative effects of contemporary agriculture on biodiversity, but not much is known about their effectiveness. We investigated the ecological effects of Dutch agri-environment schemes aimed at promoting botanical diversity or meadow birds, and we tested whether the effectiveness of the schemes depends on landscape type or structure. In three different types of landscape, we surveyed plants, birds, bees, and hover flies on 78 paired fields that either had agri-environment schemes or were managed conventionally, and we collected data on a range of different environmental variables. Neither plant species richness nor abundance of meadow birds was higher on fields with agri-environment schemes. Landscape type had a significant effect on both species groups, but the effects of the schemes were independent of landscape type. Neither the diversity of plants nor the abundance of birds was related to any of the environmental variables. Agri-environment schemes designed to promote plant species richness or bird abundance did have positive side-effects because they enhanced the species richness of bees and hover flies, irrespective of the type of landscape. Furthermore, landscape type, groundwater level (hover flies), and area of wooded edges (bees) significantly affected both species groups. The failure of the schemes to promote the target species may be related to the high intensity of land use in The Netherlands. Simple conservation measures taken by farmers may not be sufficient to counteract the impact of factors that are often controlled at the landscape level (e.g., hydrology). Similar studies in other countries are needed to place the results of our study into a European context.     

Fragmentation of Landscape as a Cause for Genetic Subdivision in Bank Voles

Abstract: We studied the barrier effects of various roadways on the genetic subdivision of bank vole (Clethrionomys glareolus) populations. Allele frequencies, genetic variability, and genetic distances of natural populations were calculated based on polymorphism of seven microsatellite markers. We compared bank vole populations in control areas without such barriers with animals from both sides of a country road, a railway, and a highway. Using F and R statistics, we demonstrated significant population subdivision in bank vole populations separated by the highway, but not in populations on either side of the other roadways or in the control area. Correlations between geographic and genetic distances were revealed by an extended method based on a Mantel analysis. This allowed us to measure genetic barrier effects and express them as additional geographic distances. For instance, statistically significant differences in allele frequencies in all seven loci examined existed among populations in southern Germany and Switzerland, which are separated by the Rhine River and Lake Constance. The real geographic distance between bank vole populations in Konstanz and those in Lengwil, Switzerland, was 6 km. According to this analysis the genetic barrier effect of the Rhine could be defined as an additional distance of 7.7 km. This study shows for the first time that not only old geographic barriers but also more recent fragmentation of landscape by, for example, highways has an important effect on gene flow and the genetic substructuring of populations, which should be considered in future environmental impact assessments.     

渤海湾淤泥质海岸带典型地区景观空间格局分析

以景观多样性、景观破碎度和景观分离度作为评价指标,分析渤海湾淤泥质海岸带典型地区景观空间格局以及人类活动对景观结构的影响。将研究区域分为耕地、荒地、村镇、盐田、虾池、滩涂、库塘以及河流沟渠8个景观要素。分析表明,景观多样性主要受耕地和荒地的影响和支配;耕地和荒地的破碎度大,分离度小;盐田和河流沟渠的破碎度最小;村镇和滩涂的分布状况导致其分离度大。     

Estimate of the Area Affected Ecologically by the Road System in the United States

Abstract: In view of an extensive road system, abundant and rapidly growing vehicular traffic, and a scattered literature indicating that some ecological effects of roads extend outward for > 100 m, it seems likely that the cumulative ecological effect of the road system in the United States is considerable. Two recent studies in The Netherlands and Massachusetts ( U.S.A.) evaluated several ecological effects of roads, including traffic noise effects, and provide quantitative evidence for a definable "road-effect zone." Based on the approximate width of this asymmetric convoluted zone, I estimate that about one-fifth of the U.S. land area is directly affected ecologically by the system of public roads. I identify a series of assumptions and variables suggesting that over time this preliminary estimate is more likely to rise than drop. Several transportation planning and policy recommendations, ranging from perforating the road barrier for wildlife crossings to closing certain roads, offer promise for reducing this enormous ecological effect.     

Impacts of road deicing salt on the demography of vernal pool-breeding amphibians.

