Invasive Alien Plants Research Articles

Impacts of Livestock Grazing on Vegetation and Soil in Lowland Grassland Ecosystem of Nepal

Livestock grazing is one of the largest sectors for land use globally, and contrasting impacts (negative, neutral, and positive) of livestock grazing on vegetation and soil have been observed. In Koshi Tappu Wildlife Reserve (KTWR), livestock grazing is one of the major problems but has been feebly addressed in previous research. This study, therefore, aims to determine the impacts of livestock grazing on vegetation and soil quality in grasslands of core and buffer zones of KTWR. Less grazing intensity was observed at the core zone compared to the buffer zone. Livestock grazing was observed with negative impacts on the richness and diversity of the plant species causing changes in the community assemblages. Invasive plant species richness, however, was found higher in the low grazed areas. Differences in soil pH, phosphorus, and potassium content between high and low grazed areas were not observed. In contrast, soil electrical conductivity, bulk density, and nitrogen content were significantly higher in the high grazed areas. Controlled grazing is recommended at buffer zone grasslands of KTWR to enhance plant diversity and nutrient availability. The core areas of the reserve should be managed for reducing the abundance and distribution of invasive alien plant species.

Climatic Variability Caused by Topographic Barrier Prevents the Northward Spread of Invasive Ageratina adenophora.

Ageratina adenophora (Spreng.) R.M.King & H.Rob. is one of the most threatening invasive alien plants in China. Since its initial invasion into Yunnan in the 1940s, it spread rapidly northward to southern Mount Nyba in Sichuan, which lies on the eastern edge of the Qinghai-Tibet Plateau. During fieldwork, we found an interesting phenomenon: A. adenophora failed to expand northward across Mount Nyba, even after the opening of the 10 km tunnel, which could have served as a potential corridor for its spread. In this work, to explore the key factors influencing its distribution and spread patterns, we used a combination of ensemble species distribution models with the MigClim model. We found that the temperature annual range (TAR), precipitation of driest month (PDM), highway density (HW), and wind speed (WS) were the most predominant factors affecting its distribution. The north of Mount Nyba is not suitable for A. adenophora survival due to higher TAR. The spatial-temporal dynamic invasion simulation using MigClim further illustrated that the northward invasion of A. adenophora was stopped by Mount Nyba. Overall, Mount Nyba may act as a topographic barrier that causes environmental differences between its south and north sides, preventing the northward invasion of A. adenophora. However, other suitable habitats on the northern side of the mountain still face challenges because A. adenophora is likely to invade via other routes. Therefore, long-term monitoring is needed to prevent human-induced long-distance spread events.

A Method of Invasive Alien Plant Identification Based on Hyperspectral Images

Invasive alien plants (IAPs) are considered to be one of the greatest threats to global biodiversity and ecosystems. Timely and accurate detection technology is needed to identify these invasive plants, helping to mitigate the damage to farmland, fruit trees and woodland. Hyperspectral technology has the potential to identify similar species. However, the challenge remains to simultaneously identify multiple invasive alien plants with similar colors based on image data. The spectral images were collected by a hyperspectral camera with a spectral range of 450–998 nm, and the raw spectra were extracted by Cubert software. First derivative (FD), Savitzky-Golay (SG) smoothing and standard normal variate (SNV) were used to preprocess the raw spectral data, respectively. Then, on the basis of preprocessing, principal component analysis (PCA) and ant colony optimization (ACO) were used for feature dimensionality reduction, and the reduced features were used as input variables for later modeling. Finally, a combination of both dimensionality reduction and non-dimensionality reduction is used for identification using support vector machines (SVM) and random forests (RF). In order to determine the optimal recognition model, a total of 18 combinations of different preprocessing methods, dimensionality reduction methods and classifiers were tested. The results showed that a combination of SG smoothing and SVM achieved a total accuracy (A) of 89.36%, an average accuracy (AA) of 89.39% and an average precision (AP) of 89.54% with a test time of 0.2639 s. In contrast, the combination of SG smoothing, the ACO, and SVM resulted in weaker performance in terms of A (86.76%), AA (86.99%) and AP (87.22%), but with less test time (0.0567 s). The SG-SVM and SG-ACO-SVM models should be selected considering accuracy and time cost, respectively, for recognition of the seven IAPs and background in the wild.

