Impact of invasive alien plants on native plant communities and Natura 2000 habitats: State of the art, gap analysis and perspectives in Italy

Investigation of the Allelopathic Effect of Two Invasive Plant Species in Rhizotron System

A key question in plant invasion biology is why invasive plants are more competitive in their introduced habitat than in their native habitat. Studies show that invasive species exhibit allelopathy, influencing other plants by releasing chemicals. Research on allelopathy uses in vitro tests, investigating effects on seed germination and seedling development. Although soil plays a role in modifying allelopathic effects, observations with soil are rare and almost nothing is known about the root development of test plants developing in soil and the effects of allelopathic compounds on root architecture. Our study evaluates the allelopathic effects of false indigo-bush (Amorpha fruticosa L.) and common milkweed (Asclepias syriaca L.) on oilseed rape growth as a model plant. The rhizotron system was used to study the effect of morphology and root architecture. Leaf-soil mixtures at 0.5%, 1%, and 5% concentrations were used. Shoot and root development was strongly inhibited at 5%. But there was no difference between the allelopathy of the two species, and the application of lower concentrations did not show any effect, demonstrating that soil has a significant modifying effect on their allelopathy. Our results highlight that the development of roots growing in the soil is also worth investigating in connection with allelopathy, which can strengthen the ecological importance of allelochemicals during successful invasions.

Alien Plants of Kyrgyzstan: The First Complete Inventory, Distributions and Main Patterns

The first inventory of casual and naturalised alien plants of Kyrgyzstan is based on an overview of published data, which were re-assessed and re-evaluated using modern standards. Altogether, 151 alien species were registered in the country, of which nearly 40% became naturalised. The total number of alien plant species and the proportion of casual aliens are relatively low due to the harsh climatic conditions (high aridity and continentality) and predominantly high elevations. The highest number of alien plant species in Kyrgyzstan originated from the Mediterranean, which can be explained by some common climatic features between this area and Central Asia, but half of the ten most harmful aliens originated from the Americas. The intensity of plant invasions was the greatest during the period of the Russian Empire and the USSR, and this rapid accumulation of alien plants continues in independent Kyrgyzstan. The uneven distribution of alien plants in Kyrgyzstan is explained by different elevations and climatic conditions across its regions, as well as by the concentration of agricultural activities and human population along warm lowland depressions. More research is required to uncover pathways and particular times of introduction and to produce detailed distribution maps.

Dense Cover, but Not Allelopathic Potential, of Naturalized Alien Cenchrus echinatus L. Threatens the Native Species in Urban Vegetation

Exotic plants usually exhibit problems for native species where they coexist. This study evaluated the effect of naturalized alien Cenchrus echinatus L. on native plants in urban vegetation. A field trial was conducted to assess the effect of this species on the cover and diversity of the native vegetation. The allelopathic potential of such species was examined. Sites comprising C. echinatus had a lower cover than some native species. Lower floristic diversity was observed at higher densities of this plant. The soil under this plant attained lower N, P, and K contents. This soil had no effect on the germination and growth of native species. It also comprised germinable seeds of some species which were absent from the standing vegetation. Exotic C. echinatus may exert negative effects on the native vegetation of the urban plant communities. A dense cover of this species may inhibit the germination of native species, leading to a reduction in their cover. Reduction in cover and diversity of native species may not be attributed to allelopathy. These results suggest that naturalized C. echinatus may be more competitive than the native ones, particularly at higher densities. Furthermore, it may represent a threat to the native plants in the urban vegetation.

Adsorption performance and kinetics of Cr(VI) onto activated carbons derived from the waste leaves of invasive plants Rhus typhina and Amorpha fruticosa

To maximize the potential of biomass from invasive plants, waste leaves from Rhus typhina (RT) and Amorpha fruticosa (AF) were used to prepare activated carbons (ACs) for the efficient removal of chromium from wastewater. Six ACs were prepared by CO2 activation at 850 °C with varying flow rates (500, 1000, and 1500 mL/min) and characterized by yield, pH, N2 adsorption isotherm, FTIR, SEM, TG, and XPS. The adsorption isotherm and kinetics for chromium removal were analyzed. The outcomes showed that the ACs had mesoporous structures with specific surface areas of 408.05-701.01 m2/g and pore volumes of 0.360-0.653 cm3/g. The pores are distributed among the agglomerated nanoparticles on the surface of the granules. The existence of two kinds of chromium compounds and two valance states, Cr(III) and Cr(VI), in spent ACs was identified by the FTIR and XPS spectra. The Cr (VI) equilibrium data and adsorption kinetics were well-fit with the Langmuir isotherm (R2 = 0.936-0.967) and pseudo-second-order kinetic models (R2 = 0.795-0.937). The maximum Langmuir Cr adsorption capacities of ACRT1.0 and ACAF0.5 were estimated to be 266.54 and 255.21 mg/g at pH = 2.0, respectively. Concentrations of Cr(III) and Cr(VI) in filtrates after equilibrium, combined with XPS and TGA analysis of spent ACs, illustrated that Cr(VI) was converted to the less harmful trivalent chromate Cr(III) during the adsorption processes. Cr(III) and Cr(VI) probably formed compounds with carbon and nitrogen atoms on the surfaces of ACs. ACs with abundant surface N-H groups achieved high Cr adsorption performance. The waste leaves from these invasive plants are suitable for producing cost-effective and efficient ACs for removing Cr (VI) from water by chemical adsorption.

