Can grassland plant communities be preserved on road and railway verges?

Abstract. Semi‐natural grasslands are a threatened biotope type in many countries. Typical grassland plant species are adapted to continuous grazing or mowing that keeps the environment open. With the decline in grassland area, these species are ever more reliant on alternative habitats such as road verges. To find out whether plant communities comparable to those of semi‐natural grasslands can be maintained on modern road and railway sides, the vegetation of 92 grasslands and 90 road and railway verges was studied. These biotope types were compared with each other according to their community structure, total number of species, number of grassland species and restricted‐range diversity. Further study of the vegetation of road and railway verges was carried out in order to identify the treatments and environments which are most likely to support diverse plant communities. The species number and the restricted‐range diversity proved to be higher next to roads and railways than on grasslands. Grassland species were, however, most abundant on grasslands. Furthermore, the community structure of these biotope types was totally divergent. In their present state, road and railway verges are not a substitute for semi‐natural grasslands. Nevertheless, the occurrence of grassland species in verges may be enhanced by a suitable mowing regime, by giving up the use of de‐icing salt and herbicides and by allowing natural establishment of vegetation on the verges.     

Road Verge and Rangeland Plant Communities in the Southern Karoo: Exploring What Influences Diversity, Dominance and Cover

Road verges in the Prince Albert district, South Africa were examined to determine whether they are important refugia for plant species in the Karoo biome. Vascular plants at 50 sites on road verges were compared with those plant communities in the adjacent grazed rangelands. Verges were found to support a greater mean number of species, total plant cover, and number of individual plants. Road verges were found to contain 11 unique species compared with 20 unique species in rangelands. Plant community composition varied with more forbs and succulents on the verge and more shrubs in the rangeland. Significantly greater cover of unpalatable plants was found on the ungrazed road verge, and no difference in palatable and highly palatable plant cover was recorded, indicating that herbivory is not a major driver in defining community differences in these environments. No significant differences in soil moisture or texture were found between verge and rangeland. We argue that road maintenance and construction activities have an over-riding controlling influence on road verge community composition. Although it is not possible to discount the possibility that road verges provide an important refuge for certain species, it appears that they are disturbed environments that do not contribute significantly to the plant conservation needs of this biome.     

Distance to semi-natural grassland influences seed production of insect-pollinated herbs

Marginal grassland fragments, such as road verges and field margins, may act as important supplemental habitats for grassland plants in the modern agricultural landscape. However, abundance of pollinators in such fragments has been found to decline with distance to larger natural and semi-natural habitats, and this could have corresponding effects on plant pollination. In this study, we performed a field experiment on road verges with three insect-pollinated grassland herbs to examine the relationship between distance to semi-natural grassland and plant reproductive success in two landscapes with contrasting farming intensities. In Lychnis viscaria and Lotus corniculatus, seed production tended to decrease with increasing distance to semi-natural grassland, but only in the landscape with high farming intensity. Seed production in Armeria maritima spp. maritima decreased with distance in both landscapes. Although many studies have investigated effects of natural habitat on crop pollination, little is known about the impact on pollination in native plants. The results from this study indicate that management of semi-natural grasslands improves not only biodiversity within the actual grassland but also pollination of native plants in the surrounding agricultural landscape.     

Resource use of specialist butterflies in agricultural landscapes: conservation lessons from the butterfly Phengaris (Maculinea) nausithous

