Based on data from available scientific publications, a review of the insects, trophically related to Impatiens glandulifera in its European invasion zone has been made. As a result, nine insect ...species (Pristerognatha fuligana, Deilephila elpenor, Xanthorhoe biriviata, Chrysolina herbacea, Siobla sturmi, Impatientinum asiaticum, Aphis fabae, Aphis nasturtii, Phytoliriomyza melampyga) were found on the invasive plant. Of the identified insects, seven species (D. elpenor, X. biriviata, A. fabae, A. nasturtii, C. herbacea, P. fuligana, P. melampyga) are widespread in the country, of which only two – C. herbacea and P. fuligana are associated with I. glandulifera. The remaining two (I. asiaticum and S. sturmi) are not pre-sented in the Bulgarian entomofauna. Тhe potential role of these insects as agents of biological control of populations of I. glandulifera in Bulgaria has been assessed.
Summary
Soil loss from riparian areas supporting the annual invasive weed, Impatiens glandulifera (Himalayan balsam), was measured and compared with equivalent values recorded at nearby, ...topographically similar areas supporting perennial vegetation over a cumulative seven‐year period, along sections of two separate river systems; one in Switzerland, and one in the UK. Soil loss from colonised locations was significantly greater than from reference locations in four of the seven measurement periods. Despite contrasting results, standard deviations, based on soil losses and gains, were predominantly higher for colonised areas at both rivers over most monitoring periods. These findings indicated that areas colonised by Himalayan balsam experience higher sediment flux in comparison with areas free of invasion. Here, we test those original interpretations by reinterrogating the datasets using a more robust analysis of inequality. Nine datasets were tested, five of which (i.e. 56%) showed that sediment flux was significantly greater at Himalayan balsam‐invaded areas than at reference areas. Three datasets showed no difference in sediment flux between invaded and reference areas (33%), and one (11%) showed higher sediment flux at reference areas. Most results uphold our original interpretations and support our hypothesis that hydrochory probably dictates where colonisation initially occurs, by depositing Himalayan balsam seeds in slack or depressional areas along river margins. Once Himalayan balsam becomes established and sufficient perennial vegetation is displaced, seasonal die‐off and depleted vegetation cover may increase the risk that some areas will experience significantly higher sediment flux.
Volunteers are increasingly involved in the delivery of nature conservation policies, usually supported by a twofold rationale: volunteering can (a) enhance citizen participation in environmental ...governance and (b) ensure a workforce is in place to support conservation work in times of budget shortages. Here, we ask how these two rationales correspond to volunteers' own motivations to engage in a specific nature conservation activity, namely the control of invasive alien species (IAS). We use qualitative interviews with professional project managers, local group leaders, and volunteers to examine the interactions between policies aiming to rationalise the management of IAS and the motivations for and goals of volunteer engagement. Our findings suggest that although volunteering can lead to positive conservation outcomes, satisfying experiences and empowerment, the different interests do not always align in practice. We investigate the implications of strategies that aim to improve the efficiency of invasive species and volunteer management, and discuss organisational arrangements that reconcile different objectives.
•The use of volunteering can have normative (public participation) and instrumental purposes.•We examine how these relate to volunteers' own interests and motivations.•Rationalisation of invasive alien species control can misalign with volunteering motivations.•Some collaborative arrangements are able to reconcile these diverging functions.
Impatiens glandulifera Royle (Himalayan balsam) is an annual plant, native to humid parts of the Himalayas. Brought to Europe in the XIX century, it has since successfully naturalized and spread ...throughout the continent, becoming one of the best-known invasive plants. Even though it has been thoroughly studied by many authors, some aspects of its biology and ecology remain unclear and debatable, such as its spreading dynamics, negative impacts in invaded ecosystems and ecological adaptability regarding moisture, nutrients, and light. This 2019 field study from the Ljubljana Marsh (Slovenia) has proved that Himalayan balsam successfully develops under mesophilic conditions, where it easily compensates moderate deviations from its ecological optimum. The species thrives in riparian zones, out-competing native vegetation, trait shown as potentially the biggest negative impact of chosen species in this context. This study additionally gave us a different insight into - usually highly emphasized - dynamics of species’ spreading. Spreading was not either dependent on hydrochory or as drastic as mentioned in literary sources, giving it a secondary role in species’ invasiveness on the chosen area. Lastly, we proposed rough estimates of eradication expenses for given area, based on our field results of species’ abundance and distribution on chosen area.