The Alien Plant Species Impact in Rice Crops in Northwestern Italy

Alien species represent one of the causes of biodiversity loss, both in natural and anthropic environments. This study contributes to the assessment of alien species impact on Western Po Plain rice field cultivations, referring to different agricultural management practices and ecological traits. Flora and vegetation were studied (the latter through the phytosociological method), and α-biodiversity was estimated through Shannon and Simpson Indices. Results highlighted a significant floristic contingent depletion and increase in therophyte and alien components, compared to pre-existing studies (1950s); higher α-biodiversity levels in organic farms, compared to conventional farms, but also a higher invasive alien species percentage. The high deterioration of the territorial-landscape context appears to play a major role in shaping these patterns. Some of these alien species are particularly aggressive (e.g., Murdannia keisak), as confirmed by two experimental rice field plots which were left unharvested, continuously flooded, making it possible to assess the competitiveness between weed species. The detected weed vegetation is attributed to the Oryzo sativae-Echinochloetum cruris-galli association, already described for Southern Europe, with two different ecological and floristic variants. Future studies, by including other sites and framing their territorial-landscape context, may further complement this overview on the alien species distribution and behavior in rice fields, hence facilitating their strategic management.

New Data on Native and Alien Vascular Flora of Sicily (Italy): New Findings and Updates

In this paper, based on fieldwork and herbaria surveys, new data concerning the presence of 32 native and alien vascular species for Sicily (Italy) are provided. Among the native species, the occurrence of the following taxa is reported for the first time or confirmed after many decades of non-observation: Aira multiculmis, Arum maculatum, Carex flacca subsp. flacca, Mentha longifolia, Oxybasis chenopodioides, Najas minor and Xiphion junceum. Furthermore, we document the presence of three native species (Cornus mas, Juncus foliosus and Limonium avei) that, despite being repeatedly observed in Sicily and reported in the literature, are inexplicably omitted by the most recent authoritative checklists regarding the flora of Italy. Finally, fifteen alien species new to Sicily (including one new to Europe, i.e., Pyrus betulifolia) are reported and seven poorly documented allochthonous taxa are confirmed for the island, and for two of them, a status change is proposed. These new or confirmed records allow us to better define the European and national distribution of the targeted taxa and offer new insights on the native and alien flora of Sicily.

Impact of the Alien Aquatic Plant Ludwigia hexapetala on the Native Utricularia australis: Evidence from an Indoor Experiment

Ludwigia hexapetala is an alien aquatic plant considered highly invasive in Europe since it alters freshwater habitats by forming dense mats both in water and along banks, outcompeting natives. Ludwigia effects on the native carnivorous plant Utricularia australis were investigated here. A 21-day indoor experiment was performed by setting up some separate tests in which Utricularia was made to grow both alone (control tests) and together with Ludwigia (arena tests). Water chemical and physical parameters and growth and morphological traits of Utricularia and Ludwigia were analysed weekly. Water samples were also analysed by UV-visible spectra to verify allelochemical (quercitrin) production by Ludwigia. In arena tests, oxygen concentration and pH were lower and conductivity higher than in control tests. Utricularia grew significantly less in arena tests in both shoot length and internode number, and its fresh weight, trap number and internode length decreased more than the control. Quercitrin was found only in arena tests as an allelochemical product released by Ludwigia. Overall, this study demonstrated Ludwigia significantly alters water parameters and negatively affects the growth of Utricularia, showing aggressive and competitive behaviour against this native species. Such evidence suggest that the widespread of L. hexapetala can represent a serious threat to the conservation of native plant diversity occurring in the freshwater habitats it invades.

