Characterisation of invasive plant proliferation within remnant riparian green corridors in Lusaka District of Zambia using Sentinel-2 imagery

Ecological impact of phytoinvasions in Ukraine

Occurrence and damage of invasive alien plants in Dehong Prefecture, western of Yunnan Province

ARTICLE HIGLIGHTS- A pioneering study of invasive alien plant species in the riparian areas of Northern Samar- Species composition, endemism, and conservation status of introduced species- Out of 65 introduced species, 32 were listed as invasiveABSTRACTRiparian areas are highly dynamic and naturally disturbed, making them particularly susceptible to invasion. Invasive Alien Plant Species (IAPS) are widely distributed in these areas due to the favorable environmental conditions that support their growth and persistence. This study is a pioneering effort to document the invasive alien plant species thriving in the riparian zones of Allen, Biri, Catarman, Gamay, Mapanas, Laoang, Lapinig, Las Navas, and Pambujan in Northern Samar. Sampling was conducted from March to December 2023. Six transect lines, each measuring two kilometers per site, were established in the riparian areas to identify existing invasive alien plants. In total, 60 transect lines were set up across all sampling areas. As a result, 65 introduced plant species belonging to 24 families and 56 genera were documented in the riparian areas of Northern Samar. The families with the highest number of species were Poaceae (13 spp.), Asteraceae (12 spp.), Cyperaceae, Fabaceae, and Lamiaceae (5 spp. each). The remaining families had fewer than five species each. The most common invasive plant species recorded was Psidium guajava L., which was present in all sampling areas. Based on life forms, the study identified two tree species, 17 shrubs, three vines, one epiphyte, and 42 herbs. Conservation status was determined using the latest IUCN and DENR listings (2017–11). One taxon was classified as Data Deficient, 32 as Least Concerned, and the remaining species as Not Evaluated. In contrast, no taxa were assessed in the DENR 2017–11 listing. Furthermore, of the 65 introduced plant species documented, 10 were recorded as invasive in the Global Invasive Species Database, while 22 were listed in the Global Register of Introduced and Invasive Species Database. Although invasive alien species have long been recognized as posing serious threats to human health, forestry, agriculture, fisheries, and natural biodiversity, no comprehensive assessment of their status, trends, causes, impacts, management, and governance issues has been conducted worldwide. Thus, this study aimed to supplement existing data on invasive plants and assist policymakers in developing policy frameworks for managing invasive alien plant species to mitigate their impacts on human health and the environment.

ABSTRACTThe spatial distribution of invasive alien plants has been poorly documented in California. However, with the increased availability of GIS software and spatially explicit data, the distribution of invasive alien plants can be explored. Using bioregions as defined in Hickman (1993), I compared the distribution of invasive alien plants (n = 78) and noninvasive alien plants (n = 1097). The distribution of both categories of alien plants was similar with the exception of a higher concentration of invasive alien plants in the North Coast bioregion. Spatial autocorrelation analysis using Moran's I indicated significant spatial dependence for both invasive and noninvasive alien plant species. I used both ordinary least squares (OLS) and spatial autoregressive (SAR) models to assess the relationship between alien plant species distribution and native plant species richness, road density, population density, elevation, area of sample unit, and precipitation. The OLS model for invasive alien plants included two significant effects; native plant species richness and elevation. The SAR model for invasive alien plants included three significant effects; elevation, road density, and native plant species richness. The SAR model for noninvasive alien plants resulted in the same significant effects as invasive alien plants. Both invasive and noninvasive alien plants are found in regions with low elevation, high road density, and high native‐plant species richness. This is in congruity with previous spatial pattern studies of alien plant species. However, the similarity in effects for both categories of alien plants alludes to the importance of autecological attributes, such as pollination system, dispersal system and differing responses to disturbance in the distribution of invasive plant species. In addition, this study emphasizes the critical importance of testing for spatial autocorrelation in spatial pattern studies and using SAR models when appropriate.