•Impatiens glandulifera is a highly invasive annual plant across large parts of Europe.•We describe the species’ taxonomy, morphology, distribution, habitat requirements, ecology, life cycle and ...genetics.•We further synthesize all known impacts on biodiversity and ecosystem functioning.•We shortly summarise potential eradication and management strategies for the species.
This paper presents all current knowledge on the biology of the invasive therophyte Impatiens glandulifera Royle (Himalayan Balsam), and covers aspects of taxonomy, morphology, distribution, habitat requirements, ecology, life cycle, genetics, history of invasive spread, ecological impact and management. Although a few review papers have been published on this species in previous decades, a great deal of insights have been gained in the last three decades, owing to the species’ notorious reputation as one of the most problematic invasive species in Europe. This study consequently focusses on this novel information, with a particular focus on information from Central Europe.
Aim: Riparian habitats are amongst the most invaded ecosystems world-wide.The great abundance of invasive species in river corridors is attributed to the efficient transport of alien species' ...propagules and reduced competition from native plants due to regular flooding. Once an invasive species has become established, river corridors can serve as stepping stones for spread into other habitats. We have chosen the Himalayan balsam Impatiens glandulifera Royle, highly invasive annual in riparian areas, as a model for spread of invasive species from linear river corridors. Location: Central Europe. Methods: We mapped its distribution and recorded its abundance in over 1200 patches along four rivers in central Europe, differing in the time of balsam's introduction (1900-1995). The patches were characterized in terms of the distance from the riverbank, height above the river surface, degree of soil disturbance and flooding regime. Results: The patches at sites subject to flooding had twice as many individuals as those that were not subject to flooding, regardless of their distance from the riverbank and height above the river surface. There was a strong effect of the river identity, with river invaded 20 years ago being less infested than those invaded earlier. The distance from the riverbank at which the populations occurred differed and did not depend on river identity/residence time. The patches in tributaries were on average two times further from the bank of the main river than those located elsewhere. Main conclusions: Flooding is an important factor affecting the abundance of I. glandulifera, and accounts for its spread and dominance along river corridors probably due to spreading the seeds, increasing nutrient availability and disturbing native vegetation. It is likely that the number of I. glandulifera populations will increase in the future, especially along small water courses.
The impact of exotic annual Impatiens glandulifera on invaded European vegetation is ambiguous; there are studies reporting considerable negative as well as weak or even no impact of this invader on ...species richness and diversity of the invaded communities. The effect of invasion by I. glandulifera on species richness, diversity and the composition of resident vegetation was studied in the northern foothills of the Tatra Mountains in southern Poland. Two approaches were used: comparing diversity measures of the invaded and uninvaded plots and analysing changes in species richness and diversity in plots grouped according to increasing cover percentage of I. glandulifera. Invaded plots harboured 0.27 fewer species per 4 m² and had significantly reduced values of the Shannon and Simpson diversity indices and Pielou’s measure of evenness. Analysis of changes in diversity measures with the increase in I. glandulifera cover revealed that an increase in I. glandulifera cover was from the onset related to a decrease in the diversity of the invaded plant communities, but after exceeding a 80 % cover, this species dramatically reduced the diversity of the invaded vegetation. Non-metric multidimensional scaling analysis indicated a significant shift in the composition of invaded plots in relation to uninvaded plots, which resulted from the proportional increase in the more shade tolerant and nutrients demanding species. Our results suggest that in species-rich vegetation, such as fresh meadows and related communities, I. glandulifera may suppress weak competitors and, thus, negatively impact plant diversity.