Monitoring the distribution pattern and invasion status of Ageratina adenophora across elevational gradients in Sikkim Himalaya, India

Understanding the spread intensity and population dynamics of invasive plant species is a prerequisite for developing management strategies in the Himalayan Forest ecosystems that are experiencing an accelerated rate of climate change. Although there are studies on the occurrence of few invasive species in the Himalayan ecosystems, systematic information on their intensity of spread and species association is still missing. Considering existing data gaps, we aimed to assess the intensity of spread and distribution pattern of A. adenophora, one of the high-concern invasive species (HiCIS) of India that is causing havoc in the Himalayas, across an elevational gradient. Field data were collected in 2018 and 2021 in the Indian federal state of Sikkim, located in the Eastern Himalayas. We analyzed the population status and species association of A. adenophora along an elevational gradient ranging from > 600 m to 2700 m above sea level, which was divided into seven gradients of 300 m width, and each gradient was further randomly sampled. Overall, 81 species were present in association with A. adenophora, including 58 herbs, 19 shrubs, and 4 climbers, belonging to 30 families and 67 genera in the region. No other species continuously co-occurred along with A. adenophora throughout the elevation ranging from > 600 m to 2700 m. The species observed increased frequency (100%), density (40.51 ind./100 m²), and basal cover (11.25 cm²/m²) in the elevational gradient 1500-1800 m in 2018. In 2021, A. adenophora dominated the highest elevational gradient (< 2400-2700 m) with increased frequency (99.96%), density (58.41 ind./100m²), and basal cover (42.54 cm²/100m²), which demonstrated rapid invasion and improved plant health and reproductive vigor in comparison to the lower elevational gradient in Sikkim Himalaya. Despite being completely absent at the highest elevation (< 2400-2700 m), in 2018, it observed gregarious spread at the highest elevation in 2021, which is of serious concern to ecologists. The presence of the targeted species in all seven studied altitudinal gradients reflects stage III of the species invasion. An enormous shift in the distribution pattern along elevational gradients within a short time span is alarming for the Himalayan ecosystem since it is becoming a thriving habitat for invasive species owing to anthropogenic activity. We mapped the potential geographical extent using the species distribution model (SDM) and predicted the suitable habitat of distribution in Sikkim Himalaya. In order to curtail the spread and counteract the negative impact of this species on native vegetation in Sikkim Himalaya and ultimately reverse the process, local and regional initiatives for its biological control and management must be taken.

Influence of urbanisation on phytodiversity and some soil properties in riverine wetlands of Bamenda municipality, Cameroon

In urban areas, human activities result in the discharge of a variety of chemical substances into the environment. This affects soil quality, plant species diversity and human security. To suggest appropriate management strategies that ensure soil quality and human security amid urbanization, this study assessed the relationship between macrophyte diversity and some soil characteristics of wetlands that are adjacent to urban, peri-urban and rural areas in Bamenda Municipality, Cameroon. Plant communities were sampled for species composition and relative abundance, using the Braun-banquet method. Species richness was evaluated using Simpson's diversity index. Twenty-one soil samples (0-25 cm depth) were randomly collected within the wetlands and analyzed for their physicochemical characteristics using standard methods. The hierarchical cluster analysis (HCA) was used to group the wetlands under managing units. The dominant species ranked in order of abundance in the rural wetland were Raphia farinifera > Ludwigia hexandra > Coix spp. > Leersia hexandra > Ehchinochloa paramidelis. The Peri-urban wetland dominant species stood at Commelina bengalensis > Leersia hexandra > Cyperus distance > Ehchinochloa pyramidalis. In the Urban segment, Pennisetum purpureum > Echinochloa pyramidalis > Tithonia diversifolia > Leersia hexandra were the abundant species. The Simpson index of diversity was 0.94 for the urban and 0.96 for the peri-urban and rural sites respectively. The soils were slightly acidic with pH KCl ranging from 4.87 to 5.41. From the coefficient of variability classes, Sand, pH-H₂O, pH-KCl, and Na consistently varied slightly across the three sites. Two significant clusters (management units) representing a combination of urban, and peri-urban/rural were formed from the hierarchical dendrograms. The Mann-Whitney U test revealed a significant (P < 0.05) lower exchange acidity in the rural than the urban sites indicating contamination of the urban site, reducing its macrophyte diversity. Intensification and extension of urbanisation are gradually reducing the macrophyte diversity and also contaminating the soils of the wetlands of the Bamenda municipality in Cameroon, warranting monitoring. The chemical composition of soils in the urban cluster needs early remediation by encouraging the planting and monitoring of certain plants that can already take up the elements.