Most of the European grassland butterfly species are dependent on species rich grasslands shaped by low intensity farming. Conservation of these specialist species in agricultural landscapes relies on knowledge of their essential resources and the spatial distribution of these resources. In The Netherlands, the dusky large blue Phengaris (Maculinea) nausithous butterflies were extinct until their reintroduction in 1990. In addition, a spontaneous recolonization of road verges in an agricultural landscape occurred in 2001 in the southern part of The Netherlands. We analyzed the use of the essential resources, both host plants and host ants, of the latter population during the summers of 2003 and 2005. First we tested whether the distribution of the butterflies during several years could be explained by both the presence of host plants as well as host ants, as we expected that the resource that limits the distribution of this species can differ between locations and over time. We found that oviposition site selection was related to the most abundant resource. While in 2003, site selection was best explained by the presence of the host ant Myrmica scabrinodis, in 2005 it was more strongly related to flowerhead availability of the host plant. We secondly compared the net displacement of individuals between the road verge population and the reintroduced population in the Moerputten meadows, since we expected that movement of individuals depends on the structure of their habitat. On the road verges, butterflies moved significantly shorter distances than on meadows, which limits the butterflies in finding their essential resources. Finally we analyzed the availability of the two essential resources in the surroundings of the road verge population. Given the short net displacement distances and the adverse landscape features for long-distance dispersal, this landscape analysis suggests that the Phengaris population at the Posterholt site is trapped on the recently recolonized road verges. These results highlight the importance of assessing the availability of essential resources across different years and locations relative to the movement of the butterflies, and the necessity to careful manage these resources for the conservation of specialist species in agricultural landscapes, such as this butterfly species.     

Road-related landscape elements as a habitat: A main asset for small mammals in an intensive farming landscape

Road construction creates new habitats for a variety of species. In intensive farming landscapes, road verges may be the only suitable habitat for rodents. However, little attention has been paid to other road-related landscape elements (RRLEs), such as excavation slopes or the central islands of roundabouts, and their importance in a rodent territory. This study investigated all types of RRLE in terms of rodent abundances and habitat quality. RRLEs were compared with the semi-natural elements of the studied landscape using a capture-mark-recapture protocol. Four species and 3154 individuals were captured over a period of four months. Relative abundance and habitat quality were higher in RRLEs than in semi-natural elements. Mapping of the landscape showed that 86% of crop fields are accessible to Microtus arvalis (and almost 100% for Apodemus sylvaticus) from road verges. Our results highlight the importance of road verges and all other RRLEs in the conservation of species diversity in intensive farming landscapes.     

Conservation value of road verges in the semi-arid Karoo, South Africa: ants (Hymenoptera: Formicidae) as bio-indicators

Ground-foraging ants (Hymenoptera: Formicidae) were used to assess the conservation value of road verges in a semi-arid region around Prince Albert, Western Cape Province, South Africa. Ant communities were sampled using pitfall traps on 50 sites along two roads. Four transects were sampled at each site, two in the road verge and two in adjacent rangeland. A total of 43,298 individual ants of 34 species were caught, with 31 and 32 species in the road verge and adjacent rangeland respectively, but on average road verges were the more species-rich. Road verges also contained relatively more rare species (i.e. those species that occurred in <10% of the traps. Ant species richness appeared to be influenced by food availability. Although ants appeared to be negatively impacted by higher grazing intensities in the rangeland, there was no difference in species richness between fenced and unfenced road verges. Species in the road verge may benefit directly from road kills, and indirectly from lower grazing pressure on plants, increased surface run-off and differences in soil surface temperatures. No alien ant species were observed or captured at any of the sites.     

Road vegetation in Central Europe — an example from the Czech Republic

Road nets are man-made constructions in the open landscape with a specific vegetation accompaniment in a verge or band along the road or in a divider strip. A determination of six basic vegetation types of bands along roads is possible in Central Europe (tree lines, planting area, forest stand, early successful growth, bushes band, grassy-herbal associations). In the Czech Republic, grassy-herbal communities growing on road verges are mainly formed by perennials, hemicryptophyts, and species with tendency towards pollination by insects and to anemochory and exozoochory. 40% woody and 25% herbaceous species which are non-native for Central Europe form a part of them. Three halophyte species are growing in closed lines along asphalt: Puccinellia distans, Digitaria sanguinalis and Spergularia rubra. Roads and highways should be made and used with respect to the ecological potential of roadside vegetation. However, the road net functioned as a corridor for invasive (planting or spreading) plant species.     

Functional response of plant assemblages to management practices in road–field boundaries

Questions

Management practices implemented on road verges are partly established to preserve biodiversity in agricultural landscapes. Their evaluation was primarily based on the analysis of the taxonomic structure and composition of communities. What is the relationship between management practices and the functional characteristics of road–field plants within elements?

Location

West‐central France.

