Invasive Alien Plant Species Research Articles

Impact of invasive alien plants on the resident floral diversity in Koshi Tappu Wildlife Reserve, Nepal.

Invasive alien plant species (IAPS) pose a serious threat to overall plant biodiversity across the globe. Nepal's national parks and protected areas are not devoid of the impact of IAPS. Unfortunately, there is a substantial gap in knowledge regarding the extent and impact of invasion in protected areas of Nepal. This study assessed the impact of invasive alien plant species on the resident plant species of the Koshi Tapu wildlife reserve. After a preliminary field observation, we selected five major IAPS in the area, Mesosphaerum suaveolens, Chromolaena odorata, Ipomoea carnea, Lantana camara, and Mikania micrantha for this study. Ten pairs of adjacent plots sized 4 m × 4 m were surveyed for each invasive species, comprising diverse vegetation types. Each pair consisted of one "invaded plot" where the invasive species was dominant with cover greater than 50%, and another "uninvaded plot" laid out in an adjacent area with similar site conditions but without the invasive species. We calculated the Sørensen Index of Similarity for each paired plot. Wilcoxon rank-sum test was employed to compare ecological parameters between invaded and uninvaded plots for various plant species. Similarly, the difference in impact between each of the five invasive species was assessed using the Kruskal-Wallis test. Species richness varied significantly between invaded and uninvaded plots for C. odorata and I. carnea. The most significant impact on species composition of invaded communities (39.6%) was observed for C. odorata. The cover of the other dominant species varied significantly between invaded and uninvaded plots for all five species studied. The Kruskal-Wallis test showed no significant difference in the impact caused by the five studied invasive species on Species richness, Shannon-Wiener diversity index, species evenness, and height of dominant species. However, a significant difference was observed between the impacts of five studied invasive species and the cover of other dominant species. The crown cover of dominant species decreased much more in the invaded plots of L. camara and M. micrantha than in other species. Specialized management efforts are required to control highly invasive species, such as C. odorata and I. carnea, alongside proactive measures to prevent further spread in ecologically sensitive areas.

Associations between Lantana camara L. (Verbenaceae) and common native species in an African savanna

Abstract Lantana camara L. (Verbenaceae) is recognised as a problematic invasive alien plant species in many parts of the world. To eradicate or control this global invader, we need to understand the drivers of its spread and impacts and the potential for native recovery after the invader has been removed. Here, we tested for species associations between L. camara and native plant species and large herbivores in Queen Elizabeth National Park, Uganda. We inventoried 40,100‐m2 nested plots spread over a 1 × 1‐km grid cell in the park's savanna landscape, with 11 plots located in uninvaded areas. Most of the plots (30 of 40) had been affected by fire. Lantana camara covered 29 (73%) plots, 11 (38%) of which were in open grassland. Of the large herbivores that frequented areas free of L. camara, the Ugandan kob Adenota kob thomasi Sclater tended to avoid the areas invaded. The floristic composition of invaded areas differed significantly from that of noninvaded areas, with several palatable species rare or absent from L. camara‐invaded areas. Practical implication: These observations indicate the presence of potential recovery constraints that will need to be overcome after L. camara has been removed. Sustained efforts will be needed to suppress the invader and subsequently enrich and bolster native recovery.

Invasive Alien Plant Species Aqueous Extracts in a War Against the Granary Weevil (Sitophilus granarius [L.]) – are They Long-Term Effective or Can They Only Win the Battle of Cannae?

This study investigates the effectiveness of plant-based extracts in repelling the granary weevil (Sitophilus granarius), a common storage pest causing significant economic losses. The selected plant species (Canadian goldenrod, giant goldenrod, indigo bush, staghorn sumac, and tree of heaven), were examined for their repellent effects on weevils in grain samples. Surprisingly, the short-term repellent effects observed after 24 hours diminished after 3 days, suggesting potential challenges for practical applications, especially in long-term grain storage. Temperature emerged as a significant environmental factor, influencing weevil behavior. Lower temperatures created an illusion of increased effectiveness, while higher temperatures accelerated weevil reproduction. Commercial product NeemAzal, despite its reputation for effectiveness, proved the least potent among all treatments, raising questions about its applicability in such cases. Progeny emergence tests indicated no significant differences between treatments, emphasizing the ineffectiveness of the extracts in sustaining long-term repellent effects. The study concludes that while plant-based extracts may offer short-term victories in pest control, their long-term efficacy remains uncertain. The complex interplay of factors, including temperature and humidity, highlights the challenges in developing sustainable and practical solutions for grain storage pest control, necessitating careful consideration by real-world users.