The invasion history of Elodea canadensis and E. nuttallii (Hydrocharitaceae) in Italy from herbarium accessions, field records and historical literature

We analysed the invasion history of two North American macrophytes (Elodea canadensis and E. nuttallii) in Italy, through an accurate census of all available herbarium and field records, dating between 1850 and 2019, and a rich literature collection describing the initial introduction and naturalisation phase that supports the results obtained by the occurrence records. Elodea canadensis arrived in Italy before 1866 and had two invasion phases, between the 1890s and 1920s and between the 1990s and 2000s; E. nuttallii, probably arrived in the 1970s, started invading in 2000 and the invasion is still ongoing. Botanical gardens and fish farming played a crucial role in dispersal and naturalisation of both species. The current invasion range of both species is centred in northern Italy, with scattered occurrences of E. canadensis in central and southern regions. River Po represents a dispersal barrier to the Mediterranean region and a strategic monitoring site to prevent the invasion in the peninsula. The study detects differences in the niches of the two species during the introduction and naturalisation phase and a habitat switch occurred after 1980 in E. canadensis and after 2000 in E. nuttallii, during their expansion phases. For E. canadensis the switch corresponds to the second invasion round. Further research can clarify whether the second invasion round is due to confusion of the recently introduced E. nuttallii with E. canadensis, to a cryptic introduction of a new genotype, to post-introduction evolution, or just to an increased scientific interest in biological invasions.

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.

Alien flora in Calabria (Southern Italy): an updated checklist

An updated checklist of the Calabrian alien vascular flora is presented. By way of field, bibliographic, and herbarium research, we recorded 382 alien taxa (representing almost 14% of all regional flora), of which 371 are angiosperms, nine gymnosperms, and two ferns. In relation to the state of spread, the majority of alien species are casual (207 taxa; 54%), followed by naturalized (127; 33%) and invasive (48; 13%), these last include four on the list of Union Concern, sensu Regulation (EU) no. 1143/2014. The most represented families are Asteraceae (39 taxa) and Poaceae (39). Among genera, Amaranthus (nine taxa), Prunus, Euphorbia, and Oxalis (seven taxa) make up those with the greatest number of taxa. A total of 21 taxa were reported for the first time, three of them are new to the European flora (Camptosema rubicundum, Musa ×paradisiaca and, only for continental Europe, Ipomoea hederacea), two to the Italian peninsula (Pelargonium graveolens, Schinus terebinthifolia) and 16 to the Calabrian flora (Aeonium arboreum, Asparagus asparagoides, Aspidistra elatior, Bidens sulphurea, Catalpa bignonioides, Citrus ×aurantium, Crassula ovata, Cucurbita ficifolia, Dimorphotheca ecklonis, Graptopetalum paraguayense subsp. paraguayense, Kalanchoë laxiflora, Nicotiana tabacum, Phytolacca dioica, Portulaca umbraticola, Talinum paniculatum, Tecomaria capensis). In terms of residence status, there are 291 neophytes (76%), 73 archaeophytes (19%), and 18 regional aliens (5%); neophytes are the most represented group (45 out of 48) among invasive taxa. Concerning life forms, the two most abundant groups are therophytes (30.1%, 115 taxa) and phanerophytes (29.6%, 113 taxa). Regarding habitats, 72% of alien taxa occur in artificial (199 taxa, 52%) and agricultural habitats (75 taxa, 20%). The majority of alien taxa are native to the Americas (159; 41.6%), numerous aliens also originated in Asia (76; 19.9%) and Africa (56; 14.7%). The majority of taxa were introduced for ornamental purposes (55%). Over the past decade, alien taxa in the flora in Calabria have increased from 190 to the current 382 taxa. While this trend could be linked to some extent to increasing awareness of the problem of alien species and the increasing intensity of research over recent decades, it is also most probably due to new introductions resulting from the globalization that relentlessly affects the whole planet.

Assessing the Invasion Risk of Humulus scandens Using Ensemble Species Distribution Modeling and Habitat Connectivity Analysis

Given the rapid spread of invasive alien plant species in Europe and limited information regarding their distribution and dispersion patterns, we analyzed the invasive risk of Humulus scandens, a species with an increased invasive potential. We collected occurrence records from Romania within an EU funded project and literature data, in order to perform an ensemble distribution model. Environmental variables varied from downscaled topoclimatic continuous entries to categorical ones, such as soil class, texture, or land use. Results showed potential core areas of the species within the study region. By inverting the probability output of the models, we have created a resistance surface which helped us model its dispersion patterns. Further, we assessed the probability of invasion for each resulted corridor using the species dispersion ecology and created an invasion risk map. H. scandens is highly influenced by milder climates and areas with constant flooding events, thus we found that the Tisa basin and its tributaries can be under a high invasion risk, spreading through the entire catchment, in Central, Western, and Northern Romania, towards the Eastern Carpathians. The Danube acted as a dispersion corridor for major river systems in southern Romania, but the dispersion capability of the species dropped in steppe areas with higher aridity and limited water course network. This approach is useful for creating adequate action plans in relation to invasive alien plant species, and should urgently be regarded, as results show a potentially large distribution of H. scandens across entire water catchment areas, with devastating effects on natural ecosystems.

