A global examination on the differential impacts of roadsides on native vs. exotic and weedy plant species

Invasion away from roadsides was not driven by adaptation to grassland habitats in Dittrichia graveolens (stinkwort)

Invasive plants along transportation corridors can significantly threaten ecosystems and biodiversity if they spread beyond anthropogenic environments. Rapid evolution may increase the ability of invading plant populations to establish in resident plant communities over time, posing a challenge to invasion risk assessment. We tested for adaptive differentiation in Dittrichia graveolens (stinkwort), an invasive species of ruderal habitat in California that is increasingly spreading away from roadsides into more established vegetation. We collected seeds from eight pairs of vegetated sites and their nearest (presumed progenitor) roadside population. We assessed differentiation between populations in roadside and vegetated habitat for germination behavior and for response to competition in a greenhouse experiment. We also tested for increased performance in vegetated habitat with a grassland field experiment including a neighbor removal treatment. Germination rates were slightly reduced in seeds from vegetated sites, which may indicate lower seed viability. Otherwise, plants did not show consistent differences between the two habitat types. Competition strongly reduced performance of D. graveolens in both the greenhouse and in the field, but plants originating from vegetated sites did not show enhanced competitive ability. Our findings show no evidence of adaptive differentiation between D. graveolens populations from roadside and vegetated habitats to date, suggesting that invasiveness in grasslands has not been enhanced by rapid evolution in the 40 + years since this species was introduced to California. Evolutionary constraints or potentially high levels of gene flow at this small scale may limit adaptation to novel habitats along roadsides.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10530-024-03359-6.

Land‐use changes interact with geology to facilitate dispersal of the rock hyrax (Procavia capensis) and leishmaniasis across Israel and the West Bank

Geology plays a fundamental role in establishing species' habitats, determining both physical (e.g., landscape morphology, soil texture) and chemical (e.g., mineral composition, water availability) properties. In the current Anthropocene epoch, human activity is transforming Earth's geology and ecosystems. Yet to date, there have been almost no studies incorporating geology when examining the effect of such land‐use changes on species distribution. This study seeks to uncover how specific land‐use changes interact with geology, in order to explain the recent and rapid expansion of the rock hyrax (Procavia capensis) across the mountains of central Israel and the West Bank. Hyraxes are dependent on rock mounds for their habitat, and their expansion seems to be correlated with increasing infrastructure construction. However, their expansion patterns differ among locations, even when the human land‐use is similar. To explain the patterns of hyrax distribution observed over the past 46 years, we converted geological data into ecological data, which present the probability of the local bedrock breaking into boulders, whether due to either natural or anthropogenic weathering processes. We applied species distribution models (SDMs) and found that the expansion of rock hyrax populations was facilitated by means of the interaction of specific geological units with land‐use practices (e.g., roads and construction), which resulted in the accumulation of large boulders, creating novel habitats and stepping stones in previously unsuitable areas for hyraxes. Since rock hyraxes are major hosts of the leishmaniasis pathogen, the findings from this study offer important insights into the progression and potential outbreaks of the disease in human populations. Understanding the role that geology plays in shaping a species' niche is expected to prove useful in studying the distribution of other wildlife species and is fundamental in studies seeking to predict the potential ecological impacts on local biodiversity associated with land‐use change.

The Matthew effect: Common species become more common and rare ones become more rare in response to artificial light at night