Methods

We sampled the berm, the embankment and the field margin of 40 road–field boundaries located in west‐central France, an area where delayed mowing of some berms has been practised since 2009 for biodiversity reasons. We characterized management practices implemented on the different elements, i.e., the frequency and timing of mowing (early summer or late summer), the frequency of herbicide treatment in field margins and the N input rate. We retrieved from databases seven functional traits and types known to be influenced by management practices. To identify relationships between traits or types and environmental variables we first performed partial RLQ analyses to remove any potential confounding effect of the landscape context studied. We then computed fourth‐corner statistics to quantify relationships between traits or types, environmental variables and partial RLQ axes.

Results

Late mowing of the berm promoted nitrophilous species within berms and competitive rather than ruderal species within arable field margins. The frequency of herbicide treatment in field margins promoted broad‐leaf species within this element and, to a lesser extent, within embankments. Finally, the functional characteristics of communities of the three elements were not influenced by the level of N input in field margins.

Conclusions

In our environmental context, managing road verges affected the functional structure of plant assemblages both within them and within their adjacent arable field margins. We suggest a single early mowing of berms as a valuable practice for both conservation purposes and weed risk control in adjacent field margins.     

Easy technique for assessing pollination rates in the genus Erica reveals road impact on bird pollination in the Cape fynbos,South Africa

Road traffic is one of the most pervasive forms of anthropogenic disturbance, but its impact on pollination, a potentially sensitive ecosystem process, has not been investigated. Such an assessment is needed in order to evaluate the potential for roadside verges to act as biodiversity refugia and corridors in otherwise transformed landscapes. Here, we document the impact of a two‐lane tar road on pollination by birds in the Cape fynbos of South Africa. To do so, we developed a quick and widely applicable method of determining pollination rates in bird‐pollinated members of the large genus Erica. Experiments with caged birds showed that the status of the anther ring (broken/perfect) indicated a sunbird visit with 92% accuracy, while field surveys confirmed anther ring status also serves as a proxy for pollen receipt to stigmas. Using this technique we determined pollination rate in Erica perspicua at three distances from the road (0–10, 20–30 and 40–50 m). After controlling for flower colour, robbing rate and plant density, significantly fewer anther rings were disturbed in close proximity to the road. The documented twofold decline in pollination along roadsides could have important implications for the way we view and manage road verges as refugia for species and ecological processes.     

Ecological response hides behind the species abundance distribution: Community response to low‐intensity disturbance in managed grasslands

Land‐use and management are disturbance factors that have diverse effects on community composition and structure. In traditional rural grasslands, such as meadows and pastures, low‐intensity management is maintained to enhance biodiversity. Maintenance of road verges, in turn, creates habitat, which may complement traditional rural grasslands. To evaluate the effect of low‐intensity disturbance on insect communities, we characterized species abundance distributions (SAD) for Carabidae, Formicidae, and Heteroptera in three grassland types, which differed in management: meadows, pastures, and road verges. The shape of SAD was estimated with three parameters: abundance decay rate, dominance, and rarity. We compared the SAD shape among the grassland types and tested the effect of environmental heterogeneity (plant species richness) and disturbance intensity (trampling in pastures) on SADs. The shape of SADs did not differ among the grassland types but among the taxonomic groups instead. Abundance decay rate and dominance were larger for Formicidae, and rarity smaller, than for Carabidae and Heteroptera. For Carabidae and window‐trapped Heteroptera, rarity increased with increasing plant species richness. For Formicidae, dominance increased with trampling intensity in pastures. Although the SAD shape remained largely unchanged, the identity of the dominant species tended to vary within and among grassland types. Our study shows that for a given taxonomic group, the SAD shape is similar across habitat types with low‐intensity disturbances resulting from different management. This suggests that SADs respond primarily to the intensity of disturbance and thus could be best used in monitoring communities across strong disturbance and environmental gradients. Because taxonomic groups can inherently have different SADs, taxon‐specific SADs for undisturbed communities must be empirically documented before the SAD shape can be used as an indicator of environmental change. Because the identity of the dominant species changes from management type to another, the SAD shape alone is not an adequate monitoring tool.     