Blue-Sky Albedo Reduction and Associated Influencing Factors of Stable Land Cover Types in the Middle-High Latitudes of the Northern Hemisphere during 1982–2015

Land surface albedo (LSA) directly affects the radiation balance and the surface heat budget. LSA is a key variable for local and global climate research. The complexity of LSA variations and the driving factors highlight the importance of continuous spatial and temporal monitoring. Snow, vegetation and soil are the main underlying surface factors affecting LSA dynamics. In this study, we combined Global Land Surface Satellite (GLASS) products and ERA5 reanalysis products to analyze the spatiotemporal variation and drivers of annual mean blue-sky albedo for stable land cover types in the middle-high latitudes of the Northern Hemisphere (30~90°N) from 1982 to 2015. Snow cover (SC) exhibited a decreasing trend in 99.59% of all pixels (23.73% significant), with a rate of −0.0813. Soil moisture (SM) exhibited a decreasing trend in 85.66% of all pixels (22.27% significant), with a rate of −0.0002. The leaf area index (LAI) exhibited a greening trend in 74.38% of all pixels (25.23% significant), with a rate of 0.0014. Blue-sky albedo exhibited a decreasing trend in 98.97% of all pixels (65.12% significant), with a rate of −0.0008 (OLS slope). Approximately 98.16% of all pixels (57.01% significant) exhibited a positive correlation between blue-sky albedo and SC. Approximately 47.78% and 67.38% of all pixels (17.13% and 25.3% significant, respectively) exhibited a negative correlation between blue-sky albedo and SM and LAI, respectively. Approximately 10.31%, 20.81% and 68.88% of the pixel blue-sky albedo reduction was mainly controlled by SC, SM and LAI, respectively. The decrease in blue-sky albedo north of 40°N was mainly caused by the decrease in SC. The decrease in blue-sky albedo south of 40°N was mainly caused by SM reduction and vegetation greening. The decrease in blue-sky albedo in the western Tibetan Plateau was caused by vegetation greening, SM increase and SC reduction. The results have important scientific significance for the study of surface processes and global climate change.

Anthropogenic and environmental determinants of alien plant species spatial distribution on an island scale

Mediterranean islands are considered especially vulnerable to biological invasions by alien plants. However, there is a lack of studies on island scale regarding the factors that determine alien plant's spatial distribution, and the way they affect invasion process. A roadside survey of alien plant species was conducted on Lesvos, the 8th largest island in Mediterranean basin. Data on species counts and explanatory variables were aggregated to a 1 sq. km vector grid and brought together into a single GIS layer. Alien species counts were modelled by using a Negative-binomial model while a Generalised Additive Model was used to examine possible non-linear relationships to the predictors by using splines. A subset of significant factors, related both to human activities and the environment, shaped the spatial distribution of aliens and influenced, in various ways, their future invasion outcome. Transformed areas with high levels of anthropogenic pressures and disturbances, including high population numbers, dense road network, ports, and intensive land use, as is the case for coastal zones, promoted the presence of alien species. Contrary, modified areas, such as grazed lands, seemed to restrict alien species occurrences, possibly due to the long grazing history these areas present, a regime in which aliens are not adapted. Alien plants presence was positively associated with high levels of NPP, diversity of geological substrates, and a west-facing aspect. Anthropogenic determinants of alien spatial patterns were primarily connected to increased propagule pressure, whereas environmental factors demonstrated the preference of alien plants for resource-rich environments.

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.

Italian Vascular Flora: New Findings, Updates and Exploration of Floristic Similarities between Regions

The tradition of floristic studies in Italy has made it possible to obtain a good knowledge of plant diversity both on a national and regional scale. However, the lack of knowledge for some areas, advances in plant systematics and human activities related to globalization, highlight the need for further studies aimed at improving floristic knowledge. In this paper, based on fieldwork and herbaria and literature surveys, we update the knowledge on the Italian vascular flora and analyze the floristic similarities between the administrative regions. Four taxa, all exotic, were recorded for the first time in Italy and Europe. In detail, Elaeodendron croceum, Kalanchoë blossfeldiana, and Sedum spathulifolium var. spathulifolium were found as casual aliens, while Oxalis brasiliensis was reported as historical record based on some herbarium specimens. Furthermore, Kalanchoë laxiflora was confirmed as a casual alien species for Italy and Europe. Status changes for some taxa were proposed at both national and regional levels, as well as many taxa were reported as new or confirmed at the regional level. Currently the Italian vascular flora comprises 9150 taxa of which 7547 are native (of which 1598 are Italian endemics) and 1603 are exotic at the national level. The multivariate analysis of updated floristic data on a regional scale showed a clear distribution along the latitudinal gradient, in accordance with the natural geographical location of the regions in Italy. This pattern of plants distribution was not affected by the introduction of alien species. Despite some taxonomic and methodological issues which are still open, the data obtained confirm the important role of floristic investigations in the field and in herbaria, as well as the collaborative approach among botanists, in order to improve the knowledge of the Italian and European vascular flora.