Artificial light at night (ALAN) has been and still is rapidly spreading and has become an important component of global change. Although numerous studies have tested its potential biological and ecological impacts on animals, very few studies have tested whether it affects alien and native plants differently. Furthermore, common plant species, and particularly common alien species, are often found to benefit more from additional resources than rare native and rare alien species. Whether this is also the case with regard to increasing light due to ALAN is still unknown. Here, we tested how ALAN affected the performance of common and rare alien and native plant species in Germany directly, and indirectly via flying insects. We grew five common alien, six rare alien, five common native, and four rare native plant species under four combinations of two ALAN (no ALAN vs. ALAN) and two insect-exclusion (no exclusion vs. exclusion) treatments, and compared their biomass production. We found that common plant species, irrespective of their origin, produced significantly more biomass than rare species and that this was particularly true under ALAN. Furthermore, alien species tended to show a slightly stronger positive response to ALAN than native species did (p = .079). Our study shows that common plant species benefited more from ALAN than rare ones. This might lead to competitive exclusion of rare species, which could have cascading impacts on other trophic levels and thus have important community-wide consequences when ALAN becomes more widespread. In addition, the slightly more positive response of alien species indicates that ALAN might increase the risk of alien plant invasions.

Are Trees Planted along the Roads Sustainable? A Large-Scale Study in the Czech Republic

Trees provide a wide variety of ecosystem services to society and form the character of the environment and landscape. The analyses of tree populations and their resistance to changing conditions related to climate change typically focus on urban tree communities or forest trees. Similar studies on non-forest trees in the open landscape are largely missing; even the evidence on tree species abundance and distribution is sporadic. The article aims to expand the current evidence by a large-scale study on roadside trees in the Czech Republic. Using an extensive dataset that covers 91.2% of the total tree population along roads in nine NUTS3 regions, we assess the state and observed practices in selecting tree genera for roadside planting and discuss the implications for sustainable tree planning and management. Our survey documented 133,169 tree individuals belonging to 116 species and 40 genera. The results show that 75% of the total roadside plantings along second-class motorways and first-class roads are represented by seven main genera of deciduous trees (Acer, Fraxinus, Tilia, Malus, Betula, Populus, and Quercus), the distribution of which is similar across most Czech regions. New plantings have shifted only a little from the original species distribution. Traditional roadside species are becoming a more popular choice among new plantings, and the effort not to let the invasive trees outgrow into the mature stage is apparent. Most of the original and newly planted species are relatively suitable for emerging risks related to climate change. To achieve more sustainable patterns in roadside tree species composition in the future, especially the susceptibility of some commonly planted roadside tree species to emerging pests and diseases (e.g., Fraxinus excelsior) and to unfavorable site conditions typical for roadside tree stands (Tilia cordata) is of relevance to tree managers. The relative abundance of tree genera was proven to be similar in most studied regions, which makes the recommendations equally relevant for roadside tree managers across the country.

Assessing the Impact of Road and Land Use on Species Diversity of Trees, Shrubs, Herbs and Grasses in the Mountain Landscape in Southern Africa

Mountain landscape, described as a global biodiversity hotspot due to high endemism, is threatened by land-use change, including management and modification of vegetation. However, there is little knowledge about how road and land use affect plant diversity in mountains landscapes, particularly in southern Africa. Previous studies have studied the impact of the road or land use on plant species diversity separately and have concentrated on a single plant species. Here we compare the plant diversity of regenerated trees, shrubs, herbaceous plant, and grasses among Forest, Fallow, Agriculture, and Road in the Moribane Forest Reserve (MFR), in Eastern Chimanimani Mountain landscape in Mozambique. To assess how land-use change affects plant diversity, we conducted 45 transects along the roadside and randomly established 24 quadrats in the Agriculture fields and Fallow and 26 quadrats in the pristine Forest. In each transect and quadrats, we recorded the occurrence of four plant life forms (regenerated trees, shrubs, herbaceous, and grass species) to determine the alpha and beta-diversity across land-uses, and we assessed the invasiveness of each species. Species composition varied significantly among the land-uses types. Roadside had higher species diversity and the highest number of invasive species (138 total species of all plant life forms; 31 invasive species), following Agriculture (72; 30), Fallow (81; 20), and Forest (78; 19). There was no similarity in species between roadsides and other land-uses. Furthermore, roadside recorded the highest average species turnover for all plant life forms following Agriculture, Forest, and Fallow. Among the plants, the most important life form was herbaceous with 143 species, following grass with 86 species, shrubs with 86, and regenerated trees with 65 species. The land-use pattern makes the landscape more diversified in the study area and, as a result, increase the plant species richness and diversity by species replacement. This study is unique in collecting and analyzing data on different plant life forms on roadsides linked with a range of different land-use types within a small region of a mountain landscape in southern Africa.

