Invasive Plant Research Articles

Organic Waste from the Management of the Invasive Oxalis pes-caprae as a Source of Nutrients for Small Horticultural Crops.

The management of invasive plants is a challenge when using traditional control methods, which are ineffective for large areas, leading to the abandonment of invaded areas and the subsequent worsening of the situation. Finding potential uses for waste resulting from invaders' management could motivate their control in the long-term, concurrently providing new bio-based resources with different applications. Oxalis pes-caprae is an invasive plant, widely distributed worldwide, which spreads aggressively through bulbils, creating a dense ground cover. This study was designed to assess the potential of Oxalis aboveground waste for use as fertilizer and in ameliorating deficit irrigation effects in growing crops. Diplotaxis tenuifolia (wild rocket) seedlings were planted in pots with soil mixed with Oxalis waste at 0, 2.2 and 4.3 kg m-2 or with commercial fertilizer, left to grow for 27 days and then irrigated at 100% or 50% field capacity for 14 days. The incorporation of the Oxalis waste improved the biomass, photosynthesis, sugars, total phenols and total antioxidant capacity in the crop, achieving commercial fertilization values, as well as increasing the phosphorus in soils. However, Oxalis waste seems not to directly affect plants' relative water contents. Our results support the use of Oxalis waste as fertilizer, which can encourage the long-term control of this invasive species.

The influence of environment on invasive Carpobrotus sp. populations across genetic clusters

The study aims to explore the natural variation in the metabolome of different populations of the invasive plant Carpobrotus from different genetic clusters and geographical origins to enhance our comprehension of its involvement in the adaptation process and phenotypic diversity. The metabolomic profile of shoots was analysed in four populations from two different genetic clusters (Cluster A: Cádiz and A Lanzada; Cluster B: La Marina and Samil) and two different biogeographical regions in Spain (Atlantic: Samil and A Lanzada; Mediterranean: Cádiz and La Marina), collected in the field and subsequently grown in the greenhouse. In addition, climatic, and physiological parameters were analysed. The Mediterranean populations (Cádiz and La Marina) showed lower initial weight and length measurements in morphological parameters than the Atlantic populations. On the contrary, only root parameters showed significant differences in growth parameters among populations. The analysis of ion levels revealed a consistent pattern of higher concentrations in shoots compared to roots, with significant differences among populations, particularly in sodium (Na+) and chlorides (Cl−) levels. Regarding metabolomic analysis, clear correlations between the metabolome, genetic and climatic conditions of Carpobrotus sp.pl populations are described. Pairwise comparisons using t-tests and Principal Component Analysis (PCA) indicated that the differences in metabolomic profile between the Samil and La Marina populations, which correspond to the same genetic cluster (cluster B), were smaller than in the rest of the comparisons indicating that populations from the same genetic cluster were more similar metabolically than those from the same climatic region. The study identified key metabolites representative of each cluster, with significant differences in amino acids, organic acids, and sugars contributing to the variation among populations. Pathway analysis highlighted the impact of climatic conditions on metabolic pathways, particularly in populations from Cluster A. In conclusion, the different populations were more similar according to the genetic cluster than to the climatic region of origin when studied at the metabolomic level. Consequently, the metabolites more representative of each cluster were also identified.

Differential effects of leaf litter and rhizosphere soil microbes on competition between invasive and native plants

Invasive plants commonly compete with native plants in the introduced range; however, how leaf litter and rhizosphere soil microbes influence the competition between invasive and native plants with varying microbial sources and seedling densities remains to be characterized. In this study, the invasive plant Ageratina adenophora (Asteraceae) and two cooccurring native plant species, Senecio scandens (Asteraceae) and Achyranthes bidentata (Amaranthaceae), were used as experimental plants to test their impacts in a greenhouse. We observed that leaf litter and rhizosphere soil microbes negatively or neutrally impacted invasive or native plant growth when competing. However, microbes enhanced the competitive dominance of A. adenophora over S. scandens but weakened its competitiveness over A. bidentata. Leaf litter microbes were more beneficial for A. adenophora growth and thus made it more competitive than rhizosphere soil microbes when competing with S. scandens. Regardless of the presence or absence of microbes, conspecific inoculation was better for A. adenophora growth and thus enhanced competition dominance more than heterospecific inoculation when competing with A. bidentata. A high seedling density was more beneficial for A. adenophora competition dominance than a low density was when A. adenophora was competing with S. scandens. Nonetheless, the relative competitiveness of A. adenophora was greater than that of the two native species; in particular, A. adenophora had stronger competitive dominance over A. bidentata than over S. scandens. Our data confirmed that the important role of leaf litter microbes in the competition between invasive and native plants cannot be ignored.