Evaluation of Species Invasiveness: A Case Study with Acacia dealbata Link. on the Slopes of Cabeça (Seia-Portugal)

One of the main causes of biodiversity loss in the world is the uncontrolled expansion of invasive plants. According to the edaphoclimatic conditions of each region, plants acquire different invasion behaviors. Thus, to better understand the expansion of invasive plants with radial growth, it is proposed to use two equations, the Annual Linear Increment (ALI) and the Annual Invasiveness Rate (AIR). These equations are applied using spatiotemporal data obtained from the analysis of orthophotomaps referring populations of Acacia dealbata Link. in areas located in Serra da Estrela, Portugal. As a result, the area occupied by this species in the parish of Cabeça was evaluated and a 20-year projection was carried out. The data produced by these equations contributed to improving the knowledge about the invasion behavior of exotic species in a rigorous and detailed way according to local ecological conditions. This study may serve as the basis for the application of other similar situations concerning invasive species in other territories, to improve the efficiency of future projections for these species. Local technical and scientific knowledge will contribute to improving spatial and management planning, enabling a better adequacy and effectiveness of the control measures to be adopted.

Unmanned Aerial Vehicle (UAV)-Based Mapping of Acacia saligna Invasion in the Mediterranean Coast

Remote Sensing (RS) is a useful tool for detecting and mapping Invasive Alien Plants (IAPs). IAPs mapping on dynamic and heterogeneous landscapes, using satellite RS data, is not always feasible. Unmanned aerial vehicles (UAV) with ultra-high spatial resolution data represent a promising tool for IAPs detection and mapping. This work develops an operational workflow for detecting and mapping Acacia saligna invasion along Mediterranean coastal dunes. In particular, it explores and tests the potential of RGB (Red, Green, Blue) and multispectral (Green, Red, Red Edge, Near Infra—Red) UAV images collected in pre-flowering and flowering phenological stages for detecting and mapping A. saligna. After ortho—mosaics generation, we derived from RGB images the DSM (Digital Surface Model) and HIS (Hue, Intensity, Saturation) variables, and we calculated the NDVI (Normalized Difference Vegetation Index). For classifying images of the two phenological stages we built a set of raster stacks which include different combination of variables. For image classification, we used the Geographic Object-Based Image Analysis techniques (GEOBIA) in combination with Random Forest (RF) classifier. All classifications derived from RS information (collected on pre-flowering and flowering stages and using different combinations of variables) produced A. saligna maps with acceptable accuracy values, with higher performances on classification derived from flowering period images, especially using DSM + HIS combination. The adopted approach resulted an efficient method for mapping and early detection of IAPs, also in complex environments offering a sound support to the prioritization of conservation and management actions claimed by the EU IAS Regulation 1143/2014.

Diversity of Macrophytes and Environmental Assessment of the Ljubljanica River (Slovenia)

The present research aimed to determine the diversity of macrophyte taxa in the Ljubljanica River and its relationship with environmental parameters. In each of the 19 river sections, the presence and abundance of plant taxa were recorded, and basic physical and chemical parameters were measured. Additionally, selected environmental parameters were assessed using a modified version of the Riparian, Channel and Environmental (RCE) method. We compared the obtained data set with survey data from the year 2004. In 2019, a total of 34 macrophyte taxa were recorded. The dominant taxa with the highest abundance were Sparganium emersum, Callitriche sp., and the invasive alien species Elodea canadensis. The species richness and diversity of macrophytes decreased with distance from the source, an increase in pH, and alterations of the riverbed structure due to interference in the riverine ecosystem in the lower part of the Ljubljanica River and its catchment. The comparison of 2004 and 2019 surveys revealed a decrease in the overall presence and abundance of P. natans and in the frequency of occurrence of the species Myriophyllum spicatum and an increase in the presence and abundance of the invasive alien species Elodea canadensis.

Comparison of different methods to assess the distribution of alien plants along the road network and use of Google Street View panoramas interpretation in Sicily (Italy) as a case study

The survey by foot in the field is compared to the survey from a car, the photo-interpretation of Google Street View (GSV) panoramas continuously and at intervals of 1.5 km and the photo-interpretation of Google Earth aerial images on a 10 km stretch of road in Sicily. The survey by foot was used as reference for the other methods. The interpretation of continuous GSV panoramas gave similar results as the assessment by car in terms of the number of species identified and their location, but with lower cost. The interpretation online of aerial photos allowed the identification of a limited number of taxa, but gave a good localisation for them. Interpretation of GSV panoramas, each of 1.5 km, allowed the recognition of twice as many taxa as the interpretation of aerial photos and taking half the time, but did not allow a complete localisation.

None of these methods alone seems sufficient to carry out a complete survey. A mixture of different techniques, which may vary according to the available resources and the goal to be achieved, seems to be the best compromise.