Plant dispersal by motor cars

Mud from a car driving more than 15 000 km in the growing season of 1986 in the area surrounding Göttingen (FRG) was sampled systematically to assess the size and nature of the car-borne flora. The sludge from front and back mudguards, wheels and other lower parts of the car was set out for germination in a greenhouse. Until the end of 1987, 124 plant species with a total of 3926 seedlings were identified and counted. Germination success was significantly related to the sampling date, the front or back position of the car and the influence of low temperature during exposure. The nature of this potentially car-dispersed flora was compared with the local flora as a whole as well as the flora and plant communities of road verges in the studied area. It can be supposed that almost all plant species growing in plant communities along roadsides can be carried by cars and therefore belong to the car-dispersed flora.     

Unpaved roads disrupt the effect of herbivores and pollinators on the reproduction of a dominant shrub

Anthropogenic linear developments, such as trails and firebreaks, also called soft linear developments (SLD), can influence animal behavior, altering the ecological interactions in which animals are involved. For example, SLD can affect the behavior of pollinators and herbivores, but little is known about the combined effect of these three elements on plant reproduction.We evaluated the combined effect of SLD, insect pollinators and herbivores (ungulates) on three reproductive output variables (fruit set, seed set, and seed mass) of a Mediterranean shrub (Halimium halimifolium). We considered two different habitats (SLD verges vs. adjacent scrublands), two scenarios of herbivory (with and without ungulates), and three scenarios of pollinator activity (without pollinators, with manual pollination and with natural pollination).SLD had contrasting effects on H. halimifolium reproduction. In the absence of herbivores, overall fruit set was lower in the verges of SLD than in adjacent scrublands, probably due to lower flower pollination rates. Where herbivores were present, overall fruit set was similar between habitats, because ungulate browsing was lower in SLD verges than in adjacent scrublands. The quantity and weight of seeds per fruit was similar in both habitats, probably because all fertilized flowers received similar amounts of pollen.SLD can alter the interaction among pollinators, herbivores and plants, leading to changes in the reproductive performance of the latter. These changes can have strong negative impacts on endangered plants that rely on fruit and seed production to persist. However, SLD verges could be safe places for plants particularly sensitive to herbivory by ungulates.     

Switchgrass (Panicum virgatum L.) Genotypes Differ between Coastal Sites and Inland Road Corridors in the Northeastern US

Switchgrass (Panicum virgatum L.) is a North American grass that exhibits vast genetic diversity across its geographic range. In the Northeastern US, local switchgrass populations were restricted to a narrow coastal zone before European settlement, but current populations inhabit inland road verges raising questions about their origin and genetics. These questions are important because switchgrass lines with novel traits are being cultivated as a biofuel feedstock, and gene flow could impact the genetic integrity and distribution of local populations. This study was designed to determine if: 1) switchgrass plants collected in the Long Island Sound Coastal Lowland coastal Level IV ecoregion represented local populations, and 2) switchgrass plants collected from road verges in the adjacent inland regions were most closely related to local coastal populations or switchgrass from other geographic regions. The study used 18 microsatellite markers to infer the genetic relationships between 122 collected switchgrass plants and a reference dataset consisting of 28 cultivars representing ecotypes, ploidy levels, and lineages from North America. Results showed that 84% of 88 plants collected in the coastal plants were most closely aligned with the Lowland tetraploid genetic pool. Among this group, 61 coastal plants were similar to, but distinct from, all Lowland tetraploid cultivars in the reference dataset leading to the designation of a genetic sub-population called the Southern New England Lowland Tetraploids. In contrast, 67% of 34 plants collected in road verges in the inland ecoregions were most similar to two Upland octoploid cultivars; only 24% of roadside plants were Lowland tetraploid. These results suggest that cryptic, non-local genotypes exist in road verges and that gene flow from biofuels plantations could contribute to further changes in switchgrass population genetics in the Northeast.     

Living on the verge: are roads a more suitable refuge for small mammals than streams in Mediterranean pastureland?