HPLC-DAD-MS Identification and Quantification of Phenolic Components in Japanese Knotweed and American Pokeweed Extracts and Their Phytotoxic Effect on Seed Germination.

We performed a detailed HPLC-MSn analysis of the phenolic compounds from the extracts of two invasive alien plant species (IAPS): Japanese knotweed (Fallopia japonica (Houtt.) Ronse Decr.) and American pokeweed (Phytolacca americana L.). The major phenolic groups were hydroxycinnamic acids and flavanols in Japanese knotweed (J. knotweed) and flavonols, hydroxycinnamic acids, and stilbenes in American pokeweed (A. pokeweed). We investigated the influence of solvent type and extraction time on the extraction efficiency of the phenolic compounds. The solvent 80% methanol had a higher polyphenolic extraction efficiency than water, since 14.5 times more flavonols and 2.3 times more stilbenes were extracted from J. knotweed and 5.2 times more flavonols and 2.6 times more stilbenes were extracted from A. pokeweed. In contrast, with water, we obtained a 52% higher hydroxycinnamic acids (HCA) content from J. knotweed. Hydroxycinnamic acids were best extracted in water after 24 h, flavanols after 12 h, stilbenes between 12 and 24 h, and flavonol glycosides after 48 h of extraction. We also tested the allelopathic effect of the aqueous extract of A. pokeweed and J. knotweed on seed germination and shoot and root growth of perennial ryegrass. The results showed that the water extract of J. knotweed resulted in 38 to 48% lower seed germination of perennial ryegrass, and the extract of A. pokeweed resulted in 83 to 90% lower seed germination. The phytotoxic effect of the extract of J. knotweed and A. pokeweed was also reflected in a characteristic reduced growth of shoots and roots of perennial ryegrass. The phytotoxic action of IAPS could also be applied for beneficial purposes, since this would be an effective strategy for their control and a reduction of their spread in the environment.

Retraction Note to: Major environmental factors and traits of invasive alien plants determining their spatial distribution

Retraction Note to: Major environmental factors and traits of invasive alien plants determining their spatial distribution

Potential global geographical distribution of Lolium temulentum L. under climate change.

Invasive alien plants posed a significant threat to natural ecosystems, biodiversity, agricultural production, as well as human and livestock health. Lolium temulentum, an annual invasive alien weed with fibrous roots, can reduce wheat production and cause economic losses. Moreover, the consumption of grains or cereal products mixed with darnel can cause dizziness, vomiting, and even death. Therefore, darnel is regarded as one of ″the worst weeds around the world″. In the present study, we predicted the potential global geographical distribution of L. temulentum using an optimal MaxEnt model, based on occurrence records and related environmental variables. The mean AUC, TSS, and KAPPA were 0.95, 0.778, and 0.75, indicating the MaxEnt model accuracy was excellent. The significant environmental variables, including the mean temperature of coldest quarter (bio 11), precipitation of coldest quarter (bio 19), temperature annual range (bio 7), and annual precipitation (bio 12), produced a great impact on the potential global geographical distribution of L. temulentum. Under the current climate, L. temulentum was primarily distributed in south-eastern Asia, Europe, and south-eastern North America. The widest total suitable habitat was distributed in Asia, covering nearly 796 × 104 km2. By the 2050s, the potential geographical distribution of L. temulentum was expected to decrease in the Northern Hemisphere, and shrink gradually in southern America, Africa, and Oceania. Moreover, the distribution center of L. temulentum was expected to shift from Asia to Europe. Based on these predictions, changes in the suitable habitats for L. temulentum between Europe and Asia warrant close attention to prevent further spread.