Native root hemiparasites form haustorial attachments with multiple invasive and expansive species

Parasitic plants are known for shaping plant communities, mainly by suppressing dominant species. This suppression, in some cases, fosters species coexistence and boosts overall diversity. Recent studies reveal that certain parasitic plants can curb invasive alien plants or expansive native species. In this study, we followed previous case studies, investigating the ability of three common Central European hemiparasitic species to attach to roots and form functional haustoria across a broad range of invasive and expansive hosts. For each host-hemiparasite pair, we posed two questions: (i) Do the hemiparasites produce haustoria on the host's roots or rhizomes? (ii) Does the anatomical structure of the haustoria include all features necessary for their functionality? We cultivated three hemiparasitic species, Melampyrum arvense L., Rhinanthus alectorolophus (Scop.) Pollich, and Odontites vernus subsp. serotinus (Dumort.) Corb., in pots with 18 candidate hosts. After cultivation, we dissected the root systems to determine haustoria abundance and to collect them for anatomical study to assess their functionality. Hemiparasite individuals in each pot were also counted. The hemiparasitic species produced haustoria on the majority of tested hosts (37 out of 44 combinations), with little difference between native expansive and alien invasive plant species. In 13 host-hemiparasite combinations (including eight combinations with invasive species), we identified abundant functional haustoria and good establishment of the hemiparasites. Remarkably, all three hemiparasitic species formed functional haustoria on invasive Asteraceae hosts. By contrast, Melampyrum arvense performed poorly when cultivated with grasses. We identified a series of hemiparasite-host combinations, which should be further tested for the potential hemiparasite effect on host fitness in the field. The abundance and anatomical structure of the haustoria indicates that the recognised low specificity of the hemiparasitic interactions applies also to associations with alien invasive species, with which they do not share a common evolutionary history.

Community-level impacts of plant invasion in tropical forests of Northeast India

Community-level impacts of plant invasion in tropical forests of Northeast India

Revealing the long-term impacts of plant invasion and reclamation on native saltmarsh vegetation in the Yangtze River estuary using multi-source time series remote sensing data

Understanding the long-term dynamics of saltmarsh vegetation and their driving factors is crucial for the restoration of degraded coastal wetlands. Reclamation and plant invasion, identified as the two most significant environmental contributors to saltmarsh vegetation degradation, profoundly influence the evolution of saltmarsh vegetation. However, the long-term impacts of reclamation and plant invasion on native saltmarsh vegetation remain unclear. This study utilized multi-source time series remote sensing data to quantify the long-term impacts of Spartina alterniflora invasion and reclamation on native saltmarsh vegetation in the Yangtze River estuary from 1985 to 2020. Unlike other studies, this study generated annual saltmarsh cover data using image composite, zoning classification, object-based phenology algorithm, and random forest algorithm, which largely addressed the problem that existing studies could not capture transient change and gradual change because of insufficient observation frequency. Results showed that: (1) Reclamation had resulted in a loss of 503.93 km2 of native saltmarsh vegetation from 1985 to 2020, including 286.16 km2 of Phragmites australis community and 217.77 km2 of Scirpus spp. community; Spartina alterniflora invasion had resulted in a loss of 78.96 km2 of native saltmarsh vegetation from 1985 to 2020, including 12.48 km2 of Phragmites australis community and 66.48 km2 of Scirpus spp. community; (2) Significant differences of spatial-temporal evolution patterns of native saltmarsh vegetation were observed under different degrees of Spartina alterniflora invasion and reclamation, including irrecoverable scenario under severe plant invasion and excessive reclamation, recoverable scenario under moderate degree of reclamation and plant invasion, and competitive scenario under plant invasion and without reclamation.; (3) From a long-term remote sensing perspective, spread limitation determined by reclamation intensity was a decisive factor in the evolution of Phragmites australis community in the study area, while interspecific competition between invasive Spartina alterniflora and Scirpus spp. determined the evolution of Scirpus spp. community. This study provides a theoretical basis and baseline for the protection strategies of native saltmarsh vegetation in the study area.