The retention of natural habitat corridors is a useful and practical conservation tool that can attenuate the effects of habitat loss and fragmentation on wildlife. Linear structures may contribute to the conservation of biodiversity by providing additional habitats for small fauna living in highly modified environments. We assessed the importance of road verges as refuge areas for small mammals, in highly intensified grazed pastures, within a Mediterranean landscape and compared the role of road verges as refuges with that of riparian galleries, which have been described as important shelter locations for small fauna. For this purpose, a small mammal trapping study was undertaken on two road verges and beside two small streams in southern Portugal. We captured 457 individuals of five different species, with Mus spretus the most common species captured, followed by Crocidura russula. Captures were 4.6-fold higher immediately beside both roads and streams than 12 m away in the surrounding matrix. Individuals captured in the matrix presented a smaller body size and lower body condition, suggesting that this suboptimal habitat is occupied mainly by subadults. M. spretus was 46% more abundant by roads than by streams, while C. russula was present in similar numbers in both habitats. M. spretus individuals were larger near streams but exhibited no difference in body condition between habitats. C. russula had a better body condition and slightly higher body lengths at roadsides. Our results show that roadside verges in intensively grazed Mediterranean landscapes act as important refuges and constitute equally vital habitats for small mammals as do riparian vegetation strips in landscapes where other suitable habitats are scarce.     

Grassland plant species occurring in extensively managed road verges are filtered by urban environments

Background: Urbanisation filters species in communities depending on their adaptability to conditions in built-up areas, especially in semi-natural habitats. Roadside vegetation is widespread along urban-rural gradients and is therefore a good place to study landscape-scale factors influencing plant community composition.

Aim: Our study aimed to assess how plant species distributions vary between urban and rural landscape contexts and to identify biological traits favoured in urban areas.

Methods: Presence/absence data for 63 indigenous common species were collected in 296 road verge patches distributed along the urban–rural gradient in three French cities. We investigated the effects of landscape composition on species assemblages and related individual species responses to urbanisation to functional traits associated with dispersal and persistence capacity.

Results: Many grassland species were negatively affected by increasing proportion of built-up areas in the landscape. Insect-pollination and high seed production appeared to be key traits favoured in grassland communities in urban areas, whereas dispersal modes were less related to plant distribution.

Conclusions: This study has demonstrated that urban filters affect common species of widespread, managed road verges. Better knowledge of the flora of these herbaceous roadsides may contribute to the conservation of common biodiversity within other grassland habitats found in urban areas.     

Roadside verges and cemeteries: Comparative analysis of anthropogenic orchid habitats in the Eastern Mediterranean

Several important habitats have become threatened in the last few centuries in the Mediterranean Basin due to major changes adopted in land‐use practices. The consequent loss of natural and seminatural orchid habitats leads to the appreciation of small anthropogenic habitats, such as cemeteries and roadside verges. Colonization of cemeteries and roadside verges by orchids has long been known, but no study to date compared the suitability of these two anthropogenic habitats for orchids. Therefore, in this paper our aim was to survey cemeteries and roadside verges and to compare these two habitats regarding their role in conserving Mediterranean terrestrial orchids. We conducted field surveys in three Mediterranean islands, Cyprus, Crete, and Lesbos, where both cemeteries and roadside verges were sampled on a geographically representative scale. We found a total of almost 7,000 orchid individuals, belonging to 77 species in the two anthropogenic habitat types. Roadside verges hosted significantly more individuals than cemeteries in Crete and Lesbos, and significantly more species across all three islands. Our results suggest that although cemeteries have a great potential conservation value in other parts of the world, intensive maintenance practices that characterized cemeteries in these three islands renders them unable to sustain valuable plant communities. On the other hand, roadside verges play a prominent role in the conservation of Mediterranean orchids in Cyprus and Greece. The pioneer status of roadside verges facilitates their fast colonization, while roads serve as ecological corridors in fragmented landscapes.     