Artificial perches increase bird-mediated seed rain in agricultural fallow area in southern Brazil

Abstract. One of the main barriers to restoration is the arrival of diaspores in degraded areas. However, this process can be hampered in open areas without trees in the landscape. For that, artificial perches are used to attract and provide a landing area for avian seed dispersers, to enhance seed rain. Our objective was to evaluate the effect of the distance of artificial perches in relation to a forest fragment on the diversity and composition of seed rain in an agricultural fallow area, including alien invasive plant species. We also aimed to record and characterize the bird species that potentially act as seed dispersers. Thus, we used artificial perches at three different distances from a forest fragment (5, 25, and 50 m). Four seed traps were arranged under the perches at each distance, and four control seed traps were interspersed with these and distanced at 7.5 m. Furthermore, we placed four seed traps inside the forest fragment at 5 m from the edge. We also carried out 80 h of focal observation of the avifauna that used artificial perches. A total of 24 655 seeds were sampled across all treatments. There was a significant difference in seed abundance and richness between artificial perches, control seed traps, and forest seed traps. Seed deposition increased with distance from the forest fragment (50, 25, and 5 m). An ordination procedure indicated the formation of three plant seed communities, with the forest community being most distinct. The invasive exotic species Pittosporum undulatum (Australian cheesewood) was the third most abundant in the seed rain. We observed 24 bird species from 12 families using artificial perches. The Tyrannidae family was the most represented. We showed that artificial perches are efficient structures for attracting birds, increasing the richness and abundance of seed species. Artificial perches at 25 and 50 m were more efficient possibly due to the provision of greater visibility for birds. Therefore, artificial perches are efficient in increasing seed rain in the fallow area but should be used with caution in landscapes with the presence of alien species. These findings contribute to increasing knowledge about overcoming the first barrier to ecological restoration, which is the arrival of diaspores in degraded areas, and showing the importance of birds in this process.

Phylogenetic Relationships and Disturbance Explain the Resistance of Different Habitats to Plant Invasions.

Invasive alien plants have invaded various habitats, posing a threat to biodiversity. Several hypotheses have been proposed to explain the mechanisms of invasion, but few studies have considered the characteristics of the invaded communities and the effects of human interference in the invasion. In this study, we compared the invasibility of three different habitats: abandoned land, eucalyptus plantations, and natural secondary forests. We explored the effects of species diversity, phylogenetic diversity, and disturbance factors on the invasibility of different habitats. The results showed that the invasibility of abandoned land was the highest and the invasibility of the natural secondary forest was the lowest. Phylogenetic indicators affected the invasibility of abandoned land and eucalyptus plantations, and disturbance factors affected the invasibility of all three habitats, while the characteristics of the invaded communities had a weak impact. Our research provided supporting evidence for Darwin's naturalization hypothesis and his disturbance hypothesis but found no relationship between biotic resistance and invasibility. This study indicated that the differences among habitats should be considered when we prove Darwin's naturalization hypothesis in nature reserves.

Prospects for the biological control of the invasive cactus, Opuntia stricta using Dactylopius opuntiae, under conditions of rising atmospheric CO2

Opuntia stricta var. stricta (Haworth.) Haworth (Cactaceae) is an important invasive alien plant (IAP) in South Africa, that invades both disturbed and undisturbed habitats mainly within grasslands and savannas. Fortunately, substantial control has been achieved using the biological control agent, Dactylopius opuntiae (Cockerell) (Hemiptera: Dactylopiidae), a sap sucking scale insect. With rising atmospheric CO2 concentrations, many plants alter their growth traits, most notably leaf nutritional quality which in turn affects their arthropod herbivores. Therefore, we tested whether D. opuntiae fitness and its subsequent efficacy as a biological control agent is altered by O. stricta plants grown at elevated CO2. Using walk-in Conviron growth chambers, O. stricta was grown at three CO2 concentrations; 250 (sub-ambient – sCO2). 400 (ambient - aCO2) and 600 ppm (elevated – eCO2). After 70 days of growth, plants were inoculated with 20 first instar D. opuntiae crawlers and we subsequently measured parameters to assess their fitness. Plant traits were measured regularly throughout the 6.5-month experiment. Dactylopius opuntiae fitness index was significantly lowered on eCO2 plants which slowed the rate of herbivory. Dactylopius opuntiae fitness index was negatively correlated to cladode carbon/nitrogen ratios indicating reduced plant quality was a potential driver. However, despite reduced D. opuntiae fitness and slowed rates of damage, O. stricta growth at eCO2 was still inhibited by the insect, and final plant biomass did not differ from aCO2 plants, unlike that observed for the control plants. Furthermore, irrespective of CO2 treatment, all plants succumbed to D. opuntiae herbivory with plants grown at eCO2 taking approximately-three weeks longer than sCO2 and aCO2 plants to die. Despite mortality of O. stricta plants grown at eCO2 due to D. opuntiae feeding, the long-term potential cumulative effects of reduced agent fitness and their subsequent efficacy may hinder the management of this IAP with rising atmospheric CO2 concentrations.