Deicing agents, primarily road salt, are applied to roads in 26 states in the United States and in a number of European countries, yet the scale of impacts of road salt on aquatic organisms remains largely under-studied. The issue is germane to amphibian conservation because both adult and larval amphibians are known to be particularly sensitive to changes in their osmolar environments. In this study, we combined survey, experimental, and demographic modeling approaches to evaluate the possible effects of road salt on two common vernal-pond-breeding amphibian species, the spotted salamander (Ambystoma maculatum) and the wood frog (Rana sylvatica). We found that in the Adirondack Mountain Region of New York (USA), road salt traveled up to 172 m from the highway into wetlands. Surveys showed that egg mass densities of spotted salamanders (A. maculatum) and wood frogs (R. sylvatica) were two times higher in forest pools than roadside pools, but this pattern was better explained by road proximity than by increased salinity. Experiments demonstrated that embryonic and larval survival were reduced at moderate (500 muS) and high conductivities (3000 muS) in A. maculatum and at high conductivities in R. sylvatica. Demographic models suggest that such egg and larval stage effects of salt may have important impacts on populations near roads, particularly in the case of A. maculatum, for which salt exposure may lead to local extinction. For both species, the effect of road salt was dependent upon the strength of larval density dependence and declined rapidly with distance from the roadside, with the greatest negative effects being limited to within 50 m. Based on this evidence, we argue that efforts to protect local populations of A. maculatum and R. sylvatica in roadside wetlands should, in part, be aimed at reducing application of road salt near wetlands with high conductivity levels.     

Platinum pollution in road dusts, roadside soils, and tree barks in Seoul, Korea

This study presents the level of platinum in urban environment in and around Seoul, the capital city of Korea. Road dust, roadside soil, and tree bark samples were collected from the sites of various traffic volumes and from control sites in the suburbs. The above samples were analyzed for Pt by ICP-MS and other heavy metals by ICP-OES. Platinum levels in road dusts and roadside soils from Seoul were in the range of 3.8-444 ng/g (av. 115.0 ng/g) and 0.7-221 ng/g (av. 49.7 ng/g), respectively, whereas those in the suburbs were in the range of 2.3-5.2 ng/g (av. 3.9 ng/g) in road dusts and 0.4-5.1 ng/g (av. 2.4 ng/g) in roadside soils. The highest Pt levels in road dusts were found from major roads with high traffic volume. The remarkable difference in average Pt level between heavy traffic roads (av. 132.2 ng/g) and light traffic roads (av. 22.8 ng/g) reflects that an important source of Pt in roadside environment is automobile catalytic converter. High Pt level in road dust was found from the site of erratic stop-start driving condition, for example, 178 ng/g Pt in road dust around a vehicle crossing gate. Platinum level in tree barks ranged from 0.9 to 4.5 ng/g, which indicates the existence of Pt-containing particulate matter in the atmosphere. Road dusts with high Pt level were enriched in traffic-related heavy metals.     

Habitat Matrix Effects on Pond Occupancy in Newts

Abstract: In farmlands, the population viability of many amphibians is suspected to depend on the resistance the matrix of crop fields presents to movements between ponds and terrestrial sites and movements among ponds. Over recent decades the increase in cereal growing at the expense of cattle breeding has caused a drastic change in habitat matrix in many European regions. We investigated the effect of such change on populations of three newt species (   Triturus helveticus , T. alpestris , and T. cristatus ) by comparing their abundances in sites that varied in amount of cultivated ground. A multivariate regression analysis of the relationship of newt abundance to both pond and landscape variables demonstrated the negative influence of cultivated ground on abundance. The width of the uncultivated sector linking the pond to the forest was a good predictor of abundance after the influences of both pond area and fish presence were removed. Moreover, newt presence was positively related to the number of ponds within that 50-ha surrounding area, highlighting the role of metapopulation functioning in newt occupancy of ponds. The relationship between newt abundance and width of uncultivated sectors agrees with present knowledge of the orientation mechanisms that underlie migration movements in urodeles. Such a relationship between connectedness and sector width shows that narrow, linear corridors such as hedgerows may not be useful in newt conservation. Our study also highlights the need to incorporate a behavioral component of habitat use into models of connectivity in conservation biology.     

Effects of Road Fencing on Population Persistence

Abstract:  Roads affect animal populations in three adverse ways. They act as barriers to movement, enhance mortality due to collisions with vehicles, and reduce the amount and quality of habitat. Putting fences along roads removes the problem of road mortality but increases the barrier effect. We studied this trade-off through a stochastic, spatially explicit, individual-based model of population dynamics. We investigated the conditions under which fences reduce the impact of roads on population persistence. Our results showed that a fence may or may not reduce the effect of the road on population persistence, depending on the degree of road avoidance by the animal and the probability that an animal that enters the road is killed by a vehicle. Our model predicted a lower value of traffic mortality below which a fence was always harmful and an upper value of traffic mortality above which a fence was always beneficial. Between these two values the suitability of fences depended on the degree of road avoidance. Fences were more likely to be beneficial the lower the degree of road avoidance and the higher the probability of an animal being killed on the road. We recommend the use of fences when traffic is so high that animals almost never succeed in their attempts to cross the road or the population of the species of concern is declining and high traffic mortality is known to contribute to the decline. We discourage the use of fences when population size is stable or increasing or if the animals need access to resources on both sides of the road, unless fences are used in combination with wildlife crossing structures. In many cases, the use of fences may be beneficial as an interim measure until more permanent measures are implemented.     