The decline of native plant species associated with alien plant invasion is often assumed to be driven by competitive exclusion. However, invasive alien plant species could also directly or indirectly impact native plants by limiting reproductive success. Here, we tested whether invasive alien plants influence seed production, viability, and germination using the Benjoin [ Terminalia bentzoe (L.) L.f. subsp. bentzoe ], a critically endangered tree endemic to the Mascarene Islands (southwest Indian Ocean), as a model species. Seed production was estimated from seed densities under the canopy of adult individuals from one of the largest remaining subpopulations of the species (in Cirque de Mafate, Reunion Island). Seed viability was determined using a tetrazolium test on the different sets of seeds collected in the field. Densities of seeds and viable seeds were then tested for correlation with the percentage cover of invasive alien plant species in the liana, tree, shrub, and herbaceous forest layers. Seed germination was studied by sowing seeds in soils where three alien invasive plants, three endemics, and T. bentzoe subsp. bentzoe had previously been grown. Seed production and viability decreased with increasing abundance in invasive alien plants in the liana and tree strata but not in the lower vegetation strata. Mechanisms specific to tall-statured invasive alien plants could include competition for resources, interference with pollinator behavior and mechanical constraints. Seed germination was inhibited by the invasive alien succulent Mauritius hemp [ Furcraea foetida (L.) Haw.] and T. bentzoe subsp. bentzoe itself, but enhanced by the endemic tree species Poupartia borbonica J.F.Gmel. These species may differ in their resource use intensity, associated microbial communities, and allelopathic effects. Our findings therefore suggest that plant invasions can significantly contribute to the decline of native plants through reduced reproductive ability and induce an extinction debt due to a lack of regeneration.

In support of the prediction of the enemy release hypothesis regarding a growth-defense trade-off, invasive alien plants often exhibit greater growth and lower anti-herbivory defenses than native plants. However, it remains unclear how nutrient enrichment of invaded habitats may influence competitive interactions between invasive alien and co-occurring native plants, as well as production of anti-herbivore defense compounds, growth-promoting hormones, and defense-regulating hormones by the two groups of plants. Here, we tested whether: (i) nutrient enrichment causes invasive alien plants to produce greater biomass and lower concentrations of the defense compounds flavonoids and tannins than native plants; and (ii) invasive alien plants produce lower concentrations of a defense-regulating hormone jasmonic acid (JA) and higher concentrations of a growth-promoting hormone gibberellic acid (GA3). In a greenhouse experiment, we grew five congeneric pairs of invasive alien and native plant species under two levels each of nutrient enrichment (low vs. high), simulated herbivory (leaf clipping vs. no-clipping), and competition (alone vs. competition) in 2.5-L pots. In the absence of competition, high-nutrient treatment induced a greater increase in total biomass of invasive alien species than that of native species, whereas the reverse was true under competition as native species benefitted more from nutrient enrichment than invasive alien species. Moreover, high-nutrient treatment caused a greater increase in total biomass of invasive alien species than that of native species in the presence of simulated herbivory. Competition induced higher production of flavonoids and tannins. Simulated herbivory induced higher flavonoid expression in invasive alien plants under low-nutrient than high-nutrient treatments. However, flavonoid concentrations of native plants did not change under nutrient enrichment and simulated herbivory treatments. Invasive alien plants produced higher concentrations of GA3 than native plants. Taken together, these results suggest that impact of nutrient enrichment on growth of invasive alien and co-occurring native plants may depend on the level of competition that they experience. Moreover, invasive alien plants might adjust their flavonoid-based defense more efficiently than native plants in response to variation in soil nutrient availability and herbivory pressure. Our findings suggest that large-scale efforts to reduce nutrient enrichment of invaded habitats may help to control future invasiveness of target alien plant species.

Invasive process of alien species is affected by not only the invaded habitats, but also the surrounding landscape matrix. Understanding the effects of landscape matrix on alien species is of great significance for controlling invasive alien species. We surveyed plant communities along the water-level fluctuating zone (WLFZ) of the Three Gorges Reservoir. Invasive status of alien plant species was evaluated. Totally 10 spatial scales of the surrounding landscape matrix in the scope of 2000 m (including WLFZ) were classified, and 14 landscape indices were applied to analyze the landscape matrix composition and configuration. Using the principal component analysis and correlation analysis, the effects of landscape matrix on the alien invasive plant species and associated scale effect were tested. Results showed that a total of 42 alien invasive plant species were found in the WLFZ, belonging to 17 families and 36 genera. Fuling was a dividing place to differentiate invasive species distribution. The number of the alien invasive species between Fuling and the Three Gorges Dam was found more than that between Fuling and Jiangjin. For the all scales (within 2000 m). The higher the landscape matrix fragmentation was, the more difficult the alien species invading. The higher landscape connectivity was, the easier the alien species invading. The effects of landscape matrix composition and configuration on the invasive plant diversity at large scales (1200-2000 m) was more significant than those at small scales (200-1000 m), in which landscape matrix composition and configuration at 1200-1400 m showed the strongest effect, demonstrating a significant spatial scale effect. Different invasive plant species showed the scale effects of landscape matrix composition and configuration. At all scales, Xanthium strumarium and Bidens frondosa showed weak correlations with landscape indices, but Bidens tripartita and Erigeron canadensis showed strong correlations. Landscape matrix was closely related to invasive plant species, and demonstrated a significant scale effect. The alien invasive plant species could be traced to the landscape matrix at large scales. Grassland and forest patches at the small scales could be used as the 'stepping stone' for the alien species transiting before they arrived at the WLFZ. In order to control alien plants in the WLFZ, land-use management and optimization should be strengthened at different scales of landscape matrix on the basis of enhancement of habitat management. A diversified comprehensive control for alien species should thus be taken into account.