Invasive Glossy Buckthorn (Frangula alnus) Has Weak Impact on Native Understory Plant and Saprophagous Macroarthropod Communities

Glossy buckthorn (Frangula alnus Miller) is an invasive alien plant species (IAPS) rapidly expanding in North America but is largely understudied compared to the common buckthorn (Rhamnus cathartica). Our study investigated the effects of a 27-year-old F. alnus invasion on native understory plant and saprophagous macroarthropod communities in a wet deciduous woodland in Southern Québec, Canada. We hypothesized a decreased taxonomic diversity and a change in community composition of both indicator taxa with increasing F. alnus density. The understory plant and saprophagous macroarthropod communities were characterized, respectively, through vegetation surveys and pitfall trapping across a density gradient of 43 plots invaded by F. alnus. Our results demonstrated that F. alnus did not exert a strong influence on species community composition, although the homogenization of understory plant communities was observed. Despite several decades of F. alnus invasion at our study site, the consequences on the selected indicator taxa were overall relatively small, suggesting that the magnitude of effects is variable. We suggest that further investigation at a larger scale should be performed to evaluate the effect of F. alnus on a broad diversity of indicators and understand any context dependency.

Integrating UAV imagery and machine learning via Geographic Object Based Image Analysis (GEOBIA) for enhanced monitoring of Yucca gloriosa in Mediterranean coastal dunes

Effective monitoring and early detection of invasive alien plant species (IAPs) are crucial for mitigating their spread and safeguarding native habitats. Unmanned Aerial Vehicles (UAVs) offer a cost-efficient solution, providing high resolution images. In this study, we aimed to develop a semi-automated methodology using a machine learning algorithm, spatial metrics, and clustering techniques on UAV images to monitor, map, and suggest management measures to counteract Yucca gloriosa, an invasive plant colonizing coastal fixed dunes in central Italy.UAV flights were conducted using two drones: one for the visible spectrum and the other for multispectral bands (Blue, Green, Red, Red Edge, and Near Infrared) along with a Digital Surface Model (DSM). Derived vegetation indices were also utilized. For mapping Y. gloriosa distribution, a Geographic Object Based Image Analysis (GEOBIA) approach was applied to the orthophoto segmentation, followed by a Random Forest algorithm in a training phase, considering three variable combinations (DSM + vegetation indices, DSM + spectral bands, DSM + mixed variables). The most accurate Y. gloriosa map was used to suggest management measures combining the spatial pattern of invaded patches (size, height, isolation level, and aggregation degree) and a mixed clustering approach (hierarchical and partitioning).The results highlighted that the most accurate prediction map was based on the DSM + mixed variables dataset, showing the important role of using a combination of spectral bands and vegetation indices. In all three cases, the DSM emerged as the pivotal variable for discriminating Y. gloriosa from the surrounding environment. Additionally, our results demonstrate the advantages of incorporating vegetation indices in discerning the target invasive alien plant (IAP) from the broader environment, particularly considering its distinctive photosynthesis process and biomass production. From a managerial standpoint, our pilot study indicates that the UAV-based mapping methodology represents an optimal balance between field efforts and costs. This approach allows for the precise identification of containment and removal areas of Y. gloriosa, without compromising the accuracy of the method. The generated prediction maps also hold potential significance for the conservation of coastal dune ecosystems, providing a promising tool for the effective management of invasive species and biodiversity conservation by suggesting management measures for Y. gloriosa.

Allelopathic potential of invasive alien plant species, Xanthium strumarium L., water and methanol extracts on germination and seedling growth of Guizotia abyssinica (L.f.) Cass., and Linum usitatissimum L.