Effects of Soil Amelioration and Vegetation Introduction on the Restoration of Abandoned Coal Mine Spoils in South Korea

In order to ecologically restore coal mine spoils, tolerant species were selected through vegetation surveys on the abandoned coal mine spoils and natural forests established on the poor environment similarly to there. In addition, tolerant species were selected through cultivation experiments in the laboratory. Many C4 plants were included among the tolerant species selected through cultivation experiments. Soil was ameliorated by applying commercial organic fertilizer that can improve both physical and chemical properties of soil at the same time. Vegetation introduced for restoration was prepared by combining plant species tolerant to the degraded environment of coal mine spoils and the reference information. The treatment with a soil ameliorator improved the chemical properties of soil, such as the pH and nutrient contents, and promoted the growth of sample plants significantly. However, additional improvements were required compared with the chemical properties of healthy forest soil. The sites restored by ameliorating soil and introducing tolerant species showed a more similar species composition to the reference sites compared with the afforested and non-restored sites in both lowland and upland areas. However, such restoration did not play a significant role in increasing species diversity or excluding exotic plants. In this respect, more active restoration is recommended.

Urban sprawl facilitates invasions of exotic plants across multiple spatial scales

Exotic plant invasions are considered one of the major threats to biodiversity causing important impacts at the population, community, and ecosystem levels. Understanding the drivers of plant invasions across multiple spatial and temporal scales often requires a landscape approach. The effect of landscape composition on biological invasion has been extensively studied, whereas landscape configuration effects were seldom considered or the analyses were limited to single species. Here, we aimed to analyze how the expansion of urban and agricultural areas can affect exotic species richness (both neophytes and archaeophytes) at three spatial scales, namely regional (scale: 37.5 km2), landscape (scale: 7.1 km2) and local (scale: 100 m2). We considered the possible contribution of urban and agricultural areas both in terms of composition (i.e. habitat cover) and configuration (i.e. shape complexity of patches). First, we found that increasing urbanization coupled with high shape complexity of urban elements were major drivers of both neophyte and archaeophyte invasions across heterogeneous landscapes. In particular, shape complexity seemed to be a key driver of plant invasions at large spatial scale, whereas the type of recipient habitat and urban cover determined the exotic success at the patch level. Second, archaeophytes were also affected by agriculture land use, i.e. agricultural patches shape complexity increased their spread at both regional and landscape scales. High shape complexity of highly disturbed habitats is expected to increase the exchange surface that exotic plant use to spread their propagules across the landscape mosaics. Our findings suggest that urban planning aimed at curbing urban fragmentation by both reducing shape complexity and diffuse urban sprawl might greatly improve the resistance of landscapes to biological invasions.

Evaluating the impact of roads on the diversity pattern and density of trees to improve the conservation of species

Roadside trees alter biotic and abiotic factors of plants diversity in an ecosystem. Rows of plants grow along the roadside due to the interplay between the arrival of propagule and seedling establishment, which depends on the road's specifications, land pattern, and road administration and protection practices. A field study was conducted to measure the roadside tree diversity in the city of Karachi (Pakistan). A total of 180 plots, divided into three primary road groups, were surveyed. The highest quantity of tree biomass per unit area was found on wide roads, followed by medium roads. On narrow roads, the least biomass was detected. A single species or a limited number of species dominated the tree community. Conocarpus erectus was the most dominant non-native species on all types of sidewalks or roadsides, followed by Guaiacum officinale. A total of 76 species (32 non-natives and 44 natives) that were selectively spread along the roadsides of the city were studied. There was a significant difference in phylogenetic diversity (PD), phylogenetic mean pairwise distance (MPD), and phylogenetic mean nearest taxon distance (MNTD) among wide, medium, and narrow roads. Management practices have a significant positive correlation with diversity indices. Our study identified patterns of diversity in roadside trees in Karachi. It provides the basis for future planning for plant protection, such as the protection of plant species, the maintenance of plant habitats, and the coordination of plant management in Karachi.