Impatiens glandulifera is one of the most widespread invasive plant species in the UK. Although aspects of its biology are known, there is little information about its association with microbial ...communities, both above ground and below ground. Furthermore, it is unknown whether this species exhibits any form of plant–soil feedback (PSF), commonly seen in other invasive weeds. We conducted a PSF experiment, in which plants of I. glandulifera were grown in soil that supported the species and compared with plants grown in a control soil from the same locality. Soil nutrients were measured, and the soil and foliar microbial communities were assessed. Impatiens glandulifera grew larger and faster in conditioned soil compared with the control. Higher levels of phosphate were also found in conditioned soils. Arbuscular mycorrhizal fungal (AMF) colonisation was lower in conditioned soils, suggesting that I. glandulifera may rapidly alter AMF communities in invaded areas. PSFs had a significant effect on the foliar endophyte community, with clear separation of species between conditioned and control soils. These results show that I. glandulifera displayed a positive PSF and the PSF mechanism extended beyond the soil microbial community to affect foliar endophytes. The observed increase in endophytes in plants grown in conditioned soil could enhance resistance to herbivory, thus further accentuating the invasive properties of this species.
The annual plant Impatiens glandulifera (Himalayan balsam) is the most widespread invasive non‐native weed in the British Isles. Manual control is widely used, but is costly and laborious. Recently, ...biological control using the rust fungus Puccinia komarovii var. glanduliferae has been trialled. We designed an experiment to assess the impact of these control methods on invertebrate communities in relation to unmanaged and uninvaded habitats, and to determine whether mycorrhizal inoculation aided post‐control recovery of these communities. Sixty invaded and twenty uninvaded field soil blocks were transplanted to the experiment site, where a mycorrhizal inoculum was added to half of all blocks. Biological and mechanical control treatments were applied to twenty invaded blocks independently; the twenty remaining invaded blocks were left intact. Above‐ and belowground invertebrate samples were collected from the blocks at the end of the growing season. Overall, aboveground invertebrate abundance increased with the removal of I. glandulifera, and several groups showed signs of recovery within one growing season. The effect of mechanical control was more variable in belowground invertebrates. Biological control did not affect aboveground invertebrate abundance but resulted in large increases in populations of belowground Collembola. Our experiment demonstrates that mechanical removal of I. glandulifera can cause rapid increases in invertebrate abundance and that its biological control with P. komarovii var. glanduliferae also has the potential to benefit native invertebrate communities.
Riverbanks as Battlegrounds Pattison, Zarah; Vallejo-Marín, Mario; Willby, Nigel
Ecosystems (New York),
04/2019, Volume:
22, Issue:
3
Journal Article
Peer reviewed
Open access
The abundance of invasive alien plants (IAPs) can vary dramatically over small spatial scales for reasons that are often unclear. Understanding these could offer key insights for containing ...invasions, accepting that eradication is often no longer feasible. This study investigated determinants of IAP cover on riverbanks, a well-known hotspot of invasion, using Impatiens glandulifera, a prolific invader across the Northern Hemisphere, as a model species. Within this framework, we included the potential for dominant native vegetation cover, mediated by favourable environmental conditions, to resist invasion by I. glandulifera through negative association. Our analyses, using structural equation modelling, showed that I. glandulifera is more sensitive to environmental conditions than dominant native vegetation. High soil moisture was a key determinant of I. glandulifera cover, having negative effects across the riparian zone. Spatially, I. glandulifera and dominant native vegetation responded differently to environmental conditions. Sites with steeper banks had less dominant native vegetation at the water’s edge, potentially favouring I. glandulifera cover through reduced competition. In general, greater abundance of dominant native vegetation presented a more invasion-resistant community. Maintaining dominant native vegetation at high abundance is thus key to preventing large monospecific I. glandulifera stands from forming. Our findings highlight the opportunities to indirectly limit plant invasions in general via targeted environmental management and restoration, as well as understanding future risks from long-term environmental change.
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