Effects of Rhus typhina Invasion on Soil Physicochemical Properties and Carbon Emissions in Urban Green Spaces

Alien plants invasion have become a hot issue in the field of ecology. The invasion of alien plants is usually accompanied by changes in the physical and chemical properties of the soil, the ensuing negative feedback creates a favorable environment for its own growth and expansion. Invasive plans have a strong ability to sequester carbon, which can greatly affect the original local ecological environment. In this study, we selected Rhus typhina, an invasive plant widely used for greening, as the experimental subject and natural growing grassland as the control. The aims were to investigate the effects of different degrees of invasion of R. typhina on soil physicochemical properties and carbon emissions, and to explore the influential factors on carbon emission. The results showed that R. typhina invasion significantly increased soil pH, total nitrogen content, easy extraction of glomalin-related soil protein (EEG) and cumulative CO2 emissions (CEM). It is worth noting that the CEM increased significantly during the severe invasion by R. typhina. The significant increase in soil NH4+-N content and the decrease in soil NO3−-N content indicate that the soil after the invasion of R. typhina has better uptake of NH4+-N. Temperature and soil moisture content had significant direct effects on CEM, while NH4+-N, NO3−-N, EEG and temperature sensitivity of soil organic carbon mineralization Q10 (30 °C/20 °C) had a direct but non-significant effect on CEM. The above findings suggest that R. typhina can generate positive feedback by influencing the physicochemical properties and CEM of the soil, opening the way for its own expansion, which can be targeted to prevent the destruction of local ecosystems during the introduction of cultivation and subsequent management.

First record of alien naturalized populations of the crop Cucurbita moschata (Cucurbitaceae) in Spain, with remarks on typification status

As a result of a floristic survey carried out in riparian ecosystems of the southeastern Iberian Peninsula ( a first report of well established populations of the allochthonous cultivated plant species Cucurbita moschata Duchesne is here provided for the Iberian Peninsula. Data about the morphological description (compared to other Cucurbita species), certain clarification aspects about the typification status of this name and related synonyms, and ecological and climatic conditions of the riparian area are given together with a key identification of the Cucurbita species to facilitate further identification. The alien status and distribution of C. moschata together with its relatives C. ficifolia C. pepo and C. maxima are reviewed for the Spanish references. This study outlines the first record of a naturalized population of C. moschata in Spain, well supported by the stability of the population along the years and ecological conditions. Finally, the detailed ecological data indicate that the agricultural activities together with riparian habitats, respectively, are starting points and corridors for seed dispersal for the process of invasion of alien plants in the southeastern Iberian Peninsula.

Invasive Alien Plant Species for Use in Paper and Packaging Materials

Invasive plant species can impede the establishment and growth of native plants and affect several ecosystem properties. These properties include soil cover, nutrient cycling, fire regimes, and hydrology. Controlling invasive plants is therefore a necessary, but usually expensive, step in restoring an ecosystem. The sustainability of materials with an emphasis on the use of local resources plays an important role in the circular economy. The use of alternative fibers from invasive plants promotes local production in smaller paper mills that offer the protection of local species and the reduction of waste and invasive plants. A synthesis of the literature is needed to understand the various impacts of invasive plants and their practical control in the context of papermaking applications and to identify associated knowledge gaps. To improve our understanding of the practical application of invasive species in the paper industry, we reviewed the existing literature on invasive plant species in the area of fiber production, printability, coating solution production, dyes, and extracts, and collected information on the major invasive plant species in Europe and the methods used for various applications.