Highway verges as habitat providers for small mammals in agrosilvopastoral environments

The Mediterranean Basin has an important conservation value given its high biodiversity and high number of endemic species, which have co-existed with human traditional practices for centuries. However, northern areas as the Iberian Peninsula have experienced intensification in livestock production in recent past, with consequent reduction in habitat quality. In this study we assessed the importance of fenced highway verges as habitat for small mammals in Mediterranean agrosilvopastoral landscapes. More specifically, we compared small mammal abundance between highway verges and the adjacent two main land uses (“montado” and open areas); compared the vegetative structure among these land uses; and addressed how vegetation structure influences species occupancy. Thirty-six sites were sampled in agrosilvopastoral system areas in southern Portugal (sampling effort 8,840 trap-nights). A total of 351 individuals from target species were captured: 157 wood mice (Apodemus sylvaticus), 95 western Mediterranean mice (Mus spretus) and 99 greater white-toothed shrews (Crocidura russula). Capture–mark–recapture analyses were performed to estimate population size. Our data suggests that fenced highway verges promote better vegetative structure conditions which in turn favor a higher animal abundance therein. We suggest the adoption of management practices to increase the height and cover of herbaceous and shrub layers in road verges, together with creating grazing controlled areas in highway vicinity, particularly in “montado” patches, linked by vegetated linear features. This would increase habitat and refuge for a large numbers of species, including small mammals, and thus benefiting the trophic chain and the whole agrosilvopastoral system.     

Not only the butterflies: managing ants on road verges to benefit Phengaris (Maculinea) butterflies

Obligate myrmecophilic butterfly species, such as Phengaris (Maculinea) teleius and P. nausithous, have narrow habitat requirements. Living as a caterpillar in the nests of the ant species Myrmica scabrinodis and M. rubra, respectively, they can only survive on sites with both host ants and the host plant Great Burnet Sanguisorba officinalis. After having been reintroduced into a nature reserve in the Netherlands in 1990, both butterfly species expanded their distribution to linear landscape elements such as road verges and ditch edges outside this reserve. As additional habitat of both butterfly species, vegetation management of these landscape elements became important. Our results show that a management beneficial for Phengaris butterflies should aim to increase the nest density of Myrmica species, at the same time reducing the density of nests of the competitor Lasius niger or at least keeping them at a low density. Unfavourable grassland management under which L. niger thrives, includes not mowing or flail-cutting the grass, or depositing dredgings along the side of the ditch. Management favourable for the two Myrmica species differs, demanding some flexibility if both species are to benefit. M. scabrinodis is best supported with early mowing of the road verge vegetation or late mowing in the nature reserve, both of which result in an open vegetation and warm microclimate. In contrast, the nest sites of M. rubra should be left undisturbed during the summer, and mown in late autumn. Mowing of butterfly habitat should be avoided between mid-June and mid-September as this would remove the flowerheads of the Sanguisorba plants, on which the butterflies lay their eggs.     

Roadside verges can support spontaneous establishment of steppe-like habitats hosting diverse assemblages of bees and wasps (Hymenoptera: Aculeata) in an intensively cultivated central European landscape

Anthropogenic habitats, which are frequently occupied by otherwise endangered species of the open landscape, suffer from a lack of sustainability. Here, we analyzed one of the few sustainable anthropogenic habitats, roadside verges. We hypothesized that steppe-like habitats at upper parts of south-exposed slopes of roadside verges may serve as the only strongholds of threatened species ousted from the surrounding intensively cultivated landscape, with direct consequences for plant pollination and other ecosystem services. We examined bees and wasps alongside Highway 7 constructed 14–28 years ago in the northwestern Czech Republic. The sampling sites were located 4–17 m from paved road with traffic intensity of 9523 to 38,688 vehicles × 24 h^?1, and they consisted of steppe-like habitats with patches of bare soil (sand, loess and claystone) that formed and were maintained spontaneously. The sites were not connected to any permanent grasslands or forests, and they were surrounded mostly by arable fields. We found 139 species of herbs (nine threatened) in vegetation surveys along transects. We identified 164 species of bees and wasps, with a dominance of 0.052 and a Fisher’s alpha of 45.0; 32 species were threatened, including a second Czech record of Chrysis gribodoi spilota and four critically endangered species (Andrena florivaga, Halictus scabiosae, Sphecodes spinulosus and Nanoclavelia leucoptera). The captured specimens consisted of a higher number of loess specialists and other steppe species compared to specimens associated with other anthropogenic habitats that provide bare ground (sand pits and ash deposits). In conclusion, the formation of spontaneously maintained steppe-like habitats at roadside verges should be considered to be an appropriate tool supporting the biodiversity in the highly cultivated landscape of central Europe.