No abstract

Over the last few decades, road construction has increased dramatically, and new surfaces have appeared in most landscapes. Standard roadside reclamation practices often fail, because vegetation establishment appears to be limited by microsite availability. We considered soil properties as a key factor driving vegetation establishment on roadslopes over time. We address the following questions: (i) Are soil features conditioned by type of roadslope, position thereupon or applied hydroseeding? (ii) Is there any evidence of soil development at the roadside four years after road construction? (iii) Do mutual interactions exist between soil features and vegetation cover? We designed an experimental set‐up on a highway in Central Spain (Madrid). We selected 15 roadslopes (nine roadcuts and six embankments) with three hydroseeding treatments (commercial, alternative and untreated). Four years after the road construction, we considered three roadslope positions (top, middle and bottom) to take into account the geomorphological gradient. We monitored soil features and vegetation cover over 4 years after the road construction. Soil chemical differences were found between roadslope types, mainly resulted from topsoil spreading on embankments and the weathering of the newly exposed materials on roadcuts. Applied amendments do not affect soil fertility or vegetation cover. In the course of time, vegetation establishment and geomorphological gradients operate differentially on roadcuts and embankments. Accordingly, cycling back of organic compounds or geomorphological processes differs between roadslopes types. Restoration efforts should be directed to guarantee key ecological processes and support soil formation. Copyright © 2011 John Wiley & Sons, Ltd.

Road barrier effect is among the foremost negative impacts of roads on wildlife. Knowledge of the factors responsible for the road barrier effect is crucial to understand and predict species’ responses to roads, and to improve mitigation measures in the context of management and conservation. We built a set of hypothesis aiming to infer the most probable cause of road barrier effect (traffic effect or road surface avoidance), while controlling for the potentially confounding effects road width, traffic volume and road age. The wood mouse Apodemus sylvaticus was used as a model species of small and forest-dwelling mammals, which are more likely to be affected by gaps in cover such as those resulting from road construction. We confront genetic patterns from opposite and same roadsides from samples of three highways and used computer simulations to infer migration rates between opposite roadsides. Genetic patterns from 302 samples (ca. 100 per highway) suggest that the highway barrier effect for wood mouse is due to road surface avoidance. However, from the simulations we estimated a migration rate of about 5% between opposite roadsides, indicating that some limited gene flow across highways does occur. To reduce highway impact on population genetic diversity and structure, possible mitigation measures could include retrofitting of culverts and underpasses to increase their attractiveness and facilitate their use by wood mice and other species, and setting aside roadside strips without vegetation removal to facilitate establishment and dispersal of small mammals.

Some small mammal species use road verges as a habitat for sheltering. As a result, their populations suffer mortality from roadkill in an unknown extent. We analysed the road mortality of small mammals and the population impact of roadkill on wood mouse along 1 year on a 4‐km motorway stretch. To account for potential bias in carcass sampling, we conducted walking surveys with the traffic interrupted and we performed three carcass persistence experiments to estimate total number of roadkills. The estimations were contrasted with previous studies and the population abundance on the road verges. The spatial pattern and the effects of seasonality and traffic volume on roadkill were analysed. We recorded 84 rodent carcasses with a mean carcass persistence of 6.65 days (SE = 0.41). The estimations of roadkill ranged between 190.2 and 238.3 individuals km−1 year−1, with a mean value close to a monthly 6 % mortality for the most common specie. Roadkill was more frequent during the hottest and driest months, and showed a unimodal relation with traffic peaking at 8100 vehicles day−1. A spatial aggregation of roadkill was detected with 80–190 m clustering. Our results suggest that, although rodents suffer greater roadkill mortality than previously reported, it affects a small percentage of the wood mouse population in our study area. This source of mortality is unlikely to affect population viability in the short term. Our results show that roadkill surveys should be specifically designed for small mammals to have a more accurate analysis of the effects of roadkill on their populations.

Linear infrastructures represent one of the most important human impacts on natural habitats and exert several effects on mammal populations. Motorways are recognized as a major cause of habitat fragmentation and degradation and of biodiversity loss. However, it is unknown whether motorways lead to increased physiological stress reactions in wild animal populations. We analysed faecal corticosterone metabolites (FCM) in wild populations of wood mice (Apodemus sylvaticus) living in a well-preserved Mediterranean agro-pastoral woodland at different distances (verge, 500 m and 1000 m) from the AP-51 motorway in Spain. Wood mice were captured with Sherman live traps, and fresh faecal samples from 424 individuals were collected and analyzed in the laboratory. The quantification of FCM was performed by a 5α-pregnane-3β,11β, 21-triol-20-one enzyme immunoassay. Results showed that females had higher FCM levels than males, and these levels were higher in breeding females. In addition, FCM levels were positively correlated with body weight of individuals. Wood mice captured where cattle were present showed higher FCM levels than individuals living where cattle were not detected. FCM levels were higher in non-breeding individuals living close to the motorway compared with FCM levels in those individuals captured further from the motorway. This is the first study showing evidence of the motorways' impact on physiological stress reactions in wild wood mice populations. Understanding how free-living animals are influenced by human interventions could help to understand other subtle changes observed in wild animal populations. Since mice are used world-wide as research models these results could open new perspectives testing human influence on the natural environment and trade-offs of species in degraded ecosystems.