The objective of this study was to investigate the allelopathic impact of Xanthium strumarium on the seedling growth and germination of Guizotia abyssinica and Linum usitatissimum. Plant specimens and samples of Xanthium strumarium were collected from the Minjar-Shenkora district in Ethiopia. In the laboratory, a series of dilutions of extracts from the leaves and roots of Xanthium strumarium were prepared using distilled water and methanol (99.85%) as solvents. Twenty-five grams of root and leaf samples were soaked separately in 250 mL of the specified solvent to create the stock solution. The experiment was carried out using Petri dishes in a completely random manner, with three replications repeated twice. Various concentrations of the extracts (25, 50, 75, and 100%) were applied as treatments, while distilled water served as the control. Each petri dish contained 25 seeds of each test crop and 5 mL of the corresponding extract. The number of Linum usitatissimum and Guizotia abyssinica seeds germinating was recorded every 24 hours until 12 and 14 days, respectively. Both descriptive and inferential analyses were conducted. When Guizotia abyssinica and Linum usitatissimum seeds were treated with 100% concentrations of water extract from leaf samples, germination percentages were inhibited by 72 and 77.4%, respectively. In methanol extracts, the entire inhibition of germination was observed in both test plant species at ≥ 50% and ≥ 75% concentrations of leaf and root samples, respectively. Therefore, the inhibitory effect of water and methanol extracts showed a concentration-dependent pattern, with increasing concentrations resulting in greater inhibition. The inhibitory effect of leaf extracts was more pronounced compared to root extracts, suggesting the presence of herbicidal activities. Further phytochemical and molecular studies are recommended to identify the active compounds in Xanthium strumarium. Additionally, utilizing isolated allelopathic substances as a means of controlling invasive alien species is suggested.

Phylogenetic relatedness of plant species co‐occurring with an invasive alien plant species varies with elevation

AbstractDarwin's naturalization conundrum posits that the alien species either succeed in the introduced region because they are phylogenetically related to the native species and thus tend to have niches similar to those of native species, or they are phylogenetically dissimilar to native species and thus occupy unfilled niches. This conundrum has received a lot of attention, but the findings regarding these two hypotheses have been contradictory. To reconcile the two seemingly contradictory hypotheses, we assessed the phylogenetic relationship of a highly widespread and invasive species, Anthemis cotula L. (focal species), separately with the native species and all its co‐occurring species (including native and non‐native species) along an elevation gradient. Our results show that the abundance of A. cotula declined continuously with an increase in elevation and with an increase in the number of both all co‐occurring and native species only. The phylogenetic distance between the focal species and the native species based on weighted mean pairwise distance (MPDaw) declined with elevation as well as native species richness. Our study also revealed that soil nutrients strongly influence the abundance of A. cotula; however, their effect on the phylogenetic distance between the focal and other species is negligible. These findings suggest a strong role of microecological factors and spatial heterogeneity in the abundance distributions of invasive species and community assembly. Thus, it could be concluded that the phylogenetic relationship of A. cotula with co‐occurring all or only native species varies with elevation and species richness, adding another layer of complexity to the resolution of Darwin's naturalization conundrum.

Landscape, Human Disturbance, and Climate Factors Drive the Species Richness of Alien Invasive Plants on Subtropical Islands.

Invasive alien plants (IAPs) pose a significant threat to island biodiversity and severely impact ecosystems. Understanding the species-area relationship and environmental determinants of growth forms for IAP species on subtropical islands is crucial for establishing an IAP's early warning mechanism, enhancing island ecological management, and protecting the ecosystems of Fujian and other subtropical islands. The study identified significant species-area relationships for IAPs and different life-form plants (trees, shrubs, and herbs), with slopes of 0.27, 0.16, 0.15, and 0.24, respectively. The small island effect does not apply to all species. Isolation has little effect on species richness, and the IAPs on Fujian islands do not conform to the isolation effect in island biogeography. Landscape factors are the main determinants of IAPs and different life-form species richness, with area, shape index, and perimeter-area ratio being the three primary landscape factors. These environmental factors are closely related to habitat heterogeneity. Besides landscape factors, different life forms respond differently to environmental factors. Climate drives the species richness distribution of shrubs and herbs, while trees are mainly influenced by human activities. Overall, landscape, human disturbance, and climate jointly drive the distribution of IAPs, with landscape factors being the most significant.