Platinum pollution in road dusts,roadside soils,and tree barks in Seoul,Korea

This study presents the level of platinum in urban environment in and around Seoul, the capital city of Korea. Road dust, roadside soil, and tree bark samples were collected from the sites of various traffic volumes and from control sites in the suburbs. The above samples were analyzed for Pt by ICP-MS and other heavy metals by ICP-OES. Platinum levels in road dusts and roadside soils from Seoul were in the range of 3.8–444 ng/g (av. 115.0 ng/g) and 0.7–221 ng/g (av. 49.7 ng/g), respectively, whereas those in the suburbs were in the range of 2.3–5.2 ng/g (av. 3.9 ng/g) in road dusts and 0.4–5.1 ng/g (av. 2.4 ng/g) in roadside soils. The highest Pt levels in road dusts were found from major roads with high traffic volume. The remarkable difference in average Pt level between heavy traffic roads (av. 132.2 ng/g) and light traffic roads (av. 22.8 ng/g) reflects that an important source of Pt in roadside environment is automobile catalytic converter. High Pt level in road dust was found from the site of erratic stop–start driving condition, for example, 178 ng/g Pt in road dust around a vehicle crossing gate. Platinum level in tree barks ranged from 0.9 to 4.5 ng/g, which indicates the existence of Pt-containing particulate matter in the atmosphere. Road dusts with high Pt level were enriched in traffic-related heavy metals.     

Platinum pollution in road dusts,roadside soils,and tree barks in Seoul,Korea

This study presents the level of platinum in urban environment in and around Seoul, the capital city of Korea. Road dust, roadside soil, and tree bark samples were collected from the sites of various traffic volumes and from control sites in the suburbs. The above samples were analyzed for Pt by ICP-MS and other heavy metals by ICP-OES. Platinum levels in road dusts and roadside soils from Seoul were in the range of 3.8–444 ng/g (av. 115.0 ng/g) and 0.7–221 ng/g (av. 49.7 ng/g), respectively, whereas those in the suburbs were in the range of 2.3–5.2 ng/g (av. 3.9 ng/g) in road dusts and 0.4–5.1 ng/g (av. 2.4 ng/g) in roadside soils. The highest Pt levels in road dusts were found from major roads with high traffic volume. The remarkable difference in average Pt level between heavy traffic roads (av. 132.2 ng/g) and light traffic roads (av. 22.8 ng/g) reflects that an important source of Pt in roadside environment is automobile catalytic converter. High Pt level in road dust was found from the site of erratic stop–start driving condition, for example, 178 ng/g Pt in road dust around a vehicle crossing gate. Platinum level in tree barks ranged from 0.9 to 4.5 ng/g, which indicates the existence of Pt-containing particulate matter in the atmosphere. Road dusts with high Pt level were enriched in traffic-related heavy metals.

     

LANDIS and forest landscape models

This paper provides contextual documentation of the LANDIS model development to provide a framework for the other papers in this special issue. The LANDIS model of forest landscape disturbance and succession was developed since the early 1990s as a research and management tool that optimizes the possible landscape extent (100 s ha to 1000 s km²), while providing mechanistic detail adequate for a broad range of potential problems. LANDIS is a raster model, and operates on landscapes mapped as cells, containing tree species age classes. Spatial processes, such as seed dispersal, and disturbances such as fire, wind, and harvesting can occur. LANDIS development benefited from the modelling and research progress of the 1960s to the1980s, including the growth of landscape ecology during the 1980s. In the past decade the model has been used by colleagues across North America, as well as in Europe and China. This has been useful to those not able to undertake the cost and effort of developing their own model, and it has provided a growing diverse set of test landscapes for the model. These areas include temperate, southern, and boreal forests of eastern North America, to montane and boreal western forests, coastal California forest and shrub systems, boreal Finnish forests, and montane forests in Switzerland and northeastern China. The LANDIS model continues to be refined and developed. Papers in this special issue document recent work. Future goals include integration within a larger land use change model, and applications to landscape and regional global change projection based on newly incorporated biomass and carbon dynamics.     

Estimating the effect of air pollution on road safety using atmospheric temperature inversions

Does air quality influence road safety? We estimate the effect of increased air pollution on the number of road traffic accidents in the United Kingdom between 2009 and 2014. To address concerns of spurious correlation we exploit atmospheric temperature inversions as a source of plausibly exogenous variation in daily air pollution levels. We find an increase of 0.3–0.6% in the number of vehicles involved in accidents per day for each additional 1 μg/m³ of PM_2.5. The finding suggests that less safe roads may present a large and previously overlooked cost of air pollution. The results are robust to a number of specifications and across various sub-samples.     