Natura 2000 Areas, Road, Railway, Water, and Ecological Networks May Provide Pathways for Biological Invasion: A Country Scale Analysis

Invasive species are a major threat to biodiversity worldwide. Controlling their rapid spread can only be effective if we consider the geographical factors that influence their occurrence. For instance, roads, railway networks, green and blue infrastructure, and elements of ecological networks (e.g., ecological corridors) can facilitate the spread of invasive species. In our study, we mapped the occurrence of five invasive plant taxa (tree of heaven, common milkweed, Russian olive, black locust, and goldenrods) in Hungary, using field photos from the EUROSTAT Land Use and Coverage Area Frame Survey (LUCAS) database from the year 2015. Species point occurrence data were compared with the spatial characteristics of linear transport infrastructure and with the green and blue infrastructure. We found that the occurrence of tree of heaven and Russian olive was strongly related to the road and railway network. The average Euclidean distance of LUCAS points infected with these species from railway embankments and roads was much smaller than that of uninfected points. However, black locust and goldenrods were more common only along the road network. According to our results, the occurrence of some investigated invasive plants was over-represented in the HEN and within Natura 2000 areas of Hungary compared to non-infected points. Our results may provide important information for predicting the rate of invasion and for applying targeted management within the HEN, and Natura 2000 protected areas.

Four challenges when conducting bibliometric reviews and how to deal with them

The evidence base in environmental sciences is increasing steadily. Environmental researchers have been challenged to handle massive volumes of data to support more comprehensive studies, assess the current status of science, and move research towards future progress. Bibliometrics can provide important insights into the research directions by providing summarized information for several end users. Here, we present an in-depth discussion on the use of bibliometric indicators to evaluate research outputs through four case studies comprising disciplines in environmental sciences. We discuss four big challenges researchers may face when conducting bibliometric reviews and how to deal with them. We also address some primary questions researchers may answer with bibliometric mapping, drawing lessons from the case studies. Lastly, we clarify some misuses of review concepts and suggest methodological principles of systematic reviews and maps to improve the overall quality of bibliometric studies.

Climate change and micro-topography are facilitating the mountain invasion by a non-native perennial plant species

Mountainous areas and their endemic plant diversity are threatened by global climate change and invasive species. Mountain plant invasions have historically been minimal, however, climate change and increased anthropogenic activity (e.g. roads and vehicles) are amplifying invasion pressure. We assessed plant performance (stem density and fruit production) of the invasive non-native forb Linaria dalmatica along three mountain roads, over an eight-year period (2008–2015) in the Greater Yellowstone Ecosystem (GYE), USA. We evaluated how L. dalmatica performed in response to elevation, changed over time, responded to climate and how the climate of our sites has changed, and compared elevation, climate, micro-topography (slope aspect and angle), and fruit production among sites with differing temporal trends. Linaria dalmatica stem density and fruit production increased with elevation and demonstrated two temporal groups, those populations where stem densities shrank and those that remained stable or grew over time. Stem density demonstrated a hump-shaped response to summer mean temperature, while fruit production decreased with summer mean maximum temperature and showed a hump-shaped response to winter precipitation. Analysis of both short and long-term climate data from our sites, demonstrated that summer temperatures have been increasing and winters getting wetter. The shrinking population group had a lower mean elevation, hotter summer temperatures, drier winters, had plots that differed in slope aspect and angle from the stable/growing group, and produced less fruit. Regional climate projections predict that the observed climate trends will continue, which will likely benefit L. dalmatica populations at higher elevations. We conclude that L. dalmatica may persist at lower elevations where it poses little invasive threat, and its invasion into the mountains will continue along roadways, expanding into higher elevations of the GYE.