Capacity and capability of remote sensing to inform invasive plant species management in the Pacific Islands region.

The Pacific Islands region is home to several of the world's biodiversity hotspots, yet its unique flora and fauna are under threat because of biological invasions. These invasions are likely to proliferate as human activity increases and large-scale natural disturbances unfold, exacerbated by climate change. Remote sensing data and techniques provide a feasible method to map and monitor invasive plant species and inform invasive plant species management across the Pacific Islands region. We used case studies taken from literature retrieved from Google Scholar, 3 regional agencies' digital libraries, and 2 online catalogs on invasive plant species management to examine the uptake and challenges faced in the implementation of remote sensing technology in the Pacific region. We synthesized remote sensing techniques and outlined their potential to detect and map invasive plant species based on species phenology, structural characteristics, and image texture algorithms. The application of remote sensing methods to detect invasive plant species was heavily reliant on species ecology, extent of invasion, and available geospatial and remotely sensed image data. However, current mechanisms that support invasive plant species management, including policy frameworks and geospatial data infrastructure, operated in isolation, leading to duplication of efforts and creating unsustainable solutions for the region. For remote sensing to support invasive plant species management in the region, key stakeholders including conservation managers, researchers, and practitioners; funding agencies; and regional organizations must invest, where possible, in the broader geospatial and environmental sector, integrate, and streamline policies and improve capacity and technology access.

Rapid morphological change in UK populations of Impatiens glandulifera

The highly invasive Impatiens glandulifera (Himalayan balsam) is one of the most prolific and widespread invasive plants in the British Isles. Introduced in the early nineteenth century, it has now been reported in almost every vice county across the UK and is a fierce competitor that has adverse effects on the local community structure. Despite the negative impacts that invaders like I. glandulifera have on local communities, there have been very few studies which address the morphological changes that invasive plant populations have undergone since their initial introduction. This is the first study of its kind to investigate the morphological changes that have occurred in I. glandulifera. 315 herbarium specimens dating from 1865 to 2017 were used to measure changes in morphological traits such as leaf size, flower length and stomatal characteristics. We found that since 1865, there has been a significant reduction in overall leaf size, a significant reduction in stomatal density and a significant increase in the overall flower length. These results highlight the importance of monitoring the evolutionary change in prolific alien species over the course of their invasion, providing useful insights into changes in competitive ability which may prove useful in managing dispersal and providing options for potential management.

Anthropogenic disturbance has altered the habitat of two Azorean endemic coastal plants

BackgroundAnthropogenic threats are causing alteration of coastal areas worldwide. Most of the coastal biodiversity is endangered, taking a particular toll on island ecosystems, like the Azores. To better understand the biotic and abiotic factors constraining the distribution and conservation status of two endemic plants, Azorina vidalii (Campanulaceae) and Lotus azoricus (Fabaceae), we performed a global survey of coastal plant communities in the archipelago, also covering environmental descriptors, natural and anthropogenic threats. Moreover, we revised their IUCN conservation status and estimated the population fractions within protected areas.ResultsNon-indigenous plants were commonly found in plots with or without the target endemics, contributing to the absence of well-defined coastal plant communities. Nonetheless, indigenous taxa commonly occurred at the plots with L. azoricus. With a larger area of occurrence, A. vidalii ecological niche differed from that of L. azoricus, the latter being restricted to dry and rocky sea cliffs, mostly in Santa Maria Island. Besides the presence of invasive plants, signs of habitat destruction, trampling and grazing, and of natural threats, such as coastal erosion, were commonly observed.ConclusionsOccurrence data indicated an endangered status for both species, although this would change to critically endangered for L. azoricus when using smaller-sized occurrence cells. Both species are threatened since their habitat is restricted to a very narrow vegetation belt, strongly limited by sea influence and human pressure, and with the frequent presence of invasive plants. While focusing on two endemic plants, our study allowed a broader view of the impact of anthropogenic disturbance on Azorean coastal plant communities.