Invasive alien plant species have been identified as a major threat to biodiversity and the relationship with native avian dispersers may increase their invasion potential. The impact of invasive plant species needs to be quantified using comparable assessment tools across different habitats and species to allocate limited resources to high-priority species. Here, we used the Generic Impact Scoring System (GISS) to assess the impacts of 16 fleshy-fruited alien invasive plant species in South Africa generally dispersed by native avian species. The results showed that fleshy-fruited invasive species have both environmental and socio-economic impacts. The cumulated impact scores for lantana (Lantana camara) and the tree of heaven (Ailanthus altissima) were the highest, with scores of 42 and 32, respectively. Some species, such as white mulberry (Morus alba), camphor tree (Cinnamomum camphora), American bramble (Rubus cuneifolius) and Brazilian pepper tree (Schinus terebinthifolius), had low overall impact scores of 8, 18, 14 and 16, respectively, but scored the maximum impact of 5 for certain mechanisms. Environmental impacts of fleshy-fruited invasive plant species had a high impact magnitude through effects on the ecosystem and vegetation. Socio-economic impacts were mainly through effects on forest production, agriculture and human health. Species with large crop sizes, small seeds and fruit sizes had higher environmental and socio-economic impact magnitude. The information generated in this study is important for guiding resource allocation and preventing the uncontrolled introduction of invasive species in South Africa. The impact of the fleshy-fruited invasive species transcended sectors and, therefore, effective management of invasive species will require the collaboration of multiple and inter-sectoral stakeholders in South Africa.

Invasion of alien plant species can have irreversible effects on ecosystems. Although alien plants often distribute in disturbed area, understanding of the initial invasion process soon after disturbance is poor. We compared forest floor vegetation between thinning treatment plots and intact control plots in a red pine (Pinus densiflora) forest in central Japan to test whether the thinning treatment (i.e. disturbance) induced invasion of alien plants. We also examined how invasion of aliens is influenced by the environment, plant traits, and buried seeds in the soil. In control plots, few alien plants emerged at the herbaceous layer and only a few buried seeds of alien plants were found. In treatment plots, on the other hand, many alien plants were observed both at the herbaceous layer and in the soil seed bank. Treatment plots had a larger percentage of canopy openness than control plots. In treatment plots, the cover of alien plants was negatively correlated with the distance from the nearest primary road. Alien plants had taller maximum plant height, larger leaves, and greater leaf nitrogen concentration than native species in treatment plots. This indicates that alien plants were superior to native plants in growth, competition, and carbon assimilation abilities. Alien plants tended to have seeds with long dispersal abilities, such as anemochory and zoochory, and short life histories, such as annual and biennial histories. These findings suggest that thinning promoted invasion of alien plants and that alien plants had the potential for further invasion by rapid dispersion, establishment, and growth.