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.

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.

Phenological alignment of a galling insect used as biocontrol agent for an invasive tree following hemisphere translocation

Acacia longifolia is one of the most widespread invasive alien plant species along coastal areas in Portugal. In South Africa, this species is also invasive and has been controlled for over 40 years by the Australian gall wasp Trichilogaster acaciaelongifoliae. This biological control agent was introduced in Portugal in 2015, being released immediately after import, i.e., without a laboratory rearing period to adjust the life cycle, and is now established in many locations along the coast. When released in the northern hemisphere, the agent came from the austral spring, with the host-plants having tiny buds, and faced boreal winter with host-plants having large buds. As such it had to synchronize its life cycle with the seasons and phenology of the host-plant in this new location. Both locations have mild summer Mediterranean climates. The present work aims to better understand the life cycle of T. acaciaelongifoliae in the northern hemisphere and how it has aligned its phenology to these new conditions, namely different host-plant phenology and seasons. Two sites were selected (Pataias and São Jacinto), and monitored monthly, from November 2021 to October 2022, to: i) describe the early stages of the life cycle, since oviposition, by collecting and dissecting A. longifolia buds of 5 branches/five trees/site; ii) characterize the stages of the life cycle of T. acaciaelongifoliae inside the developing galls, by collecting and analysing 50 galls/site; and iii) monitoring the development of galls on 10 A. longifolia marked branches/ five trees, in the field. The results suggest that T. acaciaelongifoliae in the northern hemisphere has a univoltine life cycle, but the generations are not completely synchronized at the two sites and even within each site. It is not excluded that two generations may occur throughout the year, i.e., a bivoltine cycle, in some individuals. The alignment of the life cycle may not yet be stabilized. The life cycle seems to be more advanced in the site located further south, Pataias, where adults emerged earlier. Reproductive galls dominated in almost all months, as in South Africa. The present work advances the knowledge on the life cycle of T. acaciaelongifoliae, especially in the northern hemisphere, providing details about the timings and duration of each life cycle stage in this new location. These results are relevant for the management of A. longifolia, stressing the plasticity of the agent life cycle which can facilitate the planning of the biocontrol agent releases in new locations.

Unveiling the ecological alarm: People's perception towards exploring the impact of invasive plants on biodiversity and ecosystem services in the Western Himalaya

This paper presents the insights from both an ecological and people's perception study, aimed at understanding the ecological status of selected two common Invasive Alien Plants species (IAPs), i.e., Ageratina adenophora (Sprengel) King & Robinson and Lantana camara L., and the perspectives of local communities towards their use, status, and influence on biodiversity and ecosystem services as well as controlling measures of these species. For the examination of the distribution and spread of these invasive species in the forests, a quadrat-based phytosociological assessment was conducted in the three dominant forest types [Sal (Shorea robusta Gaertn f.), Chir-pine (Pinus roxburghii Sarg.), and Banj-oak (Quercus leucotrichophora A. Camus)] of Uttarakhand State. However, to assess the perception and awareness of local communities towards these IAPs and their impacts on local biodiversity, ecosystem services, and processes, a questionnaire-based study was conducted in seven villages of the Nainital district, spanning three different vegetation zones: Sal, Chir-pine, and Banj-oak forests. Perception data were gathered from 112 households through questionnaire surveys and interviews with key informants such as teachers, elders, community leaders, and researchers. The results of the ecological assessment indicate that the mid-elevation zone, particularly the Chir-pine forest, is highly prone to species invasion. However, findings from the perception study reveal that the people are aware of these invasive species, and their negative impacts on human and animal health, native biodiversity, ecosystem services, and ecological processes. Interestingly, over the past decade, invasive alien plant species (IAPs) have interfered with forests in the study area, leading to a decline in native species. According to local perceptions, factors such as deforestation, forest fires, climate change, increased transportation, no use of species in daily life, and grazing have contributed significantly to the spread of these IAPs. However, some people use these species as fencing wood, firewood, and for composting, etc. The results of this study indicate that awareness and educational initiatives could play a crucial role in mitigating and managing invasion in the Himalayan region.