Senecio inaequidens DC. will thrive in future climate: A case study in a Mediterranean biodiversity hotspot

Monitoring the expansion of invasive non-native plants under current and future climatic conditions is crucial for understanding biodiversity threats, addressing the ecological impact, and developing effective management strategies. This study focuses on modelling the expansion and distribution of Senecio inaequidens DC. on the island of Sardinia (Italy) to address these environmental challenges. The objectives were to identify bio-climatically suitable areas under current conditions, project potential future distribution, and evaluate invasion dynamics on the island to localize suitable areas for effective management strategies.Species data were collected from 1991 to the present, supplemented by global databases and analyzed using an ensemble species distribution model approach. This approach utilized presence data, high-resolution current bioclimatic variables (40 m2), developed explicitly for our study area, and two future scenarios derived from the newly Coupled Model Intercomparison Project Phase 6 (CMIP6) under Shared Socio-economic Pathways (SSP2–4.5 and SSP5–8.5 for 2040 and 2060).The ensemble model's findings suggest a close alignment between the currently documented occurrences of S. inaequidens and its bio-climatically suitable habitats in Sardinia. Moreover, predictions indicate high bioclimatic suitability for S. inaequidens in the western and southwestern coastal regions, contrasting with its known occurrences at higher altitudes. Notably, the model also forecasts high bio-climatic suitability across most small islands surrounding the region and in central-east Sardinia, potentially indicating habitats at lower altitudes compared to current records.Under the SSP2–4.5 scenario, suitable areas are expected to nearly double by 2040 and more than double by 2060, compared to current conditions. Under the SSP5–8.5 scenario, the increase in suitable habitats is projected to be about 83.31% by 2040 and more than double by 2060. These results highlight the species' ability to thrive under climate change, with a more pronounced range expansion under the pessimistic management regime (SSP5–8.5) than under the intermediate one (SSP2–4.5), particularly in the central region of the island. This expansion under the more severe management scenario is particularly alarming as it reflects limited implementation of environmental management policies.The study underscores the potential ecological risk posed by S. inaequidens due to its potential range expansion and ability to invade different habitat types, from coastal regions to mountainous areas, under current and future scenarios. Based on these findings, we propose targeted management actions for monitoring and eradicating the species, leveraging prior information and local experiences to mitigate its impact.

Agitated and temporary immersion bioreactor cultures of Reynoutria japonica Houtt. as a rich source of phenolic compounds

Reynoutria japonica Houtt. (Japanese knotweed) is an invasive plant belonging to the Polygonaceae family. However, being native to East Asia, it has been used in natural medicine for ages because of its broad range of biological activity. Although R. japonica is known as a rich source of phenolic compounds, plant biomass collected from the field may be contaminated with toxic elements like heavy metals, and the level of metabolite accumulation depends on environmental conditions. Therefore, the aim of this study was to derive Japanese knotweed tissue cultures and investigate biomass production and phenolic compound synthesis in in vitro conditions. Plants were cultivated in a traditional agar-solidified medium, in a liquid medium with rotary shaking (agitated culture), and in a temporary immersion bioreactors Plantform™, as well as in soil (ex vitro conditions). Analyses of the growth index and dry weight accumulation were performed on the collected material. In the extracts obtained from examined plants, qualitative and quantitative analysis of phenolic derivatives using DAD-HPLC was conducted to determine the sum of phenolic compounds, as well as the quantity of selected phenolic acids, catechins, and other flavonoids. Results have shown that agitated cultures and temporary immersion bioreactors increased biomass accumulation compared to solid medium cultures. Tissue cultures of R. japonica had increased synthesis of phenolic compounds compared to plants from ex vitro conditions. Shoots and roots from agitated cultures were 2.8- and 3.3-fold richer in catechins, respectively, compared to plants cultivated in soil. Based on the obtained results it can be concluded that agitated and bioreactor cultures are the best source of Japanese knotweed biomass rich in valuable secondary metabolites.