Insights into ecological drivers of alien plant invasions can be gained through comparative studies of growth and fecundity of invasive alien plants versus those of co‐occurring non‐invasive alien plants and native plants across environmental conditions in common garden settings. Habitats that harbour alien plant species in many ecosystems globally are presently experiencing light pollution resulting from artificial light at night (ALAN) and increased rates of nutrient enrichment of the soil. However, the potential interactive effects of ALAN and nutrient enrichment on invasiveness of alien plant species remain unknown. Here, we performed a common‐garden experiment to test the interactive effects of ALAN and soil nutrient enrichment on the growth of a random set of ten alien (five invasive and five non‐invasive naturalized) and seven co‐occurring native ornamental plant species that are commonly cultivated within urban and peri‐urban areas of Nairobi city in Kenya. We predicted that a simultaneous increase in photoperiod via ALAN and nutrient enrichment will favour growth of invasive alien plant species over that of non‐invasive alien and native plant species. We grew the 17 plant species under natural daylight (ALAN−) versus natural daylight followed by ALAN (ALAN+) and fully crossed with two levels of nutrient enrichment (low vs. high) and competition (competition vs. no‐competition against a native plant Ocimum gratissimum ) treatments. Under simultaneous high‐nutrient and no‐competition treatments, ALAN enhanced mean total biomass of invasive and non‐invasive naturalized alien species by 61.1% and 131.4%, respectively but decreased that of native plant species by 34%. In contrast, under simultaneous high‐nutrient and competition treatments, ALAN enhanced mean total biomass of invasive alien plant species by 68.6% and that of non‐invasive naturalized alien species by 51.9% and native species by 35.4%. High‐nutrient treatment enhanced flower formation more strongly in invasive and non‐invasive naturalized alien plants than in native plants. The invasive and non‐invasive naturalized alien species grew taller than native species across the light, nutrient, and competition treatments. Synthesis : The present findings suggest that light pollution and nutrient enrichment may jointly confer growth advantage to invasive alien plant species over that of co‐occurring native plant species and enhance invasiveness of alien plant species.

Indonesia has tremendous biodiversity, and one of its species is invasive alien plants that invade other ecosystems. Invasive species have various characteristics, usually dominate new ecosystems, and are difficult to control. Invasion of alien species occurs in forest ecosystems, aquatic ecosystems, coastal ecosystems, oceans, and rice fields, but usually in changed ecosystems. This study aims to record the spread of invasive alien plant species, influencing variables, effects, and successful control strategies in Indonesian ecosystems. The methodology used was a systematic literature review (SLR), which included preparation, execution, and reporting. This study found 13 families and 23 species. The Compositae, Fabaceae, and Asteraceae families were the most abundant known ecosystems. The forest is the ecosystem most dominated by invasive alien plants. Several factors cause the environment to be damaged, which affects the ecosystem, and the ingredients used for medicine, house construction, and food. Efforts to control invasive alien plant species through invasive plant risk assessment, eradication, ecosystem restoration, and awareness of invasive plant species and their dangers to the surrounding community. Future research is to conduct appropriate conservation for ecosystems damaged by invasive alien plants.

Due to the relevance of protected areas to the conservation of native biota, the magnitude of invasions and threats posed by alien plants are currently important issues for the preservation of these areas. The paper summarises data on invasive alien plant species presence in the most valuable protected areas in Poland, i.e. national parks (NPs). We investigated the distribution of invasive alien plant species and management attempts concerning those species. We analysed data obtained from 23 national parks originating from published and unpublished sources. Invasive plants were present in all protected areas analysed, from two to 42 species in a particular national park, and 68 in total. The most widely distributed species were: Impatiens parviflora (present in 19 NPs), I. glandulifera (17), Solidago gigantea (17), Reynoutria japonica (17), and Robinia pseudoacacia (16). The conducted analyses showed that the number of invasive species decreased with the higher altitude (asl) of the national park. The most often managed species were Impatiens glandulifera (being removed in seven NPs), I. parviflora (six), Padus serotina (four) and Quercus rubra (four). In the majority of NPs, control activities are limited to small areas and singular species, thus having an incidental character. Only in five objects (Białowieża NP, Biebrza NP, Kampinos NP, Tuchola NP, Wigry NP), management has been focused on several species. We conclude that a lack of comprehensive management of invasive plant species in the majority of national parks currently limits the effectiveness of IAS (invasive alien species) eradication. Exchange of expertise among protected areas, documenting best practice examples, synthesising lessons learnt in IAS management, as well as the development of minimum standards for invasive plants surveillance and management are pivotal.