Soil moisture prediction based on integrating the CEEMDAN decomposition technique with LSTM in the proximity of Prosopis Juliflora

Human-made adaptations in plant diversity, particularly the introduction of alien invasive plant species, can result in problems such as depletion of groundwater, extraction of natural water resources, and modifications in the local biodiversity. In addition to regulating ecosystems and accurate farming, precise forecasting of soil moisture in the vicinity of these exotic plant species can greatly assist in various other agricultural applications. In this study, we present an improved approach for predicting soil moisture levels at different depths in the vicinity of Prosopis Juliflora (IAPS) by integrating long short-term memory (LSTM) and complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN). CEEMDAN is employed as a preprocessing and denoising technique to decompose the initial soil moisture data into several intrinsic mode functions (IMF). After that, LSTM is used to predict all the IMF (Intrinsic Mode Function) parts from the CEEMDAN process. The individual prediction outcomes of each IMF are combined to obtain the final prediction results. Soil moisture measurements were collected continuously in the Coimbatore area of Tamil Nadu at multi-layer soil depths of 10 cm, 30 cm, 60 cm, and 100 cm. The provided data was utilized for training models and achieving optimal accuracy in forecasting soil moisture levels one month prior. The proposed CEEMDAN-LSTM model achieved the highest R2, ranging from 0.985 to 0.995 at various depths when compared to RNN, LSTM, EMD-LSTM, EEMD-LSTM models, and existing literature models. The results show that the proposed method works well at predicting soil moisture at different depths, which can help improve the planting pattern and schedule of native species to increase the area’s green cover.

Invasive neophytes alter ecological functions and services of riparian hardwood forests

Riparian hardwood forests, now rare in Europe, occur in small patches within agricultural landscapes and are important biodiversity hotspots protected by the EU Habitats Directive and monitored. They play a vital ecological role and provide essential ecosystem services (ES). Recent studies indicate their unfavourable conservation status with a negative trend reported by EU Member States. One of the most visible symptoms of the degradation of riparian hardwood forest is the invasion of alien plant species which can radically change ecosystem functions. In this work, we use plant functional trait analysis to develop proxies and quantify an impact of invasive alien species, specifically invasive neophytes, on specific functions of riparian hardwood forests and their potential to provide five relevant regulating services. Data from 249 phytosociological relevés across 83 Natura 2000 habitat monitoring sites in Poland were analyzed.Our findings indicate that invasive neophytes negatively affect the potential for maintaining nursery populations and habitats, as well as regulation of the chemical condition of freshwaters by these forests. On the other hand, they do not significantly influence the local climate conditions and the forests’ potential to produce antimicrobial compounds. We recommend integrating an ES assessment based on plant functional traits into habitat monitoring. This approach is cost-effective, leveraging existing data, and its results could be used in some cases as a premise for initiating additional environmental monitoring based on direct field measurements.

Anthropogenic forests simplify seed- but not pollen-dispersal networks.

Natural native forests are rapidly being replaced by anthropogenic forests often with a strong presence of invasive alien plant species. Eucalypt species are widely planted worldwide, with Eucalyptus globulus plantations being particularly expressive in Portugal. Poor forestry practices often lead to the associated expansion of invasive species, such as Acacia dealbata. However, we still know relatively little about the functioning of anthropogenic forests, such as seed and pollen dispersal services. Here, we compared bird abundance and richness and the seed and pollen dispersal networks in both forest types. Anthropogenic forests presented lower bird abundance, and smaller, more simplified, and more random (abundance-based) seed dispersal services than those of natural forests. Interestingly, the pollen dispersal network was more similar than the seed dispersal network for both forest types and dominated by opportunistic and neutral processes, given the absence of specialized nectarivorous. The proportion of birds transporting seeds decreased, while those carrying pollen significantly increased in the anthropogenic forest compared to the native forest. Our work highlights the impact of anthropogenic forests on bird abundance, with consequences for seed dispersal services and forest regeneration.