In situ allelopathic expression by the invasive amphibious plant, Ludwigia hexapetala (water primrose) across habitat types, seasons, and salinities

In situ allelopathic expression by the invasive amphibious plant, Ludwigia hexapetala (water primrose) across habitat types, seasons, and salinities

Invasive alien plants in the Qinghai-Tibetan Plateau (China): Current state and future predictions

Invasive alien plants have received increasing attention due to their worldwide environmental impacts, ecological concerns, and significant economic consequences. The Qinghai-Tibetan Plateau is an important global biodiversity hotspot hosting rich biodiversity and serving as a crucial component of the southwest ecological security barrier, with global conservation value. However, in recent years, invasive plants have been detrimental to the conservation of biodiversity and native ecosystems on the Qinghai-Tibetan Plateau. Here, 197 invasive plant species were recognized from the Qinghai-Tibetan Plateau, encompassing 133 genera across 47 families. We used the maximum entropy model (MaxEnt) method to predict the potential distribution of invasive alien plants on the Qinghai-Tibetan Plateau. Furthermore, potential geographic distribution regions suitable for 43 invasive alien plant species were found to be primarily concentrated in central and eastern Qinghai, southern and eastern Tibet, southwest Xinjiang, and the Qinghai-Tibetan Plateau part of Sichuan, Yunnan, and Gansu in China. Notably, the current potential distribution area for all 43 invasive alien plant species accounts for 29.92 % of the total area, with an increase of 32.72–59.39 % projected by 2050. Moreover, risk screening results confirm the high risk of invasion of most alien plants on the Qinghai-Tibetan Plateau. This study provides a foundation for assessing the risks associated with introducing and managing invasive alien plants in the region. It also offers scientific support for conserving the Qinghai-Tibetan Plateau’s unique biodiversity, ecological originality, and sustainable development during economic growth.

Biomass of invasive plants as a resource for the development of the bioeconomy

The global spread of invasive plants is an important environmental problem and a real threat to biological diversity, with significant impacts on agriculture, forestry, and human and animal health. Invasive plant eradication produces large amounts of plant biomass, which should be safely utilized. The study reviews possibilities for using biomass of invasive plant species in the bioeconomy to safely convert them to items of value. Invasive plant biomass can be used as fuel or for energy production applying either biochemical or thermochemical processing technologies. The biomass of invasive plants also can be used for energy production or isolation of biologically active components. Invasive plants contain many groups of substances providing their defense potential against predators; these substances participate in metabolic regulation processes and others. Amongst the substances of interest for bioeconomy are lipids, polyphenols, alkaloids, carbohydrates, plant fibers, and essential oils. In the development of invasive plant biomass utilization strategies, the bio-based value pyramid and the waste hierarchy should be considered. Scientific sound strategies of invasive plant management will limit their spread and provide economic benefits via their eradication.

High Impacts of Invasive Weed Lantana camara on Plant Community and Soil Physico-Chemical Properties across Habitat Types in Central Nepal

Although the effects of invasive alien plants on natural ecosystems are well known, the effects of specific plant species can vary across habitat types and disturbance intensity. This study was carried out to analyze the effects of Lantana camara on associated vegetation and soil physico-chemical properties at invaded and non-invaded sites across three different habitat types (forest edge, fallow land, and roadside) in central Nepal. We sampled 50 pairs of 5 m × 5 m (for shrub species) and 1 m × 1 m (for herbs species) plots at invaded and non-invaded sites in each habitat and recorded community variables for each species within the sampling plots for both wet (monsoon) and dry (pre-monsoon) seasons. Further, we collected soil samples from each quadrat and determined the soil physico-chemical properties. We recorded 137 species of flowering plants (119 from non-invaded and 97 from invaded plots) and classified them in accordance with life form/habit. In invaded sites, we found a significant decline in species diversity as indicated by the Simpson and Shannon diversity indices. Specifically, L. camara reduced the species richness, Simpson index, and Shannon diversity index by 36.84%, 11.84%, and 40.21%, respectively. Soil nutrients such as total nitrogen, soil organic carbon, and available phosphorus were significantly higher in invaded sites than non-invaded ones except for available potassium and soil pH. This study provided evidence that Lantana L. camara has a substantial impact on the understory plant community assemblage and the physico-chemical properties of soil. The results suggest that the protection of native plant community requires management of L. camara by implementing appropriate measures.