Habitat degradation due to invasive plant species is identified as one of themajor threats in several protected areas managed by Department of WildlifeConservation in Sri Lanka. Bundala National Park, covering an area of 6216ha is located about 250 km Southeast of Colombo (06°08' - 06°14' N, 81°08'- 81°18'). The Bundala National Park is Sri Lanka's first Wetland ofInternational importance declared under the Ramsar Convention. The parkconsists of mainly dry thorny scrubland and lagoons, which are shallowbrackish water lagoons. They harbours a rich bird life including severalspecies of migratory waterfowls. It also contains key nesting sites for fivespecies of marine turtles. Arid and semiarid terrestrial habitats shelter a widerange of species, including elephants and other mammals, reptiles,amphibians and fish species. The introduced Prosopis julifolia, a tree speciesnative to Central and South America as a fuel wood in home gardens by theForest Department has expanded its distribution and has invaded the BundalaNational Park. There are large stands of Prosopis julifolia that prevents thegrowth of other indigenous species. Furthermore it invades the lagoon and asa result the area covered by the lagoon is also being reduced. Opuntia strictavar. dillenii, which is also a plant native to Central America, is used mainlyas a hedge species around human dwellings and from there it may haveinvaded wetland habitats in Bundala National Park. The spread of these invasive alien plant species has resulted in theprogressive deterioration of wildlife habitats and native biodiversity in thepark, and hence warranting immediate management to curtail their spread.The general methodology adopted for the invasive plant managementprogramme in Sri Lanka is based on adaptive management techniques.Adaptive management is a process that involves planning, management andmonitoring to provide a framework for testing assumptions, adaptation andlearning. Invasive species were eradicated manually and mechanically. Lackof a planned systematic research programme to compile field observations inareas subjected to invasive plant management is a major constraint. Inaddition, views of non-scientific public and lack of funds for adaptivemanagement techniques are the major constraints

Avian frugivores play a key role in seed dispersal of many plant species, including invasive alien plants. We assessed the effect of gut passage on the germination of selected invasive alien plant species in South Africa. Fruits of four fleshly-fruited invasive alien plant species: Solanum mauritianum, Cinnamomum camphora, Psidium guajava, and Morus alba, were fed to two species of indigenous turacos, Knysna (Tauraco corythaix) and purple-crested (Gallirex porphyreolophus) turacos, and to invasive rose-ringed parakeets (Psittacula krameri). Seed retention time was determined as this can influence both seed dispersal and germination success. Germination success of ingested seeds was compared with that of manually de-pulped seeds, as well as to seeds in whole fruit. The germination success of seeds of all the invasive plant species increased significantly after ingestion by both turaco species compared with seeds from whole fruits. Germination success of manually de-pulped seeds did not differ significantly from that of turaco ingested seeds. In contrast, seed passage through the digestive tract of rose-ringed parakeets significantly reduced germination success and viability of ingested invasive plant species. Our results suggest that Knysna and purple-crested turacos are legitimate seed dispersers of fleshy-fruited invasive plants, while rose-ringed parakeets are mainly seed predators. Although seed predation by rose-ringed parakeets negatively affects the reproductive success of these plants, it is unlikely that this will suppress the spread of these invasive alien plants in South Africa as they are already well established. Furthermore, they can facilitate dispersal by seed regurgitation and dropping uneaten fruits away from the parent plant. Similar trends could be expected for indigenous seeds that rose-ringed parakeets feed on and therefore these birds remain a negative influence within invaded ecosystems.

Abstract. Huda MK, Pasaribu N, Syamsuardi, Siregar ES. 2022. Diversity, risk and management feasibility of invasive alien plants in the border zone of Sicike-cike Nature Tourism Park, North Sumatra, Indonesia. Biodiversitas 23: 3156-3165. Invasive alien species (IAS) threaten native ecosystems and biota either directly or indirectly. Once colonizing, invasive plant species tend to dominate a landscape, hindering other native vegetation from growing. Thus, the invasion of alien plant species needs attention moreover in protected areas such as Nature Tourism Park (Taman Wisata Alam/TWA) Sicike-cike, Dairi District, North Sumatra, Indonesia. Besides its importance for nature conservation, TWA Sicike-cike is culturally essential for Pakpak Dairi ethnic community as well as economically for ecotourism. Yet, anecdotal evidence showed the presence of several invasive alien plants around the park. This study aimed to investigate the diversity and composition of invasive alien plants within the vegetation community in TWA Sicike-cike and to assess the risk value and management feasibility of the IAS. Purposive sampling using line transect method was conducted to collect data with a total of 120 observation plots established along 6 transects. Risk value was assessed based on invasiveness, impact and potential distribution. Management feasibility was assessed based on cost, current distribution and persistence. The results showed that Asteraceae was the most dominant family of invasive plants in the studied area with four species. At the species level, Imperata cylindrica was invasive alien plant species with the highest important value index (IVI) of 57.65% and a high-risk value of 235.8, followed by other species including Ageratum conyzoides, Chromolaena odorata, Clidemia hirta and Melastoma malabathricum. In terms of management feasibility, the existence of I. cylindrica is recommended for direct eradication, while other IAS management recommendations, included monitoring and area protection for further invasion by the species.