Modelling the current and future agro-ecological distribution potential of Mexican prickly poppy (Argemone mexicana L.) invasive alien plant species in South Wollo, Ethiopia

ABSTRACT Argemone mexicana L. is an invasive alien plant species (IAPS) that belongs to Papaveraceae family. This study aimed to identify and map its current and future (2050 and 2070) potential distribution in South Wollo, Ethiopia. Eight Kebeles were selected using a stratified random sampling method that covered two agro-ecologies ranging 1500–3200masl for species presence data collection and 204 presences data were used for modelling. Climate, topography, and land use land cover change (LUCC) variables were used to build the species distribution model (SDM). An ensemble SDM model was run consisting of five algorithms into one single model. The area under the curve (AUC) and true skill statics (TSS) of the ensemble SDM score values of 0.89 and 0.7, respectively. The predicted result on its agro-ecological distribution showed 76.75% was non-suitable and 23.26% was suitable in varied extents, currently. Suitability will be increased after LUCC and climate change except the SSP5–8.5 2070 emission scenario. It will be highest under SSP1–2.6, 2050, and SSP2–4.5, 2070 emission scenarios possessing 28.67% and 28% suitability class, respectively. A. mexicana distributed in the mid and highland agro-ecologies from 1500–3200masl both in current and future time period. It urges effective coordination among actors to minimize its distribution potential.

Density, biomass, and fruit and seed production potential of Mexican prickly poppy (Argemone mexicana L.) invasive alien plant species under different land uses and agroecology in South Wollo, Ethiopia

Density, biomass, and fruit and seed production potential of Mexican prickly poppy (Argemone mexicana L.) invasive alien plant species under different land uses and agroecology in South Wollo, Ethiopia

The effects of plant invasion, floral resources and soil characteristics on ground-nesting bees

Ground-nesting bees are susceptible to disturbances that affect foraging resources, vegetation structure and soil characteristics. We studied the effects of 12 invasive alien plant species on environmental variables and directly on ground-nesting bees to reveal their specific importance. We sampled bees along transects; flowers, vegetation, bare ground and litter in quadrats, as well as soil characteristics. Our results suggested that plant invasion reduced overall and flowering plant richness and positively affected the height of native vegetation. However, this did not affect ground-nesting bees’ abundance or species richness. Although we found invaded plots to have altered soil chemical characteristics compared to control plots, there was no correlation between soil characteristics and ground-nesting bees. The large explanatory potential of the random factors suggests that there were large differences in the abundance and species richness of ground-nesting bee species among the different habitat types and before and during the flowering of the invasive species. Although our study lacked a direct sampling of nesting bees, our results show the adverse effects of plant invasion on foraging and some nesting characteristics of ground-nesting bees. Future studies should put effort into the investigation of the number of nest holes and additional soil characteristics to get a better picture of the effects of plant invasion on ground-nesting activity.

Effects of native species richness on reproduction of invasive Bidens pilosa vary with nutrient supply

BackgroundBoth increasing native species diversity and reducing nutrient availability can increase the ability of native plant communities to resist alien plant invasions. Furthermore, native species diversity and nutrient availability may interact to influence alien plant invasions. So far, however, little is known about the interactive effect of species diversity and nutrient availability on reproduction of alien invasive plants. We constructed native plant communities with one, four or eight species under low and high nutrient supply and then let them be invaded by the invasive alien plant Bidens pilosa.ResultsAt both high and low nutrient supply, increasing native species richness significantly increased aboveground biomass of the native plant community and decreased aboveground biomass and biomass proportion of the invader B. pilosa. Reproductive biomass of B. pilosa decreased significantly with increasing native species richness under high nutrient supply, but this effect was not observed under low nutrient supply. Net biodiversity effect on seed mass of B. pilosa decreased significantly with increasing native species diversity under high nutrient supply, but not under low nutrient supply. This was mainly because the selection effect became dominant with increasing species richness under high nutrient supply.ConclusionsOur study suggest that native species richness and nutrient supply can interact to influence reproduction of invasive alien plant species and that measures to help maintain a high level of native species richness and to reduce nutrient supply could be useful for efficient invasive plant control.

Invasive Alien Plant Species: A Tool for Restoring Degraded Lands or a Threat to Native Ecosystems!

Invasive Alien Plant Species: A Tool for Restoring Degraded Lands or a Threat to Native Ecosystems!