To further test the capabilities of the survey using the interpretation of GSV panoramas every 1.5 km along the roads, we proceeded to study the alien plants along 3500 km of the road network on the island of Sicily. This survey identified only 10% of the known species for the region, but allowed us to trace the distribution of invasive species whose distribution is currently poorly recorded.

Measuring Alpha and Beta Diversity by Field and Remote-Sensing Data: A Challenge for Coastal Dunes Biodiversity Monitoring

Combining field collected and remotely sensed (RS) data represents one of the most promising approaches for an extensive and up-to-date ecosystem assessment. We investigated the potential of the so called spectral variability hypothesis (SVH) in linking field-collected and remote-sensed data in Mediterranean coastal dunes and explored if spectral diversity provides reliable information to monitor floristic diversity, as well as the consistency of such information in altered ecosystems due to plant invasions. We analyzed alpha diversity and beta diversity, integrating floristic field and Remote-Sensing PlanetScope data in the Tyrrhenian coast (Central Italy). We explored the relationship among alpha field diversity (species richness, Shannon index, inverse Simpson index) and spectral variability (distance from the spectral centroid index) through linear regressions. For beta diversity, we implemented a distance decay model (DDM) relating field pairwise (Jaccard similarities index, Bray–Curtis similarities index) and spectral pairwise (Euclidean distance) measures. We observed a positive relationship between alpha diversity and spectral heterogeneity with richness reporting the higher R score. As for DDM, we found a significant relationship between Bray–Curtis floristic similarity and Euclidean spectral distance. We provided a first assessment of the relationship between floristic and spectral RS diversity in Mediterranean coastal dune habitats (i.e., natural or invaded). SVH provided evidence about the potential of RS for estimating diversity in complex and dynamic landscapes.

Invasive Plant Species Distribution Is Structured by Soil and Habitat Type in the City Landscape

Invasive alien species (IAS) is a global problem that largely relates to human activities and human settlements. To prevent the further spread of IAS, we first need to know their pattern of distribution, to determine which constitutes the greatest threat, and understand which habitats and migration pathways they prefer. Our research aimed to identify the main vectors and distribution pattern of IAS of plants in the city environment. We checked the relations between species distribution and such environmental factors as urban soil type and habitat type. We applied data on IAS occurrence (collected in the period 1973-2015) in 515 permanent plots with dimensions of 0.5 × 0.5 km and analyzed by direct ordination methods. In total, we recorded 66 IAS. We found a 27% variance in the IAS distribution pattern, which can be explained by statistically significant soil and habitat types. The most important for species distribution were: river and alluvial soils, forests and related rusty soils, and places of intensive human activities, including areas of urbisols and industriosols. Our results provide details that can inform local efforts for the management and control of invasive species, and they provide evidence of the different associations between natural patterns and human land use.

Design a Database of Italian Vascular Alimurgic Flora (AlimurgITA): Preliminary Results

Despite the large number of data published in Italy on WEPs, there is no database providing a complete knowledge framework. Hence the need to design a database of the Italian alimurgic flora: AlimurgITA. Only strictly alimurgic taxa were chosen, excluding casual alien and cultivated ones. The collected data come from an archive of 358 texts (books and scientific articles) from 1918 to date, chosen with appropriate criteria. For each taxon, the part of the plant used, the method of use, the chorotype, the biological form and the regional distribution in Italy were considered. The 1103 taxa of edible flora already entered in the database equal 13.09% of Italian flora. The most widespread family is that of the Asteraceae (20.22%); the most widely used taxa are Cichorium intybus and Borago officinalis. The not homogeneous regional distribution of WEPs (maximum in the south and minimum in the north) has been interpreted. Texts published reached its peak during the 2001–2010 decade. A database for Italian WEPs is important to have a synthesis and to represent the richness and complexity of this knowledge, also in light of its potential for cultural enhancement, as well as its applications for the agri-food system.

Drought Disaster Risk Adaptation through Ecosystem Services-Based Solutions: Way Forward for South Africa

Ecosystem services refer to the direct and indirect benefits to humanity from an ecosystem. The ability to spatially incorporate multiple biophysical environments is crucial to ecosystem services, thus promoting cooperation between science and policy in seeking solutions to global challenges, including drought disasters. Therefore, understanding ecosystem services, for instance, from forest/vegetation in view of contributing to drought disaster risk adaptation is critical to human-nature interactions and proper sustainable conservation thereof. No known study has been done on ecosystem services and their contributions to drought management or other climate adaptation in South Africa. This study aimed at quantifying drought disaster risk adaptation based on ecosystem services in South Africa. It was identified that ecosystem services to society have been directly affected by anthropogenic and natural phenomena, thereby influencing drought severity and its impacts. These impacts and their associated risks are evident globally, including in South Africa. We found out that ecosystems in South Africa have been affected and extremely vulnerable to recurrent natural disasters, such as droughts. To achieve long-term solutions to such drought-related risks and challenges, feedback mechanisms between human-natural and related factors and ecosystem services-based drought adaptation need to be understood and planned. Timely spatiotemporal assessment, planning and management strategies need to be considered to find solutions or ways forward to South Africa in combating drought disasters.