Distribution of a Community of Mammals in Relation to Roads and Other Human Disturbances in Gabon,Central Africa

We present the first community‐level study of the associations of both roads and other human disturbances with the distribution of mammals in Gabon (central Africa). Our study site was in an oil concession within a littoral mosaic landscape. We conducted surveys along 199 line transects and installed camera traps on 99 of these transects to document mammal presence and abundance. We used generalized linear mixed‐effect models to document associations between variables related to the ecosystem (land cover, topography, and hydrology), roads (coating, width of rights of way, condition, type of vehicle used on the road, traffic level, affiliation of users, and general type of road), and other human disturbances (urbanization, agriculture, hunting, logging, gathering, and industrial activities) and the abundance or presence of 17 species or groups of mammals including elephant (Loxodonta cyclotis), buffalo (Syncerus caffer), sitatunga (Tragelaphus spekei), red river hog (Potamochoerus porcus), smaller ungulates, gorilla (Gorilla gorilla), chimpanzee (Pan troglodytes), side‐striped jackal (Canis adustus), carnivores, monkeys, and large rodents. Some types of roads and other human disturbances were negatively associated with the abundance or presence of elephants, buffalos, gorillas, sitatungas, some monkeys, and duikers. The pattern of associations of mammals with roads and other human disturbances was diverse and included positive associations with road presence (red river hog, some monkeys, and duikers), agriculture (sitatunga, small carnivores, and large rodents) and industrial activities (sitatunga, red river hog, red duikers, and side‐striped jackal). Our results suggest that the community of mammals we studied was mostly affected by hunting, agriculture, and urbanization, which are facilitated by road presence. We recommend increased regulation of agriculture, hunting, and road building in the area. Distribución de una Comunidad de Mamíferos en Relación a Carreteras y Otras Perturbaciones Humanas en Gabón, Africa Central     

The Ecological Road-Effect Zone of a Massachusetts (U.S.A.) Suburban Highway

Abstract: Ecological flows and biological diversity trace broad patterns across the landscape, whereas transportation planning for human mobility traditionally focuses on a narrow strip close to a road or highway. To help close this gap we examined the "road-effect zone" over which significant ecological effects extend outward from a road. Nine ecological factors—involving wetlands, streams, road salt, exotic plants, moose, deer, amphibians, forest birds, and grassland birds—were measured or estimated near 25 km of a busy four-lane highway west of Boston, Massachusetts. The effects of all factors extended > 100 m from the road, and moose corridors, road avoidance by grassland birds, and perhaps road salt in a shallow reservoir extended outwards > 1 km. Most factors had effects at 2–5 specific locations, whereas traffic noise apparently exerted effects along most of the road length. Creating a map of these effects indicates that the road-effect zone averages approximately 600 m in width and is asymmetric, with convoluted boundaries and a few long fingers. We conclude that busy roads and nature reserves should be well separated, and that future transportation systems across landscapes can provide for ecological flows and biological diversity in addition to safe and efficient human mobility.     

Spatial Scale and Determination of Species Status of the Green Frog

Although the importance of spatial scale in determining species status (abundance and distribution) is widely recognized, most ecological investigations have been conducted at local scales. Our goal was to investigate the importance of spatial scale in assessing the status of the green frog ( Rana clamitans melanota) in the center of its range in eastern North America. Using repeated surveys at 160 ponds from 1992 to 1994, we investigated patterns of occupancy, abundance, and turnover at local, sub-regional, regional, and geographic scales to determine the status of the green frog in southwestern Ontario, Canada. Patterns of pond occupancy were stable at the geographic scale. Occupancy was stable in two regions and decreased in one. At the sub-regional scale, occupancy was stable in six sub-regions, increased in one, and decreased in two. Patterns of adult abundance were stable at the geographic scale. At the regional scale trends in adult abundance were increasing, decreasing, or stable in each of three regions. At the sub-regional scale abundance was stable in three, increasing in one, decreasing in two, and no trend occurred in three sub-regions. At the local scale abundance was stable at 20% of ponds, increased at 17.8%, decreased at 14.4%, and no trend existed at 47.8%. Colonization and extinction rates ranged from 0 to 0.20 and 0 to 0.35 ponds/pond occupied/year, respectively, and differed among regions. Local extinctions took place at 25% of ponds during the study, but no sub-regional or regional scale extinctions occurred. Small populations (<10 adults/pond) were prone to local extinction. Determination of the status of the green frog is scale dependent. Although green frog populations are dynamic, it is common and stable at the geographic scale, but its status varies among regions or sub-regions. Although processes that negatively affect a species may operate at the local scale, a large-scale perspective is necessary to determine status.