Mapping the Distribution and Dispersal Risks of the Alien Invasive Plant Ageratina adenophora in China

Identifying the distribution dynamics of invasive alien species can help in the early detection of and rapid response to these invasive species in newly invaded sites. Ageratina adenophora, a worldwide invasive plant, has spread rapidly since its invasion in China in the 1940s, causing serious damage to the local socioeconomic and ecological environment. To better control the spread of this invasive plant, we used the MaxEnt model and ArcGIS based on field survey data and online databases to simulate and predict the spatial and temporal distribution patterns and risk areas for the spread of this species in China, and thus examined the key factors responsible for this weed’s spread. The results showed that the risk areas for the invasion of A. adenophora in the current period were 18.394° N–33.653° N and 91.099° E–121.756° E, mainly in the tropical and subtropical regions of China, and densely distributed along rivers and well-developed roads. The high-risk areas are mainly located in the basins of the Lancang, Jinsha, Yalong, and Anning Rivers. With global climate change, the trend of continued invasion of A. adenophora is more evident, with further expansion of the dispersal zone towards the northeast and coastal areas in all climatic scenarios, and a slight contraction in the Yunnan–Guizhou plateau. Temperature, precipitation, altitude, and human activity are key factors in shaping the distribution pattern of A. adenophora. This weed prefers to grow in warm and precipitation-rich environments such as plains, hills, and mountains; in addition, increasing human activities provide more opportunities for its invasion, and well-developed water systems and roads can facilitate its spread. Measures should be taken to prevent its spread into these risk areas.

Role of biological characteristics in the success of invasive alien plant species in tropical ecosystems of Thiruvananthapuram District, Kerala, India

Biological invasion is a leading threat to the abiotic and biotic equilibrium of natural landscapes and ecosystems through competition and habitat alteration in many countries, including India. The Invasive Alien Plant Species (IAPS)11IAPS, Invasive Alien Plant Species have become an important biological and ecological component in Kerala, south-west tropical province of the Indian Union. These alien plant species were deliberately or accidentally introduced to the state from different biogeographical realms and are persisting. The characteristics of IAPS, as well as their preferences and advantages in invasion, have received little attention. This article provides a summary of the identifying characteristics of 69 IAPS reported from the study area, with an emphasis on botanical passport data, nativity, ecosystem preference, life form, sociability pattern, reproductive phenology, mode of dispersal, and period of introduction. Phytosociological research was conducted using a random sampling survey and line transect technique. The ecological performance of IAPS was statistically assessed according to seven concepts of invasion success. The findings show that 25 IAPS are considerably more aggressive as a result of their reproductive advantage and generally adhere to the concepts of invasion success for characteristics such as residence time, dispersal strategy, and ecosystem preference. Thus, reproductive characteristics appear to be a key determinant of aggressiveness in IAPS. The characteristic similarities of IAPS frequently result in niche overlap, and those with structural and functional differences will be more adaptable in ecosystems. This information describing the relevant characteristics serves as an essential tool for early detection and rapid response in the systematic management of biological invasion in the state of Kerala and specifically in the district of Thiruvananthapuram.

Elevated CO2 and Increased N Intensify Competition between Two Invasive Annual Plants in China.

As multiple invaders often co-occur, understanding the interactions between different invasive species is important. Previous studies have reported on invasional meltdown and neutral and interference relationships between invasive species. However, interspecific interactions may vary with environmental change owing to the different responses of interacting invaders. To better understand the interaction of notorious invasive alien plants under CO2 enrichment and N deposition, the growth characteristics of common ragweed (Ambrosia artemisiifolia) and redroot pigweed (Amaranthus retroflexus) were studied when they were planted in monoculture (4Rag and 4Pig) or mixture (1Rag:3Pig, 2Rag:2Pig, 3Rag:1Pig) under four environmental treatments: elevated CO2, increased N, elevated CO2 + increased N and a control. Increased N positively affected almost all the traits (basal stem diameter, height, shoot biomass, root biomass and total biomass) of common ragweed, except for branch number and root-shoot ratio. But increased N only promoted redroot pigweed’s height and basal stem diameter. interspecific competition promoted basal stem diameter and number of branches but decreased root biomass of common ragweed, and the basal stem diameter was significantly higher in 1Rag:3Pig and 2Rag:2Pig compared to the other two treatments. interspecific competition inhibited almost all the characteristics of redroot pigweed. The interaction between elevated CO2 and increased N also increased the biomass characteristics (shoot biomass, root biomass and total biomass) of common ragweed. However, elevated CO2 inhibited the root biomass of redroot pigweed. The results indicated that common ragweed was a superior competitor under conditions of elevated CO2 and increased N. Moreover, environmental change might strengthen the super-invasive plant common ragweed’s competitive ability.

Impacts of the Invasive Alien Carpobrotus spp. on Coastal Habitats on a Mediterranean Island (Giglio Island, Central Italy).

Carpobrotus acinaciformis and C. edulis are well-known invasive alien plants native to South Africa, whose detrimental effects on native communities are widely documented in the Mediterranean basin and thus largely managed in coastal ecosystems. Most of the literature on these species focuses on their impacts on habitats of sandy coastal dunes, while the effects of Carpobrotus spp. invasion on other habitats such as rocky cliffs and coastal scrubs and garrigues are almost neglected. We present a study case conducted on a small Mediterranean island where Carpobrotus spp. invaded three different natural habitats listed within the Habitat Directive 92/43/CEE (Natura 2000 codes 1240, 1430, and 5320). We surveyed the presence and abundance of native species and Carpobrotus spp. on 44 permanent square plots of 4 m2 in invaded and uninvaded areas in each of the three habitats. We found impacts on plant alpha diversity (intended as the species diversity within each sampled plot) in all the habitats investigated in terms of a decrease in species richness, Shannon index, and abundance. Invaded communities also showed a severe change in species composition with a strong homogenization of the floras of the three habitats. Finally, the negative effect of invasion emerged even through the analyses of beta diversity (expressing the species diversity among sampled plots of the same habitat type), with Carpobrotus spp. replacing a large set of native species.

Invasive Plants Diversity, Ecological Status, and Distribution Pattern in Relation to Edaphic Factors in Different Habitat Types of District Mandi Bahauddin, Punjab, Pakistan

Our understanding of the diversity and distribution of living things is crucial to the conservation and sustainable use of biodiversity. Because biological invasions by alien species pose a significant threat to native biodiversity, tracking alien species at various geographical scales has recently gained prominence. The current study is designed to evaluate the diversity and composition of invasive plants in different habitats of Mandi Bahuddin, Punjab, Pakistan. The investigation explores the impact of environmental factors on the distribution of alien species in association with edaphic and geographic patterns. Diversity patterns, ecological impact, and the distribution of alien species with respect to environmental variables were recorded. A randomized sampling technique was used taking data from 120 sites with triplet quadrates in each, 360 overall, between 2019 and 2021 to record the data on alien flora and associated environmental variables. Important value indices for each alien species were determined with respect to environmental data, by cluster and ordination analysis. Overall, 43 invasive alien plants from 37 genera and 18 families were documented in the district Mandi Bahuddin. The prominent family was Poaceae with ten species (23.25%) followed by Leguuminosae with six species (13.95%), Compositae with five species (11.62%), Amaranthaceae with three species (6.97%), and Convolvulaceae, Euphorbiaceae, Malvaceae, Polygonaceae, and Scrophulariaceae with two species each (4.65%). Out of 65 alien species comprised herbs 52.13%, grasses 23.25%, shrubs 9.30%, and trees 9.30%. In case life form Therophyte (48.83%) was leading, followed by Chamaephyte with (16.27%) species, Nanophanerophyte and Megaphanerophyte with (11.62%) species each, Geophyte with (6.97%) species, and Hemicryptophyte with (4.65%) species. With leaf size spectra, microphylls (41.86%) were dominating and followed by mesophylls (27.90%), leptophylls (13.95%), nanophylls (11.62%), and macrophylls (4.65%). PCA was applied in order to further understand the species distribution and abundance pattern and to find significant connections among the species with sampling locations comprising various habitats. Ward’s agglomerative clustering technique classified the one hundred and twenty transects into four major groups. Ordination analysis showed that different ecological factors had a significant (p ≤ 0.002) influence on vegetation. The current study provides a foundation from which to comprehend the influences of environmental variables on alien plants’ composition, diversity, structure, and links. These will be useful for developing scientifically informed management strategies for use by administrative agencies in the ecological restoration of the degraded habitat of the studied area.

Long-Distance Wind Dispersal Drives Population Range Expansion of Solidago canadensis.

Canada goldenrod (Solidago canadensis L.) is a serious invasive alien plant species that exerts negative effects on natural and agricultural ecosystems in China. Few studies have addressed the dispersal of S. canadensis to explain how it rapidly spreads to large areas over long distances. Here, we quantify the dispersal of S. canadensis via wind by capturing in situ−stained diaspores. The diaspores were trapped and counted along 11 radiating transects from the center of a dispersal source. Solidago canadensis diaspores could be dispersed in all directions from the source, traveling longer distances and in greater amounts in the downwind direction than the upwind one. With a source including about 58 million diaspores and a wind speed at Beaufort scale 4, the dispersal distance in the prevailing wind direction (PWD) was at least 2000 m. Diaspores shattered at a rate of approximately 3% daily with the common wind speed of scale 4, indicating that dispersal could last for more than a month. A mechanistic model was used to fit the dispersal curve along the PWD. Although the model slightly underestimated long−distance dispersal, it still demonstrated the potential of long−distance dispersal with great source strength. Wind−dispersed diaspores to new areas persisted over winter and were able to form new plants at a density of about 2 plants per m2 at 500 m away from the source. Further experiments showed that the dispersed amount of S. canadensis diaspores was significantly positively correlated with the temperature and wind speed, but significantly negatively correlated with relative humidity, which indicated that, during a day, the maximum dispersal usually occurred in the afternoon when the temperature was the highest and the relative humidity the lowest. In addition, for an already existent population patch, the patch range can expand 2−4 m per year, mainly depending on the seedlings recruited from the rhizomes. These results provide insights into the long−distance dispersal of S. canadensis by wind and its effects on the range expansion process.

Effects of Elevated Temperature and High and Low Rainfall on the Germination and Growth of the Invasive Alien Plant Acacia mearnsii.

The impact of climate change on the germination and growth of invasive alien plants varies depending on the plant species and invasion process. We experimentally assessed the responses of the invasive alien plant Acacia mearnsii to future climate change scenarios—namely, elevated temperature as well as high and low rainfall. Acacia mearnsii was grown at an elevated air temperature (+2 °C), high rainfall (6 mm per day), and low rainfall (1.5 mm per day), and its germination and growth performance were measured over five months. We further examined changes in soil nutrients to assess if the above-mentioned climate change scenarios affected soils. Both elevated temperature and high rainfall did not influence A. mearnsii germination and seedling growth. In contrast, we observed reductions in A. mearnsii germination and growth in the low rainfall treatment, an indication that future drought conditions might negatively affect A. mearnsii invasion. We noted that elevated temperature and rainfall resulted in varied effects on soil properties (particularly soil C, N, Ca, and Mg content). We conclude that both elevated temperature and high rainfall may not enhance A. mearnsii invasion through altering germination and growth, but a decrease in A. mearnsii invasiveness is possible under low rainfall conditions.

People's knowledge and perceptions of Trachycarpus fortunei (Chinese windmill palm) invasions and their management in Ticino, Switzerland

Abstract. The introduction of alien plant species can lead to biological invasions, which have major impacts on people and the environment. Trachycarpus fortunei (Hook.) H. Wendl. (Arecaceae) is an alien plant (palm tree) that has been introduced as an ornamental into urban areas across the world, but in many regions, it has started invading forests and other natural environments leading to negative impacts. To improve understanding and guide management, this study sought to assess people's knowledge and perceptions of T. fortunei in Ticino, the region in Switzerland where invasions of the species are most common. To achieve this goal, an online survey was conducted, and a total of 487 responses were received. The formal name(s) (scientific or common names) of T. fortunei were unknown to almost all participants (89 %), and people mostly just called them “palm”. Most respondents were familiar with the term invasive alien species (IAS) (88 %) and were aware of the invasiveness (spread) of T. fortunei (73 %). The study showed that although people like to see the palm in the region (51 %) and enjoyed the related sense of place it provides, respondents have become aware of the challenges associated with invasions and the majority (65 %) would like to see more done to control the spread of T. fortunei invasions within natural areas, particularly forests. To improve management, a large number of respondents (63 %) mentioned that education and awareness programmes should be implemented to provide people with knowledge on how to deal with invasive alien plants and thus prevent further spread. Almost a third of respondents supported (32 %) the regulated sale of T. fortunei in an effort to reduce invasions. Educational level, gender, and age affected response patterns, and this needs to be accounted for within strategic management planning, in particular, within education and awareness-raising initiatives. Tailored and targeted educational campaigns and management plans need to be established to prioritise and improve control of this invasive palm in Switzerland in the long term.