Remnants of naturalness in a reclaimed land of central Italy

Wetlands are among the most fragile habitats on Earth and have often undergone major environmental changes. As a study case in this context, the present work aims at increasing the floristic knowledge of a reclaimed land now turned into an agricultural lowland with scarce patches of natural habitats. The study area is named Piana di Rosia, and it is located in southern Tuscany (Italy). The compiled checklist consists of 451 specific and subspecific taxa of vascular plants. The life-form spectrum shows a predominance of hemicryptophytes, followed by therophytes. The chorological spectrum highlights a co-dominance of Euri-Mediterranean and Eurasian species along with many widely distributed species. The checklist includes seven species of conservation concern, three Italian endemics (Crocus etruscus Parl., Polygala vulgaris L. subsp. valdarnensis (Fiori) Arrigoni, and Scabiosa uniseta Savi), 41 alien species, 21 segetal species, and 11 aquatic macrophytes of which five helophytes and six hydrophytes. This study suggests that irreversible land-use changes in wetlands can lead towards a simplification of the flora. However, despite the deep transformations that the former wetland has undergone, the presence of some aquatic and protected taxa is interesting. From a conservation point of view, the natural value of this agricultural area could be enhanced and its current management partly reconsidered, thus preserving the remnants of naturalness present.

Ailanthus altissima Forests Determine a Shift in Herbaceous Layer Richness: A Paired Comparison with Hardwood Native Forests in Sub-Mediterranean Europe

Ailanthus altissima is an invasive alien species (IAS) present throughout Europe and included in the list of alien species of Union concern. In sub-Mediterranean areas of central Italy, there is a lack of knowledge about this invasive species and its interactions with the native forest ecosystems. We aim to find what are the main differences in vegetation structure and floristic diversity between A. altissima forests and native forests through the assessment of the principal ecological parameters that differ between the forest types. We performed 38 phytosociological relevés and sampling of ecological parameters in A. altissima forest communities and neighboring native forests. We analyzed how species richness, diversity, life forms, life strategies, structural characteristics, and ecological parameters changed in A. altissima forests compared with native ones. We found that in A. altissima forests, there is a shift in herbaceous layer richness, with a higher presence of annual ruderal herbs and the absence of herbaceous species linked to the forest environment. The ecological parameters that diverge from the native forests were total nitrogen, total carbon, and C/N ratio. A. altissima forest communities could threaten the biodiversity of the native forest ecosystems in the sub-Mediterranean landscape, favoring ruderal species and inhibiting the presence of typical forest species.

Three New Alien Taxa for Europe and a Chorological Update on the Alien Vascular Flora of Calabria (Southern Italy)

Knowledge on alien species is needed nowadays to protect natural habitats and prevent ecological damage. The presence of new alien plant species in Italy is increasing every day. Calabria, its southernmost region, is not yet well known with regard to this aspect. Thanks to fieldwork, sampling, and observing many exotic plants in Calabria, here, we report new data on 34 alien taxa. In particular, we found three new taxa for Europe (Cascabela thevetia, Ipomoea setosa subsp. pavonii, and Tecoma stans), three new for Italy (Brugmansia aurea, Narcissus 'Cotinga', and Narcissus 'Erlicheer'), one new one for the Italian Peninsula (Luffa aegyptiaca), and 21 new taxa for Calabria (Allium cepa, Asparagus setaceus, Bassia scoparia, Beta vulgaris subsp. vulgaris, Bidens formosa, Casuarina equisetifolia, Cedrus atlantica, Chlorophytum comosum, Cucurbita maxima subsp. maxima, Dolichandra unguis-cati, Fagopyrum esculentum, Freesia alba, Juglans regia, Kalanchoë delagoënsis, Passiflora caerulea, Portulaca grandiflora, Prunus armeniaca, Prunus dulcis, Solanum tuberosum, Tradescantia sillamontana, and Washingtonia filifera). Furthermore, we provide the first geolocalized record of Araujia sericifera, the confirmation of Oxalis stricta, and propose a change of status for four taxa (Cenchrus setaceus, Salpichroa origanifolia, Sesbania punicea, and Nothoscordum gracile) for Calabria. The updated knowledge on the presence of new alien species in Calabria, in Italy and in Europe could allow for the prevention of other new entries and to eliminate this potential ecological threat to natural habitats.