Impact of invasive plants on vegetation in protected areas of Nepal

Impact of invasive plants on vegetation in protected areas of Nepal

The Invasive Plant Amaranthus spinosus L. Exhibits a Stronger Resistance to Drought than the Native Plant A. tricolor L. under Co-Cultivation Conditions When Treated with Light Drought.

Drought may facilitate the invasion process of invasive plants, mainly because invasive plants can obtain a stronger growth competitiveness than native plants under drought. It is therefore imperative to illuminate the mechanisms underlying the successful invasion of invasive plants under drought, with a particular focus on the differences in the resistance of invasive and native plants to drought. This study aimed to elucidate the differences in the resistance between the invasive plant Amaranthus spinosus L. and the native plant A. tricolor L. to drought under a gradient of drought. The resistance of co-cultivated A. spinosus to drought was significantly higher than that of co-cultivated A. tricolor under light drought. Hence, A. spinosus may obtain a stronger competitive advantage than A. spinosus under co-cultivation conditions when treated with light drought. The resistance of the two plants to drought may be predominantly influenced by their height and biomass. This present study also defines a method for evaluating the stress resistance of a given plant species to stress by calculating the stress resistance index. This present study offers a robust theoretical foundation for determining the stress resistance of a given plant species and the environmental management of A. spinosus under drought.

Synthetic Gene Drives in Plants: Development Strategies, Potential Applications, and Ethical Considerations

ABSTRACTWe are facing significant agricultural and environmental challenges, including herbicide‐resistant weeds that compromise crop yields and invasive plant species that disrupt local ecosystems. Traditional crop breeding methods are increasingly seen as ineffective in the face of these issues. One innovative approach involves the use of gene drives, a technology that enables targeted genetic modifications to transmit at a super Mendelian rate (>50%) and therefore, rapidly propagate through natural populations. In this perspective, we introduce the principles underlying our development of a plant synthetic toxin‐antidote drive, CAIN (CRISPR‐Assisted Inheritance utilising NPG1). We evaluate the potential of gene drives to alter the genetics of weed populations or suppress invasive plant populations. We explore various factors that influence the effectiveness of gene drives, including the emergence of suppressor mutations and life‐history traits such as sexual and asexual reproduction patterns, seed and pollen dispersal methods, and the variability in plant generation times. Additionally, we discuss the biosafety concerns related to gene drive experiments and field releases, strategies to counteract unwanted gene drives, and the ethical implications, particularly considering the risk of the intentional misuse of gene drive technology and the need for robust regulatory and monitoring frameworks.

Effects of kinship and integration between adjacent/non-adjacent ramets on the growth and feedback with soil biota in a clonal invader.

Many invasive plants can reproduce through both seeds and clonal growth. In habitats, interacting seedlings may originate from the same mother, and interacting ramets originating from the same plant may not be adjacent to each other in the stolon, particularly for vines that can show curved growth. However, in a homogeneous environment, how kinship and integration between adjacent/non-adjacent ramets affect plant growth and feedback with soil biota has been less studied. We address these questions using an invasive stoloniferous vine Mikania micrantha. We found that sibling groups and stranger groups did not differ in biomass production, root allocation and feedback with soil biota, indicating that kin recognition is unlikely in M. micrantha. For two-ramet stolon fragments in which interacting ramets were adjacent to each other, older ramets allocated more biomass to roots than younger ramets when integrated, particularly in comparison with disconnected ramets from different genotypes, indicating that a division of labor was induced. For four-ramet stolon fragments in which there were two unrooted ramets between the two rooted, interacting ramets, integration increased biomass allocation to roots, possibly because only two of the four ramets could absorb belowground resources and a lower shoot allocation decreased aboveground light competition. When inoculated with soil biota conditioned by the four-ramet integrated fragments, plants of M. micrantha also increased biomass allocation to roots. These results indicate that the distance between interacting ramets in the stolon may affect the integration effect and feedback with soil biota in clonal plants.

Changes in decomposition dynamics, soil community function and the growth of native seedlings under the leaf litter of two invasive plants

Changes in decomposition dynamics, soil community function and the growth of native seedlings under the leaf litter of two invasive plants