Linear infrastructure habitats increase landscape-scale diversity of plants but not of flower-visiting insects

Habitats along linear infrastructure, such as roads and electrical transmission lines, can have high local biodiversity. To determine whether these habitats also contribute to landscape-scale biodiversity, we estimated species richness, evenness and phylogenetic diversity of plant, butterfly and bumblebee communities in 32 km² landscapes with or without power line corridors, and with contrasting areas of road verges. Landscapes with power line corridors had on average six more plant species than landscapes without power lines, but there was no such effect for butterflies and bumblebees. Plant communities displayed considerable evenness in species abundances both in landscapes with and without power lines and high and low road verge densities. We hypothesize that the higher number of plant species in landscapes with power line corridors is due to these landscapes having a higher extinction debt than the landscapes without power line corridors, such that plant diversity is declining slower in landscapes with power lines. This calls for targeted conservation actions in semi-natural grasslands within landscapes with power line corridors to maintain biodiversity and prevent imminent population extinctions.

An uphill battle? The elevational distribution of alien plant species along rivers and roads in the Austrian Alps

Ever-increasing international trade and anthropogenic activity has led to the relocation of thousands of plant species worldwide. So far, the harsh climate of the European Alps historically has restricted the establishment of alien plants. However, new opportunities created by rising temperatures and increasing human activity might allow alien plants to spread further upwards. Here, the distribution of alien plants along an altitudinal gradient in two Austrian valleys is analyzed. Specifically, the distribution along two contrasting corridors (roads, rivers) and the spread of alien plants into adjacent habitats is examined. Following the MIREN sampling protocol, 20 transects composed of three plots along each river and main road, were established in each study region. Plant species cover and a range of site-specific factors were collected. In total, 641 plant species were recorded, of which 20 were alien. Alien species richness along roads was slightly higher compared to rivers, and the composition of the alien flora differed markedly between roads and rivers. Further, alien plant species richness decreases with distance to roads and rivers (indicating that adjacent habitats are less invaded), as well as with increasing elevation. Mowing along roadsides resulted in lower alien plant species cover, but higher alien plant species richness. Finally, compositional dissimilarity between sites showed that elevation, proximity of a plot to a river or road, and alien plant cover are important factors for higher dissimilarity. This study demonstrates that both natural (rivers) and man-made (roads) corridors play an essential role in the upward spread of different alien plants in mountains.

Patterns of Genetic Diversity in Highly Invasive Species: Cogongrass (Imperata cylindrica) Expansion in the Invaded Range of the Southern United States (US)

The spatial expansions of invasive organisms in the novel range are generally expected to follow an isolation-by-distance relationship (IBD) if the invasion is biologically driven; however, many invasions are facilitated anthropogenically. This research focused on the extant expansion patterns of cogongrass (Imperata cylindrica). Cogongrass is a widespread invasive species throughout the southern United States (US). Patterns of infestation vary among US states. Cogongrass is pyrogenic, and its invasion threatens softwood (Pinus spp.) plantations, a substantial economic market for this US region. Over 600 individuals were sampled from seven invaded US states, using amplified fragment length polymorphisms (AFLPs) to assess genetic diversity and population structure. We suspected that differences in historical management efforts among US states influenced differences in genetic diversity and structure. We detected two genetic lineages at the highest level of analysis. One genetic lineage was locally restricted, whereas the other was found throughout the study region. Admixed individuals were found in all US states and consistently co-occurred with the dominant lineage, suggesting that secondary contact and hybridization may have facilitated expansion. The widespread prevalence of only one of the two detected genetic lineages suggests a primary genetic lineage responsible for on-going